Just thought I'd start by saying that I have been reading/searching a lot for info on this topic before making this thread.

I'm away at school right now (about to go home for Thanksgiving) and my younger brother's 2000 Cadillac Deville is having some overheating issues. I'm hoping to atleast have an idea of what to work on before I get back home.

He has had the caddy since about March of this year. When I got home for the summer I needed him to take me somewhere that was about 45 minutes away on the freeway. We had to pull over before getting there because the car was getting so hot. We checked oil and filled up the reservoir and, after sitting a little bit, drove it the 5 minutes that was left. It started heating up again. So we changed the thermostat and filled everything back up and he left for home (I was getting dropped off). Well it wasn't the thermostat because he had to pull over several times on the way home to let it cool off. That seemed like the start of overheating. So he kept fluids topped off and for some reason it was doing better (he didn't really drove far distances, only 10 minutes away). Well the problem is pretty persistent now. Everytime he goes up our hill it starts overheating again.

I found a sticky and I'll try to answer all the questions on it:
By overheat I mean the temp gauge just keeps raising and we stop the car before it the gauge ends.

It mainly heats up climbing hills and on the freeway. Although there are times when it doesn't heat up going up our hill (so confusing)

There are times when the heat from the heater cuts out but not always.

The radiator fans all come on.

Not sure when the belt was changed, but the coolant was changed this summer by a local radiator shop (I don't know if they put the tablets in and I don't know if it was "burped")

Coolant appears free of oil.

It's be pretty cold as of late, but my brother says his car is not putting out anymore smoke than the other cars stopped at the stoplight are.

Can't really smell coolant, but he does have to add coolant every once in a while.

Hopefully I have most of the information in there, sorry for being so wordy/long. It's just really weird because the problem seems to go in spurts... Thanks so much for any/all help!!

Lee

One more note, the local radiator shop said that the radiator that was in the car was the stock radiator.. From what I've read, 9 years is way too long for these radiators...

 

the good news; radiators can last 100 years if the cooling system is well maintained and no physical damage is not present.

the bad news .. sounds like the headgasket has breached .. do a exhaust gas in the coolant test to verify.


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Will do... Thanks for your help man

 

Well I went out to NAPA and got that block tester kit and ran the test, the fluid stayed blue (assuming I did it right) which means "there isn't a combustion leak". I also found out that when that shop flushed the radiator he put block sealer in it (I called to find out what kind but he was closed, hopefully he'll call back). This problem really is so annoying. There have been times (while working with it) that we TRIED to get the gauge over normal operating temp going up my hill and nothing, then we'll be taking it nice and easy and it will keep getting hotter... Any idea what I should do now? Thanks again for any/all help

 

Sounds like a plugged up radiator to me. But as it was flushed a couple months ago I don't know unless the sealer they put in is causing problems. Also the water pump could be going bad. Bad belt on water pump? First thing I would do is buy a radiator cap since its cheap and eliminate that problem. Is it possible you installed the thermostat backwards?

 

We replaced the cap same day we did the thermostat. We tore down to the thermostat again after it was still overheating to make sure it was in correctly... (Don't know if this matters) When I did the test last night there was a slight change in the test fluid but it just looked more like a light blue... Certainly not yellow... Is there an easy check for the water pump? Thanks again for your help.

 

Does stop engine message come on? How high does temp gauge read? Water pump belt should be free of breaks, pulleys should not show wear or appear over heated. There is no real way to check water pump flow, it can be removed and impeller inspected for damaged. If you can get access to a infered thermal gun you can scan radiator from top to bottom and across looking for temperature differences that may indicate blockage within the radiator.

 

at the 1st posting, you stated that it overheated on hills ...

you need to push that engine to an overheat to do a proper exhaust gas in coolant test .. you need to overheat the engine to check for exhaust gas in coolant.

often, the breach only shows itself under high load, as on a climb of a long hill .. that is when the exhaust gases jump across the gasket.

if you tested in town, the test is not complete, specially if no overheating took place.

also, if you did test it on a hill and no overheating took place, the test is inconclusive.

push and load the engine to overheat, check the color of the water .. then report back.


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The gauge will go all the way up, (I told him to turn it off before it gets too far up, but it will keep rising, the turn off engine warning has come on before. We've always turned it off before it has died). It will just keep rising. It does overheat going up hills but not always. We can't plan on when it will or won't overheat, but when it does it's typically going up hill or on the freeway. Although, once it has overheated and we let it sit to cool down for a bit and then try driving it again, sometimes it will continue to overheat doing "easy/flat" driving. So I need to get the engine overheating and then take the cap off and slam the test tube in there?? The instructions said not to let antifreeze get into the test tube so I'm not sure how to get it boiling and have the test tube on there without getting antifreeze in there (haha not to mention I'm not sure how to not get burned doing it!)... Thanks again for the help

Lee

 

ohhhh no no !!! NEVER when hot.

What i meant is get the engine to overheat and after it cools down to a safe level, check the fluid.