Technical Chronic water leak - how would you fix it?

I had a leak at the housing (aluminum intake and factory aluminum neck). I simply used a small block of wood and some sandpaper and trued them. No need to use any type of ink/dykem as you can clearly see what has been hit by the paper and what hasn't. Once finished sanding I used a new gasket (regular paper gasket) and black "ultra" silicone and put her back together. I let it sit over night to cure before filling with coolant or starting the engine.
That's what worked for me

Edit: I may not have been perfectly clear ... when I stated I "trued them with sandpaper and a block of wood" I mean I sanded the T-housing AND the intake itself.

 

I have had some leaks like described and started using housing with o ring and never had another issue.
Just don't get it too tight, snug is all it needs.

 

Those T-stat housings are one area, carburetor base being another maybe, where I've just never had any luck at all trying to half-ass it or get in a real hurry. Take the time to do it right, no problem. Funny, that. A piece of plate glass is perfectly flat, or near enough, secure a piece of sandpaper to it and a figure 8 pattern sanding pattern - make sure the mating surfaces are perfectly clean and flat, and all traces of old gasket and skunge are removed from the intake flange.

Some of the modern gasket sealers are advertised as to ready for use in 90 minutes and they probably are but like others here mention I wait 24 hours or at least overnight before filling up with coolant. Never in a hurry to see leaks.

 

One thing that has not been mentioned is the possibility of porosity or maybe even a microscopic crack in the intake casting.

 

Hahahahahahahahaha, these o ring housings are the worst! I have never seen one that didn't leak. Maybe me and ALL my friends over tightened them.

 

Maybe you do. We have had great luck with them.

 

Did you pressure check the cooling system and verify where it's leaking

 

Do the thermostat housing bolts go through to the coolant or are they blind holes? If they go through to coolant, use thread sealer on them. Also, is it possible the leak is coming from the intake manifold bolts? I believe they too need sealer.

 

I can honestly say the only time I installed a thermostat housing (aluminum) with the O-ring machined in, it did not leak. Here's why ... I never got to the point of adding coolant because I broke the housing installing it

 

Yep. It shouldn't take much to seal a .004" gap. That's probably within OEM specs. A sheet of paper or a human hair tend to measure around .003" thick.

And when someone mentions "torqueing down" the outlet don't interpret that as meaning "tighten as much as possible".

 

@Thunder Road

What about the ‘recess’ for the thermostat disc? Is, or was, it in the mating surface of the T-neck….or is it in the manifold mating surface. Needs to have some accommodation for the disc or the neck and manifold will not mate. I don’t think a gasket will seal if the disc isn’t seated properly.

Ray

 

I would put RTV on both sides of a gasket and bolt it down. Let it set for 24 hours before re-filling the coolant just to be safe.

 

Update: I used a flat steel plate and suck some sticky-back 220 grit sandpaper on it and made a few passes on the blue'd mounting boss. It is now as flat as possible and the thermostat housing is as flat as I can make it. They meet and NO feeler gage will get between them. I got a new FelPro gasket and used black RTV to run a bead around both sides of the gasket. I installed the housing and only snugged the bolts down. It has been curing for about 20 hours now. Tonight I will remove one bolt at a time and put sealant on them and when both are back in place, I will tighten them to spec, put the upper hose back on and wait until tomorrow night to put coolant in it and fire it up. I want it to fully set up before I put pressure to it. I might even take my heat gun and warm that area up some to assist in curing. This is not how I put this together in previous efforts. I have new knowledge (thanks guys) and I'm using it...and I expect a better result.
I'll keep you posted.

 

What you takin' 'bout Willis ???? \_{"}_/

 

So ... @Thunder Road How'd it work out?

 

I use ground ginger.

 

Update: You know, it’s one thing to post on here asking for help but it’s quite a different thing to post on how dumb you think you are.

So, she was ready to go, fired her up, let it reach operating temp and then run another 5 minutes or so and shut it down. Went around front and what do I find- the valley behind the housing is half full of coolant- DANG!!

I started looking very close as to where is this thing leaking from…and I found two things of note. I think I had told you that I went back to a factory housing, one that had a temp sending unit in it and how I had replaced that with a plug AND I used sealant, Well, looking close at it I saw a liquid trail coming down the housing. I also noticed that there was coolant on top of the factory ‘pockets’ that are right next to the housing’s bolt holes. Logic says that coolant cannot get there unless it is coming out of the bolt holes.

At this point I realized my ‘dumbness’. Yes, I had put sealant on the bolts, and on the plug but I had put the “non-hardening” sealant and it looked like coolant was just squeezing right around/thru it.

Okay, while I was tempted to scream and throw things, and with humble apologies to member “sdluck” I went and bought a pressure test kit from HF and managed to pump the system to 12 lbs. before coolant started oozing out from under the passenger side bolt head. NOW I KNOW.

So, late last night, I cleaned everything up, used hardening sealant on the plug, used Ultra black RTV liberally, on both sides of the gasket, and used hardening sealant all over both bolts plus under the bolt heads. I reinstalled everything and snugly tightened both bolts. It has been curing since 5:30 last night.

Late this afternoon, I am going to use my pressure tester and see if I finally have this solved…or not. More to come..

PS, for those that have suggested Bar's leak or pepper or whatever to stop a leak, The radiator I am working with is A Brand New, $950.00, 4 core radiator. I really don't want to put anti-clogging stuff in there....just fyi.

 

Subscribe.

 

The results of the pressure test were conclusive...the bots didn't leak, the housing to manifold gasket didn't leak...BUT somehow, the plug in the housing still allowed coolant to squeeze out, and I had that thing gooped to death and as tight as I could get it. When Iget a housing with no hole in the top, I believe I will have this punk whipped. I will let you know.

 

Keep in mind that RTV isn't really designed to be a gasket sealer. Try using gasket sealer, instead, on the gasket.

Also, gooping things to death usually doesn't fix anything. Getting parts that fit properly is usually a better idea.

Did you figure out how the water was getting to the bolt hole, in the first place? Perhaps the gasket does not fit properly around the bolts? like it has a slot, instead of a hole? Most Chevy thermostat gaskets are designed to fit more than one application, and so they don't have enough material around the bolts.

 

Some of you are watching for the final report/outcome of this adventure (“adventure” is what I call it when things don’t exactly go as I had planned) and here it is. Sorry for the long delay in summing this up, but I counted 6 failures before the victory.

I ordered a new thermostat housing with the O-ring in it. Luckily it was made of steel. I faced the mounting surface for my own peace of mind and I had some work to do- it really wasn’t all that flat, but it is now. I installed it, put on the upper hose, run the engine up to temp…and found another leak- but NOT at the housing, it was where the radiator hose hooked to the top tank. I was counting- this was leak # 6.

So I took the hose off- Did I mention that I am using a CoolFlex upper hose?

This is the flexible metal tubing type that requires an adaptor sleeve at each end and the metal tubing is 1-3/4” OD. The tubing goes half way into the sleeve and a hose clamp secures it there, then when it is put onto a water outlet, another clamp secures it there. Since the ID of the adapter sleeves is 1-3/4” and the outlets are only 1.5” there were these rubber collars put over the outlets to ‘take up the slack’

Leak #6 occurred because the collar was old and when I put the sleeve over it, it bent the thing almost double…and it was hidden inside the adapter sleeve- no way it could clamp tight enough. OK, so I disassemble the CoolFlex hose assembly, make some new adapter sleeves out of straight radiator hose and I found me some new rubber collars and put those in, as I reassembled it all and installed it yet again…for leak test # 7.

This time I used my new pressure tester and pumped it up to a solid 10 and let it set for 10 minutes or so.

The needle never moved. I cranked her up, reached 150 on the water temp gauge – flipped on the low speed fan and 10 minutes later, it was still at 150. I looked and looked and have not found any sign of a leak or dribbling or anything unusual…so I am calling this thing DONE!!!

Those that offered their knowledge and experience- I thank you.

Happy Thanksgiving to one and all!

 

Horray! Glad I never had one that bad.

 

Makes you wonder what's next..........................

 

Should be some kind of intermittent, hard to diagnose electrical problem. Maybe brake lights, possibly ignition.

 

You could make stuff up ...

 

Oh, you last three guys are just sooo funnie- haha, but you’re late to the party and I didn’t have to make it up…it was a bad ground that ended with me making a ground cable and taking it from the trunk mounted battery all the way to the motor. Stuff like this is just what you have to do to keep the old iron running.

But hey “twenty8” that thought has crossed my mind for sure- LOL

 

If it's aluminum get rid of it. I had the same problem, did all the fixes to correct the surface, and found that it warped when I tightened it. Replaced it with a cast iron piece and it never leaked again.

 

It's a good solid cast steel piece, Bert, Thanks for the advice.

 

Some folks can break an anvil ..LOL

 

Add water, or fix the leak.