blown out freeze plug on newly rebuilt engine (1 Viewer)

[gash05]

Well the day had finally arrived. I was attempting to start my brand new rebuilt 72 F engine in old Sweet Pea. I had topped of the coolant through a brand new 3 core radiator, new hoses, water pump etc. yesterday. I had topped it off several times throughout the day yesterday as I found leaks, air escaped, my heater core leaked like a sieve etc. Anyway, back to the point. The old girl fired right up and I was adjusting the idle on the newly rebuilt carb when the freeze plug on the back of the block above the bellhousing blew out with a good bit of pressure.

I'm pretty sure that the fluid was not scallding hot as it didn't really burn my eyes, nose, mouth and face as it sprayed all up in them. She had probably run about 5-7 minutes and while I didn't look at temp gauge I figure she was probably about to crack open the 190 degree thermostat. I am at a little bit of a loss as to whether the freeze plug was not installed correctly at the machine shop or if it could possibly be that the radiator cap (either 13 or 16 pounds not quite sure) held too much pressure on the system or something else. The freeze plug has black silicone type substance on the back of it and a dent about the size of a dime in the convex front side. Any thoughts?

 

[Pighead]

Wrong size freeze plug?

 

[gash05]

it is 49mm. Looks correct and double checked the size with $OR. How much of a dent should be in the side you are looking at? The convex side you are facing when looking at the back of the block is dented about the size of a dime but the outer diameter edge doesn't appear to have gone all the way square.

 

[coonassjohn]

Sounds like a bad installation.

 

[FJ40Jim]

How much of a dent should be in the side you are looking at? The convex side you are facing when looking at the back of the block is dented about the size of a dime but the outer diameter edge doesn't appear to have gone all the way square.

Ideally, a Welch plug should be flattened for maximum expansion. If there is a dent in the center but much of the disc is still convex, then there is wasted expansion still in the disc. The hole and the lip the plug registers against should be clean & smooth. Seal the outer edge with Permatex#1 or equivalent. If the plug won't fall into the hole easily, then use a large OD socket or pipe to drive the outer edge in until it registers on the lip. Then turn the socket around and use the flat top to flatten the plug.

 

[65swb45]

I’m not in the shop with my catalogs, but im almost certain it takes a 50mm plug, not a 49. Toyota suffix code 50018.

 

[gash05]

Thanks to all! These comments help with some piece of mind and confirming my suspicions. The owner of the machine shop that rebuilt the engine is going to come by and reinstall a new plug as soon as it gets shipped in. Pain in the rear to get access to it without pulling the engine but got it done by removing he doghouse in the cab and rear mounts to drop the engine. We put a jack stand under the front bumper and lowered the lift she is on until the front wheels came up to get a little extra room to access the freeze plug hole. The firewall is covering up about 3/8 of the hole but allows enough access to get the profiles cleaned up and hammer in a new plug. Hopefully it works out. My only concern now is the rest of the plugs that dont seem to be expanded more than the original problem child. Ughhhh!!!

 

[73FJ40]

Back to basics?

From a welch plug manufacturer:

Welch Plug Installation, Expansion Plug Installation, Hubbard Plug Installation, Cupped Plug Installation, Freeze Plug Installation.

 

[MScruiser]

My engine builder told me to break in the new engine with 100% water instead of anti-freeze. He said the water will help seal the freeze plugs better than antifreeze. Once you’ve run the engine up to temperature for a while, you can take out the water and add antifreeze.

 

[65swb45]

My engine builder told me to break in the new engine with 100% water instead of anti-freeze. He said the water will help seal the freeze plugs better than antifreeze. Once you’ve run the engine up to temperature for a while, you can take out the water and add antifreeze.

That is an interesting concept. I’m going to mull that over for a while.

 

[MScruiser]

That is an interesting concept. I’m going to mull that over for a while.

I can’t recall exactly his reasoning, but it had something to do with antifreeze being “thinner” than water. By using water first, it builds pressure around the seals and helps them set properly.

If you use antifreeze first, you run th risk of having pinhole leaks around the plugs before the seals properly set.

 

[Pighead]

And this is from the guy that put in the wrong size freeze plug?

 

[Bluegrass40]

My engine builder told me to break in the new engine with 100% water instead of anti-freeze. He said the water will help seal the freeze plugs better than antifreeze. Once you’ve run the engine up to temperature for a while, you can take out the water and add antifreeze.

Wonder why that would be? Only thing I can think of is corrosion. Sounds odd but I have seen multiple sites that mentioned that after running on 100% water a bit, corrosion will begin to form causing a better seal for the core plugs. Seems odd to me. I think I’ll stick with a sealant when I put mine in.

 

[65swb45]

And this is from the guy that put in the wrong size freeze plug?

That’s an LOL point!

 

[Bluegrass40]

I can’t recall exactly his reasoning, but it had something to do with antifreeze being “thinner” than water. By using water first, it builds pressure around the seals and helps them set properly.

If you use antifreeze first, you run th risk of having pinhole leaks around the plugs before the seals properly set.

I believe that anti freeze has a higher density and viscosity than water.

Anyone else have any thoughts? Curious.

 

[Pighead]

I think that anything added to water increases it's everything.

 

[middlecalf]

Well plain water will build pressure faster because it will boil sooner than antifreeze.
PV=ρRT
Whether that’s a good thing or not depends on the system design.

 

[Vae Victus]

I think that anything added to water increases it's everything.

Except alcohol and all other low viscosity, high volatility liquids...

 

[Steamer]

There just ain't no way I'd run straight water in a freshly rebuilt engine and start the rust thing going on right away. But that's just me.