overheating

[ldreedsts]

Now I have a new radiator and a new air conditioning compressor but my wife went to the store and on the way home the car overheated. What now?

[Bruce Nunnally]

Can you start at the beginning and describe what has happened so far?

Here is what I gather:

The car was overheating. How was the cause diagnosed?

You replaced the radiator.

You replaced the A/C Compressor

The car is still overheating.

[Ranger]

What now? Check the thermostat, purge line, tensioner & cap.

[BodybyFisher]

How long was it driven after the radiator was replaced? It takes a few warm up cool down cycles for the cooling system to stabilize. If the purge line is clogged, the air will not be removed.

Was the coolant at 50/50 (50% coolant/50% distilled water)

Is the radiator cap tight and is it good?

[Regis]

When I had my coolant drained and filled 1-2 years ago it took a few days to work all the air out of the system. Everyday I checked the coolant level and needed to add more coolant/water as the air was working itself out. During that period I noticed sporadic and elevated temperatures. Recently (2-3 months ago) while performing a series of wide open throttles (WOTs) the car over heated. All kinds of bells and whistles (well no whistles per se) came on. I pulled off to the side of the road and popped the hood. Coolant had sprayed around various areas of the engine compartment. Not knowing exactly where the leak was I drove the car home and had to top off with about 2 quarts of coolant and water. I noticed that if I drove it around town, was real easy on the gas, and it wasn't a hot day then it was fine. But if I got on the highway or I was in moderate to heavy traffic then the coolant temps would rise substantially. Twice more it had overheated. After checking the oil for possible coolant intrusion and not locating any line leaks I figured it was probably the reservoir cap (radiator cap for some) getting bad in a hurry. $10 and a new AC Delco cap later everything was back to normal. A $10 fix... not often you hear of that on a Cadillac and at a dealer no less. Hope these two instances are of some help.

1. Check the coolant level

2. Replace the cap. It most likely was not replaced..... and it's only $10 at the dealer.

[Cadillac Jim]

Also check to make sure that the coolant is at least 50% antifreeze. If not, it will boil in hot spots in the head under heavy load -- either WOT, or passing or whatever on the highway. The steam bubbles will collect behind the thermostat while it is closed and you will have a temperature spike and possibly a coolant boil-off.

The factory manual says that the percentage of antifreeze should be between 50% and 70%. Flushing the radiator typically leaves the coolant less than 50% antifreeze. If it checks a bit low, add pure antifreeze anytime you have a boil-off and it should stop. If it's a lot low, drain it and refill. Figure about 40% of it is still in there and figure enough antifreeze to target about 60% when you are done.

Don't trust an aftermarket radiator cap. Make sure that the radiator cap is the GM cap for your car, and is a 15 psi cap. The wrong cap can cause problems with flow rate when you have a hot spot in the heads or a boil-off, causing a pressure peak that can split a radiator seam.

[BodybyFisher]

As per the GURU, NEVER FLUSH your cooling system, 1) as stated above you can not easily manage the 50/50 coolant concentration as water is in the engine, and 2) you introduce minerals and chlorine into the cooling system that can cause corrosion buildup.

SIMPLY drain and REFILL!