Hello everyone I've got a slight problem here that's been bugging me. I just did the lower intake manifold gasket on my 99 blazer 4.3 2wd over the weekend and now I get low heat. When I changed gaskets I also out on a new water pump and 195 degree thermostat. Odd thing I've noticed is before I did the gaskets the heat worked perfectly and I could hear the a.c. compressor engaging now it doesn't. Does anyone know if it works like home hvac and reverse to help heat? I've already back flushed the heater core and gotten the air out.does anyone know what temp the heat should be out of the vents? Any ideas would be greatly appreciated.

 

If you had heat before the gaskets were replaced, there is either a trapped air pocket in the cooling system, or a faulty thermostat. If you have automatic climate control, when the mode switch is in the off position, the compressor should not come on or cycle. Depending on sensor inputs and settings, any other position on the mode switch can allow the compressor to come on or cycle if the system deems it necessary. If you have manual HVAC, the compressor should NOT come on in the vent, heat and off positions. Maximum register outlet temp should be ~130F to ~140F on both systems.

 

Thanks you for the temp reading and clarification on the compressor. It turned out to be the thermostats I had bought, put in a duralast one and now at the vents I'm getting 145 degrees now.

 

I just had this done at my local mechanic shop. They replaced the intake gasket and water pump. It had heat before and now I do not have heat, well, I have a very little heat. Would you guys still think its a small pocket of air or thermostat?

Here is what happened. I had the mechanic replace the intake gasket because they said that was the problem and why I had a coolant leak. So I had that fixed. I picked up the truck and drove home. I then noticed that it was leaking coolant on the next day (Friday). It still had GREAT heat. I took it back to the mechanic and then they said the water pump was bad. So I had it replaced. So now, $1600 bucks later, I have a 98 Blazer V6 4WD 4DR truck with very little heat.

So sounds like the thermostat maybe bad? How would I work out an "air pocket" in the coolant lines or should I take it back and have the mechanic look at it?

Please advise.

 

If u had heat before you took it in and now it doesn't work I would make them fix it. Sounds like you might just have an air bubble somewhere.