Underwater Thread Sealant

[Greg C.]

I've seen a few drops of antifreeze in the low area left of the t-stat housing. Lately, it has become a lot, with tell tale droplets around the
t-stat housing bolt. I used a teflon pipe dope sealant on the threads, however that was probably designed for tapered pipe threads, not straight bolt
threads, and likely won't hold pressure.

Here's the question. Or questions. What thread sealant do the wise folks recommend on these t-stat housing bolts? Second question, am I going to have
to partially drain the radiator, or can I pull the bolt, hold a finger on the hole, dope the bolt, and reinsert?
--
Greg Crawford
KM4ZCR
Knoxville, TN

"Ruby Sue"
1977 Royale
Rear Bath
403 Engine
American Eagle Wheels
Early Version Alex Sirum Quad bags

 

[Matt Colie]

> I've seen a few drops of antifreeze in the low area left of the t-stat housing. Lately, it has become a lot, with tell tale droplets around the
> t-stat housing bolt. I used a teflon pipe dope sealant on the threads, however that was probably designed for tapered pipe threads, not straight
> bolt threads, and likely won't hold pressure.
>
> Here's the question. Or questions. What thread sealant do the wise folks recommend on these t-stat housing bolts? Second question, am I going to
> have to partially drain the radiator, or can I pull the bolt, hold a finger on the hole, dope the bolt, and reinsert?

Greg,

It is also possible that the T'stat housing has corroded through. If that is the case, you will have a real hard time sealing the fastener.

You will have to drain the coolant to a level that it doesn't flow out the hole when the screw is removed.

The sealant that will work is Loctite 565 or 567, there is a difference, but it won't matter to you. It is not cheap, and you may have a hard time
procuring this stuff because Henkle took them over and they are very anti-consumer. It will be worth your while to find it. Grainger and McMaster
Carr both have it, and so might Amazon.

Matt
--
Matt & Mary Colie - Chaumière -'73 Glacier 23 - Members GMCMI, GMCGL, GMCES
Electronically Controlled Quiet Engine Cooling Fan with OE Rear Drum Brakes with Applied Control Arms
SE Michigan - Near DTW - Twixt A2 and Detroit

 

[Greg C.]

Thanks Matt. The housing is new, and the aluminum intake, while pretty old, is not corroded. Looks like I'll be draining some antifreeze.

I'll try to round up one of those products.

Thanks again.
--
Greg Crawford
KM4ZCR
Knoxville, TN

"Ruby Sue"
1977 Royale
Rear Bath
403 Engine
American Eagle Wheels
Early Version Alex Sirum Quad bags

 

[Greg C.]

Matt:

I just got the Loctite 567 in from Amazon. $9+ so for a little bitty (less than 1/2 ounce) tube. I'll drain the radiator down a gallon or so, remove
the bolts from the t-stat housing and try to dry the threads in the intake before applying the sealant to the bolts and reinstalling. Going to be
raining here, so it might be a day or so.
--
Greg Crawford
KM4ZCR
Knoxville, TN

"Ruby Sue"
1977 Royale
Rear Bath
403 Engine
American Eagle Wheels
Early Version Alex Sirum Quad bags

 

[Greg C.]

Matt:

Today I drained about a gallon and a half out of the radiator, then one at a time, I removed the t-stat housing bolts. I cleaned the Permatex thread
sealer off of them with a wire brush, then cleaned them with acetone. I took a longer bolt and ran it down into the threads while squirting a little
acetone on the bolt, and worked it back and forth until it came out pretty clean. Applied the Loctite thread sealer on one bolt, installed and
tightened slightly, then repeated the process on the other side. I never took both bolts out at the same time so that I would not disturb the gasket.
Torqued to spec, and let it set for a while. Refilled the radiator, and after a little bit cranked the engine and let it run until it reached
operating temperature. Turned it off and checked it about an hour later, everything was dry. It had been dry after I shut off the engine previously,
only to come back an hour later and find antifreeze puddled in the intake. Anyway, I think, hope, that it is done.

Chuck Boyd straightened me out once when I told him I had fixed something on the coach. He said "No, you didn't fix it. You repaired it. Fixed implies
that it is permanent, and nothing is ever permanent with a GMC!" I've come to embrace that view.
--
Greg Crawford
KM4ZCR
Knoxville, TN

"Ruby Sue"
1977 Royale
Rear Bath
403 Engine
American Eagle Wheels
Early Version Alex Sirum Quad bags

 

[Matt Colie]

Greg,
Good to hear, I have has more than a little success with that stuff.

Listen to Chuck, he has been around the block a few times.....

Matt
--
Matt & Mary Colie - Chaumière -'73 Glacier 23 - Members GMCMI, GMCGL, GMCES
Electronically Controlled Quiet Engine Cooling Fan with OE Rear Drum Brakes with Applied Control Arms
SE Michigan - Near DTW - Twixt A2 and Detroit

 

[Richard RV]

> I used a teflon pipe dope sealant on the threads, however that was probably designed for tapered pipe threads, not straight bolt threads, and
> likely won't hold pressure.

All thread sealants are waterproof and will hold pressure in suitably close threads. Whether tape or brushed on goop they'll hold pressure. Tapered
threads enhance the contact at a certain location, but all bolts build contact pressure through thread deformation. If there's an issue with the seal
it's most likely the cleanliness and imperfections in the threads themselves, not the thread sealant. Revisiting the connection with more careful
attention to thread condition and cleanliness will almost always stop the leak.

Richard
--
'77 Birchaven TZE...777;
'76 Palm Beach under construction;
‘76 Edgemonte waiting its turn

 

[john r. lebetski]

If it happens again, check the hose clamp and upper hose condition. If the inside hose rubber has porosity, coolant wicks out the ends. Also the
hated spring type clamps work best as constant tension.
--
John Lebetski
Woodstock, IL
77 Eleganza II

 

[Greg C.]

Thank you for the responses. It is holding now. John, I could see the coolant seeping out from under the washer on the t-stat housing bolts. I checked
it again today, and it's still dry. Now if I can get the heater hose nipple on the back of the intake to stop dripping, I would be coolant drip free.
I guess I'll have to drain the antifreeze out once more. New radiator core, all new hoses, water pump, etc.
--
Greg Crawford
KM4ZCR
Knoxville, TN

"Ruby Sue"
1977 Royale
Rear Bath
403 Engine
American Eagle Wheels
Early Version Alex Sirum Quad bags