Father Day drive ends with a blowing freeze plug.

[62 driver]

Went out for a drive and the freeze plug blew out. It the last one on the left of my 1962 390.  When I received the car, in the trunk their was a box of 10 with 3 left in the box.  I have drove the car for about 1000 miles.  I am going to pull the exhaust manifold in hopes of replacing that one.  My question is how to properly replace it.  And what type and brand of sealer should I use? The manifold has no gasket in it now. Should I put one on?

[Jay Friedman]

What a bummer!  This once happened on my '49 while driving on an interstate.  Luckily I could pull over to the side and call a tow truck.  I can't help you with the manifold gasket but the following is my experience with freeze plugs.

I don't know about your 1962, but on a '49 the freeze plug openings are 1 31/64 inches in diameter.  (Why Cadillac couldn't make them 1½" I don't know.)  I had 2 choices, both of which I've used in the past at different times:

1. Dorman metal freeze plugs.  On these you put a little film of red RTV sealer in the seat in the hole in the block or on the perimeter of the freeze plug (or both).  You place the freeze plug in the hole which the sealer should temporarily hold in place.  Then you need 2 hammers, one of which should be a reasonably heavy ball peen hammer.  You place the ball of the head of the ball peen hammer in the center of the freeze plug and whack the other end of the head of the ball peen hammer with your 2nd hammer.  This spreads out the freeze plug slightly, locking it in place.  Depending on the location of the freeze plug on the block, it may not be possible to get a good swing with the 2nd hammer.  (It's easier of course to swing the hammer with the motor out of the car.)  In this case, you may have to go to choice #2;

2. Hard rubber freeze plugs with an integral bolt and nut in the center which can be bought in auto parts stores.  This is what I used that last time.  These are not made in the size of 1 31/64 inches in diameter, so I bought a 1½ inch diameter plug and carefully ground it down slightly on my bench grinder.  They are then inserted in the hole and the nut is tightened, which expands the freeze plug slightly, locking it in place.  It has held for about 10 years, though a couple of times since then I've had to tighten the nut a bit. 

Good luck.  BTW: though they are commonly called freeze plugs or sometimes Welch plugs, I've been told those holes in the block are for sand casting purposes.  The block is cast in sand and then the holes are for draining out the sand .

[walt chomosh #23510]

Dave,
  Check the June 2014 self starter for John Washburn's GREAT article on freeze plugs! It don't get any better.....walt...tulsa,ok

[62 driver]

Thanks!  Yes it was a bummer.  But it happen as I was just pulling out of the driveway.

[62 driver]

Walt,

I would like to read the June 2014 self starter for John Washburn's GREAT article on freeze plugs!  But I gave my paperback book away and I can't find it here to read.  Sad!    Dave

[35-709]

As I mentioned over at the MCLC (among other things) ---

Another thing to keep in mind, once one freeze plug goes the handwriting is on the wall, there will be other failures soon enough.  Jay Friedman's fix should work fine for the least effort and sweat for the time being, but --- my advice would be to pull the engine and do it right, replace all of the freeze plugs before they start failing one at a time.  Ahhh, the fun world of old cars.  Good luck.

[Jay Friedman]

In my case I later found out there was a fault in the engine which caused the freeze plug to blow: I had a faulty head gasket which was blocking certain coolant passages which caused overheating in one section of the block.  Changing the gasket fixed the problem.