I am putting my 302 back together - it has been a slow project since other stuff keeps getting in the way.

I got it mostly back installed and put coolant in it a few weeks ago and then had to stop work on it for a while.

Last weekend I went back to resume working on it and noticed on one of the heads, the center freeze plug appeared to be leaking coolant. I wiped it down good and pressurized the system with a radiator tester and sure enough after a few minutes there was more coolant collected in the well around the freeze plug.

Note that this is one of the freeze plugs in the head, not in the block. The head has 3 screwed-in Allen-head plugs under the valve cover.

The heads were rebuilt by a reputable local shop and were supposedly magnafluxed AND pressure tested. I called the machinist back up and he said he has never seen one of these plugs leak and that they don't even remove them when they rebuild a head.

I tried taking it out to see if I could just put some thread sealer on it but that plug is still in there very tight.

Someone else I talked to said that some block sealer might work on it.

Option 3 would be to take it off and send it back to the machine shop.

Have any of you ever seen one of these leak? If so, how did you fix it? I hate to do more work than is necessary - but I also hate having to re-do this job in the future.

Thanks for your sage advice on this.
RP

 

I've never had one leak. I would make every effort to remove it and reinstall it with thread sealer. I would not use block sealer, my experience with that stuff (the powdered metal and Bars-Leak) has been that not only does it seal leaks, but it plugs up the radiator tubes as well and the unused portion ends up in the radiator tank bottoms.

 

baddad,

Thanks for the input - that is exactly what I was thinking - I have too much invested in this build to put a half-a$$ band-aid on it at this point.

I spent 4 hours this morning tearing it down to get the head off and will take it back to the machine shop next week and let them fix it right.

I am glad I at least found this before I put it back on the road - I was literally down to installing the battery back when I discovered the coolant missing...

RP

 

If you're taking it off and to the machineshop, have them magnaflux that area for cracks, it could be that it is cracked around that spot and not the threads leaking.

 

I have tried to remove these threaded pipe plugs but usually the hex just rounds off, making it a tough job. I think you need a 9/16" Allen wrench. Use it to round off the hex, then drill most of the plug out and chisel the outer remains in towards the center.

I removed a few from junk heads for my parts stash because it is difficult to buy them locally. They are a special "flush mount" type, lower profile than regular pipe plugs. Out of several heads, only two unscrewed nicely.

 

I have the hex bit that fits these in 1/2" drive and used an 18" handle ratchet and could not get the thing to budge.

I decided to pull the dang head off because there is an outside chance that it is not the plug and IS a crack that somehow escaped detection.

Either way, I figure I paid to have a head mangnafluxed and pressure tested and it came back leaking, so the shop has some rework to do on their dime.

 

You are right that it is the shop's responsibility. And if you start working on the head, then the waters become muddied since the shop might think that you maybe caused the leak.

 

Block sealer would be the first choice.
I had a rebuilt head from NAPA on a 300 leak out of one of the screw in plugs. Of course it was under the valve cover and I didn't notice it until the cam was wiped out. Apparently the antifreeze ran down the oil drainback hole right onto a cam lobe.