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Engine Specific Info and Questions => IDI Engine => Topic started by: giulianot on February 09, 2009, 08:48:39 am
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hello all,
My brother has a mk2 gti with a aaz swap in it. Just last week it started building up pressure in the coolant system making the rad hoses go rock hard. he removed the t stat and had the same problem. So i advised my brother that he most likely had a blown head gasket and he wa leaking compression into the coolant. So we pulled off the head and noticed some big cracks fro the pre cups tho the vales. I told my brother that the head was probably no good any more so we decided to put a different used head on. We had 0.011" machined off the new "used" head to clean it up a bit and remove some pitting. We installed the new head and now the the engine is still building excessive pressure in the coolant :( does anyone have any clues to what it could be. Hes still driving with no t-stat in,well install a new one tonight and see what that does.
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there will always be a lot of pressure in the hoses. Rock hard hoses isn't uncommon...
It's when it gets so great that your expansion tank can't hold the pressure. I'm assuming that's what's happening though. I wouldn't expect anyone to go through all that work just because of hard hoses?
That top rad hose will always be very hard...
Does he have 50/05 coolant in it? or straight water. Straight water will make HEAPS of pressure.
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there will always be a lot of pressure in the hoses. Rock hard hoses isn't uncommon...
It's when it gets so great that your expansion tank can't hold the pressure. I'm assuming that's what's happening though. I wouldn't expect anyone to go through all that work just because of hard hoses?
That top rad hose will always be very hard...
Does he have 50/05 coolant in it? or straight water. Straight water will make HEAPS of pressure.
as well as freeze 8)
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cooling systems on the cummins diesels can make so much pressure that it will blow the freeze plugs out of the block!!
high reving water pumps make lots of PSI......I think I would worry if it is spewing coolant out the bottle..other then that hard hoses are normal....
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I wouldn't expect anyone to go through all that work just because of hard hoses?
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You didn't re-use the old head gasket, did you?
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I wouldn't expect anyone to go through all that work just because of hard hoses?
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ok my bro came by after installing new t-stat and i witnessed it myself tonight, Under light load the engine stays at normal operation temp, good coolant flow through the rad and heater core. Once you start to drive the car hard and bring up the revs and put the engine under load, the coolant all boils over and spills out the rad cap and no heat out of the heater core and the temp gauge skyrockets :?: pull over and wait till the steam settles and put some more coolant in and drove it home. Then we let it idle there with the rad cap off and it circulated fine through the hole system?
MY only guess at this point is maybe his lower rad hose is collapsing under high revs and he is loosing circulation? any other guesses? were putting a spring in the lower hose tomorrow
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ok my bro came by after installing new t-stat and i witnessed it myself tonight, Under light load the engine stays at normal operation temp, good coolant flow through the rad and heater core. Once you start to drive the car hard and bring up the revs and put the engine under load, the coolant all boils over and spills out the rad cap and no heat out of the heater core and the temp gauge skyrockets :?: pull over and wait till the steam settles and put some more coolant in and drove it home. Then we let it idle there with the rad cap off and it circulated fine through the hole system?
MY only guess at this point is maybe his lower rad hose is collapsing under high revs and he is loosing circulation? any other guesses? were putting a spring in the lower hose tomorrow
your putting in one of those hoses with the springs? good idea.
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Did you spin the crank when you had the head off to check the block (cylinder walls)?
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My money is on the head gasket or worse, case cracked head/block.
Head gasket more than likely.
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hello all,
My brother has a mk2 gti with a aaz swap in it. Just last week it started building up pressure in the coolant system making the rad hoses go rock hard. he removed the t stat and had the same problem. So i advised my brother that he most likely had a blown head gasket and he wa leaking compression into the coolant. So we pulled off the head and noticed some big cracks fro the pre cups tho the vales. I told my brother that the head was probably no good any more so we decided to put a different used head on. We had 0.011" machined off the new "used" head to clean it up a bit and remove some pitting. We installed the new head and now the the engine is still building excessive pressure in the coolant :( does anyone have any clues to what it could be. Hes still driving with no t-stat in,well install a new one tonight and see what that does.
the motor needs the t-stat installed to effectively cool it. without the T-stat, the coolant flow isn't efficient, and will give you trouble.
the used head that you had machined should have been pressure tested. it's cheap insurance to avoid doing all the work required to clamping it down, and then removing it again when you find out its bad.
as stated above, did you install a new head gasket, and new head bolts? what procedure did you follow? did you torque the head bolts in sequence? not to sound like a dick or anything, but the more info you provide, the better the answers you will receive from the more experienced members of this forum.
libbybapa does have a good suggestion about the rad cap... and they're dirt cheap.
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ok my bro came by after installing new t-stat and i witnessed it myself tonight, Under light load the engine stays at normal operation temp, good coolant flow through the rad and heater core. Once you start to drive the car hard and bring up the revs and put the engine under load, the coolant all boils over and spills out the rad cap and no heat out of the heater core and the temp gauge skyrockets :?: pull over and wait till the steam settles and put some more coolant in and drove it home. Then we let it idle there with the rad cap off and it circulated fine through the hole system?
MY only guess at this point is maybe his lower rad hose is collapsing under high revs and he is loosing circulation? any other guesses? were putting a spring in the lower hose tomorrow
sounds almost exactly like what mine was doing when my HG was blown......
check the easy stuff first..like the cap.
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Sounds exactly what mine was doing.....city driving and idle was fine.....once you took it on the highway or higher revs it would boil over and spew coolant thru the cap. Turned out it was the head gasket only after 8000 km after doing it. Trying to diagnose it changed out the t-stat, rad, cap....until finally took the head off and cyl number 1 had tiny marks of coolant leaking in.....couldnt even tell by looking at the headgasket.
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If it is building excessive pressure a simple cause could be a faulty expansion tank cap.
Andrew
This cap is our pressure regulator. If it is a 15 psi cap, it will vent if the pressure exceeds 15 psi. Hard hoses or not. Like Andrew said, replace the cap. Some shops have a cooling system tester that also will test your cap. You pump air against the cap until it vents. The pressure gauge will tell you if your cap is working correctly. Without a gauge, how could you be sure you had too much pressure in your system ?
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I agree that the t-stat installed offers better cooling control.
The used head was not pressure tested after machining because it came off a running engine, and it looked to be in good condition.
A new 2 hole V/R head gasket and new head bolts were installed when machined head went on. Bolt were torque to 30, 45 ft/lbs the 2 90 deg stages
all symptoms point to a head gasket failure but what could be causing it?
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:cry: ...
a warped block? :cry:
did you use a metal HG?
did you do the hot retorque?
is it 100% water?
If it persists you could try switching to studs?
I know for a fact that i would have this problem if i didn't use studs and a metal gasket
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I agree that the t-stat installed offers better cooling control.
The used head was not pressure tested after machining because it came off a running engine, and it looked to be in good condition.
A new 2 hole V/R head gasket and new head bolts were installed when machined head went on. Bolt were torque to 30, 45 ft/lbs the 2 90 deg stages
all symptoms point to a head gasket failure but what could be causing it?
i will also have to add my experience with a 'bad' oil cooler. i was experiencing some weird problems with my motor after getting a new headgasket put on. there was oil getting into my coolant, and my oil level was rising. i installed a new oil cooler, drained and added new oil. problem completely went away. (there was so much pressure that my oil filler cap actually came off. not sure how, but it did. maybe i didn't tighten it down enough, but still!)
apparently VW recommends changing out the oil cooler after any major engine work... probably because of its inherent weakness?
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I used a metal head gasket . We did not re-torque hot I've never felt it was necessary. There is a 50/50 mix coolant and water in now.
I have seen oil cooler failures, but i dont think it is the case here. There is no oil in the coolant or coolant in the oil.
If the problem persists after the spring is installed in the lower hose than I will have to remove the head again and try a 2nd head gasket replacement.
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It's a cracked block. The Tstat control temp not prs. It's doing the same thing as before.... The head and gasket have been replaced, next is the block.
I know this because it happen to me.
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It's a cracked block. The Tstat control temp not prs. It's doing the same thing as before.... The head and gasket have been replaced, next is the block.
I know this because it happen to me.
i wouldn't call it that just yet... remember that the AAZ head gasket must actually be deformed to work properly. if its not properly deformed, it will most likely not seal well enough. perhaps a retorque would be a good idea???
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So this morning we preformed a hot retorque, a ful90 deg on each headbolt in the proper bently order. Now we hooked up a pressure gauge to the coolant top hose to inside the dash so we can monitor coolant pressure in the cabin. It seems that the hot retorque did not work as the temp gauge still fluctuates +-1/4 scale under light to hard loads.
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it took me 110ftlbs to finally crush my MLS headgasket and stop the leaking....but that was with ARP studs not head bolts..
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my temp gauge will fluctuate like that. when i romp onto the onramp to the highway it'll go to 3/4 and then cool right down to 1/4 once up to speed and then gradually get to the middle.
it will really bounce back and forth with city driving too. I got a new sender, maybe it's more responsive or something? if you have the heat on you can feel the coolant get hot when you romp on it and then actually tell when it goes through the rad and cool right down. If it goes from hot to cold to hot to cold like i described perhaps blocking part of the rad with some cardboard might do the trick? so that it doesn't quite cool SO much and give lots of lag on the t-stat to open again.
just an idea... that came out of the gear that slowly turns in my head
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should not need to do any radiator blocking....those stock temp gauges are JUNK...my stocker reads all over the place compared to my Isspro temp gauge...the isspro holds pretty solid at 190-200* no matter what I do...the stock gauge in the mean time goes up to 3/4..then back down to 1/2.......I really would not trust the stock gauge that much..
Note I am running a cooler fan temp switch so I run slightly cooler all the time......
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So this morning we preformed a hot retorque, a ful90 deg on each headbolt in the proper bently order. Now we hooked up a pressure gauge to the coolant top hose to inside the dash so we can monitor coolant pressure in the cabin. It seems that the hot retorque did not work as the temp gauge still fluctuates +-1/4 scale under light to hard loads.
did you verify the thermostat is working properly by boiling it with a thermometer?
the temp fluctuations seem normal to me (with a cool thermostat)
don't worry about the temp, unless it gets more than 3/4 on the gauge. just keep an eye on your coolant PSI.
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What did you find out about the pressure your cap is holding ? Sounds like you are not over pressure but have gauge problems.
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How did you make out on troubleshooting?
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ive recently started using the "water wetter" performance coolant additive.and i must say its wonderfull.The temperatures are way more stable.I cant get it to move when its up to temp
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Does anyone think blocked piston oil jet (due to sloppy head gasket replacement) could cause overheating of the cylinders and contribute to head gasket troubles?
I have noticed much higher temps around the pre-combustion chambers/ glow plugs compared to the rest of the block. A difference of 90C on the block compared with 105C sometimes at the glow plugs. The hottest measured temp being at the base of the head. I have mentioned this before but found no explanation so far. To me there should be a higher temp in the area but not that high.
The implications of this is that if the surface is that temperature the coolant must be higher. If the coolant reaches that temp at idle (I measured at idle) what happens at speed? And could it produce enough boiled bubbles that it could fill the rad or cause an air block of the oil cooler?
This might be a condition of higher mileage engines only and might not be as dramatic in newer engines.
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Does anyone think blocked piston oil jet (due to sloppy head gasket replacement) could cause overheating of the cylinders and contribute to head gasket troubles?
I have noticed much higher temps around the pre-combustion chambers/ glow plugs compared to the rest of the block. A difference of 90C on the block compared with 105C sometimes at the glow plugs. The hottest measured temp being at the base of the head. I have mentioned this before but found no explanation so far. To me there should be a higher temp in the area but not that high.
The implications of this is that if the surface is that temperature the coolant must be higher. If the coolant reaches that temp at idle (I measured at idle) what happens at speed? And could it produce enough boiled bubbles that it could fill the rad or cause an air block of the oil cooler?
This might be a condition of higher mileage engines only and might not be as dramatic in newer engines.
i would imagine your pistons melting at the right temp, without the piston oil coolers. i can't see how it would affect coolant temps. i don't think the piston oil jets would get clogged unless you had some serious carbon buildup in the oil, in which they would be the least of your problems at that point...
redline water wetter, and similar antifreeze additives can significantly increase the transfer of heat to the coolant, and help eliminate hot spots in the engine. this will significantly reduce the possibility of headgasket failures due to overheating...
it also seems that the IDI engines run better the hotter the swirl chamber is (up to a certain point i believe) as some people have tried coating them in a heat reflective coating, with very negative results... don't be too concerned with it - the inconel can take the heat :wink:
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For the stories I've heard, spin the crank with the head off and check each cylinders stroke... If the head is coming off again mind you.
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Hello, first post.
It is my observation that this cannot be a cracked block because of the following. If the block is cracked you will absolutely have intermix. When you shut the engine down the 12-15 psi of coolant will force its way through the crack and run right into the crank case. The same is generally true with a cracked head.
However if the block deck is not flat, or if the machine shop surfaced the head improperly, you could get a situation where either the combustion gasses bypass under compression, or because of poor "clamping" which not only refers to the head fasteners, the head can actually lift under heavy pressures allowing gasses to bypass into the coolant. Now the reason you may not get intermix is because when you shut the engine down the head has enough "clamp" to keep the 13 psi of coolant where it belongs.
When I first read this post the first thing I thought of was the simplest, maybe there was an unbled air pocket in the system, but it seems head gasket, head and block surface are also good possibilities.
BlueMule
'86 Golf TD
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Hello, first post.
It is my observation that this cannot be a cracked block because of the following. If the block is cracked you will absolutely have intermix. When you shut the engine down the 12-15 psi of coolant will force its way through the crack and run right into the crank case. The same is generally true with a cracked head.
However if the block deck is not flat, or if the machine shop surfaced the head improperly, you could get a situation where either the combustion gasses bypass under compression, or because of poor "clamping" which not only refers to the head fasteners, the head can actually lift under heavy pressures allowing gasses to bypass into the coolant. Now the reason you may not get intermix is because when you shut the engine down the head has enough "clamp" to keep the 13 psi of coolant where it belongs.
When I first read this post the first thing I thought of was the simplest, maybe there was an unbled air pocket in the system, but it seems head gasket, head and block surface are also good possibilities.
BlueMule
'86 Golf TD
Hello BlueMule, welcome to the board and thank you for your response. I also agree with you logic and believe the problem must be to a untrue block deck surface. The head was machined by a reputable engine builder and was flat and new head bolts were used. The only thing we did not check is the if the block deck was flat with a straight edge. But what would cause a cast diesel block to suddenly warp or become untrue. And if i take the head off and find that the block deck is bad, how can i machine the deck in the car. Could it be block sanded flat?
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Hello, first post.
It is my observation that this cannot be a cracked block because of the following. If the block is cracked you will absolutely have intermix. When you shut the engine down the 12-15 psi of coolant will force its way through the crack and run right into the crank case. The same is generally true with a cracked head.
However if the block deck is not flat, or if the machine shop surfaced the head improperly, you could get a situation where either the combustion gasses bypass under compression, or because of poor "clamping" which not only refers to the head fasteners, the head can actually lift under heavy pressures allowing gasses to bypass into the coolant. Now the reason you may not get intermix is because when you shut the engine down the head has enough "clamp" to keep the 13 psi of coolant where it belongs.
When I first read this post the first thing I thought of was the simplest, maybe there was an unbled air pocket in the system, but it seems head gasket, head and block surface are also good possibilities.
BlueMule
'86 Golf TD
Hello BlueMule, welcome to the board and thank you for your response. I also agree with you logic and believe the problem must be to a untrue block deck surface. The head was machined by a reputable engine builder and was flat and new head bolts were used. The only thing we did not check is the if the block deck was flat with a straight edge. But what would cause a cast diesel block to suddenly warp or become untrue. And if i take the head off and find that the block deck is bad, how can i machine the deck in the car. Could it be block sanded flat?
some head gasket material can actually buildup on the block deck. you need to scrape it clean before putting the head on if you want it to seal properly. you might get away without following that step, but not always.
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some head gasket material can actually buildup on the block deck. you need to scrape it clean before putting the head on if you want it to seal properly. you might get away without following that step, but not always.
The blade out of an exacto knife works very well with a shop vac along side. and some solvent to loosen it all up.
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I use a regular razor blade and stand it on edge to almost a 90 deg angle and drag it around the surface to be cleaned.
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Andrew, really cool Avatar. Naturally the molecular structure of any gas or vapor vs any liquid certainly could allow a for a whole host of strange leaks etc. For example, gas could leak through a "space" that would not allow coolant to leak back the other way, or the crack could close up once the compression or combustion pressure is removed, or when cooled.
But having said this, I really doubt that this is a question of a cracked block, maybe a crack in the combustion chamber, yes. But here is where it gets dicey, I have never seen a block crack at the the top of the bore, I have seen them crack in the middle of the bore, at the bottom of the bore by a weak web casting or due to severe torsional stress. And invariably there is intermix. But I have not seen it all that is for sure. :)
Back to the OP, your lack of heater concerns me, unless you just blew out all of the coolant and there was nothing left. Do you have hot air coming out of the heater after you fill the cooling system and before it overheats?
Looking in the overflow tank is really not an accurate way of telling whether the radiator is partially plugged or not. Many vehicles with plugged radiators will sit and idle for ever and never overheat, but once you drive them and put some stress on the cooling system the vehicle overheats.
You could also get a leak-down test done on the engine when it is hot, and see if there are any bubbles in the overflow tank. This might let you know if there was a crack, if the crack does not close and only shows up under extreme pressure.
Also you said you put a pressure gauge in the cooling system, what were the readings??
Of course this is all general and nothing VW specific, someone here may have much more experience with this. Anyway I hope you figure it out.
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The fact that it is a swap might be a problem. You might have to check out just how much the water is cooling the engine especially compared to the OEM cooling. Check that the thermostat is not being held closed by cool water (or maybe lots of air) from the bottle or the heater or what ever your setup.
I tried messing around with this back in the summer.... for your reference you can read through this thread:
http://vwdiesel.net/phpBB/viewtopic.php?t=15591&postdays=0&postorder=asc&start=15
The heater increases the engine temperature:
So just a technical note: Since I am driving everyday, most of the day and I am now geeking out about the cooling of these crazy machines, I have been playing with getting the optimum temperatures. It seems like an orifice, to the expansion tank, just over 3/8" is right to control the stat so the expn. tank temp effects the stat with the most cooling with the least lag time. Disclaimer: under the conditions I am working with.... new rad, AAZ engine, Van and it's weight. I had a 3/8 line before and that proved to be too small. 1/2" is too big (too much diversion of coolant from the rad). My temperatures are being measured from the by-pass while driving and range from 87degC to 94C on a long hill at highway speed.
Oh hey... did you know how much the heater effects the engine temperature and how?
If you are over heating because of this wrong temperature in the expansion tank thing and you use your heater you are sure to see an increase in engine temps while trying to cool it down. The reason is that cool water returning from the heater blows over the thermostat cooling(closing) it causing the engine temperature to go up. I think they did this to get more heat to the heater in the winter. This is a good test too to see if this might be your trouble. If you over heating while your heater is on but not when it's off you might consider increasing the temp in the expansion tank. A few degrees C increase is fine but not if your temps are too high to start with.
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Also you said you put a pressure gauge in the cooling system, what were the readings??
We have done a lot of talking about what can cause leaks, how to fix them, etc... but giulianot has not said anything about what psi is in his cooling system, not anything about the tank cap... only that the hoses are very hard under pressure. Am I missing something here? Reminds me of drinking in a bar a bit too long such that everyone is talking but no one is listening. :-) I'll take a double of what he's drinking !! :-P
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I had a chance to hook up a pressure gauge and this is what i observed; On start up 0 psi and i did not let it sit at idle too long i took it for a drive. I Gently bring the the car up to operating speed and temp and i am seeing 13 to 14 psi coolant pressure measured from top front flange. Lots of heat coming out of the heater core. Now the test begins, I'm approaching a fairly steep incline so i roll on the pedal in fourth gear and begin to accelerate hard up the hill. Temp begins to climb and so does the psi 15 ,16 17 20, oh *** there goes all my coolant out of the bottle and down the road and all of the sudden no heat out of the heater core. The pressure is still at 19 psi and steam is blowing out of the coolant bottle. I pull over, wait till it cools down , refill coolant and bring it home. :x Reminds me of that old joke, So i told my doc, " doc my car overheats when i push it hard " he says "then don't push it hard!"
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One Scotch, One Wiskey, One Beer :lol:
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You need to pull the head, no question. This is exactly what happened with my van - heater went dead cold and shortly after the temp gauge pegged with the light flashing, all due to a warped head.
If your head was flat before, it's warped now. It doesn't take much heat to twist one up and the metal head gasket is extremely sensitive to head warp.
Pull the head and check if it's flat. The max spec for a fiber gasket is .004", I'd want it near perfect for the MLS gasket. You need a machinist grade straightedge that's not been dropped yet - your hardware store steel rule is not accurate enough. If it passes the flatness check, have it pressure tested and go from there.
Chris
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19 - 20 psi when you are getting on it? WOW !!! Is there a delay when you first get on it before the pressure comes up by a matter of some seconds ? If so, I would be looking at coolant flow - are your radiator cores clean and free flowing ? Is your water pump belt tight? Is your water pump impeller in goos condition? Are any of the hoses to / from the radiator free from bends or kinks?
Now, if your head got hot even once, yeah, its likely warped.
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giul, I agree with arb, check the radiator it might be the "cause" of failure. You might have a situation where the cooling system is causing an overheat condition, which in turn is causing other failures. The fact that you have a reconditioned head and new head gasket leads me to think that an underlying problem may still be there. Keep it simple and start over with the basics.
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Update: So I bought a new rad and replaced the rad and that seems to have solved the problem. I think that the old rad was restricting of coolant flow and the coolant was by passing through the heater core only. I'm just really glad the problem is fixed and it was not a cracked block :oops:
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I have similar symptoms, what can a person do to verify if the radiator is plugged or restricted? Only starts to overheat when the engine is worked hard, if it's a brief acceleration, the heat slowly builds and disipates just as slowly. Gauge will slowly climb to 3/4 of the way on the temp gauge slowly, but then if not pulled over, will increase fast past that point, spewing out coolant out the expansion tank. Replaced the cap, hoses, thermostat, expansion tank. Verified that the thermostat works the way it's supposed to. I have the coolant drained, no discoloration or debri when draining. Also used a rad flush once on it. Is there any harm in just filling the rad with the rad flush mix and letting it sit overnight? I would just plug the bottom discharge off the rad. Wouldn't let the rad flush sit in the engine, only the rad. Just and idea.
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I have similar symptoms, what can a person do to verify if the radiator is plugged or restricted? Only starts to overheat when the engine is worked hard, if it's a brief acceleration, the heat slowly builds and disipates just as slowly. Gauge will slowly climb to 3/4 of the way on the temp gauge slowly, but then if not pulled over, will increase fast past that point, spewing out coolant out the expansion tank. Replaced the cap, hoses, thermostat, expansion tank. Verified that the thermostat works the way it's supposed to. I have the coolant drained, no discoloration or debri when draining. Also used a rad flush once on it. Is there any harm in just filling the rad with the rad flush mix and letting it sit overnight? I would just plug the bottom discharge off the rad. Wouldn't let the rad flush sit in the engine, only the rad. Just and idea.
i doubt there would be harm by letting the rad sit with rad flush in it, but its not the way the flush was designed to work. it uses the heat from the engine to help dissolve the buildup. try using vinegar to clean really bad deposits. it'll work somewhat good, but then try with hot vinegar, and it works REALLY well! :wink: also the movement of the hot liquid will help break apart any deposits. i've had it done on my car, and i let it idle a good half hour or so with the rad flush. i used prestone's super heavy duty flush, and it worked GREAT. i've never had so much heat out of the car :lol: but i'm not sure if that flush will work if there is a complete rad blockage... if its that far gone, a new rad might be a good idea
i'd be more inclined to buy a cheap rad as well...
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after pulling the rad out, I soaked it in some rad flush, but apon inspecting, i was able to force water from one side of the rad, where the fan switch is located to the inlet/outlet of the rad, so with that flow, i feel the rad isn't plugged up too much. From what i could see on the inside of the rad, it looked like a healthy aluminum color, little to no oxidation. Running my finger along the bottom of the rad, i couldn't feel any deposits. I've got the rad installed again, having the switch out, i was able to fill the rad and get most of the air out, now it's just a matter of squeezing hoses, to work what little air is left.
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after pulling the rad out, I soaked it in some rad flush, but apon inspecting, i was able to force water from one side of the rad, where the fan switch is located to the inlet/outlet of the rad, so with that flow, i feel the rad isn't plugged up too much. From what i could see on the inside of the rad, it looked like a healthy aluminum color, little to no oxidation. Running my finger along the bottom of the rad, i couldn't feel any deposits. I've got the rad installed again, having the switch out, i was able to fill the rad and get most of the air out, now it's just a matter of squeezing hoses, to work what little air is left.
run the car with the rad cap off and give it a few good revs. let the car get up to operating temp so the t-stat opens, and you should be good to go.
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I use a regular razor blade and stand it on edge to almost a 90 deg angle and drag it around the surface to be cleaned.
i use a 90 die grinder with the softess (used) surface conditioning disc. much faster.. just don't go crazzy
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Also on the thermostats, I've had problems 2 times with anything but a German one. Don't get these from Autozone or Advance