Hey all, so the heat in my truck has been acting funny.

I will have no heat at all until the truck gets about 3/4 on the gauge or slightly higher. Then like the flip of a switch, it starts to cool back down to normal and everything is just fine. It only does it once per journey.

I changed the thermostat and I thought it had fixed it, but it started doing it again this morning.

I'm going to check the coolant level again (it was good), but I haven't noticed any coolant leaking anywhere, the oil looks good, and the tailpipe... well I'm not sure of the tailpipe.

Does anyone have any experience with this issue?

 

theres an air pocket. Put your truck on a nice incline with the front end higher Cold start with the radiator cap off until the engine starts to get hot. Top off the coolant. That should fix it.

 

Yup, - unless you installed the wrong thermostat, -it's easy to do unfortunately. You can use a 92,94,95 and 96. The 94 would be choice IMO. They can be picky. I believe 87's are the worst.

 

Update:

I parked the truck on an incline, and let it run for quite some time.

Here's what happened:

I set a level to maintain the coolant at to see if it would raise / lower.
The truck came to temp and pushed a good bit of coolant through the resevoir. I refilled to the baseline level. The truck went to 3/4 heat on the gauge and the reservoir level lowered and bubbles could be seen. The truck temp lowered to normal and it was as it should be. Again I refilled to the baseline level. After some time (roughly 30 minutes) The truck pushed a good amount of coolant from the reservoir again, but the temp did not fluctuate.

I did this 3 times.

The results change only slightly. I still do not have heat until the truck gets to 3/4 temp gauge then backs off to normal. If I do not have enough RPM, the temp will remain slightly higher and still no heat for a small time period.

The last time I drove it, the truck never reached 3/4 on the temp gauge, but there was no heat, then heat for a few minutes, then no heat, then finally working properly.

It still seems like there is an air pocket. But I have done this 4 times. I've never had to do that this many times to remove an air pocket.

Any more suggestions?

 

You had the heat temperature set on high while you burped the system, right?

 

This is correct. Should I not have?

 

You should, some people overlook that part.

It does sound like an air lock though, or you got a bad or wrong thermostat.

 

Well this morning the truck never came back down and over heated.

Any other ideas rather than just an air pocket?

Could it be the water pump? I'm hoping it's not the head gaskets.

 

Pull the thermostat completely out for a test and see what happens. You will probably get very little heat and it will run like crap, but it shouldn't overheat.

I'm thinking you do in fact have a faulty thermostat.

 

Thanks. I'm going to pull the water pump and check it out. If it looks ok I'll run it without the thermostat.