LordBledisloe

Hi folks. I'm after a bit of advice.

I have a 2013 WRX. Purchased second hand in 2015. Standard other than a down pipe and cat back exhaust. Vehicle has a full history with the original dealer, which I have continued. It was actually booked for its next service before the following happened.

In Dec 2016, the car had a main end bearing failure. Subaru covered it under warranty and provided a new shortblock. The engine had done 22,000kms at this point.

Just this month, the car spun another main bearing after 14,000kms on the new short block. When the malfunction occurred, I was cruising at 80kmh. No hard driving beforehand and only been on the road 30mins. Fairly windy area with some uphills, however. On a downhill straight, 5th gear, around 2700rpm. Foot's not on the gas here, so car is just coasting down in gear. I heard a backfire from the exhaust. And backfires are odd for the car even with that exhaust. I pulled over at the bottom of the hill and the car stalls. Restarted fine, but without the road noise and exhaust, I can hear the knock at this point. Stopped car and checked oil - fine. Worth noting there was no CEL and no high temp at any point of this drive. Even when the knocking noise was apparent at idle. In fact it had not seen the CEL once since 2016 malfunction.

Car was put on a flat bed to the dealer and engine dismantled. Confirmed a repeat of the issue on number two con rod bearing, as well as a chunk of the top edge of number two piston cracked off and lodged under valves. Sump contains extensive fine metal shavings. Oil levels fine.


Note missing chunk from top left of pistion


This time, Subaru are claiming that the piston damage suggests over-boosting and likely caused by the exhaust and down pipe. And thus not covering the short block under parts warranty. They have come to this conclusion via photos provided by the dealer. The dealer is great. They know the car well and seem genuinely surprised. But they're basically the middle man.

My question is whether this sounds like a feasible scenario? Or a more likely scenario than the bearing failure being the event that caused the piston damage? After a bit of research, it looks like that an overboost event should trigger a CEL and record a P0244 code. Yet they've not mentioned this code and I did not see a CEL. Could an aftermarket dp and exhaust prevent that from happening? Should there be confirmable history of an overboost event on the ECU?

I'd appreciate any thoughts on this overboost hypothesis. I plan to respond to Subaru after the weekend.

hedgecutter

iTrader: (5)

I'm guessing that you are not UK based; Firstly , what downpipe was it, and was it mapped in? If it wasn't oem, I'm surprised your dealer accepted it first time around. No car manufacturers accept non oem modifications to warranted cars.
Secondly, Impreza engines have known weaknesses, but yours was replaced with stock parts, which doesn't eliminate these weaknesses.

LordBledisloe

I'm in NZ. Not really sure about the downpipe and exhaust beyond that it was installed by another Subaru partner called Possum Bourne motorsport. Subaru send their own special runs there (including mine - 98 octane remap off the showroom floor). Not sure about the warranty thing. My car isn't the first I've heard with a warranty claim with an exhaust. A friend's Holden was covered for a different issue several years ago.

Understood. And I've read a bit more about those weaknesses in the Ej25. Particularly the lawsuit Subaru of America settled less than a month ago for this exact failure. I do wish they had the same suspicions back then and I would have paid to protect it rather than go through it every 20,000ks.

Any thoughts on the question. Especially around the CEL and code?

hedgecutter

iTrader: (5)

If catalysts were removed, and exhaust bore enlarged, a remap would be needed for running on boost. Damage could easily arise from this not being done. Someone with more knowledge will hopefully explain the details, but whether that caused it or not, Subaru legally will refuse a claim. In the UK, this is in the warranty small print, if modified or tracked.
Your issue seems to be with the dealer who OK ed the work? Did they pull codes?

hedgecutter

iTrader: (5)

Possum Bourne have a good reputation, so I would be surprised if they failed to map it in. My guess is that it's a standard failure and the non oem exhaust has given them the excuse to reject it. That's normal practice here

LordBledisloe

Yeah I agree on both points. If codes have been pulled, they have not shared them. All they said is "piston damage is consistent with over boosting". I think I'll start with asking them to confirm the codes and provide a possible explanation for any absence of codes and why the CEL would have never come on in the life of this shortblock. Including this failure.

Thanks for your replies.

Bazil_SW

iTrader: (4)

Broadly speaking I would say:

Removed cat and increased bore of exhaust will cause reduced back pressure for the turbo. Without mapping the turbo could overboost in peaks whilst the ecu graples to control boost, and I believe that cel is only triggered with sustained over boost (citation needed!) Rather than brief peaks.

Also from what I understand whilst head gasket and maybe bearing failure (because of oil plunger and pickup fracture?) are faults seen on stock engines, rig land is often and usually seen on modified cars with stocked internals (again citation required!).

In short, sadly, I'd very surprised if subaru onhoured warranty for it, unless you can prove that ring land is a failure seen on completely stock cars and they have acknowledged it with a service fix or something similar.

Gambit

iTrader: (6)

First one would have still been within 3yr manufacturers warranty? 2nd one now outside of it so theyll do everything to not warranty fix it.

Possum Bourne is a name long associated with Subaru id be amazed if it wasnt mapped after exhaust/header changes

stamina_daddy

iTrader: (3)

I read it that car was fitted with dp and exhaust and remapped from factory?
so did dealer send car to possum Bourne for work to be done before original 1st sale?
that's how I read it anyway.