Is it possible to remove 3FE thermostat housing without snapping bolts? (1991 FJ80)

12bit

12bit

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It seems almost every thread regarding thermostat replacement on the 3FE is accompanied by a lengthy saga of extracting broken bolts. I've got a handful of bolt extractions under my belt now, and I would like to avoid it here if at all possible.

I've got a thermostat in hand and have been soaking the bolts in PB blaster for a few days. Does anyone have any tips specific to this task to get these 4 bolts out intact? The vehicle in question is a 1991 FJ80. Picture attached for the fun of it.

Thanks

20211118 160513
 
leonard_nemoy

leonard_nemoy

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I didn't have any problems with any bolts on the housing in my 91.

The brass sensors are a whole different story.........

I would recommend not even trying to unscrew any of the sensors unless they don't work anymore.
 
Marco Lau

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I didn't have any problems with any bolts on the housing in my 91.

The brass sensors are a whole different story.........

I would recommend not even trying to unscrew any of the sensors unless they don't work anymore.
Interesting...i broke one bolt on the housing when i replaced my broken Ron Davis radiator, and while i am in there, i replaced all my brass sensors, thermostat, belts, fan shroud, fan and hoses. get new factory bolts nonetheless....the brass sensors didnt' give me any trouble at all.
 
leonard_nemoy

leonard_nemoy

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Interesting...i broke one bolt on the housing when i replaced my broken Ron Davis radiator, and while i am in there, i replaced all my brass sensors, thermostat, belts, fan shroud, fan and hoses. get new factory bolts nonetheless....the brass sensors didnt' give me any trouble at all.

Yeah, mine were practically cemented inside the thermostat housing. It was way bad
 
12bit

12bit

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Thanks for all the replies so far.

Update: I broke 2 of the 4 bolts. Guess I'll be ordering the lower housing as I don't want to mess with extracting the bolts. In removing the lower housing I caught a glimpse inside the head. Looking a little gnarly in there. Seems like some of it is corroded away. How bad is it?

(For some back story, the truck has 157,000 miles on it and spent some years sitting outdoors after an accident. I brought it back to life and the engine still seems to run well. It hasn't been back on the road yet)

20211119 135552
 
12bit

12bit

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Looks lie a good coolant flush is in the future...
I'm not too familiar with what it is supposed to look like in there. Is that big flake some sort of mineral build up or a surface that's corroded away?
 
BILT4ME

BILT4ME

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That big flake is casting flash inside the block from the original sand casting. Nothing to worry about.

If I was going to remove those bolts, I would hit the top of each bolt straight down with a pin punch, hard, a few times before trying to loosen them because it will do a vibration wave to help break the galvanic bond and corrosion on the threads.
 
jomichael

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It seems almost every thread regarding thermostat replacement on the 3FE is accompanied by a lengthy saga of extracting broken bolts. I've got a handful of bolt extractions under my belt now, and I would like to avoid it here if at all possible.

I've got a thermostat in hand and have been soaking the bolts in PB blaster for a few days. Does anyone have any tips specific to this task to get these 4 bolts out intact? The vehicle in question is a 1991 FJ80. Picture attached for the fun of it.

Thanks

View attachment 2842385
Going through this as I write. I ended up breaking one bolt on the thermostat housing. I just bought a new lower housing since the outlet tube was pretty rusty. On the water pump, there was a stud that was already broken and I tried getting it out of the block but snapped it. It was a bitch to drill that out and re tap it. To add salt to the wound, I put everything together and the damn water pump leaked between the block. I am now going for round 2. Hope to never do this again!
 

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