When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
If I were to hazard a guess, installation issues. If you had multiple broken rings, maybe fuel but just one and that cylinder is the only one that looks odd on the head, I'm going to guess that something caused the compression ring to break so maybe the ring was too tight or lubrication?
I'm going to guess that something caused the compression ring to break
Aklim, that's a broken piston, not a broken ring!
Deepa, I'm presuming the broken pieces of the piston came out with the piston, since the cylinder wall looked okay, and I don't see any signs of a chewed up piston. It's good you pulled this down when you did! Is the compression ring whole? Can you check the end gap?
If the end gap is good, I'd be wondering about hydrolock caused by a leaky injector.
If the end gap is too tight, I'd be worried about the other cylinders!
My bad. The cocking of my head was off. I got thrown off by the break and just south of the break (by the picture) it was so smooth that it looked like a thick ring broke off. I was looking at the Speed Pro piston picture and it looked like that chunk was part of the piston. That gets me curious as to why a smooth chunk like that broke off or am I seeing something wrong?
So...the more that I think about this...When I first started to notice a problem, the car would turn over, hesitate, turn over more, and start. This to me seems like a hydrolock due to a bad injector and caused the breaking of the ringlands. Roy, you hit it on the head.
The injectors are going out today to be tested...that'll give me proof of why this happened...The clean spot on the head also indicates fuel leaking into the cylinder.
The compression ring and all rings are fine. I will check end gap in the near future.
I am going to do rod bearings while it's apart. What do you guys recommend??
If it was hydro-locked, wouldn't the connecting rod be bent?
That depends on how much liquid was in the cylinder. Deepa did notice the difficulty in starting the engine, which is another clue for the hydrolock from the leaking injector. Serious hydrolock wouldn't have let him start the engine.
Hydrolock while the engine is running would have done much more damage!
Question. When much piston hit the valve and broke off a chunk of piston, it bounced around till it was small enough to go out the valve. Where did the broken pieces go? Should have screwed up the walls
Just my $0.02 - but I don't think you hydro locked it.
If the ring end gap is too tight - you'll almost certainly damage the cylinder wall and there doesn't appear to be any evidence of that.
My bet is a defective piston, or damage done during the install - it's so easy for a ring to hang as the piston is installed, and if it does that force is transmitted through the very high strength steel piston ring - to the relatively soft piston ring land.
BTW - are those two more cracks between the oil ring groove and the 2nd compression ring groove ??? That area would be difficult to crack during the install, so if those are cracks - I'll bet on a defective piston. That area would NOT be loaded during a hydrolock situation - so if those are cracks - it's almost certainly not a hydrolock.
BTW - if you do have a leaking injector - you would almost certainly see very high fuel content on an oil analysis.
So - any indications of bearing problems ??? You need to figure out what caused the oil pressure drop before you button it back up....
The motor ran GREAT for 12k miles...Ring gap or piston flaw would have been noticed much sooner. The first indication of a problem (running wise) happened at the SAME time as when the motor turned over, paused, then turned over and fired. That was when it was trying to compress fuel, which it couldn't do, until it pushed it past the rings and into the crankcase...breaking both ringlands.
I cannot analyze the oil...Its already gone and recycled. I thought about it, but opted to say screw it.
The fuel injectors arrive at FIC today. That'll be the when the truth will be found out.
The one rod bearing I pulled when I pulled the piston looks good. I am redoing all 8 rod bearings. Not touching crank bearings at this point. motor had no knocks at all. Oil pressure was good above 1500 rpms. Below that at hot idle, it would dip low on the gauge, but never would turn on the check gauges light. I never verified by a mechanical gauge.
You may well be right ! But just because something cracked - doesn't mean the cracked part will fail instantly. Many times it takes quite a while before the crack grows to the point the part actually fails.
If you had some junk get into the oil pan - it could have damaged the oil pump - so if the rod bearings all look good - I would check/replace the pump before reassembly. The oil flow the pump generates is pretty linear with engine RPM, but the engine doesn't use that much more oil at higher RPM - so progressively more oil is dumped thru the relief as the engine revs - a small amount of damage to the pump would explain the lower oil pressure at very low RPM with no pressure issues at higher RPM...
So here is where I am at. Still waiting on a piston and rings. All gasket surfaces are clean. New m-55 oil pump. Installed 7 out of 8 rod bearings (still waiting on the last piston assembly obv.)
Bought a flex hone, ring compressor, and ring tool, etc. Looking to get this all back together soon. Injectors tested out fine. no clogs, No issues, etc...
Cylinder is honed. All parts have come in. Need to have new piston installed on the rod then I can start reassembly. All new rod bearings and m55 oil pump. All gasket surfaces are prepped.
Ring gap of the top two rings were approx .019. Going to reassemble and hope for the best.
08-30-2016, 11:36 PM
I got thrown off by the break and just south of the break (by the picture) it was so smooth that it looked like a thick ring broke off. I was looking at the Speed Pro piston picture and it looked like that chunk was part of the piston. That gets me curious as to why a smooth chunk like that broke off or am I seeing something wrong?
