Replacing Thermostat?

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Mar 30, 2003
Olathe, KS
Great to see everyone over on this forum now!!

My 80 won't heat up, so I assume that the thermostat is stuck in the open position. I picked a new one up yesterday, and realized that I have no idea where it goes, besides in one of the hoses. Could someone please point me in the right direction? Also, do I have to drain the system to replace it?

I'm kind of ticked off, I just had the entire cooling system flushed and refilled at the dealer, you would think they would check the thermostat. Thanks

 What year is your 80?  If you have a 3F, it's on the head, front, follow the top hose.  If you have a 1FZ, follow the lower hose up to it. On the 1FZ be sure to get the jiggle pin at the top or you will have trouble bleeding air out of the system. You did get an OEM thermostat Of course, didn't you?

 Tell us if you need more......Regards, Dan :D

Yes, you should drain the radiator to keep the mess down. use a clean pan and you will be able to reuse the coolant. DO NOT let pets near the stuff. They will try to drink it. If the do, they die a very painful death.......

Are you pretty sure it's the thermostat? What other symptoms? What model and mileage?

Installing a new thermostat is an easy job on the 1FZ-FE; don't know about the 3FE though.

If you are fast you can replace the thermostat without draining the cooling system on the 1FZ-FE. I don't recommend it though. You will need to set a bucket under the thermostat housing and work quickly as a lot of coolant will come out.

It's best to drain the radiator using the white plastic drain plug on the bottom left side of the radiator. Then remove the thermostat housing. As C-Dan mentioned, there is a proper orientation of the new thermostat. Use only an OEM thermostat and buy a new rubber gasket. The gasket goes *around* the thermostat. Look at the gasket carefully and you will see it is grooved. Be sure to install it correctly or you'll be draining the system a 3rd time.

You didn't say how long it's been since the dealer flushed the system. Assuming it has been 6 weeks or less, then try to save the coolant in a bucket and reuse it.

If you decide to do a full cooling system flush, there is a write-up over on SOR. Retrieve it and repost it here for others to follow.

Thanks for the instructions C-Dan and B, you guys are always a great help.

It's a 97, so it has the 1FZ. I just noticed yesterday that it is not warming up at all, the gauge barely gets above "C", and it feels like it's running cold all of the time. I just assumed it's the thermostat - anything else it might be?
You didn't give the mileage but the symptoms point to a thermostat stuck open. If you're around 100k then that's probably the problem.

You can confirm the guage is working because the heater also doesn't work.
You will know if the thermostat was the problem when you remove and autopsy it. If you got an OEM one to replace it with, I would say go ahead and open it up and get a look.

Exercise caution when re-installing the housing. Be certain that the thermostat is oriented correctly and seated properly.
If it's cocked you may break one of the ears on the housing or at least leak like a sieve.....

(2 paraghaphs)......Dan 8)
I'm having the same problem on my '92 FJ80 (3FE). Needle stays in the lower third of the temp range, and the blower refuses to blow warm air. However, the A/C blows nice and cold. Now that the weather is warming up, I don't care as much about a heater, but it would be nice to be able to trust the instrument cluster in the dash - especially if it's a relatively easy fix.
Wow, that is an old thread!

The 3FE thermostat takes two gaskets. The upper one is often left out, if so it can run cold in the winter and hot in the summer or when heavily loaded.

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