miles25

I am trying to help out a friend regarding the above, I have looked through a load of old threads but am still unclear.

He took his 00UK scoob to get the cambelt done at an independent specialist, whilst there he was told that on cold start they had heard a knocking and following a road test had diagnosed it as big end bearing failure.

They said the engine could go next week or it could be in 12 months time.

Does this mean the car is not driveable? When people talk about big end failure is this what they mean or do they mean when the whole engine goes because of it?

What are his options?? I am struggling to offer any sound advice and am still unclear as to what to advise??

womandriver

Get a second opinion m8

mark6

easy way to imagine it...imagine the front wheel of a push bike,where the bearing is in the middle of the hub,imagine that been all loose and rattly so the wheel is wobbly and loose,would you go down a steep hill on it???thats the gamble you are taking with the engine,imagine if it was to fail and the front wheel collapse??thats the gamble you are taking with your engine,if it goes it takes almost everything with it.get it done now or you will regret it if it goes

miles25

By saying 'get it done' do you mean compete rebuild??

stockcar

there is no way that a "big end" that is failing loud enough to hear will last 12months!!
without knowing the car/hearing it it is far more feasible to be "piston slap" which is far more common....................
agree with above get a 2nd opinion as they can sound similiar because of the "flat" nature of the engine

alyn - asperformance.com

mark6

as it stands now,if the rest of your engine is fine then it will only require the big ends and maybe a few little things worth doing while the engine is stripped(i think),but if the big end fails altogether then it WILL be a almost total replace and rebuild,but like womandriver said,get a second opinion as the garage may be exaggerating the seriousness of the knock.i'm not that clued up on engines but the big end is the worse possible thing to go on a engine as far as i know.

p.s i'm sure someone will come along and post soon regarding costs of either big end only or big end total failure

miles25

He was told that because it has gone there will be little bits in the engine and they could be anywhere. A replacement short engine could be done, but this would not necessarily cure the problem if parts had got elsewhere?? Therefore a rebuild would be best.

Does any of this make any sense?

stockcar

think someone's telling porkies or your mate has the wrong end of the stick???

we rebuild lots of std/modified engines after big-end failure and never have any issues.........................although there is a lot of work in cleaning everything!!
where in the country are you??

alyn - asperformance.com

mark6

ah yes,it sounds like that the big end has totally gone rather then just knocking,as the bearing has collapsed, little bits of it can circulate round the engine,so if he was just to get a replacement bottom end there could still be little bits in the top end of the engine and bits could have damaged/weakend the pistons,cylinders ect,so really the whole engine needs stripping to check for further damage/scouring.i've heard people talk of anything from £1500-£3500+ engine rebuilds.

edit:- listen to stockcar man,he'll know better than me.

Bob Rawle

if they fitted the cam belt and then heard the knocking its just possible its related to the cam belt tensioner not the big ends, did your friend notice anything before it was taken in, the ends are hardly likely to fail just because they changed a cam belt (unless they did an oil change and forgot to put the oil in then started it)

sounds odd if there was no sign before hand but stranger things have happened.

bob

miles25

They said they noticed it when they first drove the car. They then did the cambelt and told him after.

We are near Birmingham. What would you recommend?

morpheous

iTrader: (9)

Defo second opinion Api in Warwick is prob closest

R19KET

If a big end has gone, or going, it's easy enough to tell. Either ditch the oil into a container, then strain it through some gause, or similar. Even a "J" cloth will work, but it's blo*dy slow.

If a bearing has gone, you'll see metal particles left in the material.

Or, if you're happy to start it, let it run for a few seconds, then check the dip stick. You may have to dip the stick a couple of times, but if you look very carefully, you'll see "tiny" metal particles suspended in the oil, usually a gold colour.

If a bearing has gone, then as Alyn has said, it is a full stip, clean, and rebuild. This includes the heads, turbo, "everything".

Mark.

GREEN SCOOBY

for defo get a second opinion from a specialist like Alyn from AS Performance or someone closer but dont take it for granted that its big end failure because you heard it from here. If that was the case Alyn would be on my third engine re-build.

pil2255

Just had to have total rebuild due to a big end failure on my99 sti 5 tp R bill reached £6901 (that hurt)!

Dont take chances get it checked QUICK!!

R19KET

That reads that a rebuild due to big end bearing failure, costs around £6900.00 to repair !!! Somewhat misleading...........

I'm sure Alyn, or David (API) will give you a better idea, but a basic rebuild should cost circa £1500> £2000.

Mark.

jjones

would go for a second opinion.

ask api david if you can take it along to his workshop. i bet someone there can tell you in minutes if you need a rebuild or not. these guys will not rip you off. well worth the journey before parting with a couple of grand that may not need to be spent.

APIDavid

iTrader: (4)

Miles is all sorted now. We'll collect his car next week.

As Mark and others state above there is no short cut to a big end failure. When it goes, debris goes everywhere and nothing less than a full strip and rebuild will do the job. Do it cheaply and it will come back and haunt you. We put more parts, costwise, into an API engine than some people charge for the whole ' rebuilt' unit, including their labour charge.

Another point of note, is that; when the big end fails the con rod is missing the white metal bearing, which the two halves have a combined thickness of about 4 mm. Thus, the piston can travel 2mm higher than it would normally do and it WILL hit the cylinder head. It is also completely mis-timed as it will be flailing around on the big end. There is every likelihood that valve damage on the broken cylinder will occur.

The valve stems of a Subaru are very thin and the strength of the valve spring will pull the valve into the seat and it will appear to be straight to the eye. Take it out spin it in a drill and you'll see how far bent it is.

In well over 500 engine builds I don't think we have ever fitted less than 2 valves and usually four. When other people or 'specialists' buy engine parts off us they rarely buy valves. ' Nothing wrong with them ' is what we get told...................

You get what you pay for is never truer.

Thanks for the recoomendations to API from members above.

David APi Engines / APi Impreza

Neil_G

Good advice David. I have just got a manual for my WRX and have been looking closely into the internals etc of the engine....quite a complicated unit so definately not worth skimping on parts when it does come to a re-build.

edge

Hi.

Are there any other signs of big end failure/problems, other than the knocking sound mentioned (difficult to isolate), and the metal particles in the oil? Before it all goes pop, obviously...

I've been told that you could also diagnose big end failing by checking the oil pressure. I've been told that the oil pressure starts getting lower than normal. Is this correct?

Cheers,

Paulo

APIDavid

iTrader: (4)

The crank's the first thing in and the last thing out - so any grief in that area and it's alot of work to fix. Unlike a 'normal' engine you can't take the sump off a SUBARU and change the shell bearings.

There is no real test other than the noise thing for B/E failure. Failing oil pressure is an indication of a problem but it's by no means cut and dried. The backs of the oil pumps can come loose and pressure will reduce because of that.

The problem is that with an engine turning at 6000 RPM which is 100 times per second, I.E. a blur, in fact a fast blur, The failure happens in no time with very little warning. Just think of a Mclaren F1 or Williams BMW at 19250 rpm.......

David API

Mike Tuckwood

Yep, particles in the oil, various distinctly different noises, (most of which are too difficulat to get into words), reduced oil pressure, heads knocking there are many things to look for some of which can be more caused by differnt things.

We had a car in this week with suspected big end failure, and once one of the heads were off, it was obvious that the piston had been contacting the squish area on the piston, it was clean as a whistle.
There was circa 1.5mm extra play on the piston in the bore, (coming up 1.5mm further than it should).

Far more to it than just putting new bearings in, no point in going in and not checking absolutely everything.

We don't charge any extra for being thorough though, it only costs more to rebuild if something else is found while stripping/examining the engine.

Mike.