COLOYOTA

Hello everyone!

I just changed the thermostat in my sons truck (3.0 liter) and now he has no heat in the cab and there is no pressure in either of the radiator hoses. The motor runs at the right temp as long as the cap isn't on but once on it tries to overheat really fast. Is this a problem with air in the system and how do I take care of it or is it something more?

Any advise would be greatly appreciated

xxxtreme22r

air bubble and maybe the thermostat is in upside down?

Did you run the engine with the cap off and the heat on when you changed the thermostat?

Why did you change the thermostat to begin with?

COLOYOTA

I originally changed the thermostat because he had a leak from around the housing. His truck was running fine prior to me changing it. I put everything back exactly the way I removed it so I think it's not in backwards. I refilled it and now no heat and no pressure on either of the radiator hoses.

justin_4runner

thinking u have an air bubble. try moving the truck to have the radiatir up higher point and let the truck run, turn on heat on high. after u know it is full i would look at the cap. it might have a bad seal and letting pressure by..

sb5walker

Did you use a Toyota thermostat? They really are better than any of the aftermarkets. Did you position the jiggle valve at the top? The longer end of the thermostat faces into the motor.

Did you use Toyota Red or the old-style Prestone Green? Any of the modern OAT or HOAT coolants cannot be used safely because they will corrode the lead solder in the radiator and heater core. That includes Toyota Pink, which despite what Toyota claims, can NOT be used safely in our trucks.

2x on elevating the front of the vehicle so the top of the rad is above all of the heater hoses, then with cap off and the heater controls all the way to hot, run the motor to try to get any remaining air out of the system.

If that doesn't work, possibly a piece of sealant got loose and is clogging the system somewhere. You can drain the coolant into a clean container (save for re-use) and then pull the thermostat back out, reattach the lower hose without the t-stat to the motor and direct the other end of the hose into a drain. Pull the upper hose off the rad and as best you can, seal a garden hose to the upper rad hose. Open the heater controls all the way to hot and turn on the hose to medium flow (not full blast). That will backflush the heater core and block, and possibly dislodge any debris. Watch for stuff coming out of the lower hose.

COLOYOTA

Elevation was the ticket!!!!!!!!! Thanks everyone who posted advise!