FJ40 OVERHEATING WHILE IDLING

Joined
Nov 7, 2020
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97
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Tacoma, WA
Weirdest thing happened today while in the drive-thru. Car has always held a temperature around 185-198 since October 2020. All of a sudden while waiting in the drive-thru line at the local Burger King for about 15min idling. I noticed the temperature rising above it normally sits at. Also felt the floor heater getting to the point where it was starting to burn my legs.

So I jumped the curb and went around to the lot and shut off the car. Let it sit for awhile. Then decided to drive home. As I was driving back home, I noticed the temperature going back down to normal operating temperature.

Questions is, does that mean the thermostat is not opening up while idling, hence the car going to 217 degrees F??

The deats is as follows:
'78 FJ
Original 2F running: Sniper EFI
New water pump, thermostat, and radiator 10/14/2020.
Running Toyota Red coolant
 
Joined
Nov 7, 2020
Messages
97
Location
Tacoma, WA
Also if your top hose is Hot, the thermostat has opened.
Upper hose was hot to the touch. I also did burp the system when installing the pump, thermostat, and new radiator back in October. But I just burped the system again when I go home.
 
Joined
May 14, 2016
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Arizona
Just tried replicating the situation once I got home. And it didn't run the same issues I had in the drive-thru.

Only thing I did was fill the over flow tank with some more coolant....That can't be the fix...

Well, these old engines using an IR gun can still perhaps give enough information to see an intermittent/impending issue.
 
Joined
Nov 7, 2020
Messages
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Tacoma, WA
Well, these old engines using an IR gun can still perhaps give enough information to see an intermittent/impending issue.
I will go invest in an IR gun. Just trying to get this issue solved before the summer rolls around. Seeing that it will be much hotter.
 

desmocruiser

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Dec 17, 2005
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Big Orange Country
I am also doing research on a similar issue and are looking closely at the fan clutch.

Since it sounds like you have new radiator, water pump, and thermostat, you might take a look there as well. There are several good threads discussing, type, with without,, etc.
 
Joined
Nov 7, 2020
Messages
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Location
Tacoma, WA
I am also doing research on a similar issue and are looking closely at the fan clutch.

Since it sounds like you have new radiator, water pump, and thermostat, you might take a look there as well. There are several good threads discussing, type, with without,, etc.
I have an aftermarket fan. Hooked up to a switch. So it stays on the entire time.
 
Joined
Jul 12, 2013
Messages
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Location
Inland Empire - California
Just tried replicating the situation once I got home. And it didn't run the same issues I had in the drive-thru.

Only thing I did was fill the over flow tank with some more coolant....That can't be the fix...
You'd be surprised... Having fluid in your reservoir helps in equalizing pressure.
Is your radiator cap new?
 

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