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Engine Overheating Problem

After 105,000 reliable miles, my minivan stalled and the temperature gauge indicated overheating. The first repair shop diagnosed this as a problem with the thermostat not opening, and I spent $400 to get it changed. Two months later, engine started knocking, white smoke bellowing from the exhaust. (At this point there was no temperature gauge problem any more.) A different repair shop saw this as a problem with the manifold gasket and fixed this (along with the water pump) for $1200. Two days later, the temperature gauge problem returned. Now I’m being told that the radiator needs to be replaced!

Looking for advice on how to narrow this problem down to a specific source, and get this fixed for good. Thank you!

What year is the Olds?

Unfortunately, none of these problems sounds either unusual or abnormal on and aging car. It is entrely possible that they were all legit and the radiator and manifold gasket were even accelerated by the the original overheating, especially if the radiator is the aluminum type with the plastic tanks.

Thank you for the ultra-fast response! This is a 1998 Olds/Silhouette.

What I find aggravating is that the first shop diagnosed the problem, did a ‘pressure test’, declared there is nothing wrong with the engine and that there were no cool spots on the radiator; that a thermostat replacement was all that was needed.

When I approached the second shop with the engine problem, they diagnosed this as a intake manifold gasket issue (requiring 7 hours of labor), also recommended changing the water pump to fix a ‘minor’ drip.

I guess my overall concern is trying to contain the extent of repairs I perform on this vehicle, before I get to a dump and buy a new vehicle decision. The chain of fix this, fix that, and now yet another problem is rather unnerving, and does not give me the confidence / assurance that I’m done for a while!

Perhaps I can narrow down the question to this:

(1) how can I tell if the thermostat problem has been ‘FIXED’?
(2) what diagnostic steps can tell if the problem is with the thermostat versus the radiator?

There is a limit to how much diagnosis can be done over the internet.
The possibilities are pretty vast on a 12 year old car.

You can actually bench test a T-stat with a hotplate, a pyrex vessel, and a thermocouple (or lab thermometer).

The only truely definitive diagnostic steps involve thermal mapping of the radiator with an infrared pyrometer and bench testing of the T-stat. Sorry. Both are simple, and both are difficult. Few techs do either.

The main problem is the price you are paying for repairs.

Take the vehicle to a shop that has an infrared thermal gun. They can take this tool and point it at the radiator to determine if any of the cores in the radiator are plugged.


The first thing to do is check the coolant level in the morning before the car has been started that day. If it is full, start it and let it idle. If the temp begins to go above normal check to see if the fan is running and pulling air through the radiator. If so keep checking the coolant guage. If it does not stop rising stop the engine. If it suddenly drops down after getting too high , there could be air in the system. There is also a temp. sending unit that could be bad , but it’s not likely.