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View Full Version : Melted piston head gasket failure question HELP

rswails
08-02-2012, 06:56 PM
Hi guys,

I just bought a kouki with a notchtop zenki s14 sr20det engine. The guy before me had it about 4 years with same setup and worked fine except was running T28, and a different radiator. Then his radiator blew and he told me it ran hot once when it blew but didn't get all the way to the H on the temp gauge; thats when he put the KA radiator in. It was tuned very rich ( poured black smoked at WOT. The tune was done at 17psi, and it gradually went down to 15.5 psi after about 3 seconds of boost and stabilized at 15.5. I have wideband and I never saw any problems, it would stay at about 10.8 at WOT. I have an ISIS RS3871 turbo, stock HG, nistune with daughterboard, 750CC injectors, BC stage 2 cams, and walbro 255. I was running a KA radiator with a crossover hose with no shroud for the clutch fan installed.

After about 2 weeks of owning the car, I decided to go to an autocross. This was a pretty fast course ( got up to 80-90mph ) and on the second run I miss shifted from 2nd into 5th. I worried this might have blown my head gasket from possible detonation. I didn't hear an knock or feel any missing though. Anyway, while in line for my 3rd run, my car started overheating. I parked, and noticed my silicone hose right at the turbo compressor had a large crack in it. This of course could have created catastrophic lean situation and maybe caused my pistons to melt, and then cause my head gasket to blow. Of course, my improper cooling setup without fan shroud could have also caused my head gasket to blow I suppose.

After that I patched the intake hose crack, refilled my coolant and tried to make it home. It overheated again 20min later. And I saw tons of white smoke/vapor in exhaust and suspected head gasket failure at that time. Also was low on coolant. Towed it home at that point.

I think took the head off and noticed coolant in #2 and #3 cylinders. #1 cylinder was melted the most. Take a look at the pics below. I also have pics of the head gasket and you can see some damaged parts near the piston holes for #2 and #3 piston on the head gasket.

I know I am going to of course buy new pistons, check the head out and have it resurfaced, check scoring of cylinder wall, buy ARP head studs, get Cosworth 1.1mm headgasket, new water pump, and thermostat.

Question 1: Why do you guys think this happened?

Question 2: Can I reuse this block? You can see the block melted a tiny bit near the cylinder wall but is that a big deal?

Question 3: Do you have any other recommendation that I need to buy, or check?

Video of the 2nd run I did that day at the autox showing temp gauge, and AFR: Subaru Showdown 2012 Carolina Motorsports Park - YouTube (http://www.youtube.com/watch?v=u3IQgF38hyg)
Pics of 2 slightly melted pistons and head gasket, and block.
http://sdrv.ms/N5Cdrj
godrifttoday
08-02-2012, 07:25 PM
Something with the fuel maybe happen? Sucks since u just bought it
AZ_BOY
08-02-2012, 07:41 PM
1. Your coolant system incorrect. That's why it happens.
2. Your ISIS TURBO is slappy recommend u to change that.
3. Get your head gasket machine.
Check your piston try to move then side to side and see how bad are they. If there's so much of move ment that means your piston rings are bad. But if you got the money change them.
AZ_BOY
08-02-2012, 07:44 PM
Something with the fuel maybe happen? Sucks since u just bought it

That could be ya.

Clean you gas tank too
rswails
08-02-2012, 07:45 PM
1. Your coolant system incorrect. That's why it happens.
2. Your ISIS TURBO is slappy recommend u to change that.
3. Get your head gasket machine.
Check your piston try to move then side to side and see how bad are they. If there's so much of move ment that means your piston rings are bad. But if you got the money change them.

I am going to go with forged pistons for sure. But I am hesitant to blame this on ISIS so far. I definitely would prefer a T28 S15 turbo, and am on the lookout for one.
AZ_BOY
08-02-2012, 07:48 PM
I am going to go with forged pistons for sure. But I am hesitant to blame this on ISIS so far. I definitely would prefer a T28 S15 turbo, and am on the lookout for one.

Ya that s15 turbo is good you don't get much hp out of it but better then IsIs that u have :coolugh:
Sileighty_85
08-03-2012, 09:25 AM
1. Your coolant system incorrect. That's why it happens.
2. Your ISIS TURBO is slappy recommend u to change that.
3. Get your head gasket machine.
Check your piston try to move then side to side and see how bad are they. If there's so much of move ment that means your piston rings are bad. But if you got the money change them.


What the fuck are you saying?

None of that makes any sense at all.

his turbo is slappy? WTF is that?
Get head gasket machined?

Seriously shut the fuck up. OP dont listen to this retard.

His coolant system is not incorrect just inefficient,

Def sounds like your engine over heated, not sure on the melted piston since I cant see pics at work.

Might as well do rods and bearings if your going this far into it if you have the money.

get the block to a reputable machine shop and they can tell you if the block is still good.
di-devol
08-03-2012, 09:42 AM
What the fuck are you saying?

None of that makes any sense at all.

his turbo is slappy? WTF is that?
Get head gasket machined?

Seriously shut the fuck up. OP dont listen to this retard.

His coolant system is not incorrect just inefficient,

Def sounds like your engine over heated, not sure on the melted piston since I cant see pics at work.

Might as well do rods and bearings if your going this far into it if you have the money.

get the block to a reputable machine shop and they can tell you if the block is still good.

^lol, I think this as well.

The pictures of the pistons show detonation. Engine must of been running hot. Usually with a leak in a coupler will make you run rich. Do you have a peak on your boost gauge?
rswails
08-03-2012, 10:32 AM
^lol, I think this as well.

The pictures of the pistons show detonation. Engine must of been running hot. Usually with a leak in a coupler will make you run rich. Do you have a peak on your boost gauge?

I am kinda leaning towards the leak causing me to run too lean, if you look at the video, you'll see the AFR's are dangerously lean in some places while on boost. With a leak anywhere in the intake behind the MAF, I should cause engine to run more lean, not rich. Why do you say rich?

The video shows it peaked at the same 16-17psi that is has since I've owned it.
brndck
08-03-2012, 10:41 AM
With a leak anywhere in the intake behind the MAF, I should cause engine to run more lean, not rich. Why do you say rich?


This is incorrect. On a boosted car with a maf setup, a boost leak will cause you to run rich. For example, the maf says you have x amount of air, so it injects y amount of fuel. You have a boost leak so in reality you have LESS than x amount of air going into the cylinders, But you still have y amount of fuel being injected.
rswails
08-03-2012, 10:44 AM
This is incorrect. On a boosted car with a maf setup, a boost leak will cause you to run rich. For example, the maf says you have x amount of air, so it injects y amount of fuel. You have a boost leak so in reality you have LESS than x amount of air going into the cylinders, But you still have y amount of fuel being injected.

Hmm,

Extra air that the MAF does not know about is entering the intake. This would make it run more lean I believe. This is not a boost leak, this is a vacuum leak. The crack was immediately after the MAF, where the turbo sucks air in through the air filter.
di-devol
08-03-2012, 11:04 AM
^Yep, I believe that is correct. You didn't say where it was, ha. If it is in the intake TO the turbo, then yes, you got a lean machine, that explains everything. It would have to be a pretty good leak though, and a lean condition would torch a piston.
brndck
08-03-2012, 11:58 AM
Hmm,

Extra air that the MAF does not know about is entering the intake. This would make it run more lean I believe. This is not a boost leak, this is a vacuum leak. The crack was immediately after the MAF, where the turbo sucks air in through the air filter.

^Yep, I believe that is correct. You didn't say where it was, ha. If it is in the intake TO the turbo, then yes, you got a lean machine, that explains everything. It would have to be a pretty good leak though, and a lean condition would torch a piston.

you guys are correct. i didn't notice that it was his INTAKE pipe between the maf and the inlet of the turbo. i thought he had a bad coupler between the turbo and throttle body. he has an intake leak, not a boost leak, and yes, that would cause a VERY lean condition.