Blown head gasket/cracked piston?

[MistaScott]

87 GN, 105K miles on original motor/tranny, 9” K&N, test pipe. Purchased in August and in the process of tuning and then upgrades. All spring cleaning was done except plugs/wires and fuel filter.

After running car at WOT, noticed smoke coming from under the hood and found oil all over driver’s side and dipstick blown out. Grayish smoke and a little oil were coming out of the tailpipe. I took it to a Buick mechanic who took of the filler cover and said he heard blowby of exhaust into the crankcase. He then told me I "need a new engine"...but I decided I'd like to know a little more.

I pulled the plugs, the passenger middle (unsure of the cylinder number) was wet and coated with oil, the rest had a very small amount of oil. I did a compression test and found the passenger middle cylinder with 0 psi, the rest had 150. Dropped some oil in the cylinder but compression remained at 0 (rules out rings). So, I am left thinking it could either be a head gasket or a cracked piston/block. How likely is it that I cracked a piston (running almost stock)? Is there any way to narrow it down further without opening it up?

 

[ChrisCairns]

These pistons are tough....I doubt you've cracked one if you're stock.

Sounds like a blown gasket to the topside. Into the valley. Compression pushes the oil vapors and splash oil out the dipstick tube and also out the breathers. Then on the intake stroke it sucks oil vapors back into the cylinder and eventually out the exhaust.

You shouldn't need a new engine....just a new headgasket.

Now is the time to do it yourself and learn. Ain't hard, just time consuming. Oh, and if there isn't any compression at all then you've blown it big time and you can just remove the intake and see the gasket and fire ring sticking into the valley.

 

[Hawaiian Turbo]

I'll have to agree with Chris. Blown head gasket.

 

[Intercooler]

I have a friend that just picked up his new motor this Thursday because of the same symptoms. He had a cracked piston in one hole and a melted #6 piston. The #6 piston had melted at the top ring gland leaving the rings intact but a nice melt-gap for oil to escape between the rings and piston. Regardless, time to pull the motor and have a look. Good luck!

 

[getchasum]

Originally posted by Intercooler
I have a friend that just picked up his new motor this Thursday because of the same symptoms. He had a cracked piston in one hole and a melted #6 piston. The #6 piston had melted at the top ring gland leaving the rings intact but a nice melt-gap for oil to escape between the rings and piston. Regardless, time to pull the motor and have a look. Good luck!

Jesse, did your friend have stock or aftermarket pistons? Just wondering what name brand they were if after market?

 

[Intercooler]

He had more than one cracked but it was due to improper piston to wall (too much). All of these were cracked at the skirt (Federal-Mogul/TRW). He was your typical plug in a race chip and crank the boost up on 93 pump gas without knowing what he even had and no scan tool. I changed his ways but it was too late when I got in touch with him. The melted piston was from being extremely lean! He also had a bad seal on the turbo and was dumping oil in the intake. Sad part is..... he will put the new turbo (60) and motor in and still not buy the scan tool. Motor builds are going to get expensive for him

 

[Quick6'n'-K.C.]

hopefully the headgasket just popped and replacing both should get you back on the road....

how long did you stay into it after it slowed down and became a crop duster?

you really should just pull the motor, do both head gaskets, timing chain, rod and main bearings and all the seals....

im sure there is a few turbo buick guys near you in VA...


HTH
BW

 

[MistaScott]

Drove it less than 10 miles just to get it to the Buick dealer. I made sure it had plenty of oil. I will open it up and see for myself what happened. I just find it hard to believe I could have messed up a piston on a stock setup.

Thanks for the help everyone. I am new to TRs so I appreciate talking to some people with more experience. Does anyone know any good TR people in northern va? Anything else I should do while I have her opened up? Vavle springs?

 

[Quick6'n'-K.C.]

go post in the lounge and ask if there are any VA mechanics that could answer a few questions or lend a hand or two...

since the headgasket blew, you might have a mixture of oil and antifreeze in the crankcase... or if your lucky, just blew into the intake area and didnt make a mess of the engine- thats what it sounds like

if you do have milkshake, make the decision of if you want to replace the bearings or start changing the oil right now a few times to clean out the antifreeze milkshake-

if the car has close to 100K, i would pull the motor, and change the seals, bearings, check the cam to see if #5 or#3 has a flat cam lobe, change the valve springs, timing chain, rear main seal, roller cam button, port the lower intake, weld the crack in the drivers side header, replace both motor mounts, new seal in the timing cover,oil pickup tube, and headgaskets

for me its actually faster to do those things on the stand then to do it in the engine bay...

now, you have to figure out why the head gasket blew.
more than likely it was too much boost( wastegate hose blew off)
or a different chip in the car with too much timing and pushed the head gasket out-

get a walboro fuel pump and hotwire kit for it, a scan tool and do the receipe to stop this from happening in the future

http://www.gnttype.org/techarea/recipes/recipepage.html

hope this helps, best way to find a good turbo buick guy is at the local track

BW

 

[MistaScott]

No milkshake... and I didn't notice the wastegate hose blown off so I am still puzzled as to what exactly happened. I'll let you know what I find...

 

[MistaScott]

The Verdict

Well the results are in: I blew my headgasket, passenger-side, into the crankcase. The other side was a matter of time and it was gonna go too.

The cause was a little bit hard to figure out. Wastegate hose was fine. We noticed my engine was spotless -- pistons, etc. looked shiny and brand new. That's strange on a 16 year old car. Then, noticed the fuel pressure regulator line had come off so I was basically shooting a WOT fuel load into the engine at all times. This made me run richer than Bill Gates though it cleaned my engine up real nice

The question I have now is, would this be the definite cause of the blown HG or does this sound like the previous owner had a chip and didn't tell me?

Let's just say Scanmaster is in my immediate future.

 

[azgn]

are you talking about the vac line that goes to the regulator?....if so, anytime you were under boost, your fuel pressure could not track boost and you were running extremely lean...thus the gasket

 

[bruce]

Re: The Verdict

Originally posted by MistaScott


We noticed my engine was spotless -- pistons, etc. looked shiny and brand new. That's strange on a 16 year old car.

Not that unusual, sounds like the gasket had been going for a while, and up until it's complete faliure, you had some water injection going. WI acts like steam cleaning to some degree.

What I think happens is:
One cylinder detonates a little.
Headgasket lifts a little, and then there is a slight amount of WI.
The WO masks the timing/leaness problem.
Then engine all of sudden pops a headgasket, in a big fashion.

 

[MistaScott]

Originally posted by azgn
are you talking about the vac line that goes to the regulator?....if so, anytime you were under boost, your fuel pressure could not track boost and you were running extremely lean...thus the gasket

The FP regulator somehow got detached from the vacuum.

I've heard that if you are running extremely rich, like max. FP at idle, you can run rich enough to detonate and hence blow the HG. The only reason I think it was running rich is because of the sparkling clean engine (no carbon buildup). It may be that I was lean...

 

[Quick6'n'-K.C.]

under boost the vacuum turns to pressure and raises the fuel pressure with that vacuum line to the regulator...

so, when you go into boost the pressure from the hose raises the fuel pressure so you wont blow a head gasket, if the hose comes off, then BOOOOOM blown HG

 

[Ormand]

Yeah, what he said..

Bryan explained it right. With hose off, fuel pressure will be too high under vacuum, so you'll be rich at idle and cruise. Then, under boost, pressure will be WAY low, and suddenly you'll be much too lean, and then... Can also happen when the regulator goes bad, decides not to regulate. Looks good, hose in place, so it's hard to check without using the FP gauge while you drive it.