Hi folks,
Before I drain the radiator for what is I think, the 5th time I thought it would be a good idea to seek some divine (or otherwise) help.
With some other parts I bought from Summit (down to me in NZ) I threw in a chromed steel water thermostat housing for my '65 Cutlass 330 V8.I used a high temp silicone product as well as the supplied gasket to seal the housing but after a short time the fitting started to weep just under where the small hose connects to the housing.It was actually quite difficult to see if it was the small lower hose connection or the housing mating point that was causing the problem.Redid the process, same result.
The 3rd time I noticed that the gasket wasn't in good shape as it had torn through and was going a bit mushy so I discarded it and used silicone alone.
Same result, as the engine got warm and the radiator got under pressure the same place started to leak very slightly.
4th time I bought and used a different (and supposedly better) high temp silicone from Permatex called Ultra Copper which seemed good until I went for a longer run,the engine got hotter the radiator pressure went up and the same place leaked again.I have tried tightening the bolts down hard when the leak first appears in fact breaking one of the bolts right off at one stage.
One thing I have noticed is that the mating surface on the underside of the thermostat housing is also chrome plated with a few lightly ridged lines on it.
I am wondering whether I should grind the chrome off the back of the housing as the chrome can't be the easiest surface to seal.
What do you think? The other question is, should I make a new gasket up and use that and the silicone or just use the gasket alone?
I won't be able to get a manufactured gasket down here in New Zealand hence why I am thinking of making one with a suitable gasket paper.
I would appreciate any help on this so I can get back to the other (also small) problems I am experiencing at the moment!Thanks

 

I don't think I would grind it. Maybe take a sheet of emery paper placed on a hard flat surface and rub the housing over it.

 

That was your first mistake.

Those things are notoriously problematic.

Your second mistake was tightening it down tightly, which very likely bent the ends downward, leaving a gap at the middle, where it is leaking.

You may be able to salvage it by rubbing it against fairly aggressive sandpaper, laid on a very flat surface (such as a piece of glass), but I would just throw it out and use the original.

You can easily make a gasket with some gasket material and a razor knife, so I'd do that as well.

- Eric

 

Do you have a factory part that you can use?
Seems like that might be beneficial, if you want no leaks.

 

You can try double gasketing, and using weatherstrip cement or shellac. Assemble and let dry for at least 24 hours.. I hate the chrome water necks, but some just want to use them.

 

X2 on what both Eric's said. I have seen some of those that actually used an o-ring. Most the ones I have seen leak like crazy. I would never use one for that reason. It seems like such a simple thing but it can be a real pain in the butt.

 

You know what makes for great gasket material? Cereal boxes do.
You could use the rtv stuff called The Right Stuff. Best there is.

 

Try gasket eliminator. Clean surface well and dry. Anaerobic adhesive.

Pat

 

When I bought my 70 Cutlass it had a chrome housing, it looked good but leaked. I gave up on it after a few months. The original housing came with the car in a box of parts. I cleaned it up down to bare metal and put it back. No leaks, looks fine.

 

...echo of post #4....

 

Also be aware that the 2 bolts enter the water jacket. Apply RTV to the bolt threads and around the base of the hex before you assemble. I will also fill the void between the bolt and the stat housing then use either a captive washer style bolt or a proper fitting washer under a grade 5 bolt to sandwich the RTV in. Stainless bolts work good with stainless washers.

 

X2, I totally agree with you about the chrome housing. They leak no matter what silicone you use. I threw my housing in my scrap metal bin and bought a cast iron housing. No more leaks.

 

I changed my mind about grinding the chrome off on the back but I did try using heavy grade emery paper.The chrome must be very hard as I hardly made any difference to the surface and had to give up on that idea for now at least.

 

Yes as per normal anything I do can be changed back to as I always keep the original part.

 

Tightening down the housing was a last resort sort of thing and I did try "sanding" the back but that didn't do much. I did check the part with a straight edge and from what I could see the mounting base is flat.I've gone the gasket route now.

 

well, sure, so you pays your money and you takes your pick.

good call on the sealing of the bolts. One of the few Olds engine bolts that goes into a juicy cavity instead of a sealed blind hole.

One more sealer I recommend highly for such applications - Yamabond, from your Yamaha dealer. It is so good it may even seal a chromed tstat housing

 

I managed to buy a roll of thin gasket paper marked 0.04 and cut out a new gasket last night.When you use a gasket with the Permatex Ultra Copper silicone the instructions say to apply a thin film on each of the mating surfaces and then secure straight away which is what I did.
You have to allow 24 hours for the silicone to cure properly and can't put the coolant back in until the 24 hours is up either.I actually bought some of the old style shellac with a brush on mounted to the top but chose not to use it as I thought the silicone would be better.
I cut out 5 gaskets but have only cut out the holes in the one I installed so I can add more gaskets if I need to.
From some of the other posts here it looks like my chances of success aren't that good but all I can do is wait now.Thanks for your post.

 

Leaking on these housings is very common by the look of it and they are a great time waster for sure.I can put the original one back on if I have to but I want to try again one of the reasons being that I had to pay over $40 for a suitable hose
that I cut down for use on the secondary port on the housing.Parts are expensive here in Godzone!

 

Do you have a picture or link to the one you are using?

 

You would think it a fairly simple thing to manufacture these things properly but no......The housing's mating surface looks flush so I wish I new why these things leak the way they do.
Driving around I have been a bit worried about the silicone blowing out and possibly losing all of the coolant on the roadside.
The silicone cures into a very rubbery sort of gasket and I think it's most likely a good product but maybe not in my situation.

 

You'd think, huh. Never had the gasket on one blowout with a catastrophic flood of coolant pouring out. It has always been the incessant weeping.

 

I wasn't sure which you wanted so here is the thermostat that I got from Jegs (not Summit) http://www.jegs.com/i/JEGS+Performan...11300/10002/-1

and here is the info on the silicone
http://www.permatex.com/documents/TD...tive/81878.pdf

 

It looks to be of good quality. If it leaks again, disassemble and clean it really well. Make sure that there is no interference with the thermostat installed preventing it from laying flat and seated. I like the Felpro 35130 gasket. First make sure the mating surfaces are clean and oil free by wiping them down with MEK or Acetone. I would use weatherstrip adhesive applied first to the housing then both sides of the gasket and to the manifold. It is a contact adhesive that needs to skin over and then be assembled quickly. Make sure to use thread sealant on the bolt threads. Let dry for 24 hours. If that does not work nothing will.

 

Good point, I hadn't thought about the bolt holes at all because the leak is directly under the small hose where the housing meets the engine block.I had assumed that the bolt holes dead ended in the inlet manifold, In my casE a Edelbrock Performer RPM.
If as you say the bolt holes go all the way through the manifold there remains the possibility that near boiling water is forced up the sides of the bolt holes until it finds the path of least resistance.This pressure then opens up a leak which doesn't necessarily have to be at the bolt holes themselves.
Hopefully using the HT silicone and a gasket will work but if I have do it over again I will take the bolt holes into consideration.Thanks very much.

 

The Permatex Ultra Copper is a high temperature (includes exhausts) silicone gasket maker which I assume is similar to "gasket eliminator".Is that correct

 

Make sure you do not over torque those bolts trying to stop the leak. It is not hard to strip out the aluminum intake. Ask me how I know.

 

Nope! please read the following link.

http://www.permatex.com/products-2/p...t-maker-detail

Pat

 

Look where its made...that will answer your question. If your really hell bent on chrome why not have an OEM part powder coated? Have the coater not apply the coating to the gasket face. Use SS 18-8 or 3 series washers n bolts and toss the chepo in the trash. Ill bet you will have less than 50 into it with the SS fasteners.
Another tip like if we haven't confused you yet; I guess you could try each of our suggestions to attempt to get the chineasium piece to not leak.
In the not so distant past I was a large engine builder. I learned from the old guys to use 3M gasket spray adhesive to stick the gasket to the part then apply a thin film of what ever you choose between the gasket and the parent part. Never had a leak but nothing was chineasium either. I like the "Right Stuff" for the tougher parts such as to delete the front and rear intake to block rubbers which are totally useless. This spray n stick technique also allows for easy removal down the road. The silicone side will lift right off. Then you dont have to chisel the gasket off the intake.; rather you can take the housing over to a bench and make the mess there vs in the engine compartment. 42 ways to skin the cat.

 

The last and hopefully final time I had the thermostat housing off the inlet manifold I checked out the bolt holes.The threads don't enter the water jacket and dead end an inch or so into the manifold.My car's inlet manifold is a Edelbrock Performer RPM which may well be different to the factory one in this respect.

 

I used my homemade gasket and a generous amount of the Ultra Copper silicone after cleaning everything up and wiping off with Brakeclean solvent.I waited the required 24 hours before refilling the coolant. Funny thing the radiator wouldn't take all of the fluid, must be because the thermostat was closed.Filled the overflow so hopefully it will suck back and all will be well.BTW my Edelbrock manifold's boltholes don't go all the way through into the water jacket.
Anyway I took the Cutlass for a 45min highway coast drive and let the temp get to a max of 190F and no leaks so far ..........
Hopefully this will continue so no more posts (optimistic maybe) so thanks for all your help and advice.

 

I honestly have had nothing but weeping even with the cast iron and RobMc aftermarket billet aluminum housing. That is with a gasket, sealant on both sides and bolt holes. I ended up getting a factory aluminum housing on the last 350 I bought. I found the best solution is double gaskets and RTV on both sides and sealant on the bolts.

 

When I saw your post I said "ouch" and laughed at the same time.Sorry about that.Have you got a Performer RPM manifold on your Old's? Seems to me that a these manifolds aren't all that suitable for an engine that isn't a real rev machine.

 

I was a bit more liberal with the RTV silicone than what the instructions suggested when using a (homemade) gasket.
I took the Cutlass out for another drive today and let the temp get up to 200F before switching the fan in.The housing is still sealed atm so crossed fingers it will stay that way.Maybe having an actual gasket makes the difference......

 

My manifold is a Performer 2711. I am very happy with it. I have seen other posts on this site complaining about the low end response on the Performer RPM.
Thankfully it was not this manifold that I stripped the bolt hole on. Good luck on fixing your leak. Something like that can be very frustrating.

 

actually it sounds to me like it could be the homemade gasket that could be the winner in this test!!!