Thermostat leak - Forums - Official C3 Vette Registry - C3 Corvette Registry

Home page

☰

SPONSOR AD

Support our Vendors! | Advertise Here

Topic: Thermostat leak

in Forum: C3 Cooling and Heating Systems

Already a Member?
Login
Not yet a Member?
Register for Free!

Hide Signatures

Thermostat leak (1/17)
8/10/11 12:49pm

LarryT
Former Member
Send Private Message

Worthington, OH - USA

Vette(s):
1972 Black C3 automatic with red interior. Options include AC, PS, PB, Am/Fm Wonderbar stereo.

Joined: 8/4/2009
Posts: 74

There appears to be a leak around my thermostat. I have tried to tighted it down, but after I drive the car there is still coolent around the thermostat. I don't see the leak at idle, but driving make everything damp. Before I take off the connector, what should I look for? Is there one gasket (under the thermostat) or two (above and below the thermostat)?

Our Sponsors help support C3VR

Thermostat leak (2/17)
8/10/11 1:13pm

Lifetime Member

Lifetime Member
Moderator
Send Private Message

Duncanville, TX - USA

Vette(s):
#1-1974 L-48 4spd Cp Med Red Metallic/Black deluxe int w/AC/tilt/tele./p/w-p/b/ Am-Fm/map light National/Regional/Chapter NCRS "Top Flight" #2-1985 Bright Red/Carmine Cp.L-98/auto Member: NCRS, NCRS Texas, Corvette Legends of Texas

Joined: 11/8/2003
Posts: 20128

Only one gasket involved. Couple of questions, tho...is this an aluminuminum manifold, or cast iron?
Is the thermostat housing original/original style, or aftermarket chrome?
Sometimes, a small leak around the housing will stop after driving a while. If the car doesn't get much use, that can contribute to the leakage. Of it's driven frequently, the gasket will stay pliable, and seal well. If it sits for lengths of time, the gasket tends to shrink somewhat, and you'll see some seepage until it seals again.
If this is an aftermarket chrome housing, the only way you'll ever stop the leakage is to grind/file the bottom of the housing to get the chrome off of it. Chrome doesn't make a very good sealing surface, no matter what kind of sealant you may use. Grinding the chrome off give the gasket a nice, rough-ish surface to seal against.
It's also possible that the housing is warped. This can be made better by filing, also, to get it flat again.
hth

another afterthought....it could also be the hose itself leaking, and running down around the housing. Might wanna check that while you're at it, in case the housing has corroded, and is digging into the hose.

Adams' Apple2011-08-10 10:16:59

______________

Joel Adams
C3VR Lifetime Member #56
My Link

(click for Texas-sized view!) NCRS

"Money can't buy happiness -- but somehow it's more comforting to cry in a CORVETTE than in a Kia"

Thermostat leak (3/17)
8/10/11 4:10pm

LarryT
Former Member
Send Private Message

Worthington, OH - USA

Vette(s):
1972 Black C3 automatic with red interior. Options include AC, PS, PB, Am/Fm Wonderbar stereo.

Joined: 8/4/2009
Posts: 74

It has an Edelbrock aluminum manifold with a chrome thermostat housing. I don't have any grinding equipment, so grinding off the chrome is a non-starter. Maybe I need to look into an new thermostat housing. Since I'm dealing with aluminum manifold should I look for an aluminum thermostat housing or does it matter since the thermostat will keep the housing and manifold separate?

Thermostat leak (4/17)
8/10/11 4:12pm

LarryT
Former Member
Send Private Message

Worthington, OH - USA

Vette(s):
1972 Black C3 automatic with red interior. Options include AC, PS, PB, Am/Fm Wonderbar stereo.

Joined: 8/4/2009
Posts: 74

P.S. Hose is not leaking. I can tell by the leak pattern.

Thermostat leak (5/17)
8/10/11 10:18pm

Lifetime Member

Lifetime Member
Moderator
Send Private Message

Duncanville, TX - USA

Vette(s):
#1-1974 L-48 4spd Cp Med Red Metallic/Black deluxe int w/AC/tilt/tele./p/w-p/b/ Am-Fm/map light National/Regional/Chapter NCRS "Top Flight" #2-1985 Bright Red/Carmine Cp.L-98/auto Member: NCRS, NCRS Texas, Corvette Legends of Texas

Joined: 11/8/2003
Posts: 20128

You might be able to file the bottom of the housing, if you have a good mill file. Otherwise, I would definitely start looking for a different thermostat housing. Most housings will be aluminuminum to start with....not that that makes any difference. The gasket will separate the two metals, but the bolts will be touching both, anyway. When you get ready to change it, make sure the area is clean...that make the most difference in whether or not they will seal. You might still see a small amount of seepage for the first couple of times you start it, but that will stop...unless there is another issue with either the manifold, or the new housing. If you use a regular, paper style gasket, you can use a SMALL amount of 3M Weatherstrip adhesive on both side of the gasket, and not have to worry about a leak. If you use one of the blue, silicon impregnated gaskets, use it DRY, with no sealer.
hth

______________

Joel Adams
C3VR Lifetime Member #56
My Link

(click for Texas-sized view!) NCRS

"Money can't buy happiness -- but somehow it's more comforting to cry in a CORVETTE than in a Kia"

Thermostat leak (6/17)
8/10/11 10:29pm

LarryT
Former Member
Send Private Message

Worthington, OH - USA

Vette(s):
1972 Black C3 automatic with red interior. Options include AC, PS, PB, Am/Fm Wonderbar stereo.

Joined: 8/4/2009
Posts: 74

Thanks for the help. This time I buy one of the better quality thermostat housing with the rubber ring too. The one in there came with the car and knowing the person I bought the car from, I'm sure it was cheap. Little by little, I've had to replace most of the cheap parts he installed. :-(

Thermostat leak (7/17)
8/14/11 11:19am

KDADDY79
Former Member
Send Private Message

Dutchess County, NY - USA

Vette(s):
White '79 Corvette. It's a driver.

Joined: 8/27/2007
Posts: 2484

Hey Larry T,

I had the exact problem on my '79. The el cheapo chrome thermo. housing I put on the edelbrock aluminum intake leaked like crazy.

I finally had good luck with a polished aluminum thermo. housing from Spectre Industries. It is a 2 piece unit with the rubber ring. No problems with it at all and it's been on for well over a year.

HTH,

Kevin

KDADDY792011-08-14 08:20:46

Thermostat leak (8/17)
8/14/11 9:14pm

LarryT
Former Member
Send Private Message

Worthington, OH - USA

Vette(s):
1972 Black C3 automatic with red interior. Options include AC, PS, PB, Am/Fm Wonderbar stereo.

Joined: 8/4/2009
Posts: 74

I ordered a high quality thermostat housing with O-ring and I'm now just waiting for it to arrive. Thanks for the feedback.

Re: Thermostat leak (9/17)
1/7/12 8:09pm

Lifetime Member

Lifetime Member
Send Private Message

Pittsburgh, PA - USA

Vette(s):
1979 L-82, 3 spd auto, car was originally Lt. Beige currently painted Sportsman Red, Doeskin leather interior, 103,000 miles......

Joined: 12/4/2002
Posts: 600

Bringing back this post for an additional question.

Would I be seeing antifreeze laying all over the intake manifold if this were indeed happening??

Re: Thermostat leak (10/17)
1/8/12 12:57pm

Lifetime Member

Lifetime Member
Moderator
Send Private Message

Duncanville, TX - USA

Vette(s):
#1-1974 L-48 4spd Cp Med Red Metallic/Black deluxe int w/AC/tilt/tele./p/w-p/b/ Am-Fm/map light National/Regional/Chapter NCRS "Top Flight" #2-1985 Bright Red/Carmine Cp.L-98/auto Member: NCRS, NCRS Texas, Corvette Legends of Texas

Joined: 11/8/2003
Posts: 20128

Most likely, yes...depending on where the housing was leaking. If it leaks from the front edge, coolant may only run down the front of the engine block, toward the timing cover. In that case, you might never see any liquid coolant at all...it might evaporate before it dripped to the ground.

______________

Joel Adams
C3VR Lifetime Member #56
My Link

(click for Texas-sized view!) NCRS

"Money can't buy happiness -- but somehow it's more comforting to cry in a CORVETTE than in a Kia"

Re: Thermostat leak (11/17)
1/8/12 8:03pm

Lifetime Member

Lifetime Member
Send Private Message

HOWELL, NJ - USA

Vette(s):
1979, Targa Blue (72 Color), Pace Car rear spoiler, L88 hood, Dark blue factory interior, 525HP 406, HD 700R4, 370 gears,Steeroids, composite rear spring, TT IIs wrapped in T/A Radials.

Joined: 5/18/2004
Posts: 6812

If it evaporates, look for a green stain on the manifold...

Re: Thermostat leak (12/17)
1/8/12 9:41pm

Lifetime Member

Lifetime Member
Send Private Message

Pittsburgh, PA - USA

Vette(s):
1979 L-82, 3 spd auto, car was originally Lt. Beige currently painted Sportsman Red, Doeskin leather interior, 103,000 miles......

Joined: 12/4/2002
Posts: 600

Well I snugged up the bolts, but not before trying to investigate by removing the hose clamp. Needless to say I spent a little time cleaning the antifreeze up in the engine bay and on the garage floor........

Re: Thermostat leak (13/17)
1/9/12 2:17pm

Lifetime Member

Lifetime Member
Moderator
Send Private Message

Duncanville, TX - USA

Vette(s):
#1-1974 L-48 4spd Cp Med Red Metallic/Black deluxe int w/AC/tilt/tele./p/w-p/b/ Am-Fm/map light National/Regional/Chapter NCRS "Top Flight" #2-1985 Bright Red/Carmine Cp.L-98/auto Member: NCRS, NCRS Texas, Corvette Legends of Texas

Joined: 11/8/2003
Posts: 20128

Silly boy....

Lern frum yer mistakes, son...lern frum yer mistakes....
You never actually said, but did you suspect, or have a leak there, Dan?

______________

Joel Adams
C3VR Lifetime Member #56
My Link

(click for Texas-sized view!) NCRS

"Money can't buy happiness -- but somehow it's more comforting to cry in a CORVETTE than in a Kia"

Re: Thermostat leak (14/17)
1/10/12 10:12am

Lifetime Member

Lifetime Member
Send Private Message

Pittsburgh, PA - USA

Vette(s):
1979 L-82, 3 spd auto, car was originally Lt. Beige currently painted Sportsman Red, Doeskin leather interior, 103,000 miles......

Joined: 12/4/2002
Posts: 600

There was a little coolant present on the manifold.....lots when I loosened the hose clamp and pulled the hose away. Embarrassed

Embarrassed

( I never claimed to be the sharpest tool in the shed) ......

I suspect by the fact that I was able to snug down the bolts the problem may have been corrected. Don't know for sure yet.......

Re: Thermostat leak (15/17)
5/14/12 8:42am

Lifetime Member

Lifetime Member
Send Private Message

Pittsburgh, PA - USA

Vette(s):
1979 L-82, 3 spd auto, car was originally Lt. Beige currently painted Sportsman Red, Doeskin leather interior, 103,000 miles......

Joined: 12/4/2002
Posts: 600

Again bringing up this subject....

The leaking is still there so I'm going to change out the thermostat housing.

How much coolant should I drain from the rad before removing the hose? I dont want to repeat my previous disaster..... Embarrassed

Embarrassed

Re: Thermostat leak (16/17)
5/14/12 8:55am

Lifetime Member

Lifetime Member
Send Private Message

COPPERAS COVE, TX - USA

Vette(s):
1972 corvette stingray convertible 2007 coupe

Joined: 7/6/2002
Posts: 417

I had the same problem, I take a sheet of wet dry sand paper lay it on a piece of glass flat and take the housing and place it on top of the sand paper, keep it wet and sand back and forth. You should see the high and lows from the sanding in just a couple of minutes. Just keep moving the housing back and forth keeping it level untill nice and smooth. I do this everytime I put a motor together even with new housings you will be surprised to see the uneven surface on these housings.

Good Luck!

______________

Click for larger view

Re: Thermostat leak (17/17)
5/14/12 9:59am

yostusota
Former Member
Send Private Message

York, PA - USA

Vette(s):
1969 daytona conv. all original 350 350 380 4 sp w/air..and hard top

Joined: 5/18/2010
Posts: 1518

I'd try the sand paper method..it does work..you may have a cracked housing though since you keep snugging up the bolts..I just did my thermostat last week when I did the manifold and it doesn't leak..use a block sander on the manifold too just to touch it up..and no silicone!!! Just touch the bolts snug as it doesn't need to be that tight..put some lube on the bolts too so they don't seize in the manifold too..also make sure your thermostat is seated in the recess in the manifold...how much to drain..I jack up the pass side and drain about a gallon out then when I remove the hose I lift it straight up to drain what may be left in the bottom part of the hose which isn't much...if you do it right none will spill on the manifold.

______________

My first parade at Carlisle 2010

Our Sponsors help support C3VR