Jump to content
HybridZ

Need Ideas, Keep Popping Freeze Plugs!


Recommended Posts

Alright fellas, this was very costly the first time it happened, warped a head. since then I've been much more careful but it still happened again, and again and again. AKA 4 times now. This is just bizarre.

 

I dont have any cooling issues to speak of. I'm not overflowing coolant out of the radiator. The only thing I can say is that 3 out of the 4 times it happened when doing a burnout, then once last night when I was under full boost. I dont seem to have an headgasket sealing issues, as this has happened with both a standard headgasket and now with my metal HG which has been retorqued several times.

 

I was thinking that perhaps when I do a burnout the rpms rise so fast that the coolant doesnt have enough time to flow and pressure builds up. The plugs SHOOTING out of the block!

 

Guys I really havent heard of this happening to others and it scares me, because it usually leaves me totally stranded.

 

Ideas??

Link to comment
Share on other sites

I've done it one time before, on my l24. Missed a shift on a dirt road and hit 8k real quick, and that's when it popped out.

 

Is it the same plug every time, or does it vary? If it's the same one, perhaps the hole is a little distorted or something.

Link to comment
Share on other sites

The local machine shop here, taps 3 small holes around the edge of the freeze plugs. then screws 3 small button head bolt into them providing a mechanical way of locking the plug in place. I would first figure out why you are popping plugs, but this is an option for you. Keith

Link to comment
Share on other sites

well I will continue to investigate the cause, but like I said its been on multiple setups different headgaskets, etc.

 

This doesnt always happen on the same hole, 3 different ones now. I went ahead and replaced it with another plug and this time I JB welded the outside seams. Hopefully this works . . .

Link to comment
Share on other sites

  • Administrators

Garrett,

Hmm. How were your core plugs original installed and what is the procedure that you are currently using to install them, i.e. prep work, sealant, etc?

 

This the procedure I use on ALL of my engine build ups and to date, have not had one pop out.

 

1) clean the core plug hole with 120 grit flapper wheel or scotch brite flapper of some sort to removing and all previous sealant rust etc.

2) I use a “Permatex form-a-gasket part 1A” sealer, smear a thin fill in the core plug hole and also a small film around the outer edge of the core plug itself.

3) Using a socket or other driver that is approx 1/8 smaller than the ID of the core plug, drive the core plug to the lip is just below flush from the block, (the 1/8” smaller diameter driver allows the sides of the core plug to squeeze in without squeezing onto the driver. Don’t use too small of a driver though).

4) Remove any excess sealant that oozed out and let it set for at least 24 hours.

 

 

I prefer not to use Silicone sealant as it doesn’t offer any real holding power. JB weld on the other hand should hold it in forever if the core plug opening was thoroughly cleaned first. (I feel sorry for the poor machinist/engine builder that ends up having to remove that core plug during its next rebuild, LOL)

 

 

FWIW, engine builders/machinist prefer to call those “core plugs” or “soft plugs”, the term “freeze plugs” is a misnomer. Those plugs have absolutely NOTHING to do with protecting the block from cracking due to the coolant freezing etc. those holes in the block are there to allow the sand to be removed when the block was originally cast, i.e. “core holes” so the plugs that fill them are called “core plugs”. Back in the early years of the automobile, if a block froze with the old style core plugs, those plugs would sometimes pop out, so most people started to believe that was what those plugs were for, to relieve the pressure of the expanding ice. They were dead wrong. Their blocks and heads still broke and cracked if they froze even though the Core plugs popped out, (I’m sure many of you have experienced this on your own), but somehow, that term “freeze plug” stuck around.

Just thought some of you would enjoy that little bit of lore.

Link to comment
Share on other sites

I agree with 383 240z and dr hunt. I've heard of using three small screws to 'pin' them in. Dr hunt's idea is a good one too. I don't think there is anything 'wrong' that needs fixed, just extreme use. I've also seen a small steel strap (about a quarter inch wide) screwed to the block spanning the hole. That might be easier to do if the engine is still in the car. I've also heard the same thing about brass plugs... to soft, they're for marine applications.

How does the car cool? Otherwise no problems? Maybe slow the water pump down.

Link to comment
Share on other sites

It still sound like your building to much pressure in the cooling system and the rad cap can't blow fast enough to relieve the pressure? I can see 1 plug falling out because it was loose but several Hummm seems odd ?? what psi cap are you running? Maybe a small crack in the head it only happens under boost pressure,you said you warped it ,did you chandge the head or fix that one?

Link to comment
Share on other sites

a core plug with a remote pressure gauge to see if you are really boosting coolant? Strapping or screwing a fixture to keep the plugs is only a temporary fix if you have a pressure leak into the block, so why not (in the interest of pure science if nothing else) confirm or disprove a possible head leak by monitoring the colant pressure?

 

Otherwise, throw in a radiator cap with a lower blow off rating. If it's a reoccurring problem, there is certainly something that is constant that needs to be addressed...no?

Link to comment
Share on other sites

Its done it with both 13 and 16psi caps on the rad.

 

I've blown one on the turbo side and 3 on the pass side.

 

The head was replaced with a fresh rebuilt one after the last one warped.

 

I dont see coolant being pressurized elsewhere. Never get any Rad. overflow, dont have any cooling issues to speak of. Car runs beautifully and then every once in a while . . . POP.

Link to comment
Share on other sites

Regarding staking the plug in place......I'd think twice about using this method! Why? If you ever have to replace them, the bore the plug presses into will no longer be round, due to the staking process. The screw method sounds like the correct choice to me.

 

Tom

Link to comment
Share on other sites

Could the water pump be causing that much pressure to blow out the freeze plugs?Maybe under high RPM'S?dosen't seem like that would do it.What else could cause pressure in cooling system? Vibration?

Never heard of the water pump causing that much pressure. I had a friend miss a shift and probably hit 10,000 rpm in her Z, no freeze plugs let go. I've got friends who rev their L4s to 8000 rpm, never seen any of them lose a freeze plug.

 

I think the most likely idea so far is that there is a leak between the cylinder and the headgasket and that this is allowing the compression to pressurize the coolant. I suppose it could also be a cracked block doing the same thing.

Link to comment
Share on other sites

  • Administrators

Ditto what Mortensen said.

If it were the water pump, or other “cooling system” issue, we’d be hearing more of this same scenario, including guys with bone stock engines as well. Garrets cooling system shouldn’t be running much if any different than any other L-series cooling system.

 

Another situation could be the block is cracked across the core plugs and the block could be flexing just enough to allow those core plugs to pop out due the cracks running the through the core plug bosses. If this were the case, the cracks would be visible to the naked eye and I’m sure Garrett would’ve seen them by now.

 

More than likely, Garrett is getting combustion pressure in his cooling system somehow and that is causing his core plugs to pop out.

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

×
×
  • Create New...