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:confused: I bought a 1987 Cadillac Deville about three years ago and have spent about $3000 on cooling related problems. I've replaced hoses, belts, upgraded fans, new modules, new radiator, thermostat, water pump, etc. I've come to the conclusion that the cooling system in that model year may have been poorly engineered and will never work correctly no matter how much money I spend. I do like the car because it's comfortable, its big, has a smooth ride, and good looks. Besides, it's paid for!

Does anyone have any ideas as to modifications or other things I can try to make this car not overheat. I drive in the afternoon summer heat in central Texas where it is right around 100 degrees (Farenheit) and I frequently get stuck in traffic slowing on the freeway. Whenever I hit the "AUTO" environmental button to activate air conditioning, a red Coolant temp light comes on. It will go off if I'm cruising at 70 mph, but comes on again if I slow below 40. Even if I turn the air conditioner off entirely, the car will eventually overheat if I'm stopped for too long.
 

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Hey white hat - Welcome to the CadillacForums. Some of the more technically oriented guys will be along shortly I'm sure, but let me ask you a couple of questions. Has the car had the problem since you bought it? Have any of the things already done seemed to help? Has all of the diagnosis and repair been done at the same place? Is the A/C condenser allowing free flow of air to the radiator or are there dirty or bent fins?

Something seems wrong - I don't believe the car should overheat as easily as it does. I wonder if there is some sort of blockage in the cooling passages somewhere.

Anyhow, assuming for a moment the system is working as good as it can, have you considered (or added already) any auxillary coolers? For instance, you could get an external transmission cooler with thermostatically operated fan and disconnect the factory trans cooler in the radiator. This should take some of the strain off the cooling system. What about an external auxilliary radiator or engine oil cooler?

White hat = good guy, like in a western?
 

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Taking out the tranny heat exchanger lines will only provide a minimal improvement......

Check all fans and the condenser..... If its in sorry shape, it will need to be replaced.....
 

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The cooling fans are probably coming on late or not at all....It could be the temp sensor for the fans is non op or the fans themselves are non op ( Check both ) This can easily happen on a car that age and is fairly common. The up side is..It's a realitivly easy and inexpensive fix!
 

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it may be cheaper than you think,i've got a 92 eldo that i had the same problem with.i replaced everything top to bottom,flushed it,no help,it still got up to 230-FAST,no more than three minutes at a red light and i was shutting the thing off,my fan didn't even kick on till 233 or so,i'm no genius,but i know thats way hot.even after the fan did cut on,it only went down to about 210(still hot)after about 2 years and 2 grand,i gave up on it.i figured it still ran and hadn't popped yet so maybe it wasn't getting that hot?i replaced all sensors and relays,nothing,still hot,so i hotwired the fan to my rear defrost and called it that.then i found out that they actually make a 160 degree thermostat for all 3,4.-engines,and it's the same part for all,5 dollars and dirty hands,now it doesn't even get to 200,and on the interstate it goes down to 180,when it used to hang at 212.spend the 5 bucks,don't replace another part on your car until you try it,looking back-5 bucks would have been alot cheaper than 2000.
 

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Hey cadillackman, what a good suggestion, I too have been having overheating problems in my 93 eldo northstar equipped. Mine runs over 220 most of the time and the highest it has been is 255 YIKES !!..The thermo has been replaced with a 180, new pump, new radiator,flush no sensors or anything else has been replaced..I am not sure what temp the fans come on at but i do know they are on at 223, both of them. The 160 thermo suggestion seems reasonable to me however..on cold days won't that allow the car to always try and warm up,,run rich untill normal operating tempature is reached, which won't occur because of the low temp thermo? I am tired of limiting my driving on very hot days.and well i just want it fixed cuase it is not right.
 

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try red-line water wetter, i use it in all my cars with great success,u should flush your rad, and add some water wetter, along with your coolant and distilled water ( not tap). i've used it in my 76 caddy, 70 dodge challenger which always overheated before i used it, my 94 cavalier and 94 dodge spirit, along with my dad's chevy dump truck with a 454. try it :bouncy:
 

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anothercaddiowner said:
Hey cadillackman, what a good suggestion, I too have been having overheating problems in my 93 eldo northstar equipped. Mine runs over 220 most of the time and the highest it has been is 255 YIKES !!..The thermo has been replaced with a 180, new pump, new radiator,flush no sensors or anything else has been replaced..I am not sure what temp the fans come on at but i do know they are on at 223, both of them. The 160 thermo suggestion seems reasonable to me however..on cold days won't that allow the car to always try and warm up,,run rich untill normal operating tempature is reached, which won't occur because of the low temp thermo? I am tired of limiting my driving on very hot days.and well i just want it fixed cuase it is not right.
well,thats where the engine difference comes into play i guess,but i passed emissions ok last month and if you drive it long enough,it will reach 200,but the difference is,it'll actually cool down to 185,never got under 200 with the 180 so i guess it's a tradeoff,BUT i'll tell you this,i let that problem sweat me for 2 years,and now it shows on the engine,i wish i'd have tried it long ago and saved my car a little more stress(so to speak),of course mine got up to 255 on me once before.so that may explain the way it runs now,it idles a tad bit higher now,but goes to normal after about 180 or so,either way its totally worth it if you want the car to last :)
 

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cadillackman said:
well,thats where the engine difference comes into play i guess,but i passed emissions ok last month and if you drive it long enough,it will reach 200,but the difference is,it'll actually cool down to 185,never got under 200 with the 180 so i guess it's a tradeoff,BUT i'll tell you this,i let that problem sweat me for 2 years,and now it shows on the engine,i wish i'd have tried it long ago and saved my car a little more stress(so to speak),of course mine got up to 255 on me once before.so that may explain the way it runs now,it idles a tad bit higher now,but goes to normal after about 180 or so,either way its totally worth it if you want the car to last :)
i think we've got the exact same problem :D
 
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