Triple X

iTrader: (1)

A couple of months back i suffered from what sounded like big end failure. Anyway after a long time of creating space in the garage to make room for the strip down i eventually got to the stage of splitting the block today.

I found that big end number 1 has gone, which seems odd as this is the first to be supplied with oil isnt it? Checking the other big ends (mains were fine) i found that the top half of the big end of cylinder number 4 looked like it had took some hammering too.

PIC OF DAMAGED BEARINGS

http://img.photobucket.com/albums/v1...X/IMG_0299.jpg

PIC OF WHERE THE CRANK IS DAMAGED, DUE TO BIG END 1 (fine else where)

http://img.photobucket.com/albums/v1...X/IMG_0309.jpg

Is it possible that det could have caused such a failure, ie that the oem knock sensor could be duff and not picking anything up, i have a Knock Link which was showing some activity but since i had recently fitted a FMIC i put it down to background noise (pipework?) since it was showing nothing before.


I have a Link ECU fitted, and i know someone who is competent with Link ECU's that was taking a log of what was happening and he said there was no sign of anything dodgy happening when it went, didnt even get as far as changing anything in the map to suit the FMIC! It was only the high oil temp that made me suspect something so slowed right down and the oil temp didnt drop, pulled over and noticed oil pressure was down. Blipped the throttle and heard the damaged big end sound. Stopped the engine straight away and this is where im at.

Andy.F

Could be short term hard det or long term light det, assuming it ran on decent oil, properly primed, not thrashed from cold or overheated.
Any clues from the piston crowns ? Det marks ?

Andy

Triple X

iTrader: (1)

Pistons look in very good condition Andy, both the crowns and skirts and also the bores look good, you can still see the honing marks, no sign of scoring etc..

I suppose i should add that the car had done 65,000 miles. It was imported new and was serviced by Scoobysport and Park Lane and i can only assume that the previous owner should have known what fuel to run it on. I bought the car at 39,000 miles and had the Link fitted at around 50,000 miles.

I always changed the oil every 3000 miles using mobil motorsport 15/50 but i never disconnected the crank position sensor before cranking. Maybe changing the oil so frequently without disconneting the crank postion sensor has been more detrimental than leaving the oil in longer?!

I understand that the bearings seem to be an inherant weak spot in subaru engines, i just thought it looked odd that no 4 looked as though it had suffered quite recently too.

Have you ever known No 1 to go before?

Just trying to understand what has happened before deciding what route to take next but i think it means uprated internals as no1 rod has suffered from the spun bearing too.

ALi-B

iTrader: (1)

Possibly no4. started wearing due to starvation from lack of oil pressure at the rear of the crank caused by no1 being knackered?

Triple X

iTrader: (1)

Possibly i suppose, but 2 and 3 looked fine when compared (what you would expect from the milage anyhow!), would it not have an effect on them all getting progressively worse?

Still seems strange that number 1 went first, the one you would expect to have the best chance of longevity.

ALi-B

iTrader: (1)

Hard to say really. You would expect to see wear on mains and other bearings as well. And pressure/flow problems to show up worse at the rear of the crank. The front of the crank would be more susceptable to contamination/partical damage, but that would also be present on the front main bearing.

I still wouldn't rule out det. For example there maybe a slight fueling problem on no1 say, a slightly blocked injector. The knock sensor should address this, but it is on the other side the engine, and I'm unsure on its sensitivity to slight det

Triple X

iTrader: (1)

Cheers for your input Ali. Been ringing around a few places this morning and it would appear that it is very common that number 1 goes first, a lot of times in the event of the pressure relief valve sticking on the oil pump at high speeds.

Also spoke to a machine shop who said they have ground more subaru cranks than any other and usually because of a knackered big end on number 1.

Uprated pump is a must it would seem!

And also enough cant be said for disconnecting the crank position sensor (or any other way so the engine doesnt fire) to get the oil flowing after an oil change, i think one of the latter big ends would suffer more in not doing so.

ALi-B

iTrader: (1)

No worries, I was going to mention the pressure relief, just that you mentioned you had an oil pressure gauge. I would have thought that would have shown up before it was too late. I guess that's not the case

Triple X

iTrader: (1)

Yeah i do but to be honest i had one eye on the boost gauge and one i on the road so if there was a drop in pressure it would have gone unnoticed in those circumstances, i imagine it doest take long at high speeds for a drop in pressure to do some damage!

DeanF

iTrader: (1)

TripleX,

When you say HIGH oil temp, How high exactly as this could help others prevent further damage Etc if they have an Oil Temp gauge fitted.
Cheers

Dean

Triple X

iTrader: (1)

It went upto around 120 deg C, usually it would get as high as 110 deg C after prolonged thrashing. The thing that was more worrying was that even when i slowed right down, 40-50 mph on the motorway the temperature remained at around 120 deg C.

Also when i eventually got off the motorway and stopped the oil pressure had dropped to around 1-1.5 bar usually idle's at around 2.5 bar!