Need Ideas, Keep Popping Freeze Plugs!

[Garrett76Zt]

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.

 

If the coolant was being pressurized then wouldnt i be blowing hoses off or at least overflow from the radiator? Car runs perfectly and then just pops one out. I've been getting on the car pretty hard the past couple days since Jb Welding em and I've had no issue so far.

[Buzz]

I'm still thinking head gasket or cracked head?no water in the oil or oil in the water?happens at high RPM?could the head bolts flex under high boost?

[Garrett76Zt]

hmm, I'm not sure on that one, I dont see any other evidence of a HG issue. but i will double check and retorque it again. I suppose its possible the block has a crack in it It did get very hot the first time I popped a plug and warped a head. However it obviously didnt get CRAZY hot because i didnt loose any bearings or have any moving parts damage in the bottom end. At any rate the plugs seem fine now with some JB magic on em, haha.

[510six]

I vote for the combustion pressure getting into the coolant passages.When I ran the big shot of N20 I always have had the coolant catch can fill up.Once the block was O ringed and a NISMO HG was used the problem wasn`t as bad but it still happens.

[Garrett76Zt]

maybe i havent said it clearly so far. I'm really not having ANY other cooling issues other than this, thats why its weird. No filling of the overflow, no blown or highly pressurized hoses, no overheating, etc . . .

 

I've talked with a few people now and they all kind of concur that I shouldnt have used silicone when installing them in the first place, too slippery i guess.

[spork]

Well, hopefully all works out well, but if I were you, I'd replace the remaining core plugs before you pop one out in the middle of nowhere.

[Pop N Wood]

I thought Jon once said there is some type of test to check for hydrocarbons in the cooling system.

 

If you had HG issues I would think you would have seen evidence of that when you pulled the head. Usually those leaks only get worse with time. Besides, I think like you do in that overpressure would blow the cap or throw hoses before it shed freeze plugs.

 

My vote is block flex. And I can see how a layer of silicone would give the plug a chance to move. That stuff is pretty squeezable. Just ask silicone boy.

[Mikelly]

My vote is block flex. And I can see how a layer of silicone would give the plug a chance to move. That stuff is pretty squeezable. Just ask silicone boy.

 

 

On a serious note, I'm with pitchinatent and boobboy...I think you've got block flex or the silicone sealer on the freeze plugs is the issue... I'd hit them all with JBWeld of tap and screw the remaining plugs.

 

Mike

[JMortensen]

I don't think silicone is the answer. My friend who built my first motor and probaby 10-15 other L's always uses Ultra Grey silicone. Mine never blew a freeze plug, neither did any of his. I hit 7500+ rpm on the motor he built me, he has done 8K+.

 

The test Pop mentions is a good idea. Just open the radiator cap and put either a smog machine tip in the opening ( don't dunk it in the coolant) or just a sniffer for A/C leaks. If there is gas in the coolant you'll know what your problem is.

[LLave]

You may want to check this out,

http://www.terrysjag.com/show/pic10.jpg

[BRAAP]

If the coolant was being pressurized then wouldnt i be blowing hoses off or at least overflow from the radiator? Car runs perfectly and then just pops one out. I've been getting on the car pretty hard the past couple days since Jb Welding em and I've had no issue so far.

 

Garrett,

Well, the only solution that I can come up with supporting the pressurization theory caused by combustion pressures getting by the head gasket and NOT blowing off your radiator hoses is this…

 

Because the thermostat is a restriction of sorts AND your water pump is pumping water into the block, (flow coming into the block will resist flow back out), if you are experiencing a very “quick” pressure rise in the cooling system due the head gasket letting go, for say one, two, or three, combustion events, it realistically could be contained only within the block as the thermostat and water pump are restrictions “out” of the block, causing the core plugs to pop out. If the head gasket were to release for a longer period of time, then yes, that quick and excess pressure build up would make its way past the thermostat and to the rest of the cooling system causing the radiator cap to release, hoses to pop off, etc.

 

I realize that this is quite a stretch/reach, but it is the only quantitative solution I can come up with to support that particular theory… Hopefully the real answer to your problem will be found.

 

Paul

[LLave]

What about a crack in the water jacket? That could have the same effect as a head gasket. I would definatly pressure test the cooling system.

Pour in 3 bottles of stop leak, drink a 6 pack and call it fixed.

[Garrett76Zt]

I'm revisiting this thread because it just happened again!

 

This last time, I was so fed up that I JB Welded the plugs in. Perhaps I didnt get this one very well since its on the manifold side of the block. So now I have to yank everything apart to replace it.

 

Why the crap does this keep happening?!

 

EDIT: I was just re-reading through this thread, there are several good ideas about this but how can i rightly discern which theory is actually taking place?

[73ZCAR]

Hey garrett,

 

Find a couple of old racer guys and ask them what they think could be causing it.

 

The old timers may have figured this out 30 years ago and we just dont know about it yet.

 

Mike.

[David K]

Garret, did you ever figure this out? It just happened to me yesterday http://forums.hybridz.org/showthread.php?t=126373

[Garrett76Zt]

Garret, did you ever figure this out? It just happened to me yesterday http://forums.hybridz.org/showthread.php?t=126373

 

Sorry man, still scratching my head on this one. Car has been down for several months since I blew the last one. I'm gonna JB weld it in good this time.

[Evan Purple240zt]

Hey buddy, sorry your still having trouble.

 

I put some thought into it. Are you sure your system is flowing well coolant wise? The only thing I can think that would cause that fast of a pressure change would be from heat... from burning out or high revs.

 

Your really heating up that coolant.

 

I would make sure your radiator is not partially plugged or something like that.

 

Could the opposite be happening too? Maybe the pump cavitates (too much turbulence) and the water does not flow through the jackets fast enough?

 

Did you change your thermostat?

 

Evan

[Thumper]

I think the head is still lifting. Thats the only way I know of that the coolant can become that pressureized (sp)

[Clifton]

I use Locktight green, recommended by my machinist, seals and holds them in, gotta be clean though. The plugs are brass. I also run a 24 psi cap and have had it pretty hot many times (220+) while road racing and haven't had any problems and I'm sure the pressure is up there.

[Tony D]

Steel Plugs, Good. I use Permatex and stake them in place out of habit.

 

The suggestion was made that you check with oldtimers...

 

But the glossing over of the most pertinent item from the first page is most relevant: Install a block coolant water pressure gauge. We have these on stationary engines and powerplants to tell if we have a cooling water pump problem, and without actually gauging the pressure present in your block (and the rate at which it rises) you won't know what is causing it. It doens't need to go into the core plug, there are other places to tap your block pressure from...but get a gauge in there so you can see what happens. You can see it when it happens. A gauge to 100psi should be more than enough. The bigger the better.

 

The characteristic rise will tell you if the pressure is seeping in, or BLOWING in...since it only happens on-boost my best bet is that it's either something lifting, or something fractured that only opens enough to cause a problem, and then closes back up under tension.

 

I have seen cracked cylinder liners act like this, as well as head gaskets.

 

If the block was cracked anywhere, a quick shot with cleaner and then Spot Chek will reveal it post haste....sometimes you won't see it with a naked eye, and with a rough casting even a relatively large crack can be camoflagued.

 

Core plugs can be incorrectly sized for an application as well---a core plug hole that has been made oversize by repeated pressing of the plugs into it may be prone to blow them out repeatedly---I'd stake them in at a minimum now, and measure the holes and plugs to ensure proper crush on installation.

 

My vote is to put the block pressure gauge on it. 40-60psi is what I recall at speed, 15-30 at idle depending on your pressure cap rating and what suction pressure you are running at the pump inlet.

 

Funny, I recall someone arguing with me that the water pump only causes flow, and the entire system has the same pressure (Cap Pressure) in it! I'm glad to see there are others who realize a thermostat restricts flow, and that the pump actually raises pressure in the block!

 

I will bet combustion pressure is the cluprit, though until the bores are measured an oversized hole could be a possibility. I believe they do make slightly oversized plugs for this situation as well....