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73-87 Chevy _ GMC Trucks => Engine/Drivetrain => Topic started by: xpatrick32x on February 09, 2015, 06:33:55 pm

Title: Engine not warming up, heat not hot
Post by: xpatrick32x on February 09, 2015, 06:33:55 pm
I have a 1984 GMC Sierra with a 350 and the temperature gauge reads only about 120-150 degrees after driving it for about 30 minutes of driving. I live in Ohio so it has been anywhere between 0 to 30 degrees. I just put in a new 195 degree thermostat a few days ago and it made little to no difference! Also my heat is pretty much useless it actually feels cold blowing on my feet.

Please give me some suggestions on what the problem could be, thank you!
Title: Re: Engine not warming up, heat not hot
Post by: ARshuter on February 09, 2015, 07:32:38 pm
Possibly the thermostat sticking open.  How big is your radiator?  I once had a 77 with a 4 or 5 core rad that wouldn't throw heat til I put a winter front on the truck.   
Title: Re: Engine not warming up, heat not hot
Post by: Kren420 on February 09, 2015, 07:35:56 pm
Not correct ratio of water to antifreeze maybe?  I had a buddy change the fluid in his Ranger, put too much water in and it froze.  Only noticed it was frozen because he wasn't getting any heat blowing in the cab I guess.
Title: Re: Engine not warming up, heat not hot
Post by: xpatrick32x on February 09, 2015, 07:49:31 pm
Possibly the thermostat sticking open.  How big is your radiator?  I once had a 77 with a 4 or 5 core rad that wouldn't throw heat til I put a winter front on the truck.   

It was happening before and after I changed the thermostat. Its a 4 core radiator, not sure how big, but it was the same radiator in it last year and I had heat. It is only about 1.5 years old to. I tried putting cardboard infront of the radiator it helped, but not very much.
Title: Re: Engine not warming up, heat not hot
Post by: ARshuter on February 09, 2015, 07:52:11 pm
How bout a trapped air bubble?
Title: Re: Engine not warming up, heat not hot
Post by: xpatrick32x on February 09, 2015, 07:54:33 pm
Not correct ratio of water to antifreeze maybe?  I had a buddy change the fluid in his Ranger, put too much water in and it froze.  Only noticed it was frozen because he wasn't getting any heat blowing in the cab I guess.

The antifreeze was just flushed out about a month or two ago, and its probably about 80% antifreeze.
Title: Re: Engine not warming up, heat not hot
Post by: xpatrick32x on February 09, 2015, 08:09:54 pm
How bout a trapped air bubble?

Is there a way to check that?
Title: Re: Engine not warming up, heat not hot
Post by: ARshuter on February 09, 2015, 08:16:17 pm
The only thing I can think of would be leaving the cap off over night.  Maybe someone else has a better answer.  The 80% anti freeze may be a problem also try getting closer to a 50/50 mix, just a thought.
Title: Re: Engine not warming up, heat not hot
Post by: Irish_Alley on February 09, 2015, 09:03:45 pm
imo our trucks really dont get bubbles i never had one in our trucks. my 79 will burn you out of the cab my 91 v3500 crew is ok as long as its not too cold or it does the same thing and wont warm up. one option is to block part of the radiator off. i wouldnt jump head first and block too much at first and i would use cardboard
Title: Re: Engine not warming up, heat not hot
Post by: xpatrick32x on February 09, 2015, 09:06:43 pm
imo our trucks really dont get bubbles i never had one in our trucks. my 79 will burn you out of the cab my 91 v3500 crew is ok as long as its not too cold or it does the same thing and wont warm up. one option is to block part of the radiator off. i wouldnt jump head first and block too much at first and i would use cardboard

I actually already tried cardboard and covered the entire radiator and still not much heat and low temps.
Title: Re: Engine not warming up, heat not hot
Post by: srozell on February 10, 2015, 01:05:56 am
Is the radiator getting warm?

Is there any chance the thermostat went in backwards? (I haven't had to do one yet, so I don't even know if it's possible.)

Is the radiator fluid topped up appropriately?

Title: Re: Engine not warming up, heat not hot
Post by: Irish_Alley on February 10, 2015, 04:35:01 am
i dealt with it in my 91, i would drive my car or my 94 if it got cold like that. but now im putting in  my cummins and from what i understand they run cooler so heat will really be a problem. dont think its the problem but curious how are your heater hoses ran?
Title: Re: Engine not warming up, heat not hot
Post by: jaredts on February 10, 2015, 08:09:42 pm
Do you have the stock fan?
Title: Re: Engine not warming up, heat not hot
Post by: swilliams on February 10, 2015, 11:08:20 pm
I have had this happen and mine ended up being to low of a level in the radiator.
Title: Re: Engine not warming up, heat not hot
Post by: ARshuter on February 12, 2015, 06:15:43 pm
Curious, did you figure anything out?
Title: Re: Engine not warming up, heat not hot
Post by: 78BIG-TEN on February 13, 2015, 08:48:46 am
A working thermostat should keep the engine at a pretty constant temp.Too much flow thru the heater could cause it to run cooler.Most Chevy's use a restrictor fitting in the heater hose usually the fitting in the manifold.It should have about a 3\8 hole and not wide open 5\8.After all the heater core is nothing more than a radiator