EvilBevel

OK, we had lots of discussions about what causes the big end failure...

But how exactly do you know (without fully opening up the engine) it has gone ? Is there an easy way/tell sign to see it's big end and not something else ?

Reason I ask is because a member from the dutch BBS (MY99, 50.000 miles, hard run up to 200 km/h) thinks he may just suffered a big end failure.

Car makes a lot of noise on idle, but it goes away when the engine warms up. That sounded more like piston slap to me, but what do I know...

Car still revs normally ... I can't imagine that being the case with a big end gone ?

Any thoughts ?

Theo

AliWrx

If the big end has gone oil pressure will be very very low at idle, enough for the oil light on the engine to come on.
Ali

R19KET

Theo,

If a bigend goes, you'd know about it. It makes a horrible loud rattling noise, and it doesn't go away.

If you ever get this, STOP the engine, and don't restart it. This way you stand a chance of re-using the crank, rods, etc'.

Mark.

EvilBevel

Mark,

Thanks for that.

In his reports he mentions he can still rev his engine, and the sound then goes away, so it is definitely not a big end then.

Ta.

Theo

EvilBevel

Ali, no reports about oil light coming on either.

scoobyboy

i have never seen the oil light on on any of the cars i have done bigend bearings on. if there are bad it sounds like a spanner flying around inside the engine the p1 i just done had spun no.4 which only rattled after 2500 revs.

Bob Rawle

Oil pressure warning light won't tell anything, even with big ends gone you can still get a couple of bar of oil pressure ... oil pressure switch is set at 0.17 bar 2.5 psi) ... yup thats 0.17 ... really useful eh ?

EvilBevel

0.17 bar ?

Erm ... very useful with a normal pressure of 6.5 bar (up to 7 when cold) whilst driving and 2.5 bar whilst idling ...

Is there a modification for this to bring it to more sensible levels ? (say 5.5 bar under power / 2.0 bar when idling) ?

Bob Rawle

Only the obvious one, change the switch, to get it to provide any meaningful info it would have to be set so that it could be on at idle. I've set my pressure gauge warning light at 2.3 bar, idle oil pressure is 2.5 bar, thinner oils could drop that to 1 bar though.

MichelleWRX1994

I would be interested to know the full syumptoms...........any more?

BugEyed

Theo

It doesn't sound like a big end bearing from your friends description. As Scoobyboy says, the noise sounds like a spanner running around inside the engine when revved. However, if it is, take Mark's advice and switch it off before you do more damage!

A simple and low cost way of telling - drain the oil and strain it through a fine gauze - the wife won't miss the tea strainer for a few minutes . If it is a bearing you will have lumps of white metal (1-2 mm diameter) in the oil. If you find these it is time to strip the engine, and the cost of replacing the tea strainer won't be significant in the overall cost. Equally, if there isn't any white metal oyu'll be so happy that replacing the tea strainer will be covered by the relief.

On the subject of oil lights - they are a waste of time. You can buy higher pressure switches, but they normally only switch at one pressure and hence will not indicate a problem when the engine is cold or running at a reasonable speed. Bob's solution is probably the best, a decent oil pressure gauge with a warning light set to cut in if the idle pressure is low.

Cheers

Duncan

EvilBevel

>>Equally, if there isn't any white metal oyu'll be so happy that replacing the tea strainer will be covered by the relief.

LOL Good thinking about the oil, the bearing shells should be the liquid form if it was really a big end failure ... they seem to evaporate really, and the oil should have a nice silver finish to it

Good advice from Mark too, but as I understand it, he has driven the car a few times since to see "if it was really broken". Not the best of ideas probably ...

This oil pressure thing is really amazing. I'm no engineer (could you tell from my posts ? LOL), but I would imagine you would only need a bit of electronics to set 3 warning zones (cold idle, warm idle, cold/warm normal). Oh well, I'm replacing my el crappo Racimex gauge with a Defi one, and I think they have an adjustable limit/warning light. May put it at 5.5 bar, and live with the light on whilst idling.

Cheers for the replies, should really help the guy.

Theo

BugEyed

Theo

It is very rare for the bearing to melt completely - they normally fail in chunks which drain out with the oil but sink to the bottom of the pan you drain the oil into, hence the tea strainer ...

On the subject of the oil pressure light - the sender is just a switch that is opened by the pressure reaching a certain point. It is not the same as a sender for a pressure gauge which measures the pressure.

The engine doesn't need 5 bar, it is unlikely to require much more than 3 bar even at max revs. Often the source of problems is oil temperature, so you might want to consider an oil temperature gauge as well.

Duncan

PS Don't drink tea at my house!

Steve Whitehorn

iTrader: (13)

I know this sounds wierd but.

Myself - The mechanic at the Subaru Dealership - And a longstnding RAC mechanic all thought that the big end had gone in my Scooby, after listening to the engine.
(Realy bad rotational clanking noise coming from deep within the engine)


Amazed to find out that it is a broken water pump!!!
So get the water pump checked out.

Cheers
Steve

EvilBevel

>>Often the source of problems is oil temperature, so you might want to consider an oil temperature gauge as well.

That was the first gauge I fitted (together with boost gauge) 2 years ago now ... I still don't understand why it's not standard in the new cars !

Not only to monitor the higher temps, but to see when the engine is finally warm enough to throw it around a bit.

The combination of Castrol 10W60 and removing the undertray has lead to cruising temps of 80°C to 85°C, and only 95°C to 100°C on track ... undertray made a difference of about 10°C, but that might be related to the position of the sensor.

Oh, and I'll skip on the tea, thanks

In the mean time the plot thickens, as the guy went to see another Subaru dealer, and he also said "yeah, will be bigend" ... whilst he has driven another 500 km with the car now. Surely the engine would have come to a grinding halt by now if it was indeed a bearing pickup ?

3 bar still OK ... didn't know that, but I never saw 5 bar yet (even on track), so putting the warning there would be a sure sign of oil pressure loss before it gets out of hand ?

Thanks for the waterpump reference as well BTW.

Theo

mrkimpreza

Hi, "I'm the guy, the member at the Dutch board with the problem"

Yesterday my engine failed at about 4500rpm in fifth gear with full throtle and turbo pressure. It's now at the dealer and will be opened anywhere next week.

Complete story is:

Saturday evening:
15 minute warmup
Hard drive through the gears, till 7000rpm. A little hesatation at 6500rpm in 4th gear, I hear a sound like "knocking". I immediately reduce speed and listen to the still running engine. Sounds OK. I drive for about 10minutes very easily and stop again to listen to the engine. Nothing. Run it to max rev. again, not with full throttle. Sounds OK. Run it to max rev. again, with full throttle. Sounds OK.

Drive home. Let it idle, cool down for about 2 minutes and shut down the engine.

Sundaymorning I start the cold engine: RATTLE. Disappairs when getting hotter (5 minutes). Runs OK. Did not do much km.

Mondaymorning I start the cold engine. Nothing. Great, drive to my work (~100km). Nothing.

Tuesdaymorning I start the cold engine. RATTLE. Drive to the dealer. Says big-end or crank bearing. Opening engine and repairing bearing is around ~3000 EURO total. New short block is about ~4000 EURO. I ask whether they are sure and whether it is not possible to investigate more. This is difficult because you can't reach / see the crank / big-end by just removing the oilpan.
Drive to my work. When warmed up, engine feels and sound great.
(again about 100km)

Wednesmorning. Same. Rattle at cold, at warm it is gone. At least in the car. With the bonnet open and your ear on the engine you might hear something. Take the car to a second dealer. Hmmm big-end or crank, very lightly (engine was warm remember !) Some story about costs and further investigation.
(about 150km)

Thursday morning. Same, rattle at cold. At warm it is gone. Drive the car warm easily (~15 minutes) and accelerate hard a few time. At 4500rpm full throttle and full turbo pressure it hesitates, see blue smoke in my rear view mirror and it start running very badly. Shutdown the engine and towed it to my dealer. They will open up the engine something next week, I hope :-(
(about 50 km till blow up)

Specs: MY99, 77000km, downpipe, K*N 57i kit and Prodrive Performance Pack (PPP == catless midsection and replacement backbox).

Mark.

R19KET

It's VERY easy to check for baring failure, just drop the oil through a strainer, of on the last one I checked, baring material was visable on the dip stick.

With the sump off, you can check the big ends, but not the mains.

I'm afraid blue smoke out of the exhaust doesn't sound like a baring to me, but more likely piston related, or a combination. Maybe a ring lan. IMO, if it was a big end, you engine wouldn't have lasted 10mins of the type of "testing" it was given.

Mark.

Adam M

why could it not be piston slap, as it seems to go when the engine is warm and the piston has expanded.

Perhaps it was so bad that enough movement of the piston caused it to pick up on the bore, making the engine seize.

BugEyed

Hi

I'm with mark on this one - sounds as if you've either torched a piston or damaged a ring. Either way, the oil smoke you are reporting is one or other of these. However, the question is how did this occur. Why did you run lean in the first place? Or, did you wash a bore due to a missfire?

Duncan

Bob Rawle

Could be a big end, the continued running maybe bent a rod and knackered a piston.
Or, cam belt has slipped and valves eventually knackered a piston. Hydraulic tensioners are known to slacken off.

WREXY

Welcome Mrkimpreza,

Sorry to hear of your engine problem. I hope you get it sorted out and hopefully it will be the smallest of damages to the engine, (if that's possible, after the smoke).

Either Theo or Mark, (Mrkimpreza), if it's not too much trouble, would you please let us know what the outcome is?

Cheers,

Wrexy.

[Edited by WREXY - 2/17/2002 11:18:26 PM]

mrkimpreza

Last Friday I saw my engine open at the workbench. There is a (small) hole in piston #2 and the cylinder has some damages too.

The boxer has not yet been split so I can't say anything about the big-end bearings. I can tell that it is almost impossible, without splitting the boxer, to look at them. You cannot reach the big-end properly (even on a bench) and it is impossible to split the big-end and look at the bearing.

I'm now orientating me on the options:

1) New standard shortblock (simple)
2) New enforced STI block (possible ? / costs ? / delivery time ?)
3) Repairing existing block

For option 3 what is the normal thing to do. New piston and repairing (boring) the cylinder again or doing that on all four cylinders.

Mark.

WREXY

Mrkimpreza,

Thanks for letting us know what's going on.

I'm not an expert, but I think if you go for option 3, you should do all the cylinders so that they are all new and even again, providing your finances allow you to.

Cheers,

Wrexy.

R19KET

If the bore is damaged beyond re-boring, then it can be re-linered. If the other bores are fine, just leave them.

First, it would be cheaper to buy a new block, than replace all the liners, and if you re-bore all the bores to either +25, or +50, you'll need to replace ALL the pistons too, not just the damaged one.

A holed piston is "usually" due to det', or the spark plugs being too hot.

If it's det', it can normally be identified. The plugs will also give a good indication of what was going on.

It could also be down to a bad tank of fuel, or even the ecu map.

Mark.

jmca

Mark,

Just wondering what indication would the plugs show/give that you would be having problems with detonation?

Is there a rough guide as to how a plug looks then it's experiencing A, B or C etc.

Regards

Johny.

BugEyed

Johny

I'll intefere (as usual) and add a few ideas - I'm sure mark will add his later!

• Greyish-brown deposits
  Plug is working at the right temperature and the engine is running well.
• Black, dry deposits
  An overly rich mixture (unburnt fuel becomes soot), low compression, clogged air cleaner or a large plug gap.
• Black, wet deposits
  A blown head gasket, worn rings or pistons.
• Silver or black specks
  Detonation inside the engine cylinder. This can look like do-it-yourself metalspraying when it goes really wrong, but if you don't turn off the engine reasonably quickly you get the version above!
• Light grey deposits
  Overheated spark plug, advanced timing or lean mixture.

Hope that helps.

Back to the engine in question, you need to tell us a lot more about the damage before you can get a measured opinion as to what to do. Of particular importance is to find the cause of your failure - and the order it occurred in.

Over boring is fine (I regularly overbore some non-subaru engines to +60 for racing - more capacity means more power ) within limits. Relining is more expensive, and you need to consider what other damage was done in the first place. A new block, particularly closed block STi is stronger, but is only needed for high boost high revving engines on the Scooby. What are your plans for the engine in the future?

Duncan

PS Have you checked your injectors and the wiring to them? I've seen this failure in other engines due to partially blocked injector or the map causing them going near to fully open (as the never get past about 90% anyway)?

jmca

Duncan,

Cheers for the info! Just I'm about to take out the spark plugs one of the next few nights & wanted to check the gap size etc. Now I figured I'd have a look at the state of them except I'm not that up on what state they should look like & what state they shouldn't.

Furtherly (?) - a friend thought he heard detonation in my car MY95 so when I do have a look at the plugs I have the use of a Hella compression tester & figured why not do a safety check.

Does anyone know a set of steps that I should follow that are specific to a MY 95 scooby when doing a compression check? If so, any tips are most welcome.


Duncan - you also mentioned about checking injectors & the wiring to them. Is that a hard thing to do? Are there any links you can point me to - so I can read up on it. Don't want to have you to feel like you have to post an essay to answer any of the above but I am very interested & would like to read as much as possible before attempting anything.

Regards

Johny.

BugEyed

Johny

Have fun getting the plugs out! More seriously though, you learn most about the mixture when doing a "plugchop" (switching off the engine at the speed/load where you believe you have the problem and taking the plug out then. Dead easy in a test cell or a race track on a car with easy access to the plugs, but on a Scooby on the road - don't go there!

To check the injectors without a test rig is difficult. You can take them out easily enough and check for large lumps of crud, but these rarely get through the filter. Best bet is to take them to an injection specilist who will clean them and flow check for you.

My comment about the wiring was where I've had the worst problems - dodgy set of joints on the clip between the harness and the injector would interupt at high revs, leaning out one cylinder with disasterous results for the piston etc. It took a while to find ....

Duncan

Ooopps - you said no essays

jmca

Duncan,

Again thanks for the info. I would love to know for my own knowledge how to take out the injectors & check for dirt as you say. You see I have a HKS Powerflow & had very bad idle there for a while. I took the MAF sensor off & it WAS very dirty. Cleaned that & it idles an after lot better. I also changed the foam element for a new one.

My point being - maybe the injectors are dirty as well. Is there any link or info out there that I could read about taking them out & checking them. If you have a few mins or anyone who may have info - if you could post some info on how I'd go about it & where locations in the engine bay etc. When the time suits to post it's be great.

Cheers

Johny.


I probably should start a new thread about the injectors & the compression testing. Maybe tomorrow....

[Edited by jmca - 2/26/2002 5:44:39 PM]

R19KET

If you want to check the state of the injectors, you do really need to get them ultasonically cleaned, and then flowed. Very few of the companies can actually tell you just "what" they are flowing, just if there is a big disparity between them.

You can give them a quick (relative) check over, by checking the no.3 injector (back, passenger side).

The injectors are fed fuel in "series", and no.3 is the first to be fed. Each injector also has it's own secondary filter, built into the body, and because of the injector, and fuel rail design, the fuel has to pass though each injector filter, to get to the next. So if you check the condition of the first injector filter, it will give a good indication if crud is causing any restrictions.

However, over time there will be a build up of crud, that is too small to be filtered, and this will start to effect the "pintle valve", and the spray pattern. It's almost impossible to check this visually.

To remove injector:

1)Disconnect plug.

2)Release fuel pressure, by undoing fuel feed hose on fuel rail. Have lots of rags, or paper towels handy.

3)Carefully remove the two bolts from the injector cap. Put parts in a safe place

4)The injector is now free to be removed, but be very carefull not to damage, or drop the "bottom" "O" rings, as you pull the injector out.

Sometimes they will just pop out with a "twisting/pulling" motion, but often they can be a TOTAL S>O>B........

Once out, check the position of the various "O" rings, and put the bottom two (1 x flat rubber/1 x smaller rubber round section/1 x white teflon) somewhere safe.

Now, if you decide to remove the top "O" ring, BE VERY CAREFULL. The SLIGHTEST NICK will cause it to leak. So use a thin blunt instrument.

Inspect the mesh filter basket, around the middle of the injector. If it's cruddy, soak/rinse it in clean fuel, or carb cleaner.

Next, rinse off all of the "O" rings, and dry them off. Inspect them for any damage. Any suspect rings should be replaced.

Next, inspect the bevelled mouth of the injector holder, for any corrosion. Double check by "feeling" for any roughness. It's normally found on the bottom half of the holder.

If you do find any corrosion, it needs to be removed BEFORE you replace the injector. To do this, carefully put some CLEAN rag, or paper towel down inside the holder. Then use some FINE wet, and dry, with a little oil on it, until the surface is smooth.

Before removing the rag/pt, wipe out any residue. Then remove the rag/pt, and clean the holder meticulasly.

"Smear" the inside of the holder with CLEAN engine oil.

Next, take the "flat rubber "O" ring, and smear a little oil on it. Then, carefully place it into the holder, making sure it's seated flat in the bottom.

Then, smear some oil on the rest of the "O" rings, and place the "O" rings back on the injector, and then run a LITTLE more oil around the rings.

MAKE SURE TO KEEP THEM FREE OF ANY BITS OF CR*P.

Carefully replace the injector back into the holder (twist, and push) making sure it seats down correctly.

Reverse the initial sequence.

Check for leaks by turning the ignition on, without the engine running, and if it's ok, with it running. Then give it a check after a mile or so, just to make sure.

Mark.