Overheating

I'm trying to help another Delorean owner with his over heating problem. His car can idle, but the moment a load is put on it it overheats. The car is equipped with a bleeder kit. To date we have done the following:

Replaced the radiator
Replace the thermostat
Filled and bled the system
Checked fan function, all ok
Checked water pump function, all ok
Flushed the system as best we can including the piping from front to back. We could not remove the plugs from the block so we pulled the manifold and Y pipe and hoses from head to water pump. Flushed both sides from inlet to outlet and reverse.

The engine has a lot of miles on it and has often had more hot water than antifreeze in it. I told Bill to use some cooling system flush for a six hour period to deep clean his cooling system. I think the water gallery around the cylinders is full of crud. I ordered a 8 mm bit from V-8 tools. Hopefully this one won't shear off from the torque like the CTA one did and we can flush the system better.

Any suggestions why it is continuing to overheat?

If the car can idle without overheating, then the only thing I could suspect is the coolant can not keep up with the demands of a engine under load, maybe look at the waterpump as the problem. Although it may not be leaking, it can still wear internally and look to function correctly, but it just can't move the coolant at higher volumes.

That is why I took off the thermostat cover and hoses to see if the impeller was slipping on the shaft, it wasn't.

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Originally Posted by Texas Twister

I'm trying to help another Delorean owner with his over heating problem. His car can idle, but the moment a load is put on it it overheats. The car is equipped with a bleeder kit. To date we have done the following:

Replaced the radiator
Replace the thermostat
Filled and bled the system
Checked fan function, all ok
Checked water pump function, all ok
Flushed the system as best we can including the piping from front to back. We could not remove the plugs from the block so we pulled the manifold and Y pipe and hoses from head to water pump. Flushed both sides from inlet to outlet and reverse.

The engine has a lot of miles on it and has often had more hot water than antifreeze in it. I told Bill to use some cooling system flush for a six hour period to deep clean his cooling system. I think the water gallery around the cylinders is full of crud. I ordered a 8 mm bit from V-8 tools. Hopefully this one won't shear off from the torque like the CTA one did and we can flush the system better.

Any suggestions why it is continuing to overheat?

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May I ask what you are seeing when you say the car is overheating?

- What is the temperature gauge reading at this time?
- Are you seeing coolant flash out of the overflow hose?

A couple things came to mind considering you've looked at or addressed many of the things likely to cause the problem:

- Instrumentation problem if your observations are based on the gauge.
- Coolant reservoir cap problem if it is not holding back system pressure to 15 psi, i.e. if the relieving portion is letting coolant out when it shouldn't (coolant is actually at an ok temperature and pressure, but cap is faulty)
- Coolant level is too high and it is expelling some in order to find that happy medium. Coupled potentially with air pockets perhaps.

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Originally Posted by Texas Twister

I
Checked fan function, all ok
?

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Does this mean that you checked that the fans will turn if you apply 12V to them, or do you mean that they come on when the otterstat reaches 220F, as designed?

Check that the fans are turning the correct way (sucking air through radiator). Did it always have this problem?

It idles at around 170 180 or so. The moment it gets under load the temp gauge shoot up to 220 at which point we park it and watch the water puke out the overflow. He has a manual switch on the fans and they do blow the correct direction.

No it did not always have this issue.

Blown head gasket.

Get a combustion-products-in-coolant tester.

What is probably happening is that idle pressures are relatively low and all is well. When you load it up, combustion gas is leaking out of the head gasket into the water jacket. This 200+ PSI combustion gas displaces the 14 psi water (which blows out the cap) and puts the temp sender in steam rather than water so the reading takes off very quickly. A compression test might prove this as well, but the leak may not be bad enough to show up. Pull the spark plugs and look for one that does not look like the others, i.e. much cleaner (steam cleaned, in fact). If it's bad enough, you might be able to see coolant in the bad cylinder through the spark plug hole after the engine cools a bit.

While it is very likely Dave S is right about the blown head gasket, it is also possible the timing is way off and/or the mechanical and/or vacuum advance is not working. Easy to check with a timing light. Meanwhile, do you see bubbles with the cap off? Put a pressure tester on and see if the pressure shoots up. Another thing you can do is remove the spark plugs and pressurize the cooling system and see if any cylinders get wet. If the plastic screen in the oil fill is melted start ordering the gasket set.
David Teitelbaum

It's looking more and more like the head gasket. The timing is fine. Saw bubbles in the overflow, but don't know if it was combustion gasses or boiling water. Will tell Bill to check. He's about 50 miles from me so it takes a bit to get up there!

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Originally Posted by Bitsyncmaster

Check that the fans are turning the correct way (sucking air through radiator). Did it always have this problem?

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How can this get reversed? My car has been acting funny too and I checked the fans for airflow. When I put my hand in front - outside the rock screen - it feels like air is blowing out the front of the car rather than being sucked in. It could also be that the air IS actually being suckedn in and my mind is tricking me into believing the air flowing past my hand is coming out instead of being sucked in.

How could it be possibe for this to have gotten reversed? How do I flip flop it to test for sure.

CHeers
Steven

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Originally Posted by mluder

How can this get reversed? My car has been acting funny too and I checked the fans for airflow. When I put my hand in front - outside the rock screen - it feels like air is blowing out the front of the car rather than being sucked in. It could also be that the air IS actually being suckedn in and my mind is tricking me into believing the air flowing past my hand is coming out instead of being sucked in.

How could it be possibe for this to have gotten reversed? How do I flip flop it to test for sure.

CHeers
Steven

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Steve,

put a post-it note against the grill and see if it sticks. Or just reach behind an compare the wind.

Mine can feel like its backwards too, but it's all smoke and mirrors!

You can look at the fans when they turn off and see if they are turning correctly by the fan blade angle. Some of the replacement fans don't have connectors and the PO may have wired them wrong.

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Originally Posted by sdg3205

Steve,

put a post-it note against the grill and see if it sticks. Or just reach behind an compare the wind.

Mine can feel like its backwards too, but it's all smoke and mirrors!

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Tested... Everything is fine.

I think I've found the problem. When I bled the system last time I didn't have the heater running and I think I have air trapped in the heater valve (or whatever it's called).
I have noticed when it starts to overheat if I turn the heater on the engine temp drops. I don't mean slowly goes back to normal. I mean like opening a faucet.

Anyway. I bought Toby's self beeder kit so regardless I should have no more porblems.

Cheers
Steven

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Originally Posted by mluder

Tested... Everything is fine.

I think I've found the problem. When I bled the system last time I didn't have the heater running and I think I have air trapped in the heater valve (or whatever it's called).
I have noticed when it starts to overheat if I turn the heater on the engine temp drops. I don't mean slowly goes back to normal. I mean like opening a faucet.

Anyway. I bought Toby's self beeder kit so regardless I should have no more porblems.

Cheers
Steven

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If the system is properly bled and you still have air in it, you could have a blown head gasket and you are pumping combustion gasses into the cooling system. The "auto-bleeder" is just a Band-Aid getting rid of those built-up gasses. it will still run hot and overheat. A properly running and bled PRV cooling system does not need an auto-bleeder. Are you bleeding the radiator? You need to loosen the small hose on the top, righthand tank and let the air out.
David Teitelbaum

FYI: The heater core is always flowing coolant (even with the mode switch OFF) The ONLY time Coolant does not flow through is during MAX A/C. + 1 on Bleeding the radiator upper right hose. Loosen the clamp wiggle the hose back in twisting motion just enough to hear the air HISS out. Be prepare slide the hose back on quickly. If your problem persists following these steps. You know what the likely cause is.

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Originally Posted by DMC5180

FYI: The heater core is always flowing coolant (even with the mode switch OFF) The ONLY time Coolant does not flow through is during MAX A/C. + 1 on Bleeding the radiator upper right hose. Loosen the clamp wiggle the hose back in twisting motion just enough to hear the air HISS out. Be prepare slide the hose back on quickly. If your problem persists following these steps. You know what the likely cause is.

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I have bled the system both at the radiator and at the water pump. I was told that you should have the heater on ful blast and blowing hot air before bleeding the system. I neglected to do that part that's why I'm thinking there maybe air trapped in there.

Cheers
Steven