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Engine Specific Info and Questions => IDI Engine => Topic started by: speedy on December 13, 2009, 04:32:27 pm
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I am having an overheating problem in my '73 bus with 1.6 Quantum TD. I just installed twin radiators under the floor of the bus and was not having this problem before, when I had one rad under the floor and one in the engine compartment.
The symptoms: Coolant temp fluctuates wildly, will sometimes go up/down 30 degrees in a couple of seconds. Water is not flowing properly through the radiators when the system comes up to temperature. There is a single fan on one of the radiators set for 85C and it never comes on. Return hose from the radiators is always cool where it meets the water pump housing. After a while, pressure builds up in the system and vents through the radiator cap on the overflow tank. Coolant boils in the overflow tank and down the large hose to the water pump. When the engine is cold, a steady stream of water flows through the small hose coming into the overflow tank but when it gets hot the stream is intermittent. Watching the temp gauge, sharp drops in temp correspond to flow through this hose where increases correspond to lack of flow through this hose.
I do not see any evidence of a blown head gasket - no oil in the water, no stinky fumes coming from the overflow tank, just smells like steam. Because of this and the fact that this problem occurred right when I made the change to the radiators makes me think it's some sort of problem with the way my hoses are routed but I can't figure out what it could be. I don't see how it could matter which way the water flows through the radiators.
Pictures of the rads and hose routing are at the link below my name. Any ideas appreciated.
Thanks,
-David
http://motorheads.net/vw/turbobus/page7.html (http://motorheads.net/vw/turbobus/page7.html)
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Looks like a lot of potential for airlock.
I'd at least measure the coolant capacity for each component, add it together, ad measure fill volume.
The return to reservoir ought to come from the top of the rad. You could accomplish this with a hose in a hose arrangement on the out rad hose...
---------rad-top-----------------
#
- ------rad-bottom-------------
[#L___________________
[#____rad_return_hose___
#\
# \ compression fitting/solder
#
#=res=return=====
Clear as mud? ???
Also radiators are more efficient with more temp differential, would running them in parallel be better than series? For sure would reduce flow resistance.
I like how they fit under the van.
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Thanks for the reply, it really got my mind going. The return line to the reservoir does actually come from the top of the radiator, or at least very close to it. The more I think about it, the more I agree with you that it is an airlock problem because (and please correct me if I'm wrong) if the water pump was moving coolant, then there would be coolant returning to the reservoir through the small hose. I used to think that only happened when the thermostat was open but after studying the diagrams I see that is not the case.
But if there is air in the system, where is it? Shouldn't be in the rads because it would be returned to the reservoir through the existing return hoses. If there is air in the water pump, wouldn't it bubble up into the head? This is beginning to make sense. Back when I had a radiator in the engine compartment, it had a return to the reservoir that was above the cylinder head level, and in fact the hose went directly up and over the engine to it. Now, both returns are well below cylinder head level. I bet I need a bleed valve near the top of the engine... and wouldn't you know it, googling "vanagon engine air bleed" pulled up this:
http://www.relitech.com/tech/19wpump/hsbleed.jpg (http://www.relitech.com/tech/19wpump/hsbleed.jpg)
I feel so stoopid now.
As for series/parallel, I did consider the latter but that arrangement requires more fittings/hoses and it cannot be guaranteed how much water will go to each radiator. Also staging the fans would not work as well. Temp differential would be the same as you still have the same amount of water flowing across the same area of radiator either way, but some say that heat will transfer better if the coolant is moving more slowly, which would be a benefit to the parallel arrangement. I may try it someday.
-David
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What pressure cap are you running?
The return line to the reservoir does actually come from the top of the radiator, or at least very close to it. The more I think about it, the more I agree with you that it is an airlock problem because (and please correct me if I'm wrong) if the water pump was moving coolant, then there would be coolant returning to the reservoir through the small hose.
This is the case.
But if there is air in the system, where is it? Shouldn't be in the rads because it would be returned to the reservoir through the existing return hoses. If there is air in the water pump, wouldn't it bubble up into the head?
I think there are two factors.
1 A small amount of air will swell to a larger volume at 200F, and if it will tend to impede flow.
2 The more linear feet you move liquid through a tube, the greater the resitance to flow, and you are at 9? times what the water pump was ever meant to see. Corners are bad too, but velocity is low, so who knows.
If resistance is great enough to let water boil in the head, all bets are off, coolant flow stops.
This is beginning to make sense. Back when I had a radiator in the engine compartment, it had a return to the reservoir that was above the cylinder head level, and in fact the hose went directly up and over the engine to it. Now, both returns are well below cylinder head level. I bet I need a bleed valve near the top of the engine...
the reservoir needs to be at the top of the cooling system to perform the bleed function properly. a seperate bleeder may work, but adds complexity, and service difficulty, esp. on the side of the road.
and wouldn't you know it, googling "vanagon engine air bleed" pulled up this:
http://www.relitech.com/tech/19wpump/hsbleed.jpg (http://www.relitech.com/tech/19wpump/hsbleed.jpg)
I feel so stoopid now.
Did yo also read the Vanagon bleed procedure?
2200 RPM on a 23 degree slope to 5 minutes?
this was conceived by a brilliant person with an engineering degree? :-\
You are not the dumb one.
As for series/parallel, I did consider the latter but that arrangement requires more fittings/hoses and it cannot be guaranteed how much water will go to each radiator. Also staging the fans would not work as well. Temp differential would be the same as you still have the same amount of water flowing across the same area of radiator either way, but some say that heat will transfer better if the coolant is moving more slowly, which would be a benefit to the parallel arrangement. I may try it someday.
-David
Ease of flow is also a factor at play, Your radiator resistance will be half, as will coolant speed. If you run a Y pipe at each end of the rad pair, the only difference between the two will be relative deposit buildup in the tubes, and flow will be pretty well equal. As is, i think rad #2 is not doing much more than acting as a tank. if you can access an IR temp gun, you can check for yourself(a lot of things).most emission shops will have one if a friend doesn't. The first 1/4-1/3 of a rad sheds about as much heat as the rest. Run the fans so they are triggered by either or both switches, extra safety factor :)
Between the big transfer pipes, and 2 rads, you have almost double stock coolant capacity, I think if the stuff were moving, you'd be fine.
Once you get flow dialed, it will be worth your time to do some experimenting with air dams encouraging flow. done right, the E-fan probably won't need to run on the highway.
Taking the Chevy RV I had for awhile as an example... a 454 in a low perf application only needs 3/8fuel line, but since it is 30 feet from tank to motor, GM used 1/2" for that run. Why? Straight line friction would have let 3/8 line perform like 1/4. You might run a slightly larger line on the bleed hose.
Can you tell I have fought this battle before? My Volvo VW diesel came from the factory with over 32 hose clamp coolant connections :o there is a theme here...
I added a very similar aux rad to a friends 350 Chevy converted Mercedes 309D bus, and it worked pretty well.
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Straight from the Bentley manual(gas version), I'll admit I might have forgot the exact degree of slope it called for.
As I remember there is a bleed at the rad in a vanagon as well
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Very interesting David!
I've been chasing many of the same demons with the Quantum engine I have in the back of my 356. I used a large aftermarket aluminum radiator from Summit mounted in the engine compartment. I tried scooping air from under the car through plastic ducting into the radiator. The idea was that the ducting would insure that only fresh outside air would pass through the rad, not air already heated by the engine.
Great plan eh? Unfortunately, no matter what I did, it always ran too hot. I tried two or three different scoops under the car, several different thermostats, shrouded fan, unshrouded fan, etc. We also took the original oil to water oil cooler out and replaced it with a forward mounted oil to air cooler. No matter what we did, the car ran between 210 and 230 all the time, hot enough to give me the heebee jeebee's every time I drove it.
Well, the car's back up on blocks in my little shop of horrors now, and I'm trying some new ideas. Now we're trying twin identical motorcycle radiators just behind the headlights up front, plumbed in parallel. For additional radiation area we're routing the hot water forward to the rad through baseboard heater elements in the space between the pan and the rocker panel. We'll see what happens ::)
For your application I think that parallel plumbing would help. The other thing is that you must, by whatever means necessary, get all the air out of the system. Even if the Vanagon system used a reservoir that was not at the high point, I don't think anyone would argue that it's good practice to do so. Try mounting the tank higher than the head, and run the engine hot with the tank open, that SHOULD get rid of all the air.
V. cool project! Good luck with it --
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Turbogreasel: The pressure cap is the stock Quantum cap, and it does seem to vent properly. :(
I have to respectfully disagree with your statement that the second rad is only functioning as a tank. That may be true under normal circumstances but when the weather turns hot and the engine is under load, that will change. To see why series/parallel doesn't matter, consider the case where the cooling needs of the engine can be met by 50% of the radiator capacity. In the series case, the first rad does all the cooling and the second rad does none (not quite true, but this is hypothetical). In the parallel case, the first half of each rad does all the cooling and the second half of each rad does none. No difference there, really. As I said before the point about coolant speed is valid and I may try parallel someday just to see how it works. Can't argue with the point about resistance either but I don't think it is significant.
If, after this bleeding issue is resolved, the engine is still running hot then I will monitor the temps at the radiators and if they are cooler than the engine I will suspect a water flow issue. This was not the case however when I had the twin rads in the engine compartment and believe it or not, there is only about 4 feet more pipe with the rads under the floor than there was with them in the engine compartment.
Andrew: My bus does not have the hose going from the center of the cylinder head to the expansion tank, and neither did the Quantum donor car. I didn't realize that the Vanagons had it until I read your oil-cooler-reroute thread. I just got back from Home Depot with stuff to build a quarter-inch barbed fitting into the line out of the cylinder head back to the expansion tank, but now I'm wondering if I need a bigger hose, a/la the 5/8" looking one on the Vanagon diesel installs, of which I have dozens of pictures. That will also require a new overflow tank since mine does not have the connection at the top for that hose. I wonder why that hose needs to be so large, considering that on the Quantum, the air gets to the rad via a large hose but then must still take a small hose to the expansion tank. Sure would be easier for me if I could get away with a smaller one.
Incidentally, you were right about the metal hose to the turbo, in fact it failed almost immediately after I installed it. I ordered a neoprene-coated spiral reinforced tube from McMaster-Carr and installed it a few days ago and oh boy, is the bus ever quiet now! Not Lexus-quiet of course, but the noise level in the drivers seat went from deafening to merely loud, or about what it was with the stock gas engine. I'm even thinking of wrapping the hose with something to further reduce the noise level. Who would have thought that all of that noise could come through that little teeny turbo?
MoT: Are you talking about a Porsche 356? Hard for me to imagine an upright engine in one of those, not to mention that the purists are probably all up in arms. :) A much braver project than mine, for sure. If the motorcycle radiators are fairly large and you can get enough air to them, I think it could work. I don't know what you are using for baseboard heater elements, but wouldn't that be bad in the summer? They do make finned copper pipe, I believe which might help although I am somewhat wary of copper in automotive applications because of fatigue. If you're using that, be sure to isolate it properly (listen to me talking about metal fatigue after I put an aluminum-foil pipe on my turbo! The nerve! ;) )
Thanks for the replies - I will probably go ahead with the small line project for the moment since I have the parts. Still need to think/learn more though.
-David
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2 pipes flow better than one dude... so, if your radiators were in a series, you would be flowing into one, then out of that one ant into the next one. so its going to have the restrictions from the first radiator, and from the second radiator, all at once with that setup. if you paralell them, ie: split them with a y pipe, you eliminate most of the restrictions. then its like having one really big less restrictive radiator.
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yea, true, but i dont think about the "what ifs" of everything. i bet the setup he has right now would work fine if it didnt have massive amounts of air in it.
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MoT: Are you talking about a Porsche 356? Hard for me to imagine an upright engine in one of those, not to mention that the purists are probably all up in arms. :) A much braver project than mine, for sure. If the motorcycle radiators are fairly large and you can get enough air to them, I think it could work. I don't know what you are using for baseboard heater elements, but wouldn't that be bad in the summer? They do make finned copper pipe, I believe which might help although I am somewhat wary of copper in automotive applications because of fatigue. If you're using that, be sure to isolate it properly (listen to me talking about metal fatigue after I put an aluminum-foil pipe on my turbo! The nerve!
Yes, it's a '65 SC coupe, and the engine fits under the rear deck quite well actually. The finned copper pipes are outside, so they will not be heating the interior of the car. They will be rubber mounted, with hose connections on both ends, so I'm not too worried about fatigue, and the rads are brass anyway so there's already copper in the system.
I'm also fitting a custom type 1 VW transmission now with very tall gearing, we're shooting for 60 mpg next summer. I don't let the 356 purists get me down, I've owned this car over 30 years now, so I'll do whatever I want with it -- though I am always looking over my shoulder in case there is a 356 Registry "Death Squad" after me.
Of course, unless they have a very special AC gasser in the back of their tub, they're not going to catch mine anyway ;)
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whats the very special AC gasser? ancient performance intrigues me...
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A ir C ooled ;)
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Andrew: My bus does not have the hose going from the center of the cylinder head to the expansion tank, and neither did the Quantum donor car. I didn't realize that the Vanagons had it until I read your oil-cooler-reroute thread. I just got back from Home Depot with stuff to build a quarter-inch barbed fitting into the line out of the cylinder head back to the expansion tank, but now I'm wondering if I need a bigger hose, a/la the 5/8" looking one on the Vanagon diesel installs, of which I have dozens of pictures. That will also require a new overflow tank since mine does not have the connection at the top for that hose. I wonder why that hose needs to be so large, considering that on the Quantum, the air gets to the rad via a large hose but then must still take a small hose to the expansion tank. Sure would be easier for me if I could get away with a smaller one.
I would have to look at and think about the vanagon hose routing to figure out why they went with such a large hose there. It may very well not be necessary, especially if the only reason for it is to purge air. Also, the vanagon hoses can be a bit deceiving. Several of them have restrictors in them and I'm not sure if that circuit does or not.
I'm pretty sure that hose does have a restrictor in it (it's been a while since I sold my diesel vanagon). You don't actually want alot of flow through this hose as it dumps hot water into the overflow tank, which will then be sucked back into the water pump.
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A ir C ooled ;)
they made a special air cooled engine? i thought you had to build one yourself to get any real power out of them?
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they made a special air cooled engine? i thought you had to build one yourself to get any real power out of them?
Well, that's what I mean -- no original air cooled pushrod Porsche engine would stay with my oil burner ;D
For the cars that have been highly tuned, or powered with big built VW type 4 engines, or even 911 six cylinder lumps -- that's a different matter!
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they made a special air cooled engine? i thought you had to build one yourself to get any real power out of them?
Well, that's what I mean -- no original air cooled pushrod Porsche engine would stay with my oil burner ;D
For the cars that have been highly tuned, or powered with big built VW type 4 engines, or even 911 six cylinder lumps -- that's a different matter!
Yea, i kinda doubted that they made a ac motor that would skool your oil burner. unless, like you said, it was heavily tuned, or swapped.
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I added a bleed hose right where the coolant exits the head and routed it to the overflow tank. I then blocked off the bleed hoses from the rads as I no longer think they are necessary in this application (rads mounted flat under the floor are nowhere near the high point of the system). Unfortunately, the bus still overheated.
Tonight, I removed the thermostat and tested it on the kitchen stove. It seemed to open a bit late (190-ish) but otherwise seemed to work. It was stamped "Made in USA", must be an old one. ::) Maybe it's a 192-degree thermostat? Just for fun, I put the system back together with no thermostat and drove it about 15 miles, mostly at WOT. It ran just fine and did not show any signs of overheating. So, I'm hoping that means that the head gasket is okay.
The temp stayed about 170 most of the time and topped out at 180 on a long stretch in 4th gear into a headwind. It's about what I would expect considering that the engine is getting a mix of cooled and recirculated water and that the outside air temp is 35 degrees. Took a long time to warm up of course.
I drove to Autozone and got a new 180-degree thermostat, guess I'll install that and try to overheat it again.
-David
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Fwiw, I bought a Caddy with a blown head gasket a couple of years ago. I tried to drive it home, but it overheated every few miles. I removed the thermostat, and was able to make it 12 miles home without the motor even heating up. I don't really know what this means as far as your cooling system problem goes. Do you get alot of pressure in your header tank after only a few momoent running? If so, you may have a headgasket issue.
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Hmmm... well I suppose I may still have a blown head gasket then. After my 15 mile drive last night, there was only a small amount of pressure in the overflow tank - about what I would expect from a warm system. With the thermostat in, there would be a lot of pressure after driving a few miles.
-David
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I had previously run the bleed hose from the top of the cylinder head to the overflow tank. Yesterday I put in the new thermostat and drove my usual 10-mile circuit around the local farm-to-market roads. No overheating. Today I tried a more ambitious 40 mile jaunt up the interstate. I was driving into a North wind going 60-65mph, 800-1000 degrees EGT (pre-turbo) and 8-10psi boost depending on the slope of the road. Went a dozen or so miles this way and just when I was beginning to feel good about things, the temp shot up from 195 to 230 - same crap as before. I pulled over and got out, observed steam and water coming from underneath the bus (via the pressure cap on the overflow tank). I drove gently to a safer spot and let it idle for a few minutes. By the time I got the engine hatch off all of the pressure was already vented and the temp was back down to 190. I added about a pint of water and got on the highway going back towards home.
Cruising 60-65 again (but with much less pedal since I now had a tailwind) I again saw the temp shoot up to 220 but it almost immediately went down to 210 and I was not by an exit so I just kept going. I slowed down to 55mph and the temp bounced around a bit more before settling back at 190. I drove all the way home and it never went back above 190 the whole way.
I need to decide whether or not to go ahead and change the head gasket. I would start tonight if I was sure that the head gasket was the problem, but I still have doubts. I don't think there was any air in the system when I started the drive, so it either came from the head gasket or from water boiling in the block. If water was boiling in the block, that would have to be from inadequate water flow. I guess I could try a new water pump.
A couple of other things - the engine has been getting harder and harder to start. Used to start and idle smoothly after 8 seconds of glow, then it started but idled roughly, and lately it has taken 2 or 3 glow plug cycles before it will get going, with plenty of smoke. Still runs like a swiss watch when warmed up. Could this simply be because it has only seen short trips around town the past two years? Or could it be another symptom of a bad head gasket?
I need to drop the drivetrain soon anyway to replace the tranny, how hard is a head gasket replacement if the engine is sitting on the garage floor? Any hints for a first-timer? I have replaced head gaskets on other OHC 4-cylinders before, I assume this one is not much different - remove timing belt, intake/exhaust, valve cover, injector pipes, water hose, head bolts? If the head surface passes the straightedge test, can I just put a new gasket on it and put it back together? Maybe I will just do it and get it over with, but I want to make sure I'm not opening Pandora's box.
I read all of the info about the various head bolts and I think I would probably just get the factory Torque-to-yield type since this is a stock engine.
If I replace the gasket and it still boils over, I am going to... <ahem> have very negative thoughts! Thanks for any wisdom you care to share.
-David
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I think the reason they made the overhead hatch the size they did was that in 1973 (the first year of the hatch) the only things that were serviced through the overhead hatch were the air filter and carbs. Everything else was serviced through the rear hatch. When the Vanagon came around, it had no rear hatch so a lot more stuff had to be serviced from the overhead hatch, therefore they made it larger. If any of you know a guy named Yannick Galipeau, he did a pretty nice job of enlarging the hatch in his baywindow to Vanagon-size.
Question - if you have everything at TDC (or at any other specific location, for that matter) when you remove the head, why would you have to worry about valve-piston clearance on installation? Assuming nothing rotates, nothing will touch, no?
If the head needs work, I am going to be in trouble. I don't know if there is anyone in Dallas/Ft.Worth that does VW diesels.
Thanks for the reply,
-David
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I went ahead and replaced the head gasket. Put on a new two-notch gasket with the Escort Cosworth ARP studs. While I was at it I re-shimmed the valves, had the injectors rebuilt by a local shop, pimped my glow plugs and installed a rebuilt tranny with 10% taller gears. I should have been able to do all that in a month, but it took me ten!
But the end result is no more overheating. I am so relieved. Thanks to everyone who took the time to reply and especially those who helped me with questions that came up during the job. The turbobus is running like a Swiss watch and I can't wait to get some real heat... and an intercooler.
-David
http://motorheads.net/vw/turbobus
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Well that's handy when fixing stuff is actually successful. Good job. :)
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Seconded.
And I've gotta say yours has been one of the more entertaining build pages... I've kept my eye on your site as you've moved along and definitely have enjoyed your exploits.