FJ40 Thermostat Installation How To (1 Viewer)

Vae Victus

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Since it has been nine years since a thread has been created discussing the installation of a thermostat on a 2F engine, and since I spent about 30 minutes yesterday trying to figure out how to do the installation correctly with the odd gaskets that are included in different rebuild kits, I thought I would quickly show the steps that one would take to properly (hopefully) install the thermostat. (Also the old thread has lost its picture links)

EDIT 8/12/19: Cool Cruisers and SOR have gaskets (upper, lower - thick and thin) readily available. Search on their sites for "thermostat gasket". Not sure (it's been a while) but there may be OEM parts available as well. Search on your favorite Toyota parts website).

1. On a cool engine, locate the thermostat. It is on the front on the straight 6 engine (F thru 3FE). In the photos below it is circled in yellow.

Thermo1.jpg
Thermostat 2.jpg



Place a bucket or pan underneath and loosen the hose clamps. Allow the coolant to drain into the bucket.

2. Remove the top half of the thermostat housing by removing the two bolts. Remove them slowly and carefully as these have a high tendency to break within the aluminum housing. They are fairly thin and long, and bind up in the aluminum due to the increased exposure to water.

IMG_6510.JPG


3. Remove the old thermostat from the housing if you are going to replace it with a new one. If you are not then you should test the thermostat to make sure it still works by placing it in a pot of water and monitoring the temperature until it reaches the proper expansion temperature. At that time the thermostat should expand.

4. Remove the old gasket. Clean the lower and upper mating surfaces of any residue from the old gasket. Use a razor blade to scrape for material from the face of the thermostat housing, and then use a cleaning agent like general spirits, brake cleaner, or other non-residue creating cleaner to remove the oil from the surface.

5. Insert the thermostat with the visible spring facing down and the domed part up. It should fit into the lip in the lower housing. Install the thermostat so the "jiggle valve", as the FSM describes it, is located at the 11 to 1 o'clock position in the housing. It allows a little circulation until the thermostat opens. (NOTE: the thermostat pictured below does NOT have a jiggle valve).

This is the bottom:

IMG_6482.JPG




This is the top:
IMG_6483.JPG
 
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Vae Victus

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6. Place the round thick flat o-ring on top of the domed part of the gasket as shown in the photo. This gasket stops water from back flowing through the system before the system has heated up.
IMG_6484.JPG



7. Place the top half of the thermostat housing onto the lower housing and look at the gap between the two. If there is very little or no gap between the two, you can use either the thin paper or the thick (rubber or cork) gasket.

Sculptor Painting.jpg



If there is a large gap between the two, you must use a thick rubber or cork gasket and not the thin one. If you use the thin one then there will be a danger of cracking or breaking the thermostat when you force the housing down on top of it.


8. Remove the top half of the thermostat housing and place the proper gasket on to the lower housing. If you choose the thin one you may use a very thin coat of gasket sealant on the gasket. Make sure it is very thin and will not squeeze into the coolant piping, potentially clogging up part of your radiator. It is my observation that sealant is not necessary if you are using the thick rubber or cork gasket.


Thin gasket
IMG_6486.JPG




Thick gasket
IMG_6489.JPG



There is some discussion that the gasket should go below the thermostat in some cases. This thread discusses that. Draw your own conclusions. F engine water outlet paper gasket installation order. My opinion - put the gasket on top of the thermostat.
 
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Vae Victus

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9. Put anti-seize on the new bolts.
IMG_6494.JPG


IMG_6496.JPG




10. Place the top on the housing and tighten the new bolts that you have purchased for the thermostat housing to around 12 foot pounds of pressure. Watch the thick gasket, especially if it is rubber, and make sure that it does not deform too much while tightening.

IMG_6492.JPG


FYI the bolts from the housing to the engine head torque to 18 ft lbs.
IMG_6498.JPG
 
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Vae Victus

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11. After everything is all buttoned up and back to the way you found it. Take a hose and wash down everything that the coolant could have dripped on. If you own any pets keep them away while you are washing the residual coolant away. They have a tendency to like the taste/smell of coolant.

12. Open up your radiator cap and set it to the side. Place a funnel over the radiator and fill it. Keeping the radiator cap off, start your truck and move the interior heat setting to high but keep the fan to off or low depending on your vehicle’s controls. Monitor the coolant level in your radiator it will take a little while for your engine to heat up. Once it does the thermostat will open and the coolant lever in the radiator will drop. Top it off once it does and monitor for a few more minutes to make sure all the air bubbles are out of your coolant system. Turn off the engine and install your radiator cap. Then top off your coolant over flow bottle (if it needs it) and you are done.

Check again in 50 miles. Top off if needed.

Thanks to this thread in the 100s area for allowing me to copy some of these steps.
 
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Racer65

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Excellent write-up. The toughest part of this job is removing the old bolts without breaking it. My only concern about your new bolts is the fact that stainless steel is softer, so it might be more prone to breaking in the future. Also I noticed that your new bolts are fully threaded, while the OE ones are only partly threaded.
 
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Excellent write-up. The toughest part of this job is removing the old bolts without breaking it. My only concern about your new bolts is the fact that stainless steel is softer, so it might be more prone to breaking in the future. Also I noticed that your new bolts are fully threaded, while the OE ones are only partly threaded.
Any tips on removing those bolts without shearing them? I may be tackling this job in the not too distant future.
 

Racer65

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Any tips on removing those bolts without shearing them? I may be tackling this job in the not too distant future.
You can try to heat it with a torch, let it cool, and reheat. Do this a few times before attempting removal. However, chances are it will still break.

I would just remove the 2 bolts to the engine, and take the whole unit out without bothering to separate the top and bottom housing.
 

rrv333

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I sprayed PB Blaster on both bolts for a week prior to taking off the top half of the housing. They came out with some resistance. I feel that if I hadn't used the PB Blaster than I would have broken at least one of the bolts, for sure.
 

Vae Victus

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Excellent write-up. The toughest part of this job is removing the old bolts without breaking it. My only concern about your new bolts is the fact that stainless steel is softer, so it might be more prone to breaking in the future. Also I noticed that your new bolts are fully threaded, while the OE ones are only partly threaded.

Thanks - yes I'm not a huge stainless fan, but figured with such a low torque situation, it was worth a try.

WRT your comment about removing the entire housing from the head - to what gain? Lower housings are getting very hard to find IIRC. I know you have some but they are becoming unobtanium (ha, see what I did there).
 

brian

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Thanks - yes I'm not a huge stainless fan, but figured with such a low torque situation, it was worth a try.

WRT your comment about removing the entire housing from the head - to what gain? Lower housings are getting very hard to find IIRC. I know you have some but they are becoming unobtanium (ha, see what I did there).

easier to work with on the bench vs in the truck if you twist a bolt off.
 

Vae Victus

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anti seize or other lube and torquing doesn't work unless you have wet torque specs.
Agree Brian, but again at low torque values for relatively large bolts, it's worth (the risk of) slightly over torquing to be able to get the bolts off in the future in my opinion.

If you apply it wet and keep to the low end of the given dry torque range, any non-critical bolt should be ok.

I would not and did not do this on my head and block (or other critical junctions), even though those bolt holes were probably "wet" due to the engine being 44 years old. It is very hard to have "dry" threads with old parts (not impossible, just hard).
 

Rigger

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I'm glad to see this thread. It taught me that my truck was missing the O ring.

:doh:
 

Vae Victus

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Part # 90430-40058. You gotta have it.
And if @Racer65 has it you should buy it from him. If not, buy something else from him.

I strongly support his efforts to bring back the hard to find parts, and have many more that will be in my truck before I'm done. This includes the mat which I stupidly cut out of my truck when it arrived.
 

Rigger

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Excellent write-up. The toughest part of this job is removing the old bolts without breaking it.

Is it the bolts that hold the top part on that are prone to breakage?

Or the ones the go into the block?
 

Bear

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For clarity, 90430-40058 is the rubber gasket on top of the thermostat, not the one sandwiched between the two halves of the thermostat housing, if that was the question.

What is the Toyota part number for the thick rubber gasket between the two halves?
 

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