Freeze Plug Warning - Don't replace unless absolutely necessary

[tsupranami]

First off, the stock "freeze" plugs should last the entire life of the motor, through several rebuilds, if the cooling system is properly maintained, and should not be tampered with unless leaking or damaged.

They are high quality steel core plugs from the factory, and steel should be used exclusively, as brass is too soft, too succeptible to deformation and heat damage, and does not provide the necessary tension to remain effectively installed.

The front plug is specially installed at the factory and is extremely prone to failure if replaced. It is staked at the edges, a process rarely performed properly by local machinists.

Here are photos an improperly installed front core plug.




You can see how it is dimpled past center. It was driven in by a pointed object, which distorted the plug, but did not expand it into the opening.

Here is what the factory plug should look like. Slightly flattened in the middle, with swage marks around the edge.



The plugs do not need to be removed for any machining or cleaning.

This is an old-school rebuilding technique used on early hot-rods that came with notoriously poor quality OEM core plugs. Early domestic galvanized plugs were prone to rust and corrosion-related failures, and therefore, machine shops replaced them as a standard part of a complete rebuild.

This is NOT recomended on the 7M engine. Leave the plugs alone if they are still in good shape.


Let your builder/machinist know - DON'T TOUCH THE PLUGS!

Thankfully, my machinist has assumed liability for the installation, so I will be able to recover some of the loss, but be warned.....you might not be so lucky!

 

[tsupranami]

In case you were wondering, so what happens if the front core plug falls out?

Well, the coolant will drain directly into the oil pan. The oil pump will switch to a coolant/oil intermix pump, and send coolant everywhere oil should be.

This makes bearings and pistons very unhappy.

The temp gauge won't move, because it measures coolant temp, and since the coolant drains instantly, no temp change will be noticed.

The driver won't notice anything until the overfilled crankcase sends sludge through the breather system and into the intake.

When the smoke comes pouring out the tailpipe, it will be too late for the engine.

This is what a 500 mile engine looks like after front core plug failure...scored cylinders, chewed cams, gouged cam journals, and a lovely broth to marinate it in....

 

[Jeff Lange]

I've replaced plugs many times (I always order them from Toyota) and have never had one fail. Sounds like you got the raw end of the deal.

That being said, I've never replaced one of those type of plugs.

Jeff

 

[91Supra313]

Holy shit man, I had everything you said on here with mine except for the caramel juice. When this happened to you did you basically lose all engine power? like the turbo would still spool up but nothing was happening? and my temp gauge did move. RAPIDLY. Maybe this is what happened to mine. BUT, I caught mine acting up at the .5 mile mark. not 500.

 

[tsupranami]

Yep, Jeff, Toyota parts are the only way to go if you do have to replace them, for sure.

My guage never moved. Once the sensor lost contact with the coolant, the sensor had nothing to measure. So it stayed right at the same, safe, normal mark just below the halfway point on the gauge.

And I lost power all right, because the engine was burning the overflow sludge. I lost power and noticed massive amounts of smoke at the same time. The car ran fine at idle, but any airflow demand sent sludge into the intake and smothered combustion.

Also, the sludge overwhelmed the accordian intake pipe, flooding my brand new $600 OEM AFM with steamy oily goo.

Sounds like you got lucky and caught it before driving it.

 

[91Supra313]

I guess so because it started but there was grinding noises from the cams, no smoke yet thank the car gods.

 

[tsupranami]

Maybe i should have titled this thread "What's a Welch Plug??" Or maybe "Blown Welch Plugs Suck!" Oh well...

A little history lesson on core plugs:

"Freeze" (core) plugs and "welch" plugs are two different animals doing basically the same job. One is weaker by design, and meant to be easily replaced, the other is decidedly not meant to be replaced often, if at all.

The plug in the front of the block is most properly called a welch plug. Welch plugs are concave metal disks which expand in diameter when flattened, seating and sealing thier outer edges against the machined bore of a countersunk hole. The plug sits on a locating ledge inside the hole They start off smaller than the hole they seal. It is an expansion plug. They were designed by the Welch brothers in Pontiac, Michigan, and patented in 1905 by the M.D. Hubbard Spring Company.



The plugs along the sides of the block are simply called "core plugs", but are often called "freeze" plugs, as they are usually the ones that come out first when water freezes in an engine block. They are cup shaped disks that do not expand when intalled. Instead, they start out larger than the hole they fit and compress the extended sides inward to create the sealing pressure against the bore of the core hole. They are slightly larger than the hole they seal. The radiused edges of the cup and the chamfered edges of the block core hole allow the plug to be driven into and seal the hole. It is a pressed (compression) plug.



Both plugs are a type of core plug used by factories to seal holes drilled into "cores" (hollow areas) during production.

These core plugs are not designed to relieve pressure from freezing water trapped in the block. They are used to seal the holes in the block used by a supporting arm of the sand "core" whick forms the hollow coolant cavities inside the engine block while molten iron was being poured into the sand mold. They are core plugs, not freeze plugs.

The larger diameter compression plugs along the sides of the block are easily replaced, but are weaker and more likely to need replacement. If they fail, the engine will lose all coolant and possibly overheat if not shut off in time.

The smaller diameter expansion plug at the front of the block is not as user-friendly. If removed and replaced improperly, it can lead to catastrophic engine failure, as previously described. If replacement of this welch plug can be avoided, I would recommend leaving it alone.

If it does need replacing, installation is fairly straightforward. Read the manual, use the right tools, and clean and inspect thouroughly. I also understand that loctite, epoxy, or at least a good sealant should be applied in all core and welch plug installations to ensure a positive and lasting seal.

 

[dubsupra209]

i replaced all 11 i think freeze plugs cause i told the machine shop not to remove them but they did anyways....but i ordered them all from toyota and ive had no problems with them since...

 

[IJ.]

"Welsh Plugs"

 

[tsupranami]

Welsh plug. LOL! Isn't that what they call a sheep shagger from Wales?:biglaugh:

 

[turbo87targa]

Welsh plug. LOL! Isn't that what they call a sheep shagger from Wales?:biglaugh:

Lmfao

 

[IJ.]

Welsh plug. LOL! Isn't that what they call a sheep shagger from Wales?:biglaugh:

LOL'd

 

[feenickz]

so if i get my block hot tanked, i dont need to replace any of the plugs? im getting ready to take my block to the machine shop and need to know. if you could PM me that would be awesome, thanks

 

[toyotanos]

All the more reason to work with a machine shop who knows what they are doing. When I showed up with my block for machining he noticed it right away.

I'm glad I used OEM plugs as well, seeing as Sean's engine dropped all its coolant due to an aftermarket one D: !

Feenicks- I had my block hot tanked because of the fix-a-leak that had been used in the cooling system, therefore I had all the block plugs replaced to prevent possible leaks.

 

[CyFi6]

Steel plugs do not need to be replaced when tanked, but brass ones definately do (they will be steel if they are original). My block was tanked and I didn't touch the core plugs. If they are not rusted, leave them alone.

 

[feenickz]

cool thanks guys