I Just Lost My Heat In My 1991 Cad Deville 4.9

100

Asked by Jan 03, 2014 at 08:38 PM about the Cadillac DeVille

Question type: Maintenance & Repair

some saying something a bough a shouter  door under dash it started after change antifreeze I took out one gallon and replace one gallon of pure antifreeze  be fore that I hade  heat now it cold tell racing the engine up

14 Answers

58,965

Sounds like your low on coolant or have air in the system. How did you drain the system to change the antifreeze? Did you use the petcock on the radiator or disconnect one of the hoses? If a hose, which one? Check the vacuum hose on the heater control valve. Cadillacs operate opposite everything else. To have heat there should be NO vacuum present at the heater control valve. If you have vacuum with the climate control set at 90°F the problem is in the programmer or control head on the dash. HTH. -Jim

3 out of 3 people think this is helpful.
100

I cyphered one gallon out where the radiator cap is at. Then removed right side top hose to thermostat. thank you Jim hi and my name is Jim to

1 out of 1 people think this is helpful.
58,965

Hi Jim. Did you do anything with the thermostat? Like remove it? If so, that'll do it too. Especially in cold weather. -Jim

2 out of 2 people think this is helpful.
100

no not the first two days still no heat then wert and got a new thermostat I never run my car with one thank you Jim

1 out of 1 people think this is helpful.
58,965

Ok Jim, that's good. Once the engine is fully warmed up carefully feel both heater hoses. They should both be hot. Be careful not to burn yourself though!! On the hose with the control valve you want to check it both ahead and behind the control valve. Keep the climate control set on 90°F as well. HTH. -Jim

100

just to be sure were is the control valve at in side the car or on the out side thank you

2 out of 2 people think this is helpful.
58,965

The control valve is in the engine compartment near the firewall closer to the passengers side. It looks like a round disc with a small vacuum hose plugged into it. It has heater hoses coming to it and leaving it. -Jim

1 out of 1 people think this is helpful.
Best Answer
100

ok I was thinking right then by looking at this picture I sent it may help some others to I just ant got out side yet am in Anderson Indiana if you seen on the news we have 8inc. of snow and win chill is 35mph and bad enough to get frostbite with in 10 minute it bad here

5 out of 5 people think this is helpful.
40

I just tore an old core out of a junk 1992 Devillle, 4.9 L. the side of the core made of plastic came away at the hose hook ups, as removing the hoses correctly is real labor intensive. The upper chamber was relatively free of debris, but the lower part was filled up with hard sediment, rising from the bottom up, the return antifreeze is only coming back through a small channel. That must be why my 1993 De Ville starts warm, but goes ambient temp after 2-3 seconds. I've blew threw the core from the hoses with a cleverly hooked up water hose with much pressure, a few times, always clear. Just restricted in the core by hard sediment that will not come through by blowing.

1 out of 1 people think this is helpful.
40

I was getting bad gas mileage for a while 17, where I should have been getting in the 20's. Getting random O2 codes, replaced O2 sensor twice, then, replaced my t-stat, and improved my gas mileage by 7 mpg. Seems, somehow, the t-stat was causing the motor to run cool, keeping a rich air/fuel mixture going, fouling or confusing the O2 sensor. Someone else put that out, have to share.

1 out of 1 people think this is helpful.
100

if blew threw the core from the hoses with a cleverly hooked up water hose with much pressure, a few times, always clear. ok don't understand that. with the hoses hooked up

100

did you remove the hoses hooked up to heater control valve I have show in the picture up above try that

1 out of 1 people think this is helpful.
40

Here is a pic

2 out of 2 people think this is helpful.
15,825

my 1994 deville has a plastic " T " top and center near firewall, replaced it and now have heat

2 out of 2 people think this is helpful.

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