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2003 Deville - cooling system problems

3850 Views 34 Replies 5 Participants Last post by  20grand
I have to do this on my Deville in the AM. It drives and rides nice but after a while at idle the gauge will increase and cold air kicks through the vents. After I rev the rpms real high, the gauge comes back down and then I have heat. I also checked the tank and she's nice and full. Was thinking maybe a faulty thermostat but will check the lines before I pull that out.
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Going out to check now. Will let you know what I find out. Would a little movement in the tensioner be an issue?
Checked the water pump belt and it's about split. Must be the pully itself that's splitting it. There is some play in the tensioner as well.


Submariner409 said:
The water pump drive belt tensioner should keep that belt tight and be absolutely quiet. No bouncing back and forth. BUT if the belt is intact and the water pump is turning that's probably not the problem - a frozen pump or tensioner pulley bearing would wreak havoc in less than 30 seconds. 20grand, You hijacked the OP's Eldorado thread. Your Deville - what year ? Post it and I'll move the replies to your post into a new thread.
2003 Deville. Was hoping my overheating problem might've helped him if I figured something out. But if I figure something out, I'll reach out to him just in case. I'm going to put a block test on it again to see what I find.


I also have steady stream from purge line at the tank end. Is it necessary to check at the opposite end by the engine?
I'm doing this right, right?


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It's pretty snug and I'm turning the bolt on the left towards to firewall. It's really tight but doesn't seem to be moving. There's a lot of pressure and in afraid of breaking something.
I'm sorry, I'm turning the bolt on the right towards the firewall, which is tightening the tool.
The drive pulley is in pretty bad shape. It seems like it's tearing the belt apart. I got it with a bad belt, replaced the belt about 20 miles or so ago and it's already split in the middle. The car wants to overheat here and there and the tensioner has quite a bit of play in it.


The drive pulley is what needs to be removed. It seems like there's a thousand pounds of pressure there. Almost seems like I would need a breaker bar to assist turning it.
So I cleaned up the pully and put the belt back on along with a new thermostat. It ran really well for about 20 minutes with no overheating. Then the hot air in the cabin turned cold and the gauge went up. When I would rev it to 3k rpm the gauge would go down and I'd get hot air out of the vents. But as soon as it dropped to 700, the gauge goes up and the hot air turns cold. I reved it 3 or 4 times to try and get any air out of the coolant system might've gotten in the line but still the same ol. I also put a block test on it and the fluid stays blue. The gauge goes up but goes one notch short of the top. Does any of this sound familiar?
Thanks Sub. I'll check her first thing in the AM. This is a pretty nice Deville I came across. 95k and really clean inside. Watching the big game tonight?
Never got much into golf besides a put put and a really cool range in Chelsea.

As far as the air pocket goes, could there be several runs to get the air out? Should I rev it once it gets hot to bring the gauge back down or park it when it gets hot?
Hey fellas. Looks like it's all good. Drove it all day today and the gauge went up just two notches for a couple of seconds. I added just a little more antifreeze earlier and so far the heat blows hot and the gauge is where it's supposed to be. Fingers crossed.

Thanks for all of the input.
Spoke too soon. After a couple of errands, the temp gauge went all the way to the top. Not sure wth is going on, but it's past annoying. No coolant spilling out either.
Maxed out. On the side of the road now. Purge line is clear. Wouldn't the water pump be turning if the belt is turning? I did a block test on it and the sob stayed blue. I did it twice.
No. Waited until the gauge went to the halfway mark.
I don't think so. It was just a random check after I let it warm up. I still have a block test at home. I'll give it a shot tonight once I make it home and let you know.


Didn't have enough fluid tester but noticed that the coolant levels are still good. I e never had to put any coolant in this car.

My first head gasket overheated right away and the other Deville that I have loses coolant. I've even seen coolant shoot to the moon. This one is a bit weird but it just maybe a HG. I don't know what else it would be. Water pumps going, new thermostat, plenty of good coolant, bottom radiator hose is cool and the top is nice and hot.
So I went and tested both of the radiator caps that I had for the Deville, and both failed. Got a new one, drove it and it and didn't overheat once. I'll keep driving it and keep you guys updated.
I have a 2000 or 2001, can't remember which year, but it has two hard coolant lines that run across the top of the motor parallel to each other. One gets hot and the other one does not. The one that gets hot, runs to the reservoir, which is the line that I believe is closest to the firewall. The one closest to the radiator is the cold line. I figure this is NOT normal. Am I correct?
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