Cadillac Owners Forum banner

1 - 20 of 29 Posts

·
Registered
Joined
·
87 Posts
Discussion Starter #1
This issue has been ongoing for like two months now.

When it first started getting cold up here in MI I noticed that the coolant temp wasnt getting up to the half way point, even at highway driving. I took it into a dealership and they said there wasn't even a thermostat installed :cookoo: so they put one in and everything seemed beautiful. I was getting warm air and the coolant temp was around 195, slightly past the half mark.

As I continued driving that week I noticed it started taking longer and longer to reach 190, eventually after a week and a half it never was reaching 190, even at highway driving, and when I would slow down from going 70mph the coolant temp would also drop. Assuming it was just a bad thermostat I took the car back and they replaced it.

Same deal now though. It's been roughly a week and a half and its acting the same exact way. I don't understand it because for the first week of operation after a new thermostat is installed, the coolant temp operates normally! Is my STS killing these thermostats some how? Anybody?
 

·
Banned
2005 STS4 1SG: GM Acc Lights, Corsa, Platnium Grille, Volant
Joined
·
15,987 Posts
While it sucks for heat running at a cooler temp is really better for your car and gas milage. As for your problem i have no idea.
 

·
Cadillac Owners Connoisseur
Joined
·
1,164 Posts
CadillacETC1997 said:
While it sucks for heat running at a cooler temp is really better for your car and gas milage. As for your problem i have no idea.
Please explain how the cooler temperatures are better for the car and gas mileage. I have never heard this before.
 

·
Super Moderator
White Diamond '03 DHS (with DTS floor shift)
Joined
·
86,781 Posts
Neither have I. Infact, that is opposite of conventional wisdom.
 

·
Registered
Joined
·
87 Posts
Discussion Starter #5
Yeah, I'm pretty sure its better for the engine to be running at a warmer temp.. anyway I did some detective work tonight.. It seems that if I turn the heat or any air completely off, the coolant temp WILL rise to 190+ if I then hit the Auto button, it drops down.

Can anyone explain how the heating system works?
 

·
Registered
13 Challenger RT, 11 CTS Coupe Premium, 94 Eldorado (RIP)
Joined
·
1,306 Posts
You get heat from air that is blown across your warm heater core. Warm engine coolant flows inside the heater core. So essentially, you are taking the heat from the warm engine coolant.
 

·
Registered
Joined
·
87 Posts
Discussion Starter #8
Heater core, that's it. We had to have that replaced on our Blazer when it was doing something very similar, the coolant temp was never warming up, and thus never blowing warm air.

Would it be safe to assume thats probably the problem I have as well? It seem's my coolant is coming warming up now if I leave the heat off. I guess the only thing that still confuses me, is why everything seems to be working fine for a week after a new thermostat has been installed.
 

·
Registered
13 Challenger RT, 11 CTS Coupe Premium, 94 Eldorado (RIP)
Joined
·
1,306 Posts
When heater cores go bad, they usually leak or plug. If it were to plug, you wouldn't get any heat, or very little. It is possible that your heater control valve is not performing properly.

What year and model car?
 

·
Super Moderator
White Diamond '03 DHS (with DTS floor shift)
Joined
·
86,781 Posts
Boy, this is a switch. An overefficient cooling system. I do not think that your heater core has anything to do with it. As for the heater control valve, I don't think there is one. I believe that coolant continuosly flows through the heater core. When heat is requested, the air mix door opens to allow heated air into the cabin. When no heat is requested, it is dumped overboard. Judging from your discription, the thermostat is suspect. Not sure why, if it have been changed but, the fact that it works fine for a week is suspicious. Have you seen it when it is was removed? Was it gunked up in any way? Maybe you need a flush if that is the case.
 

·
Registered
Joined
·
87 Posts
Discussion Starter #12
I have not seen the thermostats when they were removed, and a flush was done during the first thermostat install. I'll probably take the car to a different dealership and see what they say.
 

·
Registered
2005 SRX V6 AWD
Joined
·
429 Posts
My 95 STS will run at 90 Celcuis (194 F) all day long. Been running like this since i purchased it in 2003. Changed Thermostat last winter and water pump this summer. Heating is fine. I dont see whats wrong with this...
 

·
Registered
13 Challenger RT, 11 CTS Coupe Premium, 94 Eldorado (RIP)
Joined
·
1,306 Posts
JS, you are running correctly. HKD isn't getting above 190, normal operating temp, with the heat on.

HKD, where are you located, anyways?
 

·
Registered
Joined
·
108 Posts
is it possible that you have a low coolant level? I mean they replace the thermostat, they top off the cooling system, everything is OK for a week or so - well - if the coolant level dropped during that timeframe, your heat would gradually fade away (less hot coolant going through the system = less heat) - I don't understand how your car could be "killing" thermostats - unless there is some junk in the system that's getting trapped in the 'stat and isn't allowing it to close.
Why was there no thermostat to begin with? (just curious).

Steve
 

·
Registered
Joined
·
87 Posts
Discussion Starter #18
Coolant level is fine, reservoir is filled. I have no idea why there was no thermostat to begin with, I bought the car April of this year, so I have had no need to run the heat. I'm wondering now if I'm going to have the reverse issue though come summer, where the car overheats all the time, and that's why the previous owner just removed the thermostat.
 

·
Registered
Joined
·
87 Posts
Discussion Starter #19
Just got off the phone with two different places, one place said it could be either an air pocket in the coolant system, or a head gasket issue. Second place said I could need a heater core flushed, I told him I had a flush done less than a month ago, but I was unsure if they did the heater core.

What are some telltale signs of the dreaded head gasket failure?
 

·
Registered
White Diamond 2001 STS
Joined
·
1,317 Posts
It sounds as if you may have a problem with your cooling fans running constantly when the A/C is on. When you manually override the HVAC OFF, the temp will rise to normal. When the A/C compressor is off, the cooling fans will not engage until the coolant temperature rises to 229*F. When the A/C compressor is on, the cooling fans will cycle on and off. When you allow the A/C compressor to run (by putting the HVAC system into AUTO), you're also allowing the cooling fans to run -- but they SHOULD cycle. Perhaps they're not cycling for some reason and running full time with the AUTO setting on the HVAC panel. I wouldn't suspect either an air pocket or head gaskets -- the usual symptoms of those problems are running HIGHER temps than normal, but anything is possible I guess.

Check your cooling fans -- do they run constantly when the HVAC is in AUTO, or do they cycle on and off?
 
1 - 20 of 29 Posts
Top