Leaking thermostat housing - ideas?

[CPNE]

Replaced gasket and torqued to specs. Still leaks.

Questions:

What order does thermostat and gasket go in? Thermostat or gasket on bottom?

Will using 2 gaskets help, or should I use some kind of gasket making compound?

Other ideas?

Thanks


------------------
Jeff Jesseman
Cheyenne Parts Northeast
Franconia, NH

67 Chevy SWB Fleetside
70 GMC Burb 1/2 ton 2wd
72 Chevy Burb 3/4 ton 4x4

Parts bought and sold

[Relay]

had that problem with mine took it back off and put some seal-a-gasket on it and then put it back on and it didn't leak!

[BubbaGreen]

Is it an aluminum one or the really heavy
cast iron type. The aluminum ones seem to
corrode (sometime badly) and the cast irons
ones can rust...if the flange base looks
pitted or rusted, get a belt sander out
and hold the base of the housing to the
sander for a bit (just dont round it off)
make sure you hold it flat against the belt
This will 'resurface' the housing.
If its not too bad, RTV should work. Also
check out the manifold for pitting. Thats
a bit harder to resurface. Also make sure
the bolts the extend into the manifold have
a coating of RTV, as the coolant can push its
way up thru the threads.
Goodluck!

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71 Chevy C-10 SWB Fleetside WAS:307w/3-on-the-tree NOW:350TBI/700R4/3.73
See it at www.prismnet.com/~grzanich

[jku72]

Thermostat goes in first, then gasket.
These things leak all the time. I use a medium sandpaper, and clean up the surfaces, apply thin sealant to the gasket AND bolt threads(some penetrate into the jacket) and torque evenly. If the leak still persists, time for a die penetrant crack check, or, go the easy way and buy a cheapo NAPA housing.

[superchevy]

I use the new o-ring gaskets instead of the old paper style. No leaks. SC

[Desert Rat]

I dont use the aluminum ones or any cheapy chrome ones i stick with factory cast ones.Id check the mount suface,if pitted bad use a different one.or sand down if possible,and put RTV all around the intake-not excesive drop in thermostat,then gasket,and run a small bead on the housing,and on the bolts,Ive had this problem a few times and corrected it this way.if aluminum maybe its warped?

[69 longhorn]

Felpro has a plastic gasket,that has a rubber seal on both sides. It goes on dry ,& works well with aluminum intakes & water outlets. Its about 1/8" thick.......69

[tom hand]

You never said if you are using stock parts. I have been through this a million times and here is what I have found.

Aftermarket aluminum intake + aftermarket chrome themostat houseing will leak no matter what. There is nothing you can do to stop it. the two different types of metal will even cause other things in the system to rot out.
Give up.

Aftermarket aluminum intake + stock gm themostat housing[Cast iron one.] Work ok. If a quaity gasket is used you can make this work. Some retighting is required over time because of the two different metals.

Stock cast iron intake+ aftermarket chrome thermostat housing. Works OK. The problem with using one with an aluminum intake is the two different metals interact with each other and corrude each out from the inside out. Will work for years if a quaility housing is used.

Stock cast iron intake + newer aluminum GM themostat houseing, works ok if houseing is not warped. Most of these housing are warped so yo need to check. If it warped very much the sanding trick spoke of will not work. Give up and buy a new one. NAPA makes a cast iron replasement that works well, use one.


Stock cast iron intake + stock GM or NAPA cast iron themostat housing. If the parts are in good shape with no warping or pitting this setup can't be beat. It works no matter what.
You can use the cheapest POS gasket with no sealer and put it together with a cresent wrench and it won't leak. GOOD LUCK

------------------
72 GMC Sierra SWB almost finished---- 84 Softail
Olive Branch MS

[whateva]

spend the $6 for the o ring gasket. it works great and is reusable.

[CPNE]

Thanks for all the input. Tom it's stock all the way. Found problem. #1 son put thermostat in upside down as he was rushing in the dark last night. Sigh.

------------------
Jeff Jesseman
Cheyenne Parts Northeast
Franconia, NH

67 Chevy SWB Fleetside
70 GMC Burb 1/2 ton 2wd
72 Chevy Burb 3/4 ton 4x4

Parts bought and sold

[whateva]

you just cant get good help anymore

[71Chev]

Did ya smack him hard Jeff? Geez, some people's kids. LOL

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• 71 Chevy CST Long Fleet 350/350/3.07 leaf rear.

[Desert Rat]

Well he loses the respect i had for him.The son of the almighty CPNE whats the matter with kids nowadays?

[Fast68Chevy]

tub caulk, good for rear axles too, no joke

[COBALT]

Yeah, I used Sillicone II window and door sealant on my rear differential cover. Threw the gasket away...

------------------
'69 3/4 ton C20 2wd w/ 350ci/400THM and a wood bed!
'69 3/4 ton Custom 20 2wd w/ ORIGINAL 350ci/4sp Manual and a wood bed (parts beast).
Seattle, WA.

*See pics of my trucks and project at www.webshots.com!

[69 longhorn]

Well, thats how kids learn.......mine left a fender cover over the smallblock in the ranger,& shut the hood! It was a pretty fire when the old lady took off,but we had it out before the fire truck got there.....minimul damage(tossed the carb,& did some rewire). I should have been watchin him,but was cleanin the 69,we were headed for a local car show. Live & learn........69 longhorn.

[71402BB]

Opps my bad.....

------------------
71 SWB Stepside, was a 250, now is a 402 Big Block with 4 speed and 3.73's

72 LWB 4x4 350 4-speed 3.08's posi wearing army olive drab green (SOLD!)

68 BURB 50TH LOOKALIKE with built 350 4-speed 4.11's and posi

[1-PU70]

Take a pice of glass and put a pice of fine sandpaper on it Then sand the bottom of the houseing. Doesnt mater if the houseing is new or old chrome, chast or whatever you will see it has high and low spots.

[Justin1983]

I'm having same issue. I have all stock items. Leaking from thermostate housing. Used fel-pro gasket still leaked ,Tried black rtv didn't work , then tried fel-pro gasket again still leaks. Using the blue composit gasket. Lightly Sanded everything is smooth...any ideas or part numbers would be great guys thanks

[71CHEVYSHORTBED402]

I don't know about torquing the housing to specs. I believe the specs are 30 ft. lbs., but I quit at 10, 30 would have been way too much. Might be because I installed an aluminum housing and blue Felpro gasket.

The thermostat seats into the groove on the intake and the gasket lays on top. Past years I was told tight, not TIGHT. As in one hand on top of the ratchet and stop. Always worked, no leaks. Unless it's too tight, you should have no leaks with smooth surfaces. If they're not smooth you can apply some sealant.

[Killer Bee]

holy wake up the dead

but since we're here....

verify the leak is coming from that joint and not running down from the hose end or hole from the clamp or ??

check the bolt grip length is correct and not bottoming out preventing clamping housing down..

inspect the housing for erosion and porosities, especially on cheap chrome plated ones..

other than that, if standard gasket or rtv with bolts snug tight leaks, good chance of either;

• intake and or housing not flat
• intake and or housing cracked

use a smooth file or stone gently to check for high spots on the intake, the housing can be checked on a flat surface with fine grit paper..

if nothing noticeable there, wire wheel or blast paint and rust away and inspect for cracks..

die penetrant may be helpful for detecting cracks if you have a kit handy..

please keep us posted what you find and good luck!

[71CHEVYSHORTBED402]

Ha ha!, didn't know this was 17 years old.

[Justin1983]

Could I use k seal to fix this

[Justin1983]

All they have for sale are aluminum thermostat housing ...thoughts

[Steeveedee]

Verify that your manifold at the thermostat mount is flat, verify that your thermostat housing is flat. If not, make them flat. Then put a coat of #1 Permatex on both sides of the gasket, bolt it down and let it sit overnight to dry. This is assuming, as has been mentioned, that the radiator hose/housing mating surface isn't leaking. If your bolts penetrate the water jacket, seal those threads with #1 Permatex, too. Your leak will be history.