Freeze Plugs keep blowing out

[7Mboost]

My freeze plugs keep blowing out under high rpm/boost situations. The first set of steel freeze plugs blew out due to the poor installation of my machine shop, they tapped them in the middle of the plug with no sort of sealant. So after the rear one by the starter blew out twice I measured out a new brass one 40.2mm and correctly tapped it in and used aviation sealant. That plug lasted until after a few runs, the front one blew out. So I decided to pull off the intake and put in all new brass ones with aviation sealant, I went down the road a few times and now the rear one behind the starter blew out again. Also I pressure tested these plugs to 22psi to make sure they would stay and they did, isn't the most pressure the cooling system will ever see around 16psi?

I checked for a BHG by removing the rad cap and letting it run, it didn't overflow. And the thermostat was working as confirmed by watching temperature through the EMS while tuning a few weeks ago so I doubt the brand new Stant 192 thermostat has gone bad, any ideas?

 

[jdub]

If you're using Dorman plugs, they are a 4-5 thou too small. The Toyota OEM plugs are metric...they have to be put in with the plug lip recessed ~1/8" past the block opening surface (it's beveled).

 

[DavidBaustert]

Problem 1...Brass has a different specific heat than iron (block) so it will expand/contract at a different rate. Get steel ones. Autozone carrys dorman metric freeze plugs that I've used in a few motors and never had any problems. Check with a machine shop also to get freeze plugs. You shouldn't need any sealant. They should seal with friction just fine.

 

[IJ.]

Describe in detail how you're fitting them.

 

[7Mboost]

jdub- I went through a box of them and measured them with a micrometer and put in the ones that were just a tad bigger than 40mm (40.2mm). But they are Dorman, am I better off with OEM Toyota plugs? And what are they made out of?

IJ- I put them in with a socket that is slightly smaller than the freeze plug and tapped it in lightly and evenly as I could, picture of the others below.

Here is the front one, not the greatest picture in the world:

 

[IJ.]

jdub- I went through a box of them and measured them with a micrometer and put in the ones that were just a tad bigger than 40mm (40.2mm). But they are Dorman, am I better off with OEM Toyota plugs? And what are they made out of?

IJ- I put them in with a socket that is slightly smaller than the freeze plug and tapped it in lightly and evenly as I could, picture of the others below.

Here is the front one, not the greatest picture in the world:

If you're using the correct size plugs that there will be your problem

You need to get them in with the minimum amount of hits ie: no lots of little taps as it removes the plug's Crush fit needed to hold them in place.
(this is a very old school thing taught to me 33 years ago)

 

[7Mboost]

IJ- Alright, I put in a rubber one temporary to get the car to my shop, and just before I got there I got on it a few times after turning the boost down to 14 psi and it didn't blow out. Which makes me wonder if my rad cap isn't bleeding off, but its a Fluidyne so I just kinda expect it to work, that would blow plugs out right?

 

[jdub]

7M - OEM plugs are steel and are what you want to use. I've used Dorman plugs and had 2 of them blow as you did. Like I said, they are a bit under size for the task...from what I understand, Dorman plugs are based on English measurements, Toyota plugs are metric. I will never use them again on a Supra motor.

An OEM rad cap releases at 13 psi...higher than that is not better. If you are getting high pressure in the coolant system, you just might have a bigger problem

Follow IJ's advice...a single good whack is optimal.

 

[7Mboost]

7M - OEM plugs are steel and are what you want to use. I've used Dorman plugs and had 2 of them blow as you did. Like I said, they are a bit under size for the task...from what I understand, Dorman plugs are based on English measurements, Toyota plugs are metric. I will never use them again on a Supra motor.

An OEM rad cap releases at 13 psi...higher than that is not better. If you are getting high pressure in the coolant system, you just might have a bigger problem

Follow IJ's advice...a single good whack is optimal.

Gotcha, so should I use a OEM rad cap for my Fluidyne? Will it fit? What about a TRD one?

 

[7Mboost]

Tested: And the 22psi radiator cap goes to....... Fluidyne!

 

[Rennat]

did your cap say what "bar" it was?

and FWIW... my haste cap is 1.3 bar... which is 18.85psi...

 

[7Mboost]

Mine was suppose to be a "16psi" cap.

 

[jdub]

The TSRM spec for the rad cap is 10.7 to 14.9 psi...like I said, above that is not "better".

 

[Kckazdude]

Another vote against the Dorman plugs. The QC used to determine size is just plain non-existant. Find Clevite or Sealed Power brand freeze plugs at NAPA or Carquest or go back to Toyota for them. I prefer to use no sealant but have seen others have great success with it as well.

 

[Doward]

I used brass Napa plugs in mine - and further, MEASURED them to ensure they weren't small.

Got all mine in, in 2-3 whacks.

Jeff, didn't you say the originals had been hit in the center? That would screw up the crush of them, as well.

Have any of the ones you've replaced popped back out?

Also, you should NOT have intake pressure meeting coolant - ANYWHERE.

 

[7Mboost]

Only the 1 brass behind the starter popped out but none of the rest, and I measured the brass Dorman plugs in there now, all are 40.2mm. I'm gonna see what the new cap does.

 

[jdub]

Also, you should NOT have intake pressure meeting coolant - ANYWHERE.

If you are getting high pressure in the coolant system, you just might have a bigger problem

 

[7Mboost]

Does my rad cap have to do with intake pressure going into the cooling system? Because that's all I've said since previously..I don't mean boost pressure in any part of this thread.

 

[gaboonviper85]

Hey I already purchased dorman steel freeze plugs for my motor build...they measure 40.5mm am I safe?

 

[Zumtizzle]

You should be.

Make sure you install it in less than 5 bangs.

I've heard of people using Red Loctite.

But i'm sure permatex Hi-Tac or Aviation sealant will be fine.