I just put a rebuilt long block into my truck last week, and when I turn my heat on, my temp guage almost immediately will rise near about to the red. If I pull the lever back to cold, it starts to come back down. I have no problems while driving it until I turn the heat on. I'm guessing I have an air lock but can't seem to fix the prob.

Any help is appreciated.

 

When you put the engine in, did you replace the radiator hoses?

 

Yep, all new hoses, and I had my radiator dipped and cleaned up.

 

Okay. Had to ask. The sending unit for the gauge is above the outlet for the heater core so I though that maybe a hose was blocked and opening the heater caused coolant to divert through the core and recirculate back to the engine without getting to the radiator thus not cooling off well. By the same token, if you're getting hot air out of the heater, there's likely not a bubble.

What rating is the t-stat? ... and it is new too, right?
You're using coolant and not straight water?

 

I get hot air.
The t-stat is brand new, and it's a 195*.
Yep, well a jug of coolant and the rest water.

 

Maybe you could use a dual stage thermostat?
This is the part number you'll need to give to the Toyota dealer, otherwise they probably won't know what you are talking about. 90916-03070

 

http://www.4crawler.com/4x4/CheapTri...tml#Thermostat

 

I had same problem after my rebuild 4crawler's tip on drilling the hole worked for me.

 

Got side tracked a bit ago and was coming back to post 4Crawler's page, but he beat me to it.
That should help a lot.

 

Depending on how much it is, I may just drill some holes in mine.

Only thing that bothers me is that, my old motor would run a little warmer with the heat on , but the temp guage would never spike up close to the red like it is doing now, and my old t-stat was just a standard t-stat, just like the one I put back in.

Oh and thanks for the help guys.

 

It only takes a small change to have that issue show up. I think my engine was OK then had a new head put on and the problem showed up. Put on the dual stage t-stat and all is well and has been for about 12 years now (still the same t-stat).