I have a 1997 STI Version 3 (Jap import).
A big end bearing failure on no 3 cylinder (driver's side rear) occured about 10000 kms (6000miles) ago. The engine was re-built with new bearings and crankshaft and carefully run in.
The car has run perfectly for 10000kms, never stressed or rev'd excessively,
The big end has now failed again (same cylinder). It cannot be due to fuel as +5 octane booster has always been added.
Has anyone had a similar experience? I can't figure the cause.

 

whats the fuel like in botswana? will an extra 5 ron be enough. maybe should have asked your mapper to pull the ignition advance way back if using crap fuel. possible lack of lubrication due to thinness of oil because of the heat out there?

 

Runs on either 95 octane - obtainable in Johannesburg area - or 93 octane, available in Botswana & elsewhere. With octane booster this equals 100 or 98.

 

another point - engine temperature was never above normal. its also winter here at the moment!!

 

Were the bearing clearances checked when the engine was rebuilt? How well did you clean the block? Did you get a new oil modine? Did you replace/check clearances on oil pump?

 

Thx for ur reponse. The did renew the oil pump. Iwill ask the garage about your other points.

 

dave, i wouldn't be guessing on the octane booster. very rarely to they achieve whats on the bottle. better with a 10% methanol mix dumped in the tank. 93 ron i thought we were bad in Northern Ireland. no new modine is bad. lot of swarf in the old one which will have lead to your failure.

 

Thx again. forgive my ignorance but not sure what you mean by "no new modine is bad. lot of swarf"!

 

when your big ends go metal filings (swarf) get into the oil pump and oil modine (cooler). usually on a new build for a subaru a good mechanic will replace the oil pump and modine. some mechanics just reuse the modine which is a death sentence to a new engine as invariably the swarf from the old engine ends up there. its just a matter of time my friend before your engine lets go again. if the modine wasn't changed after the last failure i am surprised you got 10000km out of your new engine.

 

I really appreciate your input. Being in the transport business the workshops we use specialise in diesel engines! I will pass on your info to them and hopefully they will get it right this time. Thanks again.

 

all very well and good Dave but they aren't paying for your engine a second time are they. do you not have specialist subaru mechanics out there that could build your engine properly. i am sorry to say a rebuild wont be cheap. what are parts price out there like? might be cheaper to get a short block built here and shipped.

 

Was the original cause of failure ever identified? If not. Assume it hasn't been or has been misdiagnosed....


Basic checks;

Knock sensor function
MAF sensor function
AFR when running on full boost.
And how about the injector on number three? Is its spray pattern and flow rate ok?

If these aren't checked the engine will go bang agian, and again, and again.


I'm currently dealing with a Sti V7 thats just been through its second engine failure, faults thus far:

Knock sensor not working.
Second hand MAF sensor (When will people learn! Why replace a suspect item with another equally suspect item ).
Leaking (dribbling) fuel injector

AFR map yet to be checked (needs to fix the above first).

Hopefully we may have saved this engine from another premature death.

 

this is why I recommend taking a specialist car to a subaru master technician for even rudimentary servicing.

 

But we're not specialists

 

i would class a subaru as a specialist car. yes we are not specialists but we can give sound advice.

 

Thanks to you all for your input. There are specialists and dealers in Johannesburg who I can contact.

 

Judging from the number of Subarus I saw in Jo'burg after 1.5 weeks (zero) I wouldn't put too much faith in the expertise there.

In your shoes, I'd get a shortblock or second hand engine, and buy a wideband to at least make sure the fueling is correct.

My experience from Uganda is that my car had major detonation at 1bar on the fuel here (IAM was at 0!). I had to learn how to chip the stock 1995 ECU to achieve any kind of longevity with the engine. The Subaru "specialists" could also not build an engine that would last even 5000kms. I was involved in the build of my last engine myself (checking clearances, torque specs, cleaning) and at least I have confidence in it. I had to tell the "specialists" about not re-using the oil modine (they now delete the modine on rebuilds by using the short oil filter fitting from the old Legacy blocks).