Anubis1337

I have a 1988 toyota pickup and I have changed the thermostat twice. But whenever I turn the truck on the idle is normal then the engine heats up and the idle starts fluctuating from high to low. And the engine heats up close to red and if I turn the heat on it makes the temperature go up even more! Any ideas would be appreciated.

rustED

iTrader: (2)

What engine do you have? Did you try testing your thermostats? I like to test them in a pan of boiling water before installing them, I've had faulty ones right out of the box. Is it installed facing the right way? Did you check your clutch fan? Do you have any coolant dripping from around the water pump, if yes could be a sign of the water pump going out. Just a few things to check. I'm sure others will chime in. Good luck, and welcome to the forum!

Anubis1337

The engine is a 2.4L L4. I did check the thermostat before I put it in and it worked fine in hot water. I replaced the fan clutch less than 6 months ago. I have not check to see if any coolant is leaking by the water pump and thanks for welcoming me!

rustED

iTrader: (2)

Have you drained the radiator recently and refilled it, maybe your cooling system needs "burped" might have trapped air in the system?

Anubis1337

I don't think I have and I'm not really sure how to do that. Do I just fill it up and leave the radiator cap off and fill it until its over flowing a bit?

Odin

This is another subject that needs to be stickied. This comes up quite often especially with the 2.4.

Search some different terms like erratic idle, burp, purge air etc.
If there isn't already a jiggle valve in the thermostat you should probably drill about a 1/16 hole in the side of it to help allow trapped air escape. It will take a little longer to warm up though.

Your temp rising a little on the gauge when you turn the heater on is also common if you don't use the special Toyota two stage thermostat. They did the overshoot from the factory with the normal OEM thermostat so it is recommended to install the special Toyota Two Stage thermostat. Search temperature overshoot.

You should find part numbers and advice on how to deal with both situations in your search.

I will give you this bit of advice though. It's fairly common for the thermostat housing bolts to strip when removing them on this engine 2.4, 22R, 22R-E. Do yourself or the next owner a favor and apply some anti seize to the bolt threads and don't go crazy on the torque when tightening them down.

Anubis1337

Hey guys thanks for the help! I drained the radiator and then filled it back up and left the cap off until it almost overflowed. And then everything worked great! But when I started it up today it was doing the same thing. So I am pretty sure I have a bad radiator cap because the pressure is really high. Only problem is I have an after marked radiator so I have no idea where to get a new cap. Any ideas on where I could start looking? Thanks again guys!