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Cooling System Leak - Part 2

1K views 15 replies 5 participants last post by  Enterprise 4Cam 
#1 ·
Last Fall, our '04 DeVille developed a significant cooling system leak. A shop told me that the radiator was leaking, the coolant crossover pipe was leaking and there was leakage around a head gasket. Since the coolant was almost 5 years old, they suggested changing the coolant and adding some cooling system sealing tablets. They did this and the leakage stopped almost immediately and it didn't leak a drop for several months. Unfortunately the leak is back and I see a few drops under the radiator after the car has been setting for a while. The leak is bigger than that, though, because the coolant is going down fairly rapidly. Replacement of the radiator (if that's all it is) will cost hundreds of dollars and I don't want to do that right now. Will adding another set of 5 tablets as an interim fix cause any damage to the cooling system?
 
#2 ·
Adding sealants does nothing but make later repair much more difficult and raises the distinct possibility of clogging the heater core, small coolant passages, and purge system. Never should have added the obsolete recommended 3 tablets or worse, 5, in the first place.

Repair the leak correctly.
 
#4 ·
I have the ability to swap out the radiator, except that last year I injured my shoulder and I'm not in a position to do any jacking and crawling under the car. I would if I could. I just hope that the problem is only the radiator and not a head gasket. Then we'll be looking at a new car.
 
#7 ·
By a block test, I assume you mean a test to see if coolant is getting into the cylinders.

The shop told me that there was coolant leakage from a head gasket, in addition to the coolant crossover pipe and radiator. Maybe the leak from the crossover pipe was making it look like a head gasket leak. I'll have to have it checked again before I do anything.
 
#9 ·
I guess that's what I meant but didn't say it the right way. But it seems like if you shut off the engine when it's hot and the system is still under pressure, coolant might leak through the blown out section and into the cylinder.

The shop told me that I could do a crude check for exhaust gas leaking into the coolant by driving up a long hill and watching the temp gauge. If the gauge starts to increase, there is hot combustion gas going into the coolant. So far, I have not seen this occur.
 
#15 ·
The shop told me that I could do a crude check for exhaust gas leaking into the coolant by driving up a long hill and watching the temp gauge.
A couple of WOT runs will accomplish the same thing.


it seems like if you shut off the engine when it's hot and the system is still under pressure, coolant might leak through the blown out section and into the cylinder.
True. In that case your symptom will usually be a rough idle after a cold start for a few seconds until that coolant burns off.
 
#10 ·
The hot exhaust gas (if any) is not the direct cause for overheating - the gas overpressures the cooling system, blowing coolant out the surge tank overflow, the coolant level drops, the water pump loses prime and cavitates, the engine overheats.

At slow speeds and no fans commanded ON going up hills then ANY engine will gain a few degrees of coolant temp. Just as they lose temp during long mountain hill coastdowns.
 
#11 ·
Okay, Sub, so if I drove up a fairly steep hill that was several miles long and did not see ANY temperature increase or experience any coolant loss, I guess it's safe to assume that there is no combustion leakage into the cooling system and the head gaskets are okay?
 
#12 ·
2004's 'may' have a slight advantage re headbolt/block issues/GM update
Read/inspect your car carefully
 
#13 ·
I'm not gonna SWAG (scientific wild ass guess) the cooling system on a 17 year old car that I have no idea of what its service history is.

Safe to say that, if you drive up a pretty long hill, winter or summer, with little or no observed temp rise then things are probably OK.

Remember - that temperature "gauge" is heavily damped from 188 to 210 degrees - "12 o'clock" - God forbid that an owner could see a gauge actually do something - and engine coolant temp swings all over that range every time the car has a start-run-drive event.

IF you have some A/C compressor function (AUTO or DEFROST included) then fans run in SLOW all the time so the "gauge" should sit at about 12 o'clock 24/7/365.
 
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