Overheating

[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?

[Michael]

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.

[Texas Twister]

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

[Jonathan]

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?

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.

[Dangermouse]

I
Checked fan function, all ok
?

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?

[Bitsyncmaster]

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

[Texas Twister]

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.

[Texas Twister]

No it did not always have this issue.

[DMCMW Dave]

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.

[David T]

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