[nUcLeArEnVoY]

Title about describes it. Car is a 1979 Trans Am 400ci.

As part of a heater core R&R, I found it necessary to also replace the nipple on the passenger cylinder head since it contains a very important rubber restrictor in it. Good call on my part, since when I removed the original (combination of hammering a pry tool under the crimped ridge to start lifting it out the bore while twisting/turning the nipple itself with vicegrip pliers), the rubber restriction insert was completely gone. Not sure if it was re-installed in the past that way or the rubber just dissolved over 45 years because it looked to be the original nipple - not really anything in the way of rust, though, surprisingly. I'm sure the lack of that restrictor contributed to my heater core failure, though honestly the heater core was probably circling the drain, anyway, as it was the original 1978-date coded Harrison core.

Anyway, the replacement nipple I got was a repro from Firebird Central. Looked serviceable, so I figured it should be alright. A lot shinier than the original.

My install was an effin' mess. I think I may of used a socket that was way too small in diameter, just large enough to fit the nipple itself in and not contact all the way to the outer diameter of the nipple, and so by the time I pressed the nipple in, the inner circumference of it was caved in, not to mention the ridge wasn't flush to the cylinder head all the way... there was a small portion (around 35% of the total circumference) of it toward the back that I could slip my fingernail under while the rest was flush, and no matter how many times I tried hammering that spot down, it wouldn't press in further. It looks mangled to hell in that spot and sure enough, that's where the leak was. The leak occurred when I ran the car with the radiator cap on and under pressure, it didn't leak when I spent 45 minutes idling and burping the system the day before, which makes sense since there was no pressure in the system during that process since the cap was off.

I used Permatex #1 to coat the nipple skirt before install, which I think is fine since that's what Permatex #1 is for - my issue isn't sealing (well, it is, but...), it's the way it was installed, I'm pretty sure.

I'm looking for pointers on install. What size socket should I use? Or is there another tool that can guarantee a more straight, even press that won't mangle the chit out of the nipple as I press it in? It's hard to get a good visual on if the nipple is positioned perfectly before pressing it in when the engine is in the car. I removed the distributor cap which gave me clearance to do the hammering, but like I said, still difficult to gauge if the nipple is positioned straight for a smooth install.

Is this also an issue of part quality? Has anybody else ever had issues with the new repro nipples from Inline Tube or Firebird Central? Once I noticed the leak, I ordered another one - this time a NOS #499744 unit I found on eBay, still in box - hopefully it will go in smoother.

Another thing I noticed, even though the bore on my cylinder head appeared to be pretty clean and non-pitted after removing the old one, I did notice and could even feel with my finger a casting flash ridge at the bottom of the bore in a certain spot (can't remember where)... not sure if that was what was stopping that one spot of the nipple from fully pressing in or what, but then that wouldn't explain why the old one never leaked. Maybe the new repro one has a longer skirt on it, causing it to bottom out on that casting flash ridge. Not sure, I didn't have a chance to compare the repro to the original before tossing the original in the trash. Like I said, it must've been an install error because I mangled the hell out of the thing and it was not fully flush to the head.

So please, any suggestions on technique; what size socket; or another type of specialty tool for a smoother press of the nipple into the head. Thanks!

Some good news, though, the new heater core doesn't seem to leak, hahahaha.

[Gary H]

How bad of a leak is it? If it's just seeping, or a drip, then it will probably seal on it's on. I would try a couple of stop leak tablets in the radiator before I went to the trouble of hammering it back out. I just built an engine for a customer and while breaking in the engine it started leaking at a rear freeze plug on the head. It was leaking probably 2 drips per second but after running the car 30 minutes or so, it sealed. I put in a couple of Barr's stop leak tablets just to be on the safe side afterward.

[nUcLeArEnVoY]

Originally Posted by Gary H

How bad of a leak is it? If it's just seeping, or a drip, then it will probably seal on it's on. I would try a couple of stop leak tablets in the radiator before I went to the trouble of hammering it back out. I just built an engine for a customer and while breaking in the engine it started leaking at a rear freeze plug on the head. It was leaking probably 2 drips per second but after running the car 30 minutes or so, it sealed. I put in a couple of Barr's stop leak tablets just to be on the safe side afterward.

Probably enough to eventually drip. I don't think stop-leak would work, plus just piece of mind that it's properly installed is what I'm looking for. When I caught it, you could see coolant accumulating against the nearby edge of the valley pan gasket, and I even caught glimpse of it seeping out again after I wiped it dry while the car was running. Definitely not two drops a second, though; but a little more than just typical weepage. I paid a lot of attention to that spot while checking for leaks after the heater core job, since I was very suspicious and anxious about how that nipple was installed, I didn't feel confident in it at all. Turns out I was right.

I'm mostly just looking for piece of mind on proper install. I want to get to the bottom of why that one part of the nipple just wouldn't press flush with the head, and that part is exactly where the leak was coming from.

[steve25]

You will need to replace it again.
The few times I have done this fix while on the car I used a very big and thick washer as a plate to have my socket I used to drive it in rest on.

If I recall right this washer was so big in OD that I had to cut a flat on it to clear the end of the intake manifold.

I don’t even recall where I got that massive washer.

The first hit with the ball peen hammer is the most important.
If you do not start it in straight on that shot then you end up making the round part that seals oval.

I at one time stocked up on 14 of the original thick steel ones from the 60s and have gone thru them all.

Sure wish the current replacements where made that way!

[nUcLeArEnVoY]

Originally Posted by steve25

You will need to replace it again.
The few times I have done this fix while on the car I used a very big and thick washer as a plate to have my socket I used to drive it in rest on.

If I recall right this washer was so big in OD that I had to cut a flat on it to clear the end of the intake manifold.

I don’t even recall where I got that massive washer.

The first hit with the ball peen hammer is the most important.
If you do not start it in straight on that shot then you end up making the round part that seals oval.

I at one time stocked up on 14 of the original thick steel ones from the 60s and have gone thru them all.

Sure wish the current replacements where made that way!

This is exactly what I suspected may be going on. I mangled the hell out of it installing it. Like I said, I only used a socket with a very small diameter - not nearly enough to reach the other diameter of the nipple.

The thick steel ones with the bimetallic coil seem ideal, but I want to stick to what's correct and used the stamped ones with the rubber insert. At the very least, the one I have coming to me now is a NOS GM unit, so hopefully that will streamline things.

I'll definitely look into the washer, that's a damn good idea. As mentioned in my post, the socket I used was a smaller diameter than the overall diameter of the nipple, and so the socket essentially caved in the inner circumference of the nipple, since it's only stamped steel... that could not have helped things a lot.

[steve25]

All you need is like two washers to stack up with a OD at least the size of the nipple.

You can grind out the ID if need be to clear the nipple.

Also check that you don’t have a rusted on broken off section of the old mangled nipple left in the bore for it.

[Greg Reid]

I haven't done this but I imagine that if I have to, I might use a block of wood...maybe 4"x4"x4" with a hole in the center just large enough to clear the center nipple but make contact with the collar all around it. The wood won't damage the piece and will give you a visual of how straight, or not, it's going and the flat surface gives you even force over the contact area.
It's basically the same way I drive a pinion seal. Flat piece of wood with a hole to clear the pinion.

[tjs72lemans]

I would also double check the bore in the head where the nipple is being inserted. If there is a cast flange at depth, measure the depth and check your nipple. You may have to grind some length off to get it to seat at correct depth.

[steve25]

The nipple seals on its wall OD so I don’t see much logic to what’s stated in the above post.

If it only goes in even 1/2” it will still seal as required, just that on high usage daily driver it will be prone to rotting away faster.

[nUcLeArEnVoY]

Originally Posted by steve25

The nipple seals on its wall OD so I don’t see much logic to what’s stated in the above post.

If it only goes in even 1/2” it will still seal as required, just that on high usage daily driver it will be prone to rotting away faster.

I removed the nipple I installed and there is a dent at the bottom of the skirt from when I installed it, and the inner circumference as I said is caved in, which caused the nipple itself to bent at an angle rather than be straight up.

There is a rust ridge at the bottom of the bore from where the old one was, but assuming the new one has the same skirt length as the original, I don't see why the rust ridge would be an issue, since the new one should essentially stop at the same exact spot right where the rust ridge starts. Either way, for some extra insurance I'll make sure to try to sand down that rust ridge a bit. I measured to the casting ridge I was talking about and it's not an issue, it clears plenty of room from where the nipple would stop when pressed in flush.

I got the washer - nice and thick and just manages to reach to the overall diameter of the nipple.

Fingers crossed I'll be able to install it right this time. I think I can just chock this up to poor install with a bad press angle and using way to small a socket that didn't reach anywhere near the outer diameter of the nipple.

Attached are photos of my bore - like I said, not bad. Just the rust ridge. First photo shows the rust ridge , and the second photo shows the casting ridge at the top of the hole.

[nUcLeArEnVoY]

Update 07/08/2023:

Leaking still after installing the NOS fitting, this time even while burping the system and therefore no pressure. It's a very slight leak, like a seepage like before. Either way, still shouldn't happen.

I pressed it in with a thick washer this time that just reached the outer diameter of the nipple and didn't mangle it nearly as bad, but at first it still did the same thing where the rear 1/3 of it closest to the valley pan wasn't pressed flush to the cylinder head surface, and I could slip my fingernail underneath the flange in that spot. I was finally able to get it fully seated and flush after pulling the entire distributor to get me the straightest angle with the socket, but it still ended up leaking. I guess it really does come down to that first smack with the hammer. I even filed down the rust ridge pictured above. I wonder if me constantly whacking it trying to get it flush in that spot that doesn't fully seat ends up breaking the crimped seal...

May as well get the repro fitting for the third try, since the NOS one did the same chit as the first one I tried. This is really starting to piss me off, what a stupid problem and I've perused all the forums and nobody else has had a similar issue. This was the very last thing I thought would give me the most headache with this heater core job.

Screw it, for the third try, not only will I just pull the entire distributor from the get-go so I can get the straightest angle, I'll get an even wider diameter washer to further distribute the force. I'm also not going to use Permatex #1, I'm just going to smear a coat of the specialty water pump and thermostat housing RTV by Permatex. That was the only stuff that got my thermostat housing to stop leaking after using all manner of paper gaskets.

Man, I hate press-in fittings...

[nUcLeArEnVoY]

Removed the NOS fitting from the second attempt that leaked. I marked a yellow paint daub on the side where it leaks from closest to the valley pan.

Nothing glaringly wrong with the skirt itself. Still pretty round, pretty obvious it's not bottoming out on something so I guess the rust ridge was never the issue. However, notice how the inner piece in which the rubber restrictor is placed when looking from the bottom of the nipple has shifted, while looking at it from the above, the nipple itself is sort of deflected the opposite way. The inner piece when looking from under the fitting is shifted TOWARD where the leak occurs and appears to be bending the stamped steel of the outer crimped shell. You can see it is sort of caved in when looking from the above the fitting opposite of where the paint daub is.

This is clearly an issue of some sort with installation. I'm not sure if this deflection occurs from the first strike, or if it occurs during the subsequent strikes gradually since I apparently keep messing up the first, or if it happens when I try to pound down that spot that never fully seats (which is exactly where it leaks from). It's also possible this deflection occurs as I'm removing the nipple with the vicegrip pliers. I basically just grip the nipple under the raised lip and twist and turn it until it starts to move.

This is similar to how the first repro nipple I tried to install looked, only that one was way more mangled and I couldn't get that one to seat flush at all.

With both attempts, the initial press-in was done with the distributor still in place but only with the cap and Rotor removed. I'm wondering if the distributor being there is causing me to not get a true visual on if the fitting is positioned correctly for a straight press...

This is odd. What do you all make of this? Maybe it's leaking from the crimp where the outer shell is crimped to the inner piece due to the deflection of the inner piece compromising the crimped seal; rather than from coolant seeping from the between where the skirt is pressed into the bore...

[Greg Reid]

I would say that whenever you cocked that top nipple is when that happened.

Sent from my moto g stylus (2021) using Tapatalk

[Tim Corcoran]

Why don't you get a rotary file and remove that casting flash that prevents the nipple from being fully inserted?

[steve25]

Your flat spot that you made on the nipple portion itself from removal will not let a hose seal on it now.
BTDT myself.

[nUcLeArEnVoY]

Originally Posted by steve25

Your flat spot that you made on the nipple portion itself from removal will not let a hose seal on it now.
BTDT myself.

That's fine, I just bought another new one on the way.

[nUcLeArEnVoY]

Originally Posted by Tim Corcoran

Why don't you get a rotary file and remove that casting flash that prevents the nipple from being fully inserted?

I measured and the casting flash turned out never to be an issue. It doesn't get in the way at all.

I dont know what keeps causing that rear 1/3 of it to not to press flush, at least initially. I'm starting to think the angle I'm pressing it in is not fully straight, and so I end up bending it as pound it down.

[nUcLeArEnVoY]

Update 07/17/2023:

Whelp guys, after the third try with a third new fitting (this time the OER repro), I think I finally have this issue solved and can blame it on the way the first two were installed.

This time, I removed the entire distributor which is what I think made the biggest difference. I took a good look at how the socket I was using (which was a fairly long socket, at least 3") was contacting the circumference of the nipple fitting and discovered that the distributor was actually causing it to sort of cock toward the front of the nipple facing me (on the passenger side), which is exactly where you can see it's caved in on the prior photos of the second attempt. So basically, as I was striking the socket, even with a washer between it and the nipple to cushion the force, it was applying ALL the force and energy to that front part of the nipple, causing that side to cave in and the entire inner piece to bend toward that direction as well. In turn, the skirt that seals on the OPPOSITE side became stretched, which is why that opposite side never sat flush against the cylinder head, and was where it leaked from.

Not sure if that makes sense, but this time I removed the entire distributor and was able to get the correct straight, perpendicular angle with the socket and was able to see that it was making full contact with the fitting. I also used the perfectly sized washer (shown in the pics, found it at Lower's - it has a 5/8" ID and is around 1/8" thick) that is far larger in diameter than the nipple itself, but JUST clears the intake and valley pan. The washer is very much needed between the nipple and socket to distribute the force applied by each strike of the hammer into your socket of choice. After hammering down the nipple flush on this third attempt, the fitting pressed in nice and evenly all around, the flange is tight against the head surface around the entire circumference of the fitting, not to mention no sunken in parts of warpage at all - not even any marring since the washer cushioned the force so well. I couldn't have done anything better with this third install. I used RTV to dress the skirt this time as well, but honestly I think the bigger contributing factor was the correct install.

After filling the cooling system, burping it with the radiator cap off, and also letting her run up to temp with the radiator cap on and build specified pressure, the fitting has been dry as bone with no evidence of seepage.

So moral of the story, kids: If you want to R&R the passenger cylinder head heater hose nipple fitting with the engine/head still in the car, you *DO NEED* to remove the ENTIRE distributor in order to get a good, straight angle with your socket to get an even press fit and prevent warping the fitting. Maybe using a short enough socket that doesn't come anywhere near the distributor body could work, but it was easier overall not having the dizzy in the way. I don't imagine this is common knowledge, since I have a feeling most of the time this fitting is replaced is when the engine or cylinder head is out of the vehicle.

Thanks for the help, everyone.

[steve25]

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Good to hear!