i had an overcooling issue after new hoses and stat.... ran a bit colder than i'd like (about 1/4-1/3 of the guage instead of 1/2 like before) but after a 2 hour highway drive at 70-75 it overheated after coming off the freeway. couldn't get the temps down no matter what, except running down more freeway. now it runs normal if i keep the rig moving at 35mph or more, with no stop lights. stop and go driving overheats it. freeway driving overcools it even more than before. i figured it was the clutch on the fan, changed it out to a known working used unit and there has been no change. i am about to buy another fan clutch to be sure because everything points to the fan, but maybe i'm off. doesn't sound like a bad stat or water pump because both are usually all or nothing.... maybe i kicked up crap in the radiator and i'm partially plugged?

any other suggestions welcomed before i throw more money at it...


Al

 

sounds like the t stat is messed up.. maybe stuck open??

ive heard of new ones being bad.

 

but how would a wide open stat let it overheat on the road?

Al

 

you said, if you keep it moving its fine. if you go on the freeway it overcools. stop and go makes it over heat. so it could be stuck open or maybe not. it was just a thought. also its cheap and real easy to change, or even to test the one you got.

if it was fine before, and all you did was change the t-stat and hoses. the t-stat would be the first place i would look. just my $.02

 

sounds like You have a air pocket in the cooling system,get a nail and insert it into the highest hose so that you get a trickel of water,pull it back so it wont leak,get the engine warm so that the themostat is open push the nail back in and run the engine,the pressure will spew some water,but will also blow any air,trapped out also.Make sure the heat is on when you do this.

 

I dont think you need to put a hole in ANY hoses to bleed the air out..

park on a hill or jack the truck up so that the rad is the highest part of the cooling system. Pull the rad cap off and put the heater on full blast.

Squeeze the upper hose..the cooling system should burp if you have in there.

also, you can check to see if your t-stat is working properly by seeing if it pops open in hot water over the stove!.

 

You dont put a hole in the hose. Slide the nail in between the hose and the fitting. The hose will not leak until pressue builds,when pressure builds it will push the air from the system.leaving the cap off will not alow the system to build 13 lbs of pressure.

 

wow, never thought of the stove idea on the thermostat! i'll try to bleed some air first, if that doesn't work then i'll check the stat.

Al

 

Overheating in stop-go traffic points to the fan clutch:
- http://www.barneymc.com/TOY_ROOT/TECHNEEK/fan_clch.htm

And I always test a new t-stat (along with the one I removed) in a pot of hot water on the stove to see at what temp they open and how far open they go. That way you know the old one was bad (if indeed it was) and the new one is good (again if indeed it is). On at least one occasion, I have put the old t-stat back in and returned the POS new one that did not work. And I always use the OEM Toyota t-stats, they work the best and last a very long time.