FJ40 Thermostat - Gasket Issue

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Bruce Miles

Bruce Miles

10 Year 15 Year
Joined
Sep 25, 2007
Threads
20
Messages
51
Just had radiator recored & I reinstalled it on a 12/79 manufacture date FJ40. Ordered & rec'd new thermostat & "gasket". I thought I ordered the gasket for btw top & bottom halves of thermostat housing, but I was sent a smaller round washer that fits on top of the thermostat after you place it in the housing.

When I opened it all up, there was no old gasket on top of old thermostat. Is this a possible reason that the FJ ran pretty cold? Does anyone intentionally avoid using that gasket to make the rig run cooler? My temp gauge never reads over about 1/4 of the way toward hot.

Thanks in advance for any ideas.
 
most likely a PO had no idea and just didn't install it, or never had it to install
 
I also have a 1/79 fj40 and I opened up my thermostat housing for the first time in 15 years and there was only the one gasket between the 2 halves. It’s the 2 bolt housing with the 3 bvsv or plugs if desmogged. Did you end up keeping this rubber gasket that sits on top of the thermostat in? If so how is it working? Any issues?
 
Generally, no. Running a 2F too cold isn't ideal for fuel atomization or engine longevity. Most 'cool-running' issues are either a missing gasket or a thermostat that is stuck open.
 
GrubbyFJ said:
I also have a 1/79 fj40 and I opened up my thermostat housing for the first time in 15 years and there was only the one gasket between the 2 halves. It’s the 2 bolt housing with the 3 bvsv or plugs if desmogged. Did you end up keeping this rubber gasket that sits on top of the thermostat in? If so how is it working? Any issues?
Click to expand...
My genuine Toyota microfiche set shows two gaskets for your year truck.

20260318_073725.webp
 
CrammerSr said:
Generally, no. Running a 2F too cold isn't ideal for fuel atomization or engine longevity. Most 'cool-running' issues are either a missing gasket or a thermostat that is stuck open.
Click to expand...
Understandable, I was mainly just making sure we knew 100% that the 1979 came with that upper gasket. My thermostat housing appeared as though it had never been opened before and I just wanted to make sure it came with that rubber upper gasket before I installed one. Might need to buy a FSM
 
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