here's the deal. The gauge will get 3/4 of the way over then go back down. The thermostat just refuses to open until the last second, it builds a good bit of pressure untill it opens. I changed the thermostat becasue i have no heat inside. I'm pretty sure the blend doors move, the tone of the air changes when you move the *****, yet niether front or rear heat are working. Is there a special way to bleed the cooling system on the 4.2? I know the cooling lines are very long for the rear heat. Also a diagram of the heater hoses would be nice if possible. Its just one thing after another.

 

I'm pretty positive that the front and rear heater cores have no inline valves on them. The cooling system is a continuous flow system, so it should also auto-bleed itself just from the engine running. Check the input and output lines for the front and rear heater cores when the engine is at temp. Are both hot? if not, then I would suspect that your water pump is not circulating coolant thru the system. This would also explain your temp reading/gauge reaction.

 

One hose on each of them is hot while the ones coming off are cool. I know the water pump is flowing, Idk how well but when I gas it you can see it suck from the overflow a little. If the heater core is hooked up backwards will that cause a problem? Meanwhile in going to try to blow them out to make sure they aren't clogged. I have a front and rear heater core btw

 

Fun fact, if your heater cores are clogged it will cause the van to have temperature spikes and overheat occasionally. After blowing out the heater core the temp now stays nice and cool. Not to mention I now have heat!

 

Glad you got it fixed. Heater cores tend to be the internal crud collectors. That is one of the reasons that I do a full flush and fill of my cooling systems every 50,000 miles or 4 years regardless of the vehicle or coolant MFG's recommendations are. Plain and simple, coolant wears out and when it does, the electrolysis between the different metals causes the crud to build up and flake off. I replaced my thermostat last winter due to it no closing all the way. When I pulled the housing off, the inside of the block in the thermostat area was like a new block on the inside.

 

I hope you put the thermostat back in.
Do you have a block issue from the overheating?

 

Yes it's got the recommended thermostat back in. Everything seems good for the time being. I would shut it off before it got to the red. With the heater cores clogged it was doing something where the thermostat didn't want to open. I tested it once when it was having issues and it opened at about 245 degrees, I don't like getting it that hot but I just wanted to see what would happen.