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soft plug leaking

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RestoreThemAll

Jedi Warrior
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My stupid question of the day. I put water in a freshly rebuilt engine getting ready for a first startup. I noticed a slow drip coming from the soft plug in the back of the head. The engine would not fire the first time. Issues are now resolved but it hasn't started up yet. It's had water in it for four days, and has now stopped leaking water. I can see rust from the drip on the new green paint on the bell housing. Here is comes...do I pull the head and put in a new soft plug or run it and see what happens. It won't hit the road until spring. So run it will be a few minutes a couple of times per month through the NY winter.
 
Yes, the expanding metal will seal up the leak.:highly_amused:

But then there is that pressure thing.

I've had two mechanics tell me that they've seen small leaks with new rebuilds and they can stop leaking. I certainly have my doubts about that.
 
I'm very sympathetic - however some thoughts come to mind.
Not to be a doomsayer but my guess is it could get worse rather than better.
Since it hasn't run yet, you should be able to re-use the head gasket.
If you wait until springtime when you want to start driving it, it may be even more of frustrating to tear it down.
You are looking forward to enjoying the car and that will be even better if you have complete confidence when you go out, it's never as much fun when you have a nagging worry floating around in the back of your mind.
I know it's frustrating, but I would do it now and then you will be a lot more comfortable/relaxed/satisfied when you do go for a drive.
 
I agree with you guys. I think I'll spring for a new head gasket though. I hate to toss away money but I really don't want to do this again.

AH spares has a $26 and a $93 uprated head gasket. Can the uprated be THAT much better?
 
AH spares has a $26 and a $93 uprated head gasket. Can the uprated be THAT much better?

Man it would have to get really up! fore i paid that kind of silly money fo it.
 
RestoreThemAll said:
Yes, the expanding metal will seal up the leak.:highly_amused:

But then there is that pressure thing.

I've had two mechanics tell me that they've seen small leaks with new rebuilds and they can stop leaking. I certainly have my doubts about that.
Click to expand...
My company had a few semi trucks and we used "solder seal" to seal leaks and it
worked great.
 
Patrick67BJ8 said:
My company had a few semi trucks and we used "solder seal" to seal leaks and it
worked great.
Click to expand...

Good idea. I assume that the original poster is speaking about what others call frost plugs or expansion plugs. If the plug is new and is just leaking a little around the edge, dry it well, use sandpaper to rough up the surface, and then apply a little sealant. My sealant of choice would JB Weld - an epoxy type sealant. If it was not installed properly with the center dimpled correctly, that may be another matter, and it then may require replacement.
 
Wouldn't the BN7 engine have cup type plugs rather than the type you have to dimple?

Danny

I should have written BJ7
 
Last edited:
We used to use a product called Alumaseal. Add to radiator and run engine for a while to circulate throughout and leak sealed. Do not know if still available but worked wonders.
 
Back in the 1970s I used solder seal on an old ford daily driver and it worked well. It would be a nice quick fix, however, my BJ7 engine has just been rebuilt tip to toe. I'm not sure I want that stuff in a brand new classic car.

From the Moss on line catalog
[TABLE="class: PlateDetailTable, width: 100%"]
[TR="class: PlateDetailAltItem, bgcolor: palegoldenrod"]
[TD="class: PlateDetailItemProdCode, align: center"]328-265 [/TD]
[TD="class: PlateDetailItemRegPrice, align: right"]$1.69 [/TD]
[TD="class: PlateDetailItemPrice, align: right"]$1.69 [/TD]
[TD="class: PlateDetailItemDescript, align: left"]
CORE PLUG, cupped, 1 5/16"
[/TD]
[TD="class: PlateDetailItemApp, align: left"]BN7, BT7, BJ7, BJ8[/TD]
[/TR]
[/TABLE]
 
Cupped core plugs can be problematic and if you are not concerned with originality and never want to have to deal with the problem again you might want to consider using a two-piece plug such as made by Belcamp. I use them on the block of the MGA engine in my Elva Courier and have never had one fail.

You can probably find several instructional videos on youtube telling how to use them--I carefully clean the edges of the hole to get down to shiny metal, coat the inside of the hole with JBWeld and install the plug, cranking down with two wrenches. Logistically this is sometimes difficult on a block with an engine in situ but assuming you are not adverse to pulling your head the installation should be easy.

On a somewhat related note I once blew out the small brass plug that is driven into the back face of my 100's block--luckily it happened when I started the car and I actually heard the ping as it was driven by pressure into the firewall, then saw a small pool of oil on the floor of the garage. At first it looked like I was going to have to pull the engine to get access so that I could drive in a replacement bung but by removing the vertical transmission cover panel I was just able to bang the plug back into place using a long punch.

Whatever path you choose to take do something--I was lucky that this incident happened in the garage and more likely your leaking core plug will only get worse and give you a problem when you are out driving, etc.. The first thing you'll sense is the smell of coolant followed quickly by a coating on your windshield and you'll have a big mess to clean up.
 
CaptRandy said:
We used to use a product called Alumaseal. Add to radiator and run engine for a while to circulate throughout and leak sealed. Do not know if still available but worked wonders.
Click to expand...
Go to anybtruck stop or truck repair/parts place a d they have it. Don't use too much for in the Healey because the radiator and engine are a lot smaller. Another favorite is Bars Leak and it was specified in my handbook when I bought my 12 cup Jag and they called it two satchels of Bars Leak. Going from memory so don't beat me up.
 
I like the Dorman expandable copper freeze plugs vs the rubber ones, which are often considered temporary.
https://www.dormanproducts.com/c-353-expansion-plugs-quick-seal-copper.aspx
screenshot.740.jpg
 
Patrick67BJ8 said:
Go to anybtruck stop or truck repair/parts place a d they have it. Don't use too much for in the Healey because the radiator and engine are a lot smaller. Another favorite is Bars Leak and it was specified in my handbook when I bought my 12 cup Jag and they called it two satchels of Bars Leak. Going from memory so don't beat me up.
Click to expand...

I can also vouch for both Bars Leak and Alumaseal. I had an old car, and little money, during most of high school. I kept my old Ford V8 running on a shoestring, so I used Alumaseal to stop a leaking radiator tank that had a few pinhole leaks at its seam. One application lasted several months. IIRC, Alumaseal was a fine metal powder, and Bars Leak looked like molasses with rabbit pellets mixed in. We used Bars Leak to fix a weeping freeze plug on an F-250, and it worked for a long time, until we finally dismantled the engine for rebuilding, and could then get to the bad plug to fix it properly.

I will add that when I finally had enough money to get the radiator and the tank proprtly fixed, I got an "earful" from the crusty old dude that ran the local radiator shop. The first thing he said when I came to pick it up was "Did you add the GD Alumnaseal to this?" It left a residue, and had also sealed up some of the partially blocked tubes, so he wasn't happy. In the end, after I had asked about and admired the '40 Packard limousine he kept in the shop, he warmed up a bit. He only charged me 15 bucks (7 hours pay!) for the cleaning and repair - probably at least a couple of hours work. He was actually a pretty good guy.

I wouldn't hesitate to try it in an engine that was fairly clean, but if the cooling system is at all gunked up, then maybe not, given the radiator shop guy's reaction...

Note: I just saw Steve's expandable plug, so if I could get to the bad plug, without pulling the head, I would try that first!
 
Not to take this thread in another direction but are these plugs really freeze or heat protection? I like the idea of using JBweld or red thread locker, etc... but that probably would stop the plug from popping if the car overheated. It's never going to freeze so over heating would be my main concern.
 
Jim, not to argue against the Alumnaseal but your radiator guy may have cover it.

"It left a residue, and had also sealed up some of the partially blocked tubes, so he wasn't happy."
 
RestoreThemAll said:
Jim, not to argue against the Alumnaseal but your radiator guy may have cover it.

"It left a residue, and had also sealed up some of the partially blocked tubes, so he wasn't happy."
Click to expand...

Dale, you are correct, but I guess the point that I was attempting to make was that that kind of stuff can work if circumstances dictate no other real choice, and I'm all for a proper fix, whenever possible! I do like the ideal of trying an expandable plug, if it's a lot less work than pulling the head...although, I have been to Upstate NY in the winter, so I imagine that you'll have LOTS of time in the next few months. Cheers! Jim
 
Jim, Yes, we'll have plenty of indoor time soon...this weekend! Thanks for rubbing it in from NM.:playful:
I'm sure I'll hear from my son in FL how warm it is there.
 
RestoreThemAll said:
Not to take this thread in another direction but are these plugs really freeze or heat protection? I like the idea of using JBweld or red thread locker, etc... but that probably would stop the plug from popping if the car overheated. It's never going to freeze so over heating would be my main concern.
Click to expand...

We always called them "freeze plugs" and yes, I have, unfortunately, seen them work as designed! A lot of them were probably access points during the casting and machining of the block and head, but they were also designed to be pushed out if the cooling mixture freezes, so I would hesitate to epoxy them in place. When changing them during a rebuild, after the block or head was "tanked", and when replacing a couple that had pushed out in my brother's car (@<-20F), we just painted the edges with Permatex, and then drove them squarely into their bores.

I think you would have to get it very hot to blow one. The radiator cap should act as a pressure relief, if not then probably a weak hose or hose joint would fail first, and there would probably be other "issues" if it got that hot! It's probably happened, but I haven't seen it.

Oil gallery plugs are a different animal!
 
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