After dealing with a knock my new engine had, I noticed the head studs on the passenger side were weeping coolant. No big deal, I pulled the studs, put a generous amount of Permatex #2 on the threads, and reinstalled them. Around 24 hours later, I started the car, and I found that 5 of them are still leaking. Is there some trick to sealing head studs? It's hard to get to the threads in the block with the heads on, so the best I was able to do to clean them was blowing them out with compressed air; maybe that's the problem?

Before pulling my engine my cat got clogged and caused my exhaust manifolds to get red hot. Is it possible all this heat cracked my head so the coolant is seeping into the boltholes in the heads?

 

You are draining out the coolant prior to putting in fresh silicone, right?

Silicone doesn't dry very well in a wet hole. Also, you should be cleaning them studs with a wire wheel, then spraying them down with carb cleaner to ensure a good thick coat that sticks to the stud/bolt.

I like the orange high temp stuff. Squirt a big blob of it on cardboard and roll the threaded end around until you have a nice thick even coat. Then screw into (keyword) "dry" hole and repeat. Allow few hours to cure, fill coolant.

Good luck.

 

Did you drain the coolant? Maybe run a dry bolt then some sealer to help.

 

Yep, drained the coolant, blew out the holes, and cleaned off the bolts. We are out of carb cleaner though so we just used a wire brush.

Then 24hrs later put the coolant back in.

Thanks for the suggestions.

 

my 2-cents, FWIW -- I personally do not use RTV silicone, but sealant designed specifically for head bolt application. ARP sealant would be my first choice. i'm not sure about silicone on head bolts, but if you are using it, the holes must be clean, dry, and free from any kind of oil. I do use RTV silicone on intake manifold bolts.

BTW, i'd ditch the studs in favor of conventional head bolts!

 

Not being a smart ***, op, but I'm wondering at this point if you should just chuck the motor and find a donor. You have had problems since day 1 with metal in the oil, knocking, tapping, and now seeping head studs. At this point, you still don't know if the motor is any good. Search around carefully and you might be able to get a good deal on a good motor. Maybe cut you losses and the hundreds of hours you've spend on this anchor and bolt in a tried and true motor. Just an opinion. Good luck. We're all pulling for you.

 

I don't believe Permatex #2 is RTV: it's their non-hardening form-a-gasket. Still though, not sure how well it seals dirty threads. Does the ARP sealant work fine if the hole isn't clean?

Believe me, it's crossed my mind. Right now though it's not in the cards as I go back to college in less than three weeks. I'll see if I can fix these leaking studs, and if I can't sort that out or still have metal in the oil I'll look into getting a replacement or maybe rebuilding this one the right way.

I appreciate all your help and advice.

 

sorry, for some reason, I was thinking you used RTV. as far as the ARP sealant in dirty holes, I can't say with a 100% certainty, but my guess is NO. I always clean and degrease the holes, and use a thread chaser/restorer prior to assembly - especially with head bolts. even anti-freeze/ethylene glycol would contaminate the threads.

 

Any tips on how to clean out the threads with the head on? They're so far down the holes in the head that I can't think of a way to get to them.

 

Reid,
IMHO the leaking head studs are not the issue.

Pull the heads, have them pressure tested. They may need to be milled to insure they are flat.

 

Out of curiosity, what makes you think my heads are warped? Would that cause coolant to come up the bolt holes?

It did not run long with hot manifolds. Also, there is no smoke in the exhaust indicative of burning coolant, and all cylinders on that side tested well (~160 PSI) in a compression test.

Thanks Woody.

 

This is the young mans first motor change/build I have confidence that with our collective help he will get it sorted out eventually. Its a damn steep learning curve for his first go round.

 

Coolant may not be coming up the stud from the block threads the coolant could be coming from a compromised head(s) or head
gasket(s).

Not saying the heads are warped just suggesting to check that they are flat. Its normal procedure when a head is removed.

IIRC you ran the motor 3-4 hundred miles without a coolant leak it started after you glowed the headers = heads or head gasket issues.

I use Teflon pipe thread dope on head studs its in the plumbing department.

 

They ususally corrode themselves shut within a week. Is the seepage bad? Hoping you have no cracks in that thing. Why not head bolts?

 

I've gotten a few pushrod V8's from line rebuilders that had a sticking valve at first that glowed the exhaust manifold. Once it unsticks usually everything is fine.

If you really wanted to avoid changing head gaskets and such you could get a stud puller, zap each one out and replace them with ARP head bolts. I'd go 5 lbs tighter on the head bolts though because your rolling the dice with the gaskets.

I can't seem to picture what or where this coolant leak looks like but it seems like the studs are really giving you trouble.

 

Well it's getting complicated again and you have my sympathy C4. I really don't have an easy answer for ya and hope I don't make extra work for ya. At this point I would make a list of the possibilities and eliminate them 1 by 1.

For instance is the coolant only coming from the bolts or from the rocker arm indicating oil in pan/cracked block?

If coolant from head bolts only them it's like 4 possibilities.
1-head gasket/seal
2-crack in head into bolt hole (common w/head porting)
3-crack in block along bolt holes
4-head bolt threads still not sealed

No easy answers w/heads on the motor. BTW does it leak on both cylinders banks? Maybe just pull the worst head at least for a look. Sorry I'm to lazy to look back but did u use some type of sealer on the head gaskets?

Good luck young'n you really have given it a lot and will be a sbc master soon.

 

Head studs notoriously leak when not installed properly. Personally I use Loctite PST #567.

 

One of your replies makes it sound like you're trying to fix this without removing the heads, is that right? If so, I think that's part of your problem.

 

i used a dremel to cut 3 grooves in a bolt that matched the head bolt threads. for both the heads and the intake.

i squirted a bit of oil based whatever in the hole to soften the crude and give it stickiness to the cleaning bolt.

then run the bolt in and out little but at a time and the frooves pic up the crud and clean it out great. do not use a tap. it will remove a bit of the metal. take a head bolt to the hardware store and match it up. there a couple head bolt holes that if you go to far u hit some steel and u may strip the thread hole so be careful you will see what i mean.

then, i used permatex aviation form a gasket and no issues at all.


underneath that was a basic felpro head gasket that came in the kit from rock auto...but i used hylomar as a sealant. lits of opinions about sealant, i researched it and love the stuff.

 

And boy am I ever learning that the hard way.
With the number of hours I have into this engine I could have earned enough at a minimum wage job to buy a decent crate engine. But I'm in it to learn, not just to have a cool car.

I wondered about that. If I can't fix the leaks this second time around I'll send the heads to a machine shop, but there's no point in doing so now as they wouldn't be ready before I go back to VA for college.

I thought it was 300-400 miles, but my memory must have been off. Upon reconnecting the battery when I got the engine back in I saw it was more like 200.

Interesting, I didn't think to use pipe tape. Don't see why not though: seems like it should work great. Any idea how well it works in comparison to Permatex? I'd imagine it might be better for threads that aren't very clean (like mine are).

Bad enough that I wouldn't want a week's worth of seepage in the oil. It's hard to gauge or describe how quickly it's coming up, but it's enough that the oil sitting in the head turned green and gelled. Not enough that coolant could be observed flowing down the drain holes, though.

I'm using studs instead of bolts because that's what came on the engine and I knew studs achieved more consistent clamping force. I didn't see any point to toss the ARP studs in favor of bolts.

When I pulled the engine, I pulled a considerable amount of broken catalytic converter (from my precats) out of the mouth of my main cat, so I'm sure that's what was causing the glowing manifolds. Although maybe a sticking valve could have caused my knocking?

If I replace the studs with bolts, I'll probably just replace the gaskets while I was at it. But I'm going to give sealing the studs one more shot even though it's a huge pain. I'm confident the failure to seal was just due to the threads in the block being dirty and me failing to let the Permatex set up on the studs long enough before I put them in the block.

This leak is just coolant bubbling up from between the nut and the head stud, through the threads.

Yeah, it's tough, and I appreciate your continued advice throughout all my different threads.

Coolant is just seeping up through the threads in the studs and coming out between the stud and the nut. It was doing this on almost all the studs, but my attempt to reseal all the studs fixed the leak on all but 5.

1. I don't have any other reason to suspect a bad head gasket.
2. These heads have not been ported as far as I know, and the fact that resealing the studs fixed most of them seems to eliminate this as the sole source of my leaks (although it could be an additional problem).
3. Not sure how to tell if the block is cracked, but I think the fact that most studs were leaking eliminates this as the block would be falling apart from so many cracks.
4. As of right now I think this is most likely. My attempt to reseal the studs again today will hopefully confirm this.

I have a lot to learn.

Yeah, I am. Don't want to have to deal with replacing the head gaskets and resealing the china walls and intake ports if I don't have to. What is the advantage to removing the heads?

That's how I'm cleaning it too.
I was running it in dry though; thanks for the tip.

So wait, did you use Permatex for the bolts or hylomar?