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GM 350 thermostat housing gasket leaking #5428515 05/13/20 06:55 PM
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motor_oil_madman Offline OP
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Okay so I may have started a thread on this already, but I can't find it. Anyways, here are some updates on my thermostat housing gasket that keeps leaking. I verified that the housing is a steel housing and not aluminum, it is straight and not warped. This particular intake the housing bolt holes go all the way through to the coolant, so we found a special gasket that seals the bolt holes also, and it leaked even worse. I guess the next fix is just go back to the regular gasket and use rtv on it and around the bolt holes. We just have to drain the coolant in the block some to do that I guess to get it below the intake.

https://www.amazon.com/Mr-Gasket-738G-Water-Outlet/dp/B000CMF20O/ref=sr_1_10?crid=SUGC16JLVC5B&dchild=1&keywords=thermostat+housing+gasket+small+block+chevy&qid=1589413975&sprefix=thermostat+housing+gasket+%2Caps%2C175&sr=8-10

This is the expensive reusable gasket that leaked like a sive.


2007.5 dodge cummins 6.7 liter. Chevron Delo400 15w40. 7000 mile or 250-300hr intervals.

Re: GM 350 thermostat housing gasket leaking [Re: motor_oil_madman] #5428516 05/13/20 06:59 PM
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motor_oil_madman Offline OP
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After coating the gasket and bolts with rtv (probably should have done it in the first place), i'm out of ideas if that doesn't work.

Last edited by motor_oil_madman; 05/13/20 06:59 PM.

2007.5 dodge cummins 6.7 liter. Chevron Delo400 15w40. 7000 mile or 250-300hr intervals.

Re: GM 350 thermostat housing gasket leaking [Re: motor_oil_madman] #5428529 05/13/20 07:20 PM
Joined: Apr 2018
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Imp4 Offline
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Originally Posted by motor_oil_madman
Okay so I may have started a thread on this already, but I can't find it.

Click on your user name in the upper right.
Then click on your post count in the upper right.
Then select "Threads Created" in the upper right.

You'll find a nice list of every thread you've started.
Then you don't need multiple threads on the same topic.

BTW, you can see other member's post count and thread creation count this way too.
Motor_Oil_Madman has created 17 pages worth of new threads at 50 threads created per page, which seems like a lot...

Re: GM 350 thermostat housing gasket leaking [Re: motor_oil_madman] #5428544 05/13/20 07:36 PM
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motor_oil_madman Offline OP
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Well I have been on here since 2009...……


2007.5 dodge cummins 6.7 liter. Chevron Delo400 15w40. 7000 mile or 250-300hr intervals.

Re: GM 350 thermostat housing gasket leaking [Re: Imp4] #5428553 05/13/20 07:47 PM
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motor_oil_madman Offline OP
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Originally Posted by Imp4
Originally Posted by motor_oil_madman
Okay so I may have started a thread on this already, but I can't find it.

Click on your user name in the upper right.
Then click on your post count in the upper right.
Then select "Threads Created" in the upper right.

You'll find a nice list of every thread you've started.
Then you don't need multiple threads on the same topic.

BTW, you can see other member's post count and thread creation count this way too.
Motor_Oil_Madman has created 17 pages worth of new threads at 50 threads created per page, which seems like a lot...



I'm looking for solutions to my issue here, not worrying about my post count. Thank you for the help though.


2007.5 dodge cummins 6.7 liter. Chevron Delo400 15w40. 7000 mile or 250-300hr intervals.

Re: GM 350 thermostat housing gasket leaking [Re: motor_oil_madman] #5428566 05/13/20 08:09 PM
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Chris142 Offline
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Tale it apart. Clean the bolts,holes and both mating surfaces. Put a layer of mega grey or ultra black on the housing
No gasket.

Put teflon thread sealer on the bolt threads.

Put it together and run the bolts down with a socket and extension only.

Wait 30 minutes then snug the bolts down. Walk away for a few hours then refill the system.


02 Wrangler Napa high milage 10w40
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Re: GM 350 thermostat housing gasket leaking [Re: motor_oil_madman] #5428567 05/13/20 08:09 PM
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mk378 Offline
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Multiple threads about the same problem is really bad ettiquitte. Find the old thread and post new information to it. That way the readers have the back-story of what was done so far.

Re: GM 350 thermostat housing gasket leaking [Re: motor_oil_madman] #5428569 05/13/20 08:10 PM
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Timmastertech Offline
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Dont use RTV on the bolts. On a 350, make sure both sides are flat and clean, manifold and housing. Apply teflon thread sealant to the bolts and use high tack gasket sealant on both sides of a felpro paper gasket.

Re: GM 350 thermostat housing gasket leaking [Re: mk378] #5428578 05/13/20 08:25 PM
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Imp4 Offline
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Originally Posted by mk378
Multiple threads about the same problem is really bad ettiquitte. Find the old thread and post new information to it. That way the readers have the back-story of what was done so far.

approved

Re: GM 350 thermostat housing gasket leaking [Re: Timmastertech] #5428593 05/13/20 08:41 PM
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motor_oil_madman Offline OP
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Originally Posted by Timmastertech
Dont use RTV on the bolts. On a 350, make sure both sides are flat and clean, manifold and housing. Apply teflon thread sealant to the bolts and use high tack gasket sealant on both sides of a felpro paper gasket.



Like liquid Teflon thread sealant or can I use Teflon tape?


2007.5 dodge cummins 6.7 liter. Chevron Delo400 15w40. 7000 mile or 250-300hr intervals.

Re: GM 350 thermostat housing gasket leaking [Re: motor_oil_madman] #5428621 05/13/20 09:23 PM
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Randy_R Offline
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Permatex high temp sealant. High temp. I coat both sides of the gasket with hylomar.


2018 Mazda CX-5 9000 miles Zepro advanced moly 0W-20 Mazda filter
08 Saturn VUE AWD 3.5 V6 70,000 miles Schaeffer 9000 5W30 Wix 51522XP
65 Pontiac Tempest 355 Chevy Schaeffer Racing 10W30 Wix 51061
Re: GM 350 thermostat housing gasket leaking [Re: motor_oil_madman] #5428629 05/13/20 09:37 PM
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motor_oil_madman Offline OP
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I was talking about for the bolt threads.


2007.5 dodge cummins 6.7 liter. Chevron Delo400 15w40. 7000 mile or 250-300hr intervals.

Re: GM 350 thermostat housing gasket leaking [Re: motor_oil_madman] #5428646 05/13/20 09:55 PM
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jhellwig Offline
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If it is the style of thermostat that is supposed to have the rubber gasket around the flange of the thermostat make sure that it is there. Some parts places will sell you a paper gasket that will leak instead of the right gasket.


Sparks fly from my fingers.

1995 Chevy K2500 Suburban lt 5.7
2014 Toyota Sienna
1983 Chevy K5 350
Re: GM 350 thermostat housing gasket leaking [Re: jhellwig] #5428732 05/14/20 04:02 AM
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motor_oil_madman Offline OP
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Originally Posted by jhellwig
If it is the style of thermostat that is supposed to have the rubber gasket around the flange of the thermostat make sure that it is there. Some parts places will sell you a paper gasket that will leak instead of the right gasket.


How do you know if it needs a gasket around the outside of the thermostat?


2007.5 dodge cummins 6.7 liter. Chevron Delo400 15w40. 7000 mile or 250-300hr intervals.

Re: GM 350 thermostat housing gasket leaking [Re: motor_oil_madman] #5428788 05/14/20 07:27 AM
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Randy_R Offline
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Permatex high temp thread sealant. I left out the word thread.


2018 Mazda CX-5 9000 miles Zepro advanced moly 0W-20 Mazda filter
08 Saturn VUE AWD 3.5 V6 70,000 miles Schaeffer 9000 5W30 Wix 51522XP
65 Pontiac Tempest 355 Chevy Schaeffer Racing 10W30 Wix 51061
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