Should coolant be spraying/ circulating into the overflow/expansion tank when the engine is cold? It is in my truck, and according to my understanding of how coolant systems work it should not. I thought
Maybe the thermostat was stuck open so I replaced the t-stat to no avail. I thought that when the engine was cold that the coolant was restricted to the engine until it got to operating temperature and then the thermostat opens up and then coolant circulates through the radiator and overflow/expansion tank. Any help will be appreciated. Also my heat is not getting as hot as it used to so that is why I thought this could be an issue.

 

I've wondered about this to and heat gets hot when I press the gas..... Please some one fill us in

 

Hey ronald, when you start your truck, is there movement in your overflow tank before the engine is hot? That's what I'd like everyone to answer me. If its supposed to do that I will be relieved because I'm afraid I have a gasket leak or something, I'm not losing fluid though. My heat on the passenger side is hotter than the driver side( driver side heat is warm but not hot).If the coolant system is working properly then I may have air in my system, or a blocked heater core. Maybe the heat inlet door is shut? I cannot find the answer anywhere about the coolant resevoir.....

 

The thermostat restricts flow through the block while it's warming up. It doesn't however, restrict flow through the rest of the system, like the heater core.

 

The radiator cap moves based on pressure to allow fluid into or out of the overflow tank. There should not be any flow into the overflow tank on a cold engine.

Try replacing the rad cap - it's something cheap to try first. After that I'd do a flush and fill to address your heat problem. If that doesn't work the issue is probably in the dash HVAC system (blend door, maybe).

 

Yeah that is what I mean even cold water is flowing into the overfill.

 

I have am 03, but when I flushed my coolant and refilled it, there was not any movement of fluid in the overflow tank. Well except as stat opened up then it drained down a little probably due to air. But no movement of fluid. Because I left my cap off while doing this and did not notice any movement as I was burping the system.

 

What I may suggest if you have not done a coolant change lately as a maintenance item, or if it is due etc. is to go ahead and do a coolant flush and fill. While flushing it, if possible reverse the hoses to the heater core to allow fluid to travel in reverse through it, this may get out out any gunk or what ever if it is partially clogged. Then on final drain, hoses back to normal and fill with correct mixture and type of antifreeze. If no better, then I would think a blend door may be your issue. But at least the flush and fill has been taken care of.

 

Blend door???........they have nothing to do with the "engine" cooling system.
Blend doors are deep withing the HVAC system and do not interfere with any coolant movement that I am aware of??
They control the flow of air only by blocking/allowing air movement within the HVAC system .....no fluid is involved.
There is coolant flowing through the heat exchanger matrix within the HVAC system, but there always is. There's a valve which controls the flow through it, but this would not make the coolant flow back into your header tank.
I'd go for a defective Rad cap first, but I still can't get my head around why there should be coolant flowing into it when the engines cold. The thermostat should block that flow off ,until the engines hot.
Water does not flow through the rad until the thermostat opens, period!
That's it's whole purpose in life.
The only way your header tank would fill, is if the tanks being pressurisd by a cracked head/stuffed head gasket I would've thought??
Hmmmmm.....post up what you eventually find as this is very interesting.
Good luck.
Al.

 

Abarmby..... I know that a blend door has nothing to do with the coolant flow, I said that if the coolant flow was normal that THEN I could look into the blend doors etc. I don't see how I could have a cracked head or blown gasket without any fluid loss or a milkshake in my oil. Someone said something about the radiator cap? The radiator doesn't have a radiator cap but the overflow tank does. So there is pressure at the cap on the overflow tank and maybe there is something wrong with the cap?