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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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Re: Overheating please help!!

The surge tank should not be "nice and full". Proper coolant level, checked cold only, is just about at the tank midseam.

There is a COLD FULL legend molded into the top of the surge tank. Next to it is a flat arrow that runs across the tank top and down the side - it points to just about the seam line.

As advised, check the purge line and water crossover bolt/nipple for blockage. Your symptoms are classic for that.

............. and, if you see fairly constant bubbles in the surge tank with the engine running, there is a good chance of one or both head gaskets failing due to pulled head bolts.


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Re: Overheating - 2002 Eldorado

Going out to check now. Will let you know what I find out. Would a little movement in the tensioner be an issue?
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.
Re: Overheating - 2002 Eldorado

The coolant purge line flows from the water crossover nipple to the surge tank. If you have flow at/into the tank, it's good to go.
Replace that tensioner pulley - yesterday !!!!

The cover is held by two 10mm nuts on long hex headed studs and a bolt into the water crossover pad. The entire tensioner assembly itself is held by those 2 long studs. You can replace the pulley only by removing the center bolt. Use a small crescent wrencdh on the formed lug on the tensioner arm to lever it toward the firewall to remove tension. Have fun replacing the belt. NAPA.


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If that tool has a slot and slides onto the groove in the steel pulley hub, then turning the bolt to the right will pull the pulley off the cam extension. ............ and it will be TIGHT. Wait 'till you go to press it back on with the other tool.

Why are you removing the drive pulley ? If that plastic pulley and its belt grooves are not messed up you don't need to remove it. The tensioner is what seizes, THEN destroys that big plastic drive pulley.

My picture is of the tensioner assembly, not the drive pulley.


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If that tensioner pulley is loose or seized I would suspect that first. The drive pulley doesn't look THAT bad. And, did you use a flashlight to make sure the belt was correctly positioned on the water pump pulley ?

Otherwise, remove the pulley puller and hit the hub with a shot of PB Blaster overnight - PB wet rag wrapped around the small hub. You get too carried away and damage the intake cam extension or oil seal and you got troubles.

That pulley should pull off with effort - not Herculean effort.
Sure does. The system is purging itself of air and gases - after the engine cools to almost ambient, check the surge tank level - half full is correct. One of these start-runs-stops the system will fart a big bubble and the heater core will fill, leaving you a half quart or so low.
Watching the big game tonight?
Basketball ?? Nope. Bb is wasted on me. Maybe yesterday's playoff between Spieth, Walker, Holmes.
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