The engine in my 96 RA STI Version 3 went with a bang 2 days ago. Driving steady, no warnings. Hole through upper engine block at rear near turbo. Done less than 50k miles with full appropriate service history. Recently been for basic service with oil/filters/plugs.

Spoke to someone who rebuilds impreza engines who asked before I gave him any details "Has it just been serviced". He went on to say that he had seen a number of engine failures shortly after a service, but did not know why. He also suggested that the likely con rod to fail was in that position, saying it is furthest from the oil pump and in a hotter area because of the turbo.

Has anyone else experienced failure shortly after a service?
Any ideas on why this should be?
Any ideas on how to prevent it in replacement engine?

 

It is common for engines to go after a service. Various theories mainly involving the oil change.

 

Not personally (yet), but there are more than a few people round here who have.

The thought of a lot of people is that it's the damage is seeded because of temporary oil starvation after an oil and filter change. Once there's metal to metal contact, the galling will gradually worsen.

Pre-fill the new filter with oil before fitting and then turn the engine over on the starter motor for 20-30 seconds with either the spark plugs or crank position sensor disconnected to prevent the engine firing. Even better if you can remove the spark plugs.

This will establish oil supply and pressure before the bearings have combustion loads to cope with, thus minimising the chances of anything picking up.

 

Actually you should be cranking the engine over with the crank sensor disconnected for a further 20 seconds after the oil light goes.

Cheers,

George.

 

Thanks for your thoughts folks. Lessons can be very expensive! Any ideas on sources/fitting of sti engine - particularly in north yorkshire area - would be gratefully received.

 

If it's any consolation - or any use - my MY00 just died with a probable big-end failure at 61k miles, just a few weeks after the 60k service. Thinking about it, it's not the first time I've heard of engines going bang after a service either. Is anyone maintaining a database of such failures?

 

I have seen a car fail within 200 miles of an oilservice where all the above precautions (primed filter, pumped on starter to build pressure up before attempting to fire the engine) were taken, except removing the plugs to cut compression.

 

Another issue to add with earlier models that have just been serviced is:

It is a service procedure to reset the ECU in some cases as due to the oil change the knock sensor sometimes inadvertantly retards the ignition.

This is fine, but if the car has a failing MAF sensor, then the ECU we loose it's adaptive values for it, and re-advance the ignition too much. Too lean a mixture, too much boost, and too advanced ignition, will result in an increased risk of big end failure or melted pistons due to detonation.

 

Tony B YHM

 

I find it difficult to believe that the bearings can suffer in such a way with at the most a couple of seconds without oil pressure at low revs and no load. Especially when you consider the low compression ratio these engines run. The bearings will have a boundary layer of oil in them which should provide enough protection for this very short time?
In 40 years of oil changing I've never had any bearing failure. OK so I've always primed the filter and used to crank the engine with the low tension lead to the coil disconnected where possible but this was not always possible, and it's more difficult on modern engines.
What about filters that are mounted vertically or close to? They tend to drain oil as the internal rubber "one way valve" is not too clever at holding back hot, thin oil. Cold starts often see the oil pressure light on for what seems an eternity while the filter re-fills with oil! From what's been said here, and on many other threads about the apparent vulnerability of the Subaru engine, can you imagine the consquencies of such a filter layout on the life of this engine? Are these engines really this fragile?
JohnD

 

It is a bit odd, the servicing thing.
It doesn't make sense to me either.
Running long term with det - not good. Obvious engine killer (and I think this is why the Subaru engine has the 'chocolate internals' name - either a JDM is run on straight SUL, or a Euro model is run with a failing MAF).
But a couple of seconds every 7,500 (or whatever it is) miles?!? Surely unless the car is left oil-free for a few days the situation is going to be no worse than the car standing for a week & then started?

 

But why all these failures just after a service? That's what's stumped us to come to this service procedure.

I run my car only once a week and sometimes don't start it up for 3 weeks. Should I expect a failure in the future then? Only done 18000 miles and it's a MY00.

Cheers,

George.

 

Tony.b
Had the same failure on my 47000kms rebuild(wiseco forgies,shot &peened rods etc) engine.
Had swapped the VF23(running at 20+psi for 2+yrs) with 450hp Garret.Car was 15 minutes in to the dyno tuning at: 4300rpm -1.3bar-4th gear-140km/hr at 140atw when it holed the block big way.
When engine was stripped rod was almost melted and one of the pistons had signs of past det.Parts were inspected by 2 engine builders and a piston- rod specialist and the verdict wasETONATION.Besides rod etc everything else was in new condition thanks to my every 3000kms oil change ( have never prefill oil filter or disconect crank etc etc on the wrx nor on the 2 Skylines since it sits vertical).
Car was running:M48pro,fmi,water injection not on at the time,3" all the way,pod,500hp fuel pump,550cc,fuel rails.
PS.Oil was changed 2500kms before and my reason for not prefilling filter is not to have UNFILTERED oil going through engine
I always service my cars at 3000kms.

Let us know once engine is stripped.


CR

 

MY 96 Impreza standard UK car put conrod through block within 100 miles of service at 45 000 miles. Loooong chat with garage who assured me they had done nothing untoward at time - non Subaru specialist. They replaced engine in 2001 and it was not until this engine was serviced by subaru specialist(AWD Perth)in 2003 that they pointed out that a Legacy engine was used...This in turn duly failed (blocked oilway to exhaust cam)within 100 miles of service. Currently have correct engine and no problems.

 

The flat four engine design is very short and it therefore follows that the bearings are very narrow, especially given the outputs many of these engines run. It doesn't take much of an interruption in oil supply before there's metal to metal contact, and once galling starts, it tends to worsen.

Not really the same situation. To get a definative answer to this question, you'd need to send a little fibre-optic camera down the oilways and see exactly what happens, but my suspicion is that if the oil is drained, the oilways will also empty, and when the pump does reprime, it'll blow all that air out of the system ahead of the new supply of oil. This action could increase the chances of temporary oil starvation.