heating and temperature issues

[steve porch]

I have a 96 chevy c1500 1/2 ton PU with 5.0l auto trans. The heat in my truck is not working properly, the heat will be warm sometimes at idle until i drive it then it turns to colder air, on any selection on dial (top vent, bottom, top and bottom, bottom and defrost). I didnt have any problems until I recently filled up my coolant tank which was low. I use dex-cool. I did put to much coolant in it was a bit above the line when I filled it. I have had these problems since then. I was driving in the snow and at a stop light my check gages light came on and my temp gauge was maxed out without it smoking under the hood... the gauge went back down to normal temp and it continuously fluctuates from normal to hot to overheating but no smoke is coming off the hood as if it was really overheating. my blower motor works fine on each speed from low to hi just no heat. I have replaced the thermostat with no change. Please any ideas or troubleshooting would be helpful!

 

[kennythewelder]

Sounds like you have air in the cooling system. With the engine cold, open (take off ) the radiator cap, and start the truck. let it run and top it off with water am enough to open s needed. when the engine gets warm enough for the thermostat to open, is when you need to have the radiator topped off and the air should be out of the system.

 

[magimerlin]

Actually since you said it... Dex-cool is most likely your issue... I bet it had the regular green antifreeze in there.. I dont know anyone that actually uses it anymore with all the universal stuff out these days, and that includes me at the shop I'm a mechanic at.. I can not tell you the last time we had a vehicle in that still had actual dex-cool still in the system, even if it called for it from factory. If you try to combine the two, notice i didnt say mix, they make a very good impression of tapioca pudding... it gels up as they are not compatible with each other. If you look in your coolant resovour you will most likely see it. Same with taking your radiator cap off... but if this is the case you will need to do a VERY thorough coolant system flush.



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[magimerlin]

I only stress the above as you said these problems started "after" you filled the resovour back up. Going above the line will not hurt it by the way.

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[steve porch]

So I took the radiator cap off when engine cold. Started engine filled up radiator with water to the top at operating temp. I now have heat! Thank you very much