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Home > Help Needed / General Tech Chat > Compression lost on cylinder one

Steve220

107 Posts
Member #: 11017
Advanced Member

Shropshire

Hi guys,

Quick rundown of today - Went for mapping, car is running 13psi, comp ratio is around 8.6:1. On the last run i noticed a puff of white smoke come from under the car, on investigating the engine bay, white smoke was coming out of the breathers, but no colours out the exhaust. We called it a day and checked compression on all cylinders:

1 - 80psi
2 - 175psi
3 - 170psi
4 - 175psi

Clearly something wrong with cylinder one, however no oil on the spark plugs and no signs of det on the piston crowns. Got her home and whipped the head off. Cylinder one has minor scoring that cannot be felt with the finger nail.

Now, in the past when i've seen pistons get blow by, its quite a tragic loss to the cylinder, this just seems odd! Any ideas?



















Edited by Steve220 on 20th Jun, 2019.


tadge44

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Buckinghamshire

Not welcome suggestion but you need to look at that piston and it,s rings. May be that the ring lands are compressed, trapping the rings


Paul S

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8583 Posts
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Formerly Axel

Podland

Rich on inners and lean on outers. Poor fuel distribution.

Check the exhaust valve before digging deeper would be my advice.

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."


jonny f

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Dorking

I would say you need to get that piston out and have a look. Could be a broken ringland which might not damage the bore.

On 18th Jun, 2019 Paul S said:
Rich on inners and lean on outers. Poor fuel distribution.

Check the exhaust valve before digging deeper would be my advice.


Not sure if you missed it Paul but he says it is smoking out the breathers and fairly heavily. Would of thought that could only mean one thing?


Paul S

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Formerly Axel

Podland

Only quickly skimmed the pictures.

The bore damage looks like it could be caused by debri.

Is that exhaust valve even sitting on its seat?

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."


Steve220

107 Posts
Member #: 11017
Advanced Member

Shropshire




On 19th Jun, 2019 Paul S said:
Only quickly skimmed the pictures.

The bore damage looks like it could be caused by debri.

Is that exhaust valve even sitting on its seat?


Hi Paul,

Will check today. Thanks for the input guys, as you can imagine, i'm a little gutted by all this.


robert

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uranus

quickly put the head on its side and full the ports with petrol.,

Bicester scramble ,Medusa enjoyed the trip. https://www.youtube.com/watch?v=Q-7I7-nA19U


Steve220

107 Posts
Member #: 11017
Advanced Member

Shropshire

Hi all,

Quick few pics after removing the valve and after a wipe over with solvents.










Steve220

107 Posts
Member #: 11017
Advanced Member

Shropshire




On 19th Jun, 2019 robert said:
quickly put the head on its side and full the ports with petrol.,


it weeps out of the exhaust valve


Joe C

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Carlos Fandango

Burnham-on-Crouch, Essex

that could be it then, roll ithe stem on the desk to check it not bent, if not touch it back on the seat with some pase and try the petrol test again. also check the valve waggle in the guide.

On 28th Aug, 2011 Kean said:
At the risk of being sigged...

Joe, do you have a photo of your tool?



http://www.turbominis.co.uk/forums/index.p...9064&lastpost=1

https://joe1977.imgbb.com/



Steve220

107 Posts
Member #: 11017
Advanced Member

Shropshire




On 19th Jun, 2019 Joe C said:
that could be it then, roll ithe stem on the desk to check it not bent, if not touch it back on the seat with some pase and try the petrol test again. also check the valve waggle in the guide.


Joe, do you mean paste as in lapping paste?


Turbo Phil

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Lake District

Do as Joe suggests. Are there any contact marks on the piston head ?

Phil.

WWW.TURBO-MINI.COM


Steve220

107 Posts
Member #: 11017
Advanced Member

Shropshire

Stem of valve is straight, no contact marks on the piston crowns either.


Steve220

107 Posts
Member #: 11017
Advanced Member

Shropshire

Just lapped the valve in and its still leaking fuel


Steve220

107 Posts
Member #: 11017
Advanced Member

Shropshire

Cleaned the pistons up and there's no damaged to them at all, no traces of det either. If its just the valve, whats causing the smoke from the vents?


Paul S

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Formerly Axel

Podland

Check the seat on the valve. Has the paste cleaned it up all round? If not it would suggest the valve is bent.

Likewise the seat in the head. Looks OK in the photos.

How much smoke are you seeing? Just under boost on the RR or a lot at idle?

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."


Steve220

107 Posts
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Advanced Member

Shropshire

A lot at idle, under boost it didn't seem that much. When driving home from the rolling road, when i came to a stand still, it was like a smoke machine. But it didn't smell of oil and it was white.


Paul S

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Formerly Axel

Podland

Smoke from the breathers or exhaust?

White smoke is usually steam from coolant. Is the coolant level OK?

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."


Steve220

107 Posts
Member #: 11017
Advanced Member

Shropshire




On 19th Jun, 2019 Paul S said:
Smoke from the breathers or exhaust?

White smoke is usually steam from coolant. Is the coolant level OK?


From the breathers. Exhaust was fine, no smoke. Coolant ekvel was slightly slower than usual when I got back, nothing concerning.


robert

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uranus

hmm , maybe drain oil , and put all pistons level , and pop an inch of diesel or petrol on them and see if the duff cylinder dissapears faster .

Bicester scramble ,Medusa enjoyed the trip. https://www.youtube.com/watch?v=Q-7I7-nA19U


Steve220

107 Posts
Member #: 11017
Advanced Member

Shropshire




On 19th Jun, 2019 robert said:
hmm , maybe drain oil , and put all pistons level , and pop an inch of diesel or petrol on them and see if the duff cylinder dissapears faster .


Not a bad idea! About to pull the engine now.


Steve220

107 Posts
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Shropshire

And there we go. Piston 1 & 3 have cracked ringlands









*oh well*

Out of curiosity, what usually blows ringlands?


theoneeyedlizard

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The Boom Boom speaker Police!

Essex

Ouch!

In the 13's at last!.. Just


jonny f

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Dorking

Thatís a bugger that two have gone. You can sort it though.

What were ring gaps? Perhaps gone tight. I am no expert though!


Steve220

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Advanced Member

Shropshire




On 19th Jun, 2019 jonny f said:
Thatís a bugger that two have gone. You can sort it though.

What were ring gaps? Perhaps gone tight. I am no expert though!


I'm beginning to think it could be that and running hot!

These were my gaps

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