Just a thought..... Dealer drains out hot oil, fills with cold oil, takes car for "enthusiastic" test drive, eng temp normal but oil stone cold. Oil flow is reduced due to viscosity but bearings/crank are hot, letting the reduced oil flow escape quickly and not holding film between surfaces. Bearings pick up on crank but cold oil keeps it quiet. First longish run, oil gets up to temp, thins out, bearing starts to knock.

what finks ???

Andy

 

Crypt,
i think they are what use to be called "Subaru Manchester or C&K" but service etc any scoob as a specialist and not IM controlled

Tony

 

Ahhha you mean pete. Wouldnt use him myself mate, bad experience.

 

Good point Andy!

Did people that have had big end bearing failure do their oil changes, at dealers, garages etc? Also has anyone that has done their own oil change, cop bearing failure? If so, did you thrash your car after an oil change?

This info could help us find out and limit the causes, so if the people that have had bearing failure don't mind answering, please do. It would be greatly appreciated!

Cheers,

Wrexy.

 

My car has been showing symptoms of pre-letting go and that was after an oil change and service.

MY94.

How many miles on the clock did yours have Crypt?

 

Somebody suggested the problem was one of aerodynamics -- ali bonnets tend to lift at speed reducing the cooling airflow in the engine bay and leading to big end failure. Allegedly it's been verified in a wind tunnel too. I wish I could find the thread.

 

Mine had 45,000 on the clock chelle. I knew it wassent right for weeks before hand though, i could feel it.

The bonnet thing is viable as mine started to lift after 90 mph.

 

Anyone know if the Legacy suffers with the same engine trouble?

Or are more Legacy's not driven as hard?

 

I should imagine so it's basically the same engine right?

 

I believe so which is why I am interested to know if they suffer the same fate?! perhaps there is no lift on the bonnet?!

Did you not get the engine from GradeA yesterday?

Would be a nice mod to fit the twin turbo motor, sorry I don't know how easily they fit.

 

cryptwalk:
When you say you felt it for weeks could you give a little more detail so those of us in similar positions can anticipate and possibly avoid the problem ?

 

I'm very dubious about the "bonnet lift" theory. If it were responsible, then it would effect all the cars. Hands up all those who have gone for a high speed blast, and still have an intact engine.

SS: By the time you "feel" something is wrong, it's too late, and just a matter of time. I knew my head gasket was leaking, and had the choice of either pulling the engine, or trying to drive sensibly, until I'd decided what route I would take.

Shame I decided to go on track at Bedford Gasket let go, as did two bigends.....

Mark.

 

test.

 

CCs theory sounds good.

I really don't want to tempt fate but her goes anyway. I have a UK MY94 with aly bonnet and it has now covered nearly 140k with a lot of track days over the last two years.

It has run 1.2bar with Unichip day in day out for the last two years and I've had it off of the clock on quite a few occassions when travelling on the continent, although I only run .95bar when doing this as it's running at 6700rpm.

Upto 90k the car was serviced by a dealer at the regular service intervals but ever since it has been serviced at Scoobysport or by myself and I've always been in attendance. Each time the oil is changed, every 3000 miles and before and after a trackday, it is never driven hard again for at least the next twenty miles or so.

The car hasn't missed a beat apart from one dodgy sensor and three gearbox rebuilds with another one due

Surely CC is on to something here??

 

Re the fact that so many let go after a service...

How many service departments fill the new filter with oil and prime the oil system to pressure by cranking the engine slowly with the spark plugs out (so no compression loading on the bearings)...

Not many, if any, I'd guess. After all, who's going to take the plugs out just for an oil change??

So, what you have is an engine fired up, with an empty filter and zero oil pressure. No 3 & 4 share same oil supply and will be last to get the new oil feed.

Bearing wears, you may get high spots, or even some waste material.

200 miles (or whatever) later, you go for a run and it fails altogether.

Fuelling problems giving rise to det may or may not be involved, but will compound the problems of a damaged bearing. Ditto oil feed problems due to surging/wrong oil, etc.

Not exactly rocket science, is it?

Just my opinion though.

D

 

Diablo,

Interestingly, 2, and 3 share the same oil feed.

Mark.

 

Sounds very feasible.

But my car has now got 98,000miles on it and full service history.
So am I just lucky because I am damn sure that most if not all Subaru dealers do not fill the oil filter first or crank the engine.. etc.. it is not in there interest to do so is it...
It would take them an extra 10minutes which they cannot charge for and if the engine fails they get to rebuild it and charge us or Subaru Warrentee for the rebuild....

When ever I have asked what oil the reply has always been "the Semi-symthetic Subaru recommend".... could this be better than running of fully-syn?

How many other people on here with engines still running fine run on full or semi syn etc..
Mind you I bought the car just over a year ago with 73,000miles on it so it is possible it had been rebuilt already.. but no evidence in the history of the car.

Generally my car doesn't go above 95mph, and has probably seen 120 twice... since I have owned it... but redline is met frequently.
I don't do drop clutch launches either..

Are the similarities in the engine history of cars that haven't let go? we have discussed many a time the history of engines that have let go.... how about the opposite?

JGM

 

Taking it from a different angle..

What are the bearings like? are they crap.. is it nothing to do with the oil problems etc.. are they just not up to the job?

the engine firing opposingly must put some stress on them...

Can we get better quality bearings?

I always thought it was 2 and 3 that shared the oil source but only from what people have said on here before... so I could be totally wrong.

JGM

 

as mark stated above, 2 and 3 share the same oil feed!

 

as mark said, it is 2 and 3 which share the same oil feed.

I think it is interesting about allowing cranking the engine without any compression.

i think I will insist on spark plug removal when doing this from now on!

 

I presume spark plug removal and crank sensor removal is required.
Otherwise the fuel will still be injected.

Although I cannot see that cranking an engine with the spark plug in place is going to put any more stress on anything than when the engine is running. But I could be very wrong.

I get the feeling if I asked a dealer to do this they would say "Yes of course" and as soon as I was out of sight do it how ever they want.

If I going to have to stand there breathing down their neck then I may as well do the job myself.

 

Removing plugs is theoretically the best - Caterham's procedure for an oil change involves removing all plugs prior to cranking to get oil pressure (though I don't know if they follow that themselves, but I do when I do an oil change on the Caterham). This must be a better idea as virtually all load on the bearings is removed. Only reason I didn't do it on the Subaru was because they look such a pig to get at - hence at least don't let the engine run - if you did then you not only get the compression forces but also the expansion forces as the cylinder fires - these must be significantly higher than the compression forces I would have thought.

Keep this going - as many have said there seems to be a strong link between oil changes and bearing failures - assuming people are using good oil (or at any rate are continuing to use the same oil) then it seems to me it must be linked to how the oil is changed. Does make you wonder about garage servicing - no idea what they do, but I guarantee it will be whatever takes the least time!

Dave

 

That sounds reasonable as to cause. When i get this engine in i will be doing just that! I bet you it wassent done on mine.

 

I know when I go and start my summer motor the oil is all in the pan.. I tend to take this out.. replace the filter.. and top up before fitting and fresh oil... I then take the plugs out and crank the engine over.. Under no circumstances would I replace the plugs until the engine shows pressure... It can take a surprising amount of time for pressure to come up and I often end up using jump leads... The motor is 34 years old and runs a dream...

Out of interest.. I know most people don't hold with oil additives... But I once used some in a MK1 MR2.. with ptfe in.. The sump got holed, I didn't know about it for a little while so motor was still running.. Got a new pan.. topped up with oil and ran for another 10k before I sold it no problems..

 

There have been a number of threads about big end failures, which have contributed some valuable information. It seems odd that we are still unsure of the cause, doesn't it?

My own instinct is that if is there is sufficient pressurised oil (wedge) of good quality between the crankshaft and the bearing shell, then it just shouldn't happen. We know that Scoobies run very rich and therefore the oil probably deteriorates quicker than in the average engine, as some of this petrol ends up in the sump and thins the oil down. I have read somewhere that number 3 cylinder runs quite a bit hotter than the others, also any detonation puts a big load on the conrod and this is transfered to the big end, possibly forcing oil out of the bearing due to excessive load. If the bearings are getting worn i.e. excessive clearances, then it is also possible to get oil fling at high revs and to not provide enough lubrication. I suspect that some of these reasons are present in a lot of failures, although there are also apparently engines that have let go that have been well looked after. Puzzling.

As for dealers not bothering to fill the oil filter before firing up the engine after a service, well frankly I think that is just pure negligence on their part.

My own preference is to use top quality fully synthetic oil (I use Mobil 1 Motorsport 15W-50) and to change it often.

 

If WRXYoungster is reading. I notice in another post he says he builds engines at Prodrive. Do they do anything special to attempt to correct the big end failure problem???
Mine let go on my legacy ( 130Kmiles and flat out at time, so not surprising really, it was due to happen sooner or later ) But a friend built 2 engines for his car which lasted only 2000 easy miles each. The only thing the 2 engines had in common on the was cossie pistons ( oversize ) and billet flywheel/clutch assembly. The 3rd engine wich was threw together with second hand sti pistons ( std size ), re-using old head gaskets ( steel shim we were told were re-usable and we didnt want to spend any more money! ) is still running some 7000 miles later and they havent been easy miles, track days included.
When it comes to oil flow and bearings, subaru engines are **** it would appear. Apart from that they r all good nearly

 

thoght i'd add a link to this thread as its kind of related, for future ref...

**oil change precedure**
http://www.scoobynet.co.uk/bbs/thread.asp?threadid=91204

 

Just a point about main dealers doing oil changes.

I asked mine to show me exactly the proceedure to use, they do fill the filter with oil, let it settle and then refil, but they don't remove any sensors/pistons and crank the engine ....

 

"then it is also possible to get oil fling at high revs and to not provide enough lubrication."

Has anyone tried or used a product like motorup or anything?
http://www.motorup.com/catalogframe.html click the demo.

or

http://www.zx1.com/

 

There's been lots of stuff passed to & fro about the oil additives - and the conclusion seemed to be, at best, the don't do any harm. They certainly don't help! Makes sense, as if they did work, why don't the 'real' oil companies put it in in the first place?
Just adds sludge to the sump. Whoopeee.
There's been a lot of 'professional' testing as well that agrees.