[Moel]

Hey everyone

So annoyingly I think the inevitable has happened :-( 2017 M235i

My partner took the car to work this morning, got into the car park and instantly got the 'battery not charging stop immediately'

Got the AA out, serpentine belt is shredded to fuck. AA man didn't think it had gone into the front crank seal, but he's not taking the front crank to check.

Went and got another belt from BMW, fitted it, I believe he started it without the MAF plugged in, then plugged the MAF in. Reset the engine codes, and it now has a misfire on 1 and 5 according to the ECU and boost pressure code as well.

He cleared the codes again, swapped over coil 1 and 2, and the code hasn't come back but it still idles like a bag of crap.

I'm going to have it recovered back home, but please tell me how badly fucked this whole thing is and what do i need to check.

[Moel]

Ok so, some further updates

It’s now on its way home, it drove itself onto the recovery truck, apparently not sounding too bad.

There are suggestions that maybe the water pump stopped working, causing a build up of heat and that may have caused the serpentine belt to snap?

Pretty easy to rule that out when back by running the air purge procedure. However I’m still not entirely sure how that would cause 1 and 5 to misfire, unless the head is warped?

Unbelievably I think this is the best service we’ve ever had from the AA, they’ve even got another man coming out when it gets home.

[Moel]

Ok further further update

Car starts and idles fine. You know about 60 seconds after you start the car, and some sort of mechanical slide engages (that you can hear)

Then it starts becoming super lumpy and like crap.
Is that the vanos? Do these have vanos?

[XutvJet]

What year is this car again? You said 2017. There were no M235s in 2017. 2017 is the M240 and it has the B58 motor. If this is a 2017 M240, please move this to the B58 forum.

If this is a 2016 or older M235, then:

- The water pumps rarely seize. It's the electronics that fail.

- The car should start and run fine once the MAF is plugged in.

- Until you can determine that a portion of the belt didn't get sucked into the engine, I would not be running the motor at all because that belt material can go everywhere and it will become a disaster.

- I'd also look into why the belt came off. On N55s, belts fail because the oil filter housing gasket is leaking.

[Moel]

Apologies
1) it’s a 2015 m235i
2) you are right on the water pump
3) I agree, I am not starting it again until I’ve taken the valve cover and sump off
4) Yes, I annoyingly gave it all a cursory once over a month ago, but it would appear the oghf went at some point recently and I didn’t notice.

What I really really really want to know and what no one seems to be able to answer, is what solenoid or motor or valve operates shortly after idle drops on startup.

It’s a very deliberate electronic motor noise. That will I suspect tell me how borked and how much work is required.

[XutvJet]

Typically that sound is the diverted valve.

It sure sounds like the belt did get sucked into the motor.

[Moel]

Ok, so I’m not starting the engine and I’m going to get it recovered to our local bmw independent I think.

Just one more question why does it go lumpy as hell when the diverted valve kicks in?

[MLJR235]

Originally Posted by XutvJet

Typically that sound is the diverted valve.

It sure sounds like the belt did get sucked into the motor.

I am thinking you meant to say the the wastegate?

During cold start operation the wastegate is typically opened to allow more air and hotter burn for emissions or something like that. That is why that loud exhaust sound you get during cold starts is never achieved again after this cycle is completed ( 1-3 minutes ) .


Also, to answer OP, the harsh idle may be happening after the transition ( wastgate valve is closed *sound you hear ) from cold start logic into "normal" warmed up tuning/running logic.

I am no expert but this seems most probable from what you have explained thus far. Why your car si not running well may be a number of things and should probably get a good inspection done by a trained professional.

[Moel]

Thanks I think you are both definitely right…like Lord Flashheart said about his underpants, I haven’t been built to take the job on.

So definitely doing the right thing sending it off to the menders. I’m sure we’ll get it sorted, and gives me a chance to actually give the old girl a lot of TLC (it’s been abused all summer working on HS2.)

[Moel]

Well fingers crossed I get the car back in a day or two for more miles of trouble free motoring. Things that i've learnt over the last few weeks that may help others searching around the internet.

Firstly if this does happen to you, and you damage your crank seal, the car will run rough because the damaged crank seal allows air into the engine/motor.

Secondly don't be a cheapskate! I will be ordering a front seal guard to fit when I get the water pump done, it would have saved me £100's and prolonged gut twisting agony

Thirdly, always support your local BMW independent mech/garage. My local one turns out is absolutely amazing, and I love all of the little touches their new large workshop has, including a lovely mint BMW Isetta in the office, I am impressed they managed to get it in there considering it's on the first floor.

I would dread to think what a main dealer would be charging me right now.

I cannot wait to get my baby back and go out for a drive. Albeit i've been enjoying a (new to us) 2019 Rav-4 for the last few weeks.

[Moel]

For the purposes of historical accuracy and in case anyone else finds this post a quick update.

The garage have started work and it is sump off time, because and here is a new one on me, on first inspection the whole front main seal is missing.

This means one of two things.

Either it was pulled out with the belt by the AA man on replacement,
OR it’s been sucked into the sump.

So sump off time!

[Moel]

Weekly update - kids if this happens to you; don’t think you can get away with replacing the seal and thinking it will be fine. (There is at least one YouTube vid that suggests you should be ok)

Just had the call from the indie shop. So following sump take off they found a LOT of belt material in the sump, including some clogging up the oil pump chain and thankfully the oil pickup wasn’t entirely blocked so the short time it was run, should be ok.

No requirement for any further strip down, sumps going back in with new gasket etc, and we should be on the final stretch.

[60_Driver]

Sorry this happened to you but thank you for the details and updates!

[Moel]

….and we are there…

So in total we did sump off, all the belt fished out, sump put back on. Car run, car misfired, vanos valve filters cleared of shite. Flew through the MOT, so nice to have a lovely meaty engine back.

And all for a very reasonable price just north of £1100

[omg_jeremy]

We’re any codes active for this if you remember?