So been trying figure out a problem with my ranger. The cooling system seems to be building excessive pressure once it warms up. E.g. The temperature gauge reads about half way. What it does once it gets to about operating temp the reservoir will begin to fill up till it’s almost full and then pressure release on the cap starts to kick in.

I did find a small pin hole in my coolant reservoir. I fixed that hoping that was the issue. I also changed the reservoir cap. Anyways, now when I pressure test it now it holds just fine even leaving it for an hour the gauge did not move. I did try also using a combustion leak test never changed color.

So I am thinking my problem is something like the thermostat, water pump ect… I want to change the thermostat, but both O’reiley and autozone want about 140 bucks for one. The ford OEM part (1S7Z-8575-AG) the nearest dealer wants over 200 dollars for it. I do see cheaper replacements online like 30 or 40 bucks. This thermostat has built in housing as well an electrical component. Has anyone used one these cheaper ones or was it junk?

Oh Also one other thing the fan never seems to kickin before this issue at which point I shut the truck off since I don’t want coolant getting everywhere. However if I turn my heat on the radiator fan will turn plus the AC compressor turn on and off time to time, but when my heat is on the radiator fan running seems to stop this issue. I can leave idle for over an hour without issue if my heat is on.