My thermostat housing leaks. I thought it was the hose, so it was replaced. But it is still leaking.

My question is which one to buy. The Corvette parts retailers are quite expensive, ~ $60-$80. Parts and stores and non-Vette online retailers have them all over for $15-$25.

Is there a difference or are they all made on a dirt floor in an Indian foundry?

 

I would first try to determine where the leak is. With today’s sealants, should be relatively easy to repair unless the casting is cracked (which is unlikely).

 

You should find the actual leak before doing anything. But if the old one looks bad/corroded I would just replace it with a generic one that has the correct angle and a felpro gasket and be done with it. Fooling around with sealants and draining/refilling the system is not worth 15-20 bucks to me....

60

 

Should have specified that it is leaking at the hose connection. Everything is tight, no leak at the gasket. Even with a new hose there is a slow drip when hot.

 

Is it chrome? If so, just scuff it up with some sandpaper.
There is not an RTV in the world that will adhere to chrome.

Or, the hose clamp is sub par. When using a good quality clamp, tigthen with a nutdriver instead of a screwdriver.

I would drain off a few QTs of coolant. Remove the hose from the waterneck and clean the inside of the hose.
Then lightly sand the waterneck port.
Find some Permatex Waterpump & Waterneck RTV at AutoZone. Its Glycol proof.
Smear some around the neck. Twist the upper hose on and rock it back & forth.

Let all RTV sit overnight before adding coolant.
Always the possibility that is not the correct hose and is a little on the big side.

 

Matthew 7:15
Install a cast iron waterneck; some sbc/BBC used to have them OE. They don't give trouble. The piece is relatively small, so weight difference is of little consequence.
Four Seasons/Hayden and Dorman offer some cast iron waternecks. Most are Not cast iron; look closely.

most cheap chrome pieces are cast zinc and they tend to warp.

 

There are a couple things that I would check. My 3X2 intake and thermostat are aluminum. The old housing had some corrosion on it so I decided to replace it. Ordered one from one of the suppliers, installed it and it leaked a little. Took it off to check it and placed it on my bench and it rocked a little. Checked the bottom and found that it wasn't straight. Put some sandpaper on the bench and corrected the bottom. Checked the intake and found that the bolt holes were raised a little. Took my file and made them level. Put it all back together and it worked fine. Didn't think I should have to check the fit before installing a new part, but apparently, I did.

 

At the risk of promoting Phil Swift, I would then remove the hose, clean the neck with alumiprep, then apply a layer of Flextape over the contact area, reinstall the hose.

 

Install quality hose clamps. BREEZE brand in their "Liner" series does not cut into hose. BREEZE also has constant torque/tension versions employing a coil spring. BREEZE are Not cheap chinesium stuff. Mine are clearly stamped U.S.A. I sourced mine locally via Commercial Heavy Truck & Off Road Heavy Equipment parts dealer.

 

Unless the waterneck is billet....it is almost certainly not flat. If it is not flat....it is probably not going to seal.
A brand new Chrome Mr. Gasket waterneck with O-Ring is not flat. Buy one and put it on a flat stone with 80 grit and sand it around a bit....turn it over and you will see what I mean....the O-ring won't even seal becasue it is so warped.
Find the flattest surface you can find and stick a 6" DA sanding disc 80 grit to it and sand it around back and forth and in circles until it is flat....you will see very clearly when it is flat...

Take a small rag and stuff it in the hole of the intake....take a flat piece of thick aluminum as a sanding block (or something similar) and sand the gasket surface on the intake flat....if both are flat, and free of lots of pitting.....you can bolt the water neck on with a gasket and no RTV....
As far as the hose sealing....clean the inside of the hose with MEK or brakeclean....the water neck as well....work the hose on and tighten with a Quality stainless hose clamp.....or use a later model GM factory spring clamp....the hose should have a tight fit over the waterneck and if not...find out why.
People are quick to use shitloads of RTV and toss a spring clamp in favor of a POS worm clamp.
As stated above....Breeze and Ideal make quality clamps....it makes a difference.
People look at spring clamps and somehow think that they are inferior (usually an impatient driveway warrior who learned how to do it on Facebook).....but a spring clamp goes around the hose and further about 430-440 degrees...
It is a full round engagement clamp....and they flat out work.
If you need to use RTV on a rad hose....you are doing it wrong....it makes a ******* mess the next time you pull it off and can potentially get dried silicone floating around the cooling system....same at the gasket surface.

This is one area of general maintenance that has gotten so overthought that it basically has a life of its own....two flat surfaces and a clean dry hose/neck with quality clamps are all you need....

If you like to add a little clamp force to the neck to pull it down tighter....add a drop of oil to the bolt threads....it will pull it down harder with the same amount of tightening force, similar to a head bolt.

On my 72' 406....I have an original aluminum neck sanded flat....the gasket surface on the Team G intake was flat out of the box...two stainless ARP bolts with a drop of oil hold it down. The rad hose is a Zip repop slid on dry with repop GM factory hose clamps...no RTV anywhere.

You can seal almost any non-corroded waterneck with a $1 gasket and a $4 clamp. Period.

Bonus is it looks professional with no RTV squeeze coming out....and when you remove it, it comes right off and nothing to scrape.

If you doubt anything I just said....try it yourself....post your results.

Two flat surfaces will seal with a .010 paper gasket everytime.
Clean and dry waterneck/hose that has a tight (not real tight) fit will seal everytime with a $4 clamp or a factory spring clamp.

Cracks me up what people do to skirt around a root cause.....I figured this **** out in the early 90's when every S-10 and C-10's water neck would leak before you were out of warranty....

Lastly....use only distilled water and approved anti-freeze.....electrolysys is a killer of coolant systems...and water necks!

Jebby

 

When I worked in a shop during high school as a "sweeper" I was taught many tricks they don't use today. Any time we replaced a thermostat in a car or truck or built a small briggs &stratten (we worked on everything) we clamped the part in a vice ,don't crush it, and ran an 8mil bastered file very flat across the surface. Think of it as planing a head 1 or 2 thousands. Replaced thousand of thermostats and no sealer.

 

^^^THIS^^^
Many years ago, I had good fortune to make acquaintance with a group of degreed German engineers who represented a large German firm that manufactured yarn texturizing machines. They worked within a new stateside textile manufacturing plant and the project ran well over a year. I enjoyed hearing their accounts of similar jobs in chicom & elsewhere. But also, about their first year of University, Seems they spent much of that time formng a complicated metal part with only metal hand files (a part that ordinarily would be formed with machine tools including CNC).