Thought I was gonna replace the thermostat gasket but nope… Can someone tell me about replacing this gasket/resealing this part? I have no idea what you call that hole so I don't even know how to search for it.
What is this part leaking coolant called? (1 Viewer)
- Thread starter Justbuckstuff
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It seems to be your front water bypass, that transmits coolant from one cylinder head to the other and acts as a manifold for the radiator hoses (see here), but please double-check to be sure as the photo is kind of zoomed-in. I replaced the gaskets on mine when I pulled the intake manifold to replace the starter. You can get Fel-Pro gaskets for this at any parts store and they are exactly the same as the OEM gaskets (made in Japan so probably from the same factory that Toyota uses). I would probably also replace the thermostat, thermostat O-ring, and radiator hoses when doing this job. I would use a OEM Toyota thermostat and thermostat gasket but aftermarket hoses are OK.
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that should use fipg not a gasket, do a drain and fill on the cooling system and reseal the coolant neck at the same time. you will need the green fipg for coolant
If it is the front water bypass, it definitely has a gasket (they show on the Toyota parts diagrams for the 4.7 and mine had them in it when I took it apart for presumably the first time since assembly in Japan).
there is an o-ring there as well but from the pic it looks like the the neck that gets sealed with fipg.
The o-ring used in the water neck bypass is a unique size and it can leak intermittently. It then drips down into the valley and runs to the back of the engine block. The surrounding female fitting for the o-ring should be carefully cleaned (no scratches) to allow for heat movement as the metal expands and contracts. I have seen both fipg grey sealer (Asian brand) and gaskets used at the flange location beside it. If the flange has a groove cut into it I use the Asian fipg. If there is no groove I use the gasket. This leak is often miss-diagnosed as head gasket failure.
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- Thread starter
- #7
Thanks for the help yall. Any tips or tricks for working with fipg? I bought it before for my timing belt/wp (probably for this spot) but ended up having someone else do the install in a time crunch. I’ve seen the solid gaskets a while ago but no one seems to agree on whats better.
I used the Asian brand grey fipg per the service manual. Allowed it to set up before final torque according to the directions. 5000 miles later it is holding pressure just fine. The nearby o-ring is a unique size, part number Mahle #C31699. If you haven't already replaced your radiator that will be coming next.
If you're doing one, do both. They do wear out.
- Thread starter
- #10
I’ve already done my radiator, radiator hoses, timing belt/wp, thermo, alternator, spark plugs, gears, and steering rack. Somehow in all that, it worked itself a little tiny hole. So put it on, wait, finish torquing? Thats good to know. I woulda just slammed jt in there
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It has a groove, rectangle shape, that looks like an oring belongs there, it’s just sealant /fipg. Permatex ultra grey is my go to for this, OE stuff works great as well. Needs a clean service and a 1/4” bead around one surface before mating. You’ll need to clean out the rectangle groove before assembly.
I think I have a leak at the same location-noticed that I had to top off coolant twice which has never been necessary. All the surrounding hoses look good and have been replaced recently along with thermostat. No visible leaks from tstat or hoses. Any suggestions?
