2F running too cool (1 Viewer)

[wolfbak]

I could use some troubleshooting suggestions.

I recently got my '76 FJ40 back on the road after a frame off resto. Because the heater and blower still needed to be restored, I initially bypassed the heater valve. My engine has never come up to normal operating temp. The gauge barely comes off the far left cold side even in 90+ degree temps. Using a temp gun, I rarely get a reading above 160 and most of the time it's around 145.

Now that I've refinished the heater and blower and got them installed, I'm not getting enough heat out of the system, which makes sense since the motor is running too cool.

A few notes:

I checked the temp gauge, and it's operating properly.
I've checked the resistance of the temp sensor, and it's perfectly in the correct range.
I swapped out a brand new aftermarket thermostat with an OEM Aisin specific for my engine. I also verified the correct opening temp on the stove with a thermometer in a pot of water.
I double checked that the thermostat is installed correct side up.
I have a new thick rubber gasket on top of the thermostat.
I have a new thick rubber gasket below the thermostat for the housing.
When I redid the truck, I installed a new aluminum radiator.
I have a fan shroud.
I have a 6 blade plastic fan with no clutch.

My only thought is that maybe my thermostat housing is allowing bypass at the top of the thermostat. It could be due to corrosion on the top where the rubber gasket sits (although I cleaned it up really well). The other thought is that maybe the main housing gasket is too thick, raising the top of the housing above the upper gasket?

I know it's better than an overheating issue, but it's getting cold out and I need more heat.

Anyone else have similar issues? Anything else I can try?

 

[Ming89FJ62]

it's possible that you still have air trapped in the coolant system. Have you "burped" the radiator? Have the front end elevated and the radiator cap off (don't do this with the radiator hot) and see if any trapped air escapes. What temp thermostat did you use? 180 deg F is the standard.

 

[cruiserkev]

I had similar issues a few years ago with my 2F. Mine never seemed to warm up fully either. Solved the problem with a 190 degree thermostat from SOR. Plenty of heat now.

 

[Pighead]

I just put a piece of cardboard in front of the radiator when it starts to get cold outside.

 

[peesalot]

Thats not a joke, he actually, really does that, for a long time.

 

[wolfbak]

I had similar issues a few years ago with my 2F. Mine never seemed to warm up fully either. Solved the problem with a 190 degree thermostat from SOR. Plenty of heat now.

It's an Aisin THM-004, which is 180 degrees.

 

[wolfbak]

it's possible that you still have air trapped in the coolant system. Have you "burped" the radiator? Have the front end elevated and the radiator cap off (don't do this with the radiator hot) and see if any trapped air escapes. What temp thermostat did you use? 180 deg F is the standard.

Thanks. I have not tried burping it, so I will. I used an Aisin 180 degree thermostat.

 

[wolfbak]

Thanks. I have not tried burping it, so I will. I used an Aisin 180 degree thermostat.

Quick question - you raise the front end, take the cap off on a cold radiator, and then you run the engine, or just let let air move naturally?

 

[charliemeyer007]

I made a curtain out of old water proof tent floor, suspended on a piece of paracord that hangs in front of the radiator, blocking the lower half. Once when I was pushing mud with the hubs in low range low, I had to lower the curtain to 1/4 - still wanted to run hot so I pulled it out at the next down hill slope - ran fine after that.. I think the thermostat is 180. Really like my big rear heater.

 

[Paul_A]

When I lived in Ontario and it got really bitter sub-zero cold I used to put a piece of card board over 2/3 of the radiator in my 1970 1F and it worked like a charm.

 

[Chungas Revenge]

Burp kit. Runs about $20.

 

[middlecalf]

That thick rubber gasket between housing pieces should not be used, it should be a thin paper-type gasket, with sealant. I think your thermo leaking as you stated is a good assumption. And burping is also necessary. Where you at BTW?

 

[wolfbak]

Burp kit. Runs about $20.

View attachment 3498705

Nice. Where’d you find that? Is it generic?

 

[wolfbak]

That thick rubber gasket between housing pieces should not be used, it should be a thin paper-type gasket, with sealant. I think your thermo leaking as you stated is a good assumption. And burping is also necessary. Were you at BTW?

Thanks. I’ll try the thin gasket and burping. I’m in Virginia Beach.

 

[Chungas Revenge]

Nice. Where’d you find that? Is it generic?

This is the NAPA version. Available at most automotive parts stores/centers. Wally World sells them as well.