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1988 Cadillac Seville
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12 Posts
Discussion Starter #1
I had my A/C converted in July 05 to R134a. At that time I replaced the Cooling Fan Control Module as well. This is the first replacement/major repair issue I have had. I have never had a problem with this car. 189,000+miles and now I am having issues. I tried to use my heat for the first time a couple of weeks ago and the vehicle immediatley threw up an 'Engine Hot' message followed by 'A/C Compressor Shut Off'. Now the vehicle overheats about 5 minutes after starting it...everyime. The temperature goes back down after I drive it for a minute or 2, but everytime I stop, it starts to rise at 5-10 degrees per second. Going as high as 273 degress. It's giving the normal codes (B450) and some other unrelated ones. My question...Could this all be related to the A/C conversion/compressor replacement? Any ideas where my trouble might be?

Current Codes:
B120 Current
B121 Current
B441 History
B450 Current

Thanks, in advance, for any help any one can provide.
 

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White Diamond '03 DHS (with DTS floor shift)
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86,242 Posts
Check the usual stuff. How's the coolant level? Check the thermostat and radiator cap.
 

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13 Challenger RT, 11 CTS Coupe Premium, 94 Eldorado (RIP)
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1,306 Posts
Diamondzsz said:
I tried to use my heat for the first time a couple of weeks ago and the vehicle immediatley threw up an 'Engine Hot' message followed by 'A/C Compressor Shut Off'.

Sounds to me like something in the heater core came out when you called for heat and it's plugging your system somewhere. When was the last time you changed out the coolant?

The a/c system has nothing to do with your overheating.
 

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2008 SRX-V8, 1991 Eldorado
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1,543 Posts
Diamondzsz said:
I had my A/C converted in July 05 to R134a. At that time I replaced the Cooling Fan Control Module as well. This is the first replacement/major repair issue I have had. I have never had a problem with this car. 189,000+miles and now I am having issues. I tried to use my heat for the first time a couple of weeks ago and the vehicle immediatley threw up an 'Engine Hot' message followed by 'A/C Compressor Shut Off'. Now the vehicle overheats about 5 minutes after starting it...everyime. The temperature goes back down after I drive it for a minute or 2, but everytime I stop, it starts to rise at 5-10 degrees per second. Going as high as 273 degress. It's giving the normal codes (B450) and some other unrelated ones. My question...Could this all be related to the A/C conversion/compressor replacement? Any ideas where my trouble might be?

Current Codes:
B120 Current
B121 Current
B441 History
B450 Current

Thanks, in advance, for any help any one can provide.
It is easy to be an armchair quarterback but not being in the field to see and hear a problem can be difficult to say the least.

It is possible that the A/C conversion added too much oil to the system and is transient in the condenser unit causing a superheat problem. This is only a possibility, not a sure diagnostic.

I suspect that the use of the heater did not contribute to the problem, conversely it should have helped to remedy a hot condition.
 

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13 Challenger RT, 11 CTS Coupe Premium, 94 Eldorado (RIP)
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I find it very unlikely that even if the condenser was plugged, it isn't going to cause the coolant system to stop doing its job. The a/c was converted in July, problems came just a couple of weeks ago, immediately (<key word) after the heater control valve opened.

Some try to crank their heat in order to help cool an engine during an overheating. Sure it may help some. The heater still could have been the cause of a problem if it let some trash out of the heater core and into the system. Possibly causing a sticking thermostat. I have had it happen before on an older vehicle.

Check the coolant sytem and post back.
 

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1988 Cadillac Seville
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12 Posts
Discussion Starter #6
I checked the coolant system levels (rad and reservoir) and both are ok. I'm going to have the coolant changed out as a precaution (as well as remove a troubleshooting step). I will check the heater core today and get back to you. Thanks for the help.
 

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2003 Seville STS 35K
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11 Posts
About your overheat problem - I have a 1988 Eldorado, with about 250,000 miles on it. I got the car with 163,000, and it had some of the same symptoms you describe. I bought and pored over the factory service manuals, and it took me a while, but it's fixed.

My car had several problems at once - ad A/C compressor, bad cooling fan control module, and shorted wires at the A/C high side pressue and temp sensor locations. So, the error codes kept coming and going, A/C shutdown, overheat, etc..

Make sure the cooling fans (both of them) actually work. The control module could still be faulty. The wiring off the A/C high side pipe along the upper rear underhood can be checked for shorts. I replaced my water pump as well, and, no more problems.



Good luck - it's a great year car!
 

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1988 Cadillac Seville
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12 Posts
Discussion Starter #9
Re: 1988 Seville Overheating - FIXED

Thanks to all of you for the information. I had the coolant changed out on Wednesday and the car ran fine. Car was running at about 202 degrees. I noticed a little condensation around the Water Pump (couldn't quite tell if it was from the gasket or what) so I replaced it. Car runs even better than before.



I noticed the front right engine mount was cracked, so I'll replace that within the next week.



Can the belts in this model Seville be adjusted by the tensioner or is this vehicle auto-adjusting? I have one more annoying issue I am trying to solve now. I now have a constant whine from the vehicle when I first start it in the morning. It whines up to about 40 MPH and then stops. Once the engine speed and RPM's are back down less than 40MPH--here comes the whine. Any ideas?
 
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