aaz building pressure in the coolant......STILL!

[jtanguay]

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:

[FoXBoXRaCiNG]

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.

[BlueMule]

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

[giulianot]

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?

[jtanguay]

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.

[Smokey Eddy]

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.

[zukgod1]

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.

[BlueMule]

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.

[stopping]

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.

[arb]

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

[giulianot]

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!"

[BlueMule]

One Scotch, One Wiskey, One Beer  :lol:

[Luckypabst]

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

[arb]

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.

[BlueMule]

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.