I switched out to the inline thermostat upgrade and sense have had this problem. After a couple days the coolant thermostat will look almost empty but when I unscrew the cap the coolant will refill the reservoir close to full. Any ideas why this is happening? Thanks for any info!

 

Your cap might not be venting at the correct pressure. It is building pressure in the system and expanding the hoses, when you crack the cap it relieves the pressure and the hoses contract and pushes the coolant back to the tank. You can run the cap one full turn loose if you want, that is what I do, or replace the cap to see if that solves. It is possible you have the beginning of a hg leak and that is pressurizing the system, hoping that is not your issue.

 

Man, hoping its not the head gaskets! I have 2 coolant reservoir caps. 1 says 200 on the bottom and the other says 140. Does this mean anything?

 

@me 2 start by running with the cap loose if that corrects the problem there are two possible solutions:

Replace the cap - just buy a new one
Check the hose the runs from the expansion tank to the left side of the rad that allows air in and out of the system as the coolant heats and cools if it is pinched or clogged you will have weird stuff going on.

 

Good to know. I have ran it with the cap loose as the inline states to do after install to get air out. It didnt have suction during but I did loose a bit of coolant.

 

You do not want to use the 200KPA cap, that is too much pressure, it will crack the radiator, tank, and split hoses. Only run a 140 cap and I don't even like to run that tight.