The Bronco and I are not getting along. Thermostat Housing question.

[Tom Hartz]

I am about to start drinking. I had to change the thermostat housing from the stock design to one that is 90 degrees to clear the added Vintage Air compressor.

Here is the stock one I removed.



This is the one I am running now.



I have tried to seal this thing at least 5 times. There is a small seep between the manifold and the thermostat housing.
The manifold is a Edelbrock Performer on a 1969 Ford 302. The thermostat housings fit a Mustang or Explorers with a 5.0.

These are the things I have done.
1. Fel Pro gasket.
2. Stant gasket. (This one fit the best.)
3. Checked the housing on a piece of granite to be sure it is streight.
4. Permatex Ultra Black silicone and letting it dry over night. (A little, not thick.)
5. Permatex water pump / thermostat housing silicone.
6. Put a straight edge on the manifold to check it.
7. Tried a different thermostat that was a little thinner and of better quality to make sure it was not holding the housing out.
8. Clean, Clean, Clean. I have made sure all surfaces are clean. I have even wiped them down with lacquer thinner.
9. I put a small dab of silicone on the thermostat to make sure it did not drop between the gasket and housing.
10. Checked the bolts to make sure they did not bottom out first when tightning.

Before I go and spend $90.00 plus for a billet O-Ringed housing,
does anybody have any ideas that I can try?
If it will work I have no problem spending the money.
I am sick of this.

Is the problem with the earlier manifold and a later housing? They look like they should work together.

Thank you.
Tom

 

[SteveL]

If its a mr gasket cheap one they never seal worth a damn. I found a higher end one from a mustang shop

 

[Tom Hartz]

It is a die cast aluminum one from a local auto parts store. It looks like it is of decent quality. Not billet but not bad.

 

[EricLar80]

Don't waste your time with the oring type thermostat housings; I have read many times that they leak after a year or so. I have this $11 cast iron one from autozone on mine:

What are you torquing your bolts to? It may be that you are over-tightening them and that is causing it to leak. I use the grey gasket material from permatex (http://www.amazon.com/Permatex-22071-6PK-Thermostat-Silicone-Gasket/dp/B001REV86S). Clean both sides up well with a solvent, then just wipe a thin coat all around on the sealing surface and bolt it up to about 15 ft-lbs, or whatever the spec is. You can put it on both sides of the gasket if you want to use a gasket, but it isn't necessary. Wait to fill and start the engine until the next day.

Hope that helps.

Eric

 

[904Bronco]

It is a die cast aluminum one from a local auto parts store. It looks like it is of decent quality. Not billet but not bad.

It looks like the one I bought from O'reilly's... Leaked from the plug threads no matter what I did... Housing was cracked! Took it back and they gave me a new one, Counter guy said buy an aftermarket pipe plug as it will seal better than the one that came with it. Obviously they had delt with this before...

 

[bronconut73]

Got mine from Chuck at BC when I did his VA a/c kit. Never had any problems. Been about three years.

 

[toddz69]

You're going through the exact same issues I had about 3 years ago. I used the Permatex stuff - that held about for about a year - then it leaked again. I used the expen$ive Billet Specialties aluminum o-ringed housing. It's a quality piece but I had galvanic corrosion issues and it leaked after about a year.

I was swapping to an Explorer upper/lower and so swapping my lower intake finally solved my issues. I still think there was a flatness issue on my Mustang intake although I couldn't ever find it.

FRPP now sells a real nice 90 deg. aluminum housing. It's pricey at about $35 but it's probably the best quality one out there. I've found a regular Fel-Pro gasket with a thin coating of the Right Stuff on each side seems to work well. I always let it set up overnight before I add coolant to the system. I've had to replace several stuck thermostats in the past few years and so far everything holds together well.

Todd Z.

 

[Mike.thespike]

are you putting thread sealant on your bolts and never hurts to put a thin layer of high temp sealant on your gasket got the same one on mine never a problem getting it to seal and if your worried about it sealing put it all together and let it set up over night and pressure test it the next day before you fill it with antifreeze

 

[Tom Hartz]

Don't waste your time with the oring type thermostat housings; I have read many times that they leak after a year or so. I have this $11 cast iron one from autozone on mine:

What are you torquing your bolts to? It may be that you are over-tightening them and that is causing it to leak. I use the grey gasket material from permatex (http://www.amazon.com/Permatex-22071-6PK-Thermostat-Silicone-Gasket/dp/B001REV86S). Clean both sides up well with a solvent, then just wipe a thin coat all around on the sealing surface and bolt it up to about 15 ft-lbs, or whatever the spec is. You can put it on both sides of the gasket if you want to use a gasket, but it isn't necessary. Wait to fill and start the engine until the next day.

Hope that helps.

Eric

Oh. I ordered the O-Ring type from Summit in a moment of frustration. Maybe I can cancel the order.

I did get a cast iron one from Autozone however it would not fir with the bypass hose.

At first I did go easy on the bolts, then went tighter when they began to leak.

This last install I did use the Gray water pump Permatex, still leaked.

I just don't get it.

Thanks for the info.
Tom

 

[Tom Hartz]

Got mine from Chuck at BC when I did his VA a/c kit. Never had any problems. Been about three years.

I talked to Chuck about a housing with a 90 degree neck but not about the leaking issue. The Vintage Air kit did come from him. Looks like I should make a phone call.

Thanks...

 

[Tom Hartz]

You're going through the exact same issues I had about 3 years ago. I used the Permatex stuff - that held about for about a year - then it leaked again. I used the expen$ive Billet Specialties aluminum o-ringed housing. It's a quality piece but I had galvanic corrosion issues and it leaked after about a year.

I was swapping to an Explorer upper/lower and so swapping my lower intake finally solved my issues. I still think there was a flatness issue on my Mustang intake although I couldn't ever find it.

FRPP now sells a real nice 90 deg. aluminum housing. It's pricey at about $35 but it's probably the best quality one out there. I've found a regular Fel-Pro gasket with a thin coating of the Right Stuff on each side seems to work well. I always let it set up overnight before I add coolant to the system. I've had to replace several stuck thermostats in the past few years and so far everything holds together well.

Todd Z.

This is so frustrating. I can build a complete Bronco But can't get a thermostat housing to seal. LOL so sad.

FRPP, I will check it out.

Thank you...

 

[Tom Hartz]

are you putting thread sealant on your bolts and never hurts to put a thin layer of high temp sealant on your gasket got the same one on mine never a problem getting it to seal and if your worried about it sealing put it all together and let it set up over night and pressure test it the next day before you fill it with antifreeze

No thread sealant, I did not think the threads went into the water jacket on the Edelbrock manifold. I am running anti seize for the stainless bolts. I did let it set up over night one time. Maybe I should pick up a pressure tester. You can never have to many tools.

Looks like I have to take a look at it again...

 

[72Sport]

The recess in the housing is not deep enough on the die cast thermostat housing. The thermostat keeps the housing from clamping down on the gasket when you tighten down on the bolts. Lay the thermostat in the housing and put a straight edge across the flange on the thermostat and the housing. I made a fixture to hold the die cast one and took it to a machine shop and had the recess deeper for the thermostat. No more leaks.

The cast iron one that I have is very poor quality. The area that the hose clamps down on is not round and has a step in the sealing surface. I think I trashed it.

When all else fails go to the Mercedes dealer and buy a tube of their RTV. A 2 ounce tube will set you back about $20 but it will seal about anything. When it cures it is more like rubber (inner tube) rather than RTV that we are used to.

 

[gladrich]

I recently put a new intake on my 302 and when I put the thermostat housing on I noticed it leaking on the bottom. I took it off and added some gasket seal and reinstalled...still leaked. I did it again...still leaked. Turned out to be the a bad hose clamp on the little "L" shaped hose to the thermostat. It looked like it was leaking at the thermostat but was really dripping from the hose down to the thermostat housing bottom.

 

[Tom Hartz]

The recess in the housing is not deep enough on the die cast thermostat housing. The thermostat keeps the housing from clamping down on the gasket when you tighten down on the bolts. Lay the thermostat in the housing and put a straight edge across the flange on the thermostat and the housing. I made a fixture to hold the die cast one and took it to a machine shop and had the recess deeper for the thermostat. No more leaks.

I was thinking the same thing. The thermostat is about .002 thinner than the depth of the recess so I thought it may work. Thickness is one thing but if it is not flat it could push out one side. The first thermostat was thicker that is why I switched brands. I did order a high dollar housing from Summit and if I am not blown away I will sent is back and machine the one I have.

I will keep you all posted.
Thanks again.
Tom

 

[djhudson05]

I always run a fine flat file across the sealing area on the thermostat housings before I re install them. they may look flat, but when you run the file over them, Imperfections and slight warpage will show. Run the file in different directions until you get an even surface. Be sure to use a fine file so you don't take to much material off. This has worked for me on many engines.

 

[Tom Hartz]

I always run a fine flat file across the sealing area on the thermostat housings before I re install them. they may look flat, but when you run the file over them, Imperfections and slight warpage will show. Run the file in different directions until you get an even surface. Be sure to use a fine file so you don't take to much material off. This has worked for me on many engines.

I did give that a shot. I even used a fine piece of sand paper on a granite slab.
I am thinking the recess for the thermostat is not deep enough. It is so close to being flush with the gasket surface.

I have not given up yet.

 

[DirtDonk]

...I have not given up yet.

Moral support group at it's finest!

Paul

 

[patrickk1]

I am encountering this issue on my 351w now. Edelbrock Performer RPM manifold with 5.0 mustang 90 degree thermostat housing (P/N 814884 ). If you fit the housing to the manifold without the gasket on there, you will see that there is a 1/16 to 1/8 gap on the left side of the housing next to the bypass outlet. This is where mine is leaking from. Was just a drip with original gasket (would have eventually blown out). I found this out when I used RTV instead of a gasket and it was dumping water out.

 

[savage]

I've been going through the same thing since I rebuilt my motor. I have the edlebrock manifold, I know when I was read the instruction for the manifold it say not to use O-ring type thermostat housing. I tried them all mr gasket (junk),cast iron from AutoZone(junk),and bought a 90 degree cast from auto parts store, they all leaked. I though the 90 I bought look like my old one but closer look, the by pass nipple was farther apart. I ended up buying a ford racing housing from summit racing and installed it using gasket and high temp rtv,let sit for 24 hrs. No leak check to day no leak.