Thermostat Housing Assembly Leak! (Male to Female Fitting)

[ItGoesTo11]

The thermostat housing assembly on my 1999 LX470 has developed a slight leak at 160k miles. It is the round male/female fitting that goes into the engine from the thermostat/lower radiator hose. It is the round left fitting as you are looking at the engine from the front. Is this a press fit, does it use sealant when assembled, or is there a gasket?

I would like to disassemble it and re-seat/seal/gasket it so the leak stops, but I don't know what seats it into the female receiving end.

Thoughts on how to repair it?

 

[nissanh]

There are TWO male-female joints. One is bigger and the other is smaller. Both use an O-ring to make the seal. The male portion uses the O-ring and slides into the female.

Removal is the toughest part. Make sure you DONT use a metal hammer to tap it out.

You will need FIPG (buy Toyota brand).

See 27:38 mark here:

 

[ItGoesTo11]

There are TWO male-female joints. One is bigger and the other is smaller. Both use an O-ring to make the seal. The male portion uses the O-ring and slides into the female.

Removal is the toughest part. Make sure you DONT use a metal hammer to tap it out.

You will need FIPG (buy Toyota brand).

See 27:38 mark here:

Thank you, this is very helpful and exactly what I described! I can see there is an o-ring for the round male/female fitting I noticed is leaking, so I'll purchase that item. However, in the video I only see ONE joint like I described. The other is a square flat faced flange and then the two other fittings are slip fit for the small bypass hose and the main incoming radiator hose. What am I missing in not seeing *two* male/female fitting?

Also, the video uses RTV sealant (FIPG?) on the square flange, however Fel-Pro sells a gasket for this exact application...which is better? It seems the pre-made gasket would be better?

 

[nissanh]

Sorry, I was referring to the main coolant line and the by-pass line as two male-female lines. Both these lines have two O-rings. Make sure to apply small film of coolant inside the FEMALE end.

You need FIPG (Use Toyota black FIPG) for the rectangle opening.

Removal is the toughest part and must have lot of patience. Installation is easy. Install both O-rings and apply a film (as described above). Apply the FIPG and then line all ports but don't get the FIPG to come in contact with the engine side. While keeping a gap between the two parts, try to screw the two bolts slowly. Turn the two bolts one turn each to get everything to seat perfectly!

 

[ItGoesTo11]

Thanks for the clarification. But, I can't use a pre made Fel-Pro gasket for the rectangular connection? It's custom made for this exact application... it seems to me that would be the better option...

 

[ItGoesTo11]

Thanks for the clarification. But, I can't use a pre made Fel-Pro gasket for the rectangular connection? It's custom made for this exact application... it seems to me that would be the better option...

I completed the job. Everything went as expected, it seems the o-ring was very brittle and the original o-ring was re-used when I had a local shop do the timing belt service about 4 years ago. The o-ring was brittle and easily broke upon removal and there was indication of weeping coolant by the crusties around the sides and bottom of the circular fitting.. I used a Lexus OEM from the dealer o-ring ($8) and it fit perfectly.

You were correct about the Form In Place Gasket (FIPG) being necessary, thank you. When they did the timing belt, the local shop made a gasket from some sort of black, cut-it-yourself gasket material (at least that's what it looked like). Then they used some sealant in the groove on the square flange on the water bypass assembly. The gasket was also brittle but did not appear to be leaking.
Before I started the job, I bought a pre-made Fel-Pro gasket from O'Reilly Auto Parts, however it did NOT fit, it was too small and not the right shape. The packaging even has all the correct info but it does not fit whatsoever. While I was there, I remember the suggestion for FIPG and I bought a tube of Permatex Water Pump and Thermostat FIPG sealant just as backup. Well, it was just what I needed.

Everything is back together and I have to wait 24 hours before refilling coolant according to the FIPG instructions. So I'll finalize the job and report results here.