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Piston Broke after replacing valve stem seals and major service.

Obradovic

New member
Hi
So I was driving awhile with a little bit of smoke leaving my tailpipe everytime I accelerate.
I knew i had to make time to take it in after my car kept misfiring.

My mechanic told me to take it in and it will most likely be the valve stem seals.
So he did a major service on my car, replaced the valve stem seals, cleaned the carbon of the valves and replaced my piston rings.
He took about 2 months.

I went to fetch the car after he was done and got a engine light after about 50km so immediately I took it back and 3 error codes came up.
1. System too lean at idle
2. Fuel pump relay
3. Catalytic Converter P0420
They told me it was my careless exhaust sensor bringing up engine light🤔
Engine was reset and I drove off.

After another 50km - 100km engine light came back up and said oil pressure sensor: service now.
I took it back and the oil pressure sensor wasn't in place. They made sure its tight and reset the vehicle.
I drove off.
After 15km climbing off the highway a big white cloud came out of my tailpipe and epc light came off and cylinder 1 misfired.

I stopped it and had them come and fetch the car as I had no clue what is going on and did not want to break anything.
They did a compression test and all cylinders were on about 10 bar.
The car was leaking alot of oil.

They then discovered the piston rod had broken off. And that there was a small crack there before.
So I'm replacing a piston...

(Note)
I did not drive the car hard as I first want to drive in the car properly.

How is this possible and does this sound normal/legit?

Thanks
 

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Joe_Mama

Autocross Champion
It wasn't valve stem seals that were your issue. Your original issue causing the smoke was most likely failed rings causing excess oil in the combustion chamber. You get enough oil past those piston heads and you're gonna begin to see the white smoke and driving further you'll begin compressing oil in the chamber. This is what most likely caused your piston/rod to break, a failed ring on the piston head.

No one will know the damage until it is opened up and the cylinder walls are inspected. If the walls have gouges from the failed piston, it is junk and you will need a new motor. If it is just minor scoring, it can probably be re-honed, and you can throw in a new piston and call it a day.

One thing I can tell you 100% is that you should not let that shop touch your car any more. They misdiagnosed the problem and caused more damage by not properly doing the initial repairs. Find a new mechanic.
 

Obradovic

New member
It wasn't valve stem seals that were your issue. Your original issue causing the smoke was most likely failed rings causing excess oil in the combustion chamber. You get enough oil past those piston heads and you're gonna begin to see the white smoke and driving further you'll begin compressing oil in the chamber. This is what most likely caused your piston/rod to break, a failed ring on the piston head.

No one will know the damage until it is opened up and the cylinder walls are inspected. If the walls have gouges from the failed piston, it is junk and you will need a new motor. If it is just minor scoring, it can probably be re-honed, and you can throw in a new piston and call it a day.

One thing I can tell you 100% is that you should not let that shop touch your car any more. They misdiagnosed the problem and caused more damage by not properly doing the initial repairs. Find a new mechanic.
Thanks for your reply

They did open it up while I was there and luckily no gouges but slight scoring.
So they will re- hone it for me and put in the new piston + new rings. - hopefully everything is fine then.

They did say they found alot of build up on my valves...but that is probably from the failed ring?..

I'm done with these small business mechanics, they make your life miserable and you lose alot of money.

Thanks for your advise Joe
 

Joe_Mama

Autocross Champion
They did say they found alot of build up on my valves...but that is probably from the failed ring?..
The build up of carbon on the back of the valves is common across all direct injection engines. If your car has gone 40k miles without a carbon cleaning you will have excessive carbon deposits on the valves and valve stems.

This has zero to do with your motor blowing up so if the shop tries to blame you for this in any way, like by saying well it's your fault because you didn't get a carbon cleaning, you can tell them to take a piss up a pole.
 

Obradovic

New member
The build up of carbon on the back of the valves is common across all direct injection engines. If your car has gone 40k miles without a carbon cleaning you will have excessive carbon deposits on the valves and valve stems.

This has zero to do with your motor blowing up so if the shop tries to blame you for this in any way, like by saying well it's your fault because you didn't get a carbon cleaning, you can tell them to take a piss up a pole.
Makes alot of sense.

No they won't blame me for the carbon build up. They did however mention that they got a forensic out to come evaluate as to why the piston broke.
He said that their was a crack before and that when they had put everything back together, that the crack and compression had caused the piston to break.

But my question is...if they replaced my rings, liked they say they did.
Why would they put back a cracked piston/rod.

I have a feeling that they never did replace my rings and like you said that is actually the initial problem.

Hopefully they will be done by monday so that I can have my car back.
 
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