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Oil On Top Of Pistons

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#1 Ga tom

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Posted 30 September 2018 - 10:23 AM

Has anyone come across this before I've done a presure test and had the skimmed changed oil stem seals and lapped the valves fitted it all back together the car has been running really well but it's burning oil smoking a lot when cold but stops when the engine is up to temperture ,when I remove the spark plugs no.1 fine but 2-3-4 have a small amount of oil on top of the pistons near the edge (I have a camera probe to see in ) the compreson is good but the oil rings could be stuck or the valve stems could be worn I've done a leak down test to check intake and exhust valve seats no air excapeing through the exhaust, intake side,oil filler hole , dips stick hole or sparkplug holes .Ive spoken to 3 mechanics 2 think that it might be stuck oil rings because the car had been standing for a number of years with the previous owners and the other mechanic thought it was the valve stems or guides were worn, but when I lapped the valves they felt good and smooth fitting with no play the car has done 146000km which is not a lot ,I will have to strip the engine again just wondering if anyone else had any thoughts on it?

#2 AndrewC

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Posted 03 October 2018 - 03:41 PM

There are three ways oil can get to the piston crowns.

 

1. head gasket breach between an oil gallery and the combustion chamber, but this is most likely to affect one cylinder only.

 

2. valve problem - stem seals are a common weak point or worn valve guides, but new seals should reduce consumption.

 

3. rings are not sealing properly.    Ring grooves can wear, but also rings can get clogged with sludge.  They require a certain amount of combustion gases to get behind the piston rings to force them out against the walls of the cylinder.

 

On my engine I ended up replacing the rings, and at the same time honed the block in situ and fitted new big end bearings at the same time.

 

I got a set of rings from Ebay - Toyota ones, came from Dubai.    


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#3 Ga tom

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Posted 06 October 2018 - 08:55 AM

Thanks for that I will have to strip the engine again to take a look




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