Thermostat housing gasket leak

[darthvincor]

Could you guys give me some advice?

I've got coolant leaking past the new gasket:

This is an HJ60 with 2H engine.

-It was not previously leaking.
-I put in new coolant and a new thermostat.
-OEM gasket.
-FSM's 13ft/lbs for the 3 bolts.
-Scraped both surfaces clean with razor and wire brush.
-It's leaking with cold coolant after just topping it up, engine hasn't even run yet.

1st attempt: sealant + new gasket = leak.
2nd attempt: new gasket only = leak.

Very frustrating when you do things by the book with OEM materials and FSM specs, and still it goes wrong.

What's intersting to me, is that it is leaking on all 3 sides, where it is furthest from the bolts. Why is that?

 

[lovetoski]

You've done all the things I would have done, and still a leak, so I can easily emphatise with your frustration.

But, something is different from when it didn't leak. One thing is that you've installed a new thermostat, and new gaskets. Are you sure the thermostat fits right into the lower housing? I could see this causing a leak if it didn't fit right.

Another thing that comes to mind is whether the upper and lower housings have flat surfaces? Maybe use a straightedge to check them.

Can't think of anything else right now. Sorry.

 

[Benjaman]

Strange! I'd(and I do)stone both surface's and go to napa and buy some gasket material, there's some FelPro gasket that really good for water type seals.

 

[zebrabeefj40]

I've had that issue before. In one case I bought new thermostat housing halves from Toyota. In another I machined the surfaces back to flat.

Nick

 

[inkpot]

Did you re-use the same mounting bolts? If they are too long then they may bottom out. Did you torque to 13 foot pounds or 13 inch pounds? I have both torque wrenches. John

 

[darthvincor]

You've done all the things I would have done, and still a leak, so I can easily emphatise with your frustration.

But, something is different from when it didn't leak. One thing is that you've installed a new thermostat, and new gaskets. Are you sure the thermostat fits right into the lower housing? I could see this causing a leak if it didn't fit right.

Another thing that comes to mind is whether the upper and lower housings have flat surfaces? Maybe use a straightedge to check them.

Can't think of anything else right now. Sorry.

Yep, the thermostat fits in the housing nice and snug, and the disc part is at the same level as the housing.

Strange! I'd(and I do)stone both surface's and go to napa and buy some gasket material, there's some FelPro gasket that really good for water type seals.

Looks like I'm gonna need a sealant. Even though the FSM and the Toyota dealer said it would be fine without.

I've had that issue before. In one case I bought new thermostat housing halves from Toyota. In another I machined the surfaces back to flat.

Nick

I'm gonna give it one more try with a sealant (different one), and giving it time to dry this time. (last time I didn't, I just applied the sealant and added the coolant right after)

Did you re-use the same mounting bolts? If they are too long then they may bottom out. Did you torque to 13 foot pounds or 13 inch pounds? I have both torque wrenches. John

Yep, the same mounting bolts. I just double checked, it is 13 ft/lbs (18 nm).
There are holes at the bottom, so they can go all the way through if necessary.


After reading the replies which got me thinking: considering where it is leaking on all 3 sides away from the bolts, I'm guessing maybe one or both housings are bent. And the old sealant was keeping it sealed.
Or it was tightened way too much at some point which bent the housing. (previous mechanics and owner were a bunch of knuckle heads)

Can a sealant make up for a bent housing?
And should I indeed let the sealant dry a bit first before adding coolant?
And how thick should the sealant be: as thick as it comes out the tube, or as thin as possible?

 

[inkpot]

I would use a light film of sealant, like a small bead down the middle of the gasket that will spread out when you tighten it up. If the bolts were ever over-tightened, then there is a chance that either or both sides are a bit uneven. Use a large, new sharpening stone to rub over the surface, and you will be able to ID any high/low spots. Even though these castings are pretty brittle, I have seen them warp/bend. John

 

[darthvincor]

I'll try that, a small bead on the gasket.
But it really seems like there's a new upper and lower housing on the horizon for me. New bolts too to be on the safe side.

(if only I hadn't changed the thermostat...)

 

[Elbert]

I get both sides of the housing very clean....using a wire brush on a grinder for the thermostat housing where they mate together...then using the OEM gasket I use a product called fasktack ...it comes in a small container and you apply it to both surfaces and then use the gasket.

Make sure both metal surfaces are flat and clean of all gasket material prior to reassembly.