Thermostat housing is leaking - The 1947 - Present Chevrolet & GMC Truck Message Board Network

**COBALT** · 06-12-2002, 01:54 PM

I'm using the regular gaskets from NAPA, with some of that gray thermostat housing sealer that comes in a tube you get at the parts store. The gasket itself has a sticky side that goes to the housing. The sealer goes on the manifold.

I've taken it off, and resealed it twice. The stupid thing keeps leaking. Of course once it begins to leak the entire seal goes and then it leaks worse. The manifold and the housing are both clean, and I used 400 grit wet/dry sand paper to smooth them both off and take out the high spots so they're both flat. I'm also torquing both bolts to 25 ft-lbs. Since I had to rethread the short side I don't want to torque it any more.

I'm thinking about getting a new housing and a gasket from Mr. Gasket instead of NAPA. Anyone else have any suggestions? I'm getting tired of doing this same job over and over again.

tom hand · 06-12-2002, 02:02 PM

Your thermostat housing is probably warped from being over tighted. NAPA sells a cast iron replacement that is much better than the pot metal GM ones. I would not put a chrome thermostat on anything, because I have lost count of the leaks I have seen caused by them.

**COBALT** · 06-12-2002, 02:05 PM

Hmmm....well it sure doesn't look warped. I have a plate that's perfectly flat, and it laid right on it without any wiggle. Maybe it's only going out of shape when the bolts are tightened...

I'll check out the one that NAPA has and see if I can get this fixed.

Anyone else know what type of sealer would work on the underside of the gasket to the manifold itself? Anyone know of better gaskets other than the one I'm trying to use? I have 1 left.

**oldiron** · 06-12-2002, 02:34 PM

Felpro also makes a reusable gasket with an oring in it the Felpro #is 35562T. I don't think NAPA cares Felpro so try Seattle Auto Dist. 206-323-6700.

Blue68 · 06-12-2002, 03:24 PM

I've used the chrome housings for years with no leaks. Of course, they have the o-ring and are on aluminum intakes.

Reusable and no leaks. A good combo in my book.

**COBALT** · 06-12-2002, 03:28 PM

Well, I've got to stick with this manifold for a while (327 cast iron from a '69 Chevelle, Camero, Firebird, or...).

I'll check out the Seattle outfit OldIron suggested. I got a new housing lined up at NAPA...

zardiw · 06-12-2002, 04:41 PM

There's some GREAT stuff called (appropriately) 'The Right Stuff'. Just use it instead of the gasket. It's supposed to be pretty good. When you buy it make sure it comes out right there in the parts store, since sometimes it hardens up in the can. Also, you might try the FelPro Blue. Coat both sides of the gasket, and the thermostat housing and the intake manifold. Don't overtorque the bolts either. Also, make sure both the housing and the manifold area are free of oil and DRY by wiping both with acetone/paint thinner/whatever. Starter fluid is great for cleaning parts squeaky clean as well. Don't smoke while you're using it...he he..........z

68 Suburban · 06-12-2002, 04:56 PM

the o-ring gasket is the way to go.

Stepside · 06-12-2002, 06:01 PM

Draw file the thermostat housing and the intake mounting surface. Those gaskets with the sticky are good sticking on the inside of your trash can. Get the o-ring gasket as mentioned above, or a regular thick gasket and use sealer on both sides. Do not over torque. This will bow the housing in the middle... back to square 1.
Sepside

**COBALT** · 06-12-2002, 07:42 PM

Good points here.

I called the Seattle outfit for the O-ring and they have one ($9- seesh!). I'm also getting a thermostat housing from NAPA (I'm 2-for-2).

Basically, stay away from those regular NAPA gaskets. They're only sticky on one side, and I noticed that when you use sealant on that sticky side the heat from the coolant actually causes the sticky layer to come off the gasket! That's about as usefull as T!ts on a Boar!!! lol

Ok, so I'll see if I can get this fixed right either tonight or Friday evening. Thanks guys. Keep on truckin'.

*Zkast* · 06-12-2002, 08:14 PM

save yourself some time and trouble, get gaskets without the fancy sticky tape on them... they only cause trouble. Also, dont waste time on the cheap chrome housings. Problem with those things are the chroming process and type of metal used. Chances are the cheap chrome housing is already warped when you open the package

I like the suggestion of "Right Stuff". Although we dont use that in every application (only specific area's) its great stuff. I mainly use it on Intake manifold end rails, differential covers and other places not related to our trucks... I believe its about 19.00 per 8oz's though!

My tried and trued method?
Cast iron housing, gorilla snot(weatherstip adhesive) and black RTV. Apply a thin bead of the adhesive on the intake so everything stays put (themostat and gasket) then apply a small bead of RTV on the housing, torque the housing and your all set.

Never hurts to put some antiseize compound on the bolts if you have a aluminum intake!

**COBALT** · 06-13-2002, 12:39 PM

Well, I got a cast-iron housing from NAPA. If this boat anchor doesn't seal then I give up!

Do you guys recomend the High-temp RTV with copper?

72LNGHRN · 06-13-2002, 12:48 PM

Ive tried just about everything on mine and it still leaks a little.

have tried oring seals and silicone no luck.

06-12-2002, 01:54 PM	#1
COBALT Senior Member Join Date: Sep 2001 Location: Seattle, WA, USA Posts: 5,817	Thermostat housing is leaking I'm using the regular gaskets from NAPA, with some of that gray thermostat housing sealer that comes in a tube you get at the parts store. The gasket itself has a sticky side that goes to the housing. The sealer goes on the manifold. I've taken it off, and resealed it twice. The stupid thing keeps leaking. Of course once it begins to leak the entire seal goes and then it leaks worse. The manifold and the housing are both clean, and I used 400 grit wet/dry sand paper to smooth them both off and take out the high spots so they're both flat. I'm also torquing both bolts to 25 ft-lbs. Since I had to rethread the short side I don't want to torque it any more. I'm thinking about getting a new housing and a gasket from Mr. Gasket instead of NAPA. Anyone else have any suggestions? I'm getting tired of doing this same job over and over again. __________________ '69 3/4 ton C20 2wd-350ci/TH400 '69 3/4 ton Custom 20 2wd-350ci/4sp Manual '99 2wd 5.7 Chevy Tahoe Seattle, WA.

06-12-2002, 02:02 PM	#2
tom hand CCRider Join Date: Feb 2000 Location: Olive Branch,MS,USA Posts: 2,232	Your thermostat housing is probably warped from being over tighted. NAPA sells a cast iron replacement that is much better than the pot metal GM ones. I would not put a chrome thermostat on anything, because I have lost count of the leaks I have seen caused by them. __________________ 72 GMC Sierra SWB almost finished---- 84 Softail Olive Branch MS

06-12-2002, 02:05 PM	#3
COBALT Senior Member Join Date: Sep 2001 Location: Seattle, WA, USA Posts: 5,817	Hmmm....well it sure doesn't look warped. I have a plate that's perfectly flat, and it laid right on it without any wiggle. Maybe it's only going out of shape when the bolts are tightened... I'll check out the one that NAPA has and see if I can get this fixed. Anyone else know what type of sealer would work on the underside of the gasket to the manifold itself? Anyone know of better gaskets other than the one I'm trying to use? I have 1 left. __________________ '69 3/4 ton C20 2wd-350ci/TH400 '69 3/4 ton Custom 20 2wd-350ci/4sp Manual '99 2wd 5.7 Chevy Tahoe Seattle, WA.

06-12-2002, 02:34 PM	#4
oldiron Designated Grumpy Old Man Join Date: Oct 2001 Location: arlington, washington usa Posts: 3,095	Felpro also makes a reusable gasket with an oring in it the Felpro #is 35562T. I don't think NAPA cares Felpro so try Seattle Auto Dist. 206-323-6700. __________________ Never let the truth get in the way of a good story 71 Chev 1/2 ton 4X4 LWB Fleetside SOLD http://67-72chevytrucks.com/vboard/s...d.php?t=361222 http://www.youtube.com/watch?v=1LgREwtDfaA 68 Chev 1 ton flat bed http://www.youtube.com/watch?v=0bO8szzlD4A 56 Chev Handyman Wagon http://www.youtube.com/watch?v=9y-6ddpBTkM http://www.youtube.com/watch?v=lbLzZ7zY8wA 56 Chev Belair http://67-72chevytrucks.com/vboard/s...d.php?t=410667 http://www.youtube.com/watch?v=xoW0Ei7ZNIg Last edited by oldiron; 06-12-2002 at 02:39 PM.

06-12-2002, 03:24 PM	#5
Blue68 Registered User Join Date: Apr 2000 Location: Frisco, Tx, USA Posts: 606	I've used the chrome housings for years with no leaks. Of course, they have the o-ring and are on aluminum intakes. Reusable and no leaks. A good combo in my book. __________________ http://home.comcast.net/~r.landrum/w...tos.html-.html '68 C-10 LWB, '98 Z-71 350 w/accessories (Serpentine), Edelbrock Performer, Edelbrock 1405 (600cfm) carb, GM HEI, CompCam Extreme 4x4 roller cam, Thorley Headers, Carter Electric Fuel Pump, Vintage Air, 700r4, 3.73, disc brakes and power steering upgrades.

06-12-2002, 03:28 PM	#6
COBALT Senior Member Join Date: Sep 2001 Location: Seattle, WA, USA Posts: 5,817	Well, I've got to stick with this manifold for a while (327 cast iron from a '69 Chevelle, Camero, Firebird, or...). I'll check out the Seattle outfit OldIron suggested. I got a new housing lined up at NAPA... __________________ '69 3/4 ton C20 2wd-350ci/TH400 '69 3/4 ton Custom 20 2wd-350ci/4sp Manual '99 2wd 5.7 Chevy Tahoe Seattle, WA.

06-12-2002, 04:41 PM	#7
zardiw Faster horses, yw, ow, mm Join Date: Apr 2002 Posts: 184	There's some GREAT stuff called (appropriately) 'The Right Stuff'. Just use it instead of the gasket. It's supposed to be pretty good. When you buy it make sure it comes out right there in the parts store, since sometimes it hardens up in the can. Also, you might try the FelPro Blue. Coat both sides of the gasket, and the thermostat housing and the intake manifold. Don't overtorque the bolts either. Also, make sure both the housing and the manifold area are free of oil and DRY by wiping both with acetone/paint thinner/whatever. Starter fluid is great for cleaning parts squeaky clean as well. Don't smoke while you're using it...he he..........z __________________ '73 C20, 383, 3500 leaf springs, 38.5 Mickey Thompson Baja Claws (More ground clearance than an H2 Hummer), Performance Distributor (Tits!!) w/Clear cap (awesome at night), Edelbrock intake+IAS shocks, Tri Y headers, Dr. Gas Xover(for that NASCAR sound).

06-12-2002, 04:56 PM	#8
68 Suburban Registered User Join Date: Oct 2000 Location: From Chicago, Live in Phoenix, AZ Posts: 6,802	the o-ring gasket is the way to go. __________________ Just sitting here contemplating contemplation.

06-12-2002, 06:01 PM	#9
Stepside Gasser Join Date: May 2000 Location: Thomasville,NC USA Posts: 456	Draw file the thermostat housing and the intake mounting surface. Those gaskets with the sticky are good sticking on the inside of your trash can. Get the o-ring gasket as mentioned above, or a regular thick gasket and use sealer on both sides. Do not over torque. This will bow the housing in the middle... back to square 1. Sepside __________________ :thud 70 sstep tubbed, Muncie, double hump, snowflake,

06-12-2002, 07:42 PM	#10
COBALT Senior Member Join Date: Sep 2001 Location: Seattle, WA, USA Posts: 5,817	Good points here. I called the Seattle outfit for the O-ring and they have one ($9- seesh!). I'm also getting a thermostat housing from NAPA (I'm 2-for-2). Basically, stay away from those regular NAPA gaskets. They're only sticky on one side, and I noticed that when you use sealant on that sticky side the heat from the coolant actually causes the sticky layer to come off the gasket! That's about as usefull as T!ts on a Boar!!! lol Ok, so I'll see if I can get this fixed right either tonight or Friday evening. Thanks guys. Keep on truckin'. __________________ '69 3/4 ton C20 2wd-350ci/TH400 '69 3/4 ton Custom 20 2wd-350ci/4sp Manual '99 2wd 5.7 Chevy Tahoe Seattle, WA.

06-12-2002, 08:14 PM	#11
Zkast Account Suspended Join Date: May 2002 Location: Olathe, Kansas Posts: 929	save yourself some time and trouble, get gaskets without the fancy sticky tape on them... they only cause trouble. Also, dont waste time on the cheap chrome housings. Problem with those things are the chroming process and type of metal used. Chances are the cheap chrome housing is already warped when you open the package I like the suggestion of "Right Stuff". Although we dont use that in every application (only specific area's) its great stuff. I mainly use it on Intake manifold end rails, differential covers and other places not related to our trucks... I believe its about 19.00 per 8oz's though! My tried and trued method? Cast iron housing, gorilla snot(weatherstip adhesive) and black RTV. Apply a thin bead of the adhesive on the intake so everything stays put (themostat and gasket) then apply a small bead of RTV on the housing, torque the housing and your all set. Never hurts to put some antiseize compound on the bolts if you have a aluminum intake!

06-13-2002, 12:39 PM	#12
COBALT Senior Member Join Date: Sep 2001 Location: Seattle, WA, USA Posts: 5,817	Well, I got a cast-iron housing from NAPA. If this boat anchor doesn't seal then I give up! Do you guys recomend the High-temp RTV with copper? __________________ '69 3/4 ton C20 2wd-350ci/TH400 '69 3/4 ton Custom 20 2wd-350ci/4sp Manual '99 2wd 5.7 Chevy Tahoe Seattle, WA.

06-13-2002, 12:48 PM	#13
72LNGHRN Registered User Join Date: Mar 2000 Location: Tucson AZ USA Posts: 241	Ive tried just about everything on mine and it still leaks a little. have tried oring seals and silicone no luck. __________________ 72LONGHORN 350 CI TURBO 400 A/C P/S P/B HEAVY DUTY SPRINGS ALL THE BELLS AND WHISTLES. TUCSON,AZ. 2005 4X4 DODGE RAM 1500 "HEMI"LARAMIE 1961 OLDS DYNAMIC 88 394 4BBL UNDER CONST.



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