Thermostat Will NOT Seal PITA

Blown331LX · Mar 11, 2008

I have tried several different methods, everyone I know of and the T - stat elbow continues to leak at the matting surface....Its the stock housing on a Edlebrock Vic JR (carb setup). I have tried lots of RTV, dimpiling the intake and t - stat housing with a punch, 3 different gaskets.... I have never had this problem, there are no cracks in either, the only thing I can think of is the aftermarket intake doesn't like the ridge on the stock housing.

SVT32VDOHC · Mar 11, 2008

That is hell!!

I was hoping to read that you had a FMS t-state housing. THOSE ARE JUNK!! They have leaked on many members on this board, and some of my friends!

I vote for the intake surface being bad. Did the T-stat housing leak on a stock/previous intake??

rd · Mar 11, 2008

Odd question, but there are different tstat housings. Does yours have the recess for the tstat to sit in? You are not using rtv and a gasket, as that usually never seals?

If that's ok, you may try taking a flat file to the mating surface, of the intake.

I usually end up cleaning the housing mating surface and hose clamping surface on the wire wheel on my benchgrinder. Not scientific, but seems to work.

I had an Edelbrock on a 351w and it sealed fine.

Also, make sure you don't have overlapping holes, or, or corrosion paths between bolt holes and the water paths or such. You can level holes or warpage with epoxy if needed.

And sometimes a plain old paper gasket with Permatex No 2 works better than anything.

Blown331LX · Mar 11, 2008

Very good questions, the engine came from a wrecked donor car so I dont know about that but it appeard dry as a bone when stock intake was pulled about a year ago. The intake is used but like new and clean as a whistle. There is no corrosion in the holes or ports. I previously tried the paper gasket and Perematex RTV and that leaked the worst. Regular RTV only did best, but still leaked enough I had to keep a shop rag on the timing cover under the intake. I have not tried to file down the T - STat in fear of making the matting surface even more uneven. My friend has another stock housing that Im going to try. You WOULD THINK that even if the matting surface wasnt dead nuts flat the RTV would make up for the difference, hell thats why it was created. I have never had this problem, then again I never have had a stock fuel injected T - STat on a carb aftermarket intake. If the other one wont seal, and griding on this one still wont work, I might just TIG weld that BASTARD on there. Im so ****ing tired of pulling it off, cleaning it and having it still leaking and pouring coolant all over my freshly painted rebuilt block. AAAARRRRGGGGGGGHHHHH.

fastford91 · Mar 11, 2008

got the thermostat in the right way and not backwards?

Blown331LX · Mar 11, 2008

LMAO.... (#1) Ive been a ASE and certified Ford tech for 5 years and not ur run of the mill back yard do it yourselfer (#2) Its almost impossible to do on most all vehicles due to the difference in length between sides and the lack of depth on the housing but thats anyway.

85_SS_302_Coupe · Mar 11, 2008

I actually had the same problem when i was running a Victor Jr. I thought it was just me. Believe it or not one night i was screwing with it and it was late and the parts stores were closed...i had ruined the only gasket i had so i traced and cut out a gasket from a Mt. Dew 12 pack carton and used that as the gasket....didn't leak a drop

Blown331LX · Mar 11, 2008

85_SS_302_Coupe said:
I actually had the same problem when i was running a Victor Jr. I thought it was just me. Believe it or not one night i was screwing with it and it was late and the parts stores were closed...i had ruined the only gasket i had so i traced and cut out a gasket from a Mt. Dew 12 pack carton and used that as the gasket....didn't leak a drop

Mine is Carbed, hell Im almost tempted to do that....lol...Im so frustrated I just want to drive my car and this stupid **** is stoping me. I can build an engine, rebuild automatics, tune whatever, fabricate almost anything, wire about anything, BUT I CANT FIX A ******* LEAKING THERMOSTAT

Fett · Mar 11, 2008

You should use a flat edge and make sure your intake is true, same with the housing.

If everything is good to go, you might want to use a THIN layer of a good sealer on both sides of the gasket. I always use diesel gray silicone (MC P# ta-31). I place the gasket intake side down on a piece of paper and use my finger to spread a thin layer of silicone on the gasket, then place it on the housing (with thermostat in place) then do the same thing to the intake side of the gasket while it is mounted on the housing.

I have never had a leak. I recommend getting a tube of that silicone at your local Ford dealer, just ask for TA-31. I use that on just about everything....I actually...and I'm not making this up...I use it to fix a hole in a manual transmission. I had a 2" hole in the case due to a broken bolt being thrown out. I used a piece of tin I cut to cover the hole and smothered it with diesel silicone. 5 years later it doesn't even seep any fluid.

85_SS_302_Coupe · Mar 11, 2008

I guess you could always JB Weld it....that should keep it from leaking

I wouldn't recommend the cardboard thing, but in a pinch it does work. My buddy told me to do it and i called him stupid, but he actually did the whole upper section of a Suzuki Samurai engine with cardboard because he couldn't find gaskets...he did the intake and everything and it all held up fine.

One mistake i always make is trying to run the car too soon after doing the gasket.

iapexl8r · Mar 11, 2008

Usually What ends up causing the tstat housing to leak is over torquing of the bolts that hold it on. This causes the t stat housing to warp. As FETT said check this with a straight edge. you can fix a slightly warped t stat housing by placing sand paper 220 grit on a flat surface and working the t stat housing across it in all 4 directions. it definatly sounds like there is an issue of some sort good luck
Chris

Blown331LX · Mar 11, 2008

I never would use cardboard, I did on my truck on the trail one day but only in emergency situations. This evening I picked up a different housing and resealed it tonight. Im going to pressure test tomarrow before I reinstall everything else and if good Im gonna run it for a while and see what happens. I am very suspect of the housing even though I couldn't see anything wrong. I will update everyone tomarrow. One last question, how the hell do I post pictures in a thread like this?

skunk21 · Mar 11, 2008

this may sound dumb but I have had the thermostat fall out of the darn resess in housing has I was putting it in w/o knowing it. the lip or flange of t-stat slipped out and was between the intake and the housing on the underside where I couldn't see, bolted it up and she pissed right out of the bottom. I couldn't figure it out at first but I used some of the sticky yellow gasket glue on the t-stat let it tack up at stuck it to the housing to hold it in. maybe it could be the same thing I don't now but I thought I would share my stupid PIA T-Stat story .

Aryan15 · Mar 12, 2008

What method are you using to hold the t-stat while you install the housing?

mustang302fan · Mar 12, 2008

i had a problem with my fms thermostat housing leaking as-well...solution, buy the billet specialties o-ringed one from summit. it is expensive at $100 but i haven't had a problem since....o-ring is way better than the gasket.

shewitt · Mar 12, 2008

I had the same problem as greensvt 21 I wanted to shoot the thing.

mavmavv · Mar 12, 2008

I had to use an assload of RTV on mine, I finally got it to seal after try #3.

Darkwriter77 · Mar 12, 2008

I've had a similar problem with mine in the past. Previously, after cleaning the mating surfaces thoroughly and drying them, I would smear some RTV on the housing surface and press the gasket onto that, and then let it cure for awhile. This would (usually) hold the T-stat in place while placing it up against the intake and threading in your bolts.

However, a better, quicker, and faster method involves simply putting a drop of Super Glue on either end of the T-stat housing's recess and setting the T-stat in there, so it'll stay put. As mentioned above, the T-stat has a tendency to slip out of place sometimes while you're wiggling things into position to put in your bolts, and that lip of the T-stat can get caught in between the mating surfaces, thus causing a leak. It's happened to me, before.

Also, making sure that both the intake and housing surfaces are truly flat is a good idea, as well.

My problem with the Pervertible, lately, has been that the T-stat housing bolts somehow keep losing torque and loosening themselves, and I keep having to re-tighten them to stop the thing from leaking. I'm gonna have to do it a third time this weekend.

Fox8950 · Mar 12, 2008

Not saying you did or anything but with stock T-stat housing it IS possible to put them in backwards, your definitely right though most you can't. Last 2 stangs I've bought when I tore down the motor T-stat was in backwards, must be something in the water around here.

mastrdrver · Mar 12, 2008

I know my 5.0 is EFI, but I took some 80 grit sandpaper and took it to the surface of the intake and housing. Put too much RTV sealant on the housing and bolted her up. No more problems. This was after I tried just using a gasket and that not working. When I did it I was going to make sure this was the last time I would going to do it.

Thermostat Will NOT Seal PITA

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