Hi all,
Last year I had a mechanic buddy replace my fan clutch with dual 9 inch electric fans by Jeggs. At the time he replaced the hose of death and the coolant water outlet plate, then fully flushed the system. The relays he bought were set to turn the fans on when the engine temp reaches 185 degrees, and turn off at 170. The stock oem Toyota thermostat opens up at 180. So the initial problem was that the thermostat was not fully open by the time the fans kicked on. So he got an aftermarket thermostat rated for 170 - 175 F (can't remember which). Everything worked great up till about 7 months ago when my expansion tank started to overflow. My engine is not overheating as the temp gauge never gets to halfway before the fans kick on and cool things down. So right now I'm guessing that the aftermarket thermostat is not opening. Here's why: A couple days ago I tried to do the exhaust gas-in-coolant test with a kit I bought at Napa.
As the engine warmed-up I had to continually suck coolant out of the filler neck with a turkey baster. After close to 15 minutes the coolant kept coming out faster and faster until I couldn't keep up with it as well as it getting too hot to handle in the turkey baster. I shut off the engine for a couple minutes then tried to do the exhaust gas test, but once again the coolant started coming up again. My test was inconclusive.
So my plan now is to remove the current thermostat (test it to see if it stuck shut or not), then put in another aftermarket one rated at 170 F and drill a 3/16th hole in the top housing as a cheap insurance policy. In addition, my mechanic buddy is looking into changing the fans on/off temps with new relays.
I was thinking new fan temps should be: fans on at 185 F and fans off at 175 - 178 F.
Another thought is that one of the previous owners may have had the head gasket replaced with an aftermarket one and as a result, some of the water jackets are blocked... Don't want to go there quite yet.
Any ideas or thoughts on all this?