Problems with heat in 1996 C1500

[1994]

So I am wondering if anyone has had this problem before, or knows where I should start in trying to fix this issue I am having.

My '96 chevy c1500 no longer has heat. I was driving last week and my temp. gauge climbed into the red, and all of a sudden it dropped to the other extreme whilst what I guess was some smoke came billowing into my cab from my vents. Completely clouded up all of my windows and I had to pull over.

After this, my gauge no longer works, and my heat no longer works. I have noticed I am losing coolant as well, but I looked on my passenger floor and I don't see any evidence of moisture leaking into that side. (This rules out heater core right?)

I topped up my rad because I noticed it was a bit low and my reservoir still had the correct amount of fluid in it. I recently looked and my reservoir is now bone dry.
I picked up a new thermostat because I was hoping that it just failed on me, but I am starting to think I may be looking at something worse.... Thoughts? Suggestions? Thanks.

 

[Bob L]

First thing is if the water level is low in the motor you will have incorrect temp readings as the sender is near the top. When the motor is running with radiator and coolant tank at correct levels does the upper radiator hose get hot? Do the heater hoses get hot? you should be able to touch them but not hold your hand on them for more than a few seconds.
If you heater core leaked it wouldn't fix itself and you would get a sweet antifreeze smell in the passenger compartment. It can leak and run down under the carpet without showing till you lift the carpet and fell under it.
I would pressure test the system to check for leaks.

 

[Eveready]

Could have been a stuck thermostat causing overheating which in turn created the water vapor that came from under hood into cab via the rear of the hood. You likely have some air in the cooling system which would explain the drop in coolant as you probably have not replaced the volume that boiled off. You may need a new heat sensor.

It may behave after you top off the coolant and get the air out or it may need a thermostat but if you are still losing coolant there has to be a leak somewhere or it might be a head gasket. If you replace the thermostat be sure and get a good one as some of the replacements have had issues of their own. Several recent threads about that on here. Please revisit the thread when you find the problem and let everyone know what it was.

 

[1994]

I tried to top it off when I noticed it was a bit low, went to check it today and it was quite pressurized and as I opened the rad cap it squirted a bunch out. Still seeing the reservoir as having (some) but no enough coolant in it. Perhaps a hose is leaking somewhere? Not allowing the coolant to flow back into the reservoir?

I also picked up my thermostat at Auto Value for $10. It comes with a new gasket on it, but I can't recall the brand right now.

 

[east302]

Like Bob said above, you can rent a pressure tester from a parts store and probably find the leak pretty quickly. If it’s the heater core, the cover is just screwed on so it’s pretty easy to access and replace.




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[Dan12valve]

Also look at the condensation drain below the dryer for the a/c. If coolant is pouring out definitely a heater core.

If all you saw was it coming out of the vents and no where else on the truck, that's another box ticked for the core.

I assume it's not leaving wet spots on the ground?

 

[1994]

Also look at the condensation drain below the dryer for the a/c. If coolant is pouring out definitely a heater core.

If all you saw was it coming out of the vents and no where else on the truck, that's another box ticked for the core.

I assume it's not leaving wet spots on the ground?

I don't see any wet spots aside from my god damn power steering hose that must have blew again..just replaced them less than a year ago when they leaked before. Already cracked again and leaking power steering now too lol. I guess the cold/warm weather fluctuations here are doing a number on my old rig.
I grabbed some more dexcool and I topped up the reservoir to where it needs to be, I will be watching it closely the next few days to see if it's leaking lots or only slowly.

 

[1994]

I don't see any wet spots aside from my god damn power steering hose that must have blew again..just replaced them less than a year ago when they leaked before. Already cracked again and leaking power steering now too lol. I guess the cold/warm weather fluctuations here are doing a number on my old rig.
I grabbed some more dexcool and I topped up the reservoir to where it needs to be, I will be watching it closely the next few days to see if it's leaking lots or only slowly.

Also working on tracking down a 13mm and 14mm socket so I can replace my thermostat and see what happens after that.