Is this a normal diesel idle? Or bottom end knock - VIDEO

SMOKEY · Post by **SMOKEY** » Mon Nov 03, 2014 11:01 am

Hi guys

I'll preface this by saying I'm new to diesel ownership and I've put only 100km on my car in the 3 days I've owned it. I know diesels can clackety clack and carry on, so I'm not sure if this noise is normal or not - but it doesn't feel right.

I guess normally I'm in the car with the doors shut so I haven't really noticed this noise before, but I'm somewhat alarmed. This sounds to me like a bottom end knock. The car has 115km on it and what I assumed to be reasonably sound dealer service history.

I've taken a video so hopefully someone can help.

Diagnosis so far: Have run BMW Scan 1.4.0 - no error codes. Car is at operating temperature. Oil levels ok. Sounds quiet at start up but then at about the 20 second mark the knock starts to amplify. Noise is louder under the car and with the oil cap off, I can't really link the noise to tappets.

Any help would be hugely appreciated. It's a public holiday here tomorrow and I'll be stressing until I can get it in to my mechanic!

SMOKEY · Post by **SMOKEY** » Tue Nov 04, 2014 1:09 am

Hmm 75 views and no suggestions?

I have jacked the car up and isolated the noise - it's coming from the transmission bell house and with the engine at idle I can see through the inspection port and it seems like that is where the noise is coming from. Loose torque converter?

More worrying is that I can see score marks on the transmission mounting screws - looks like it's been off at some stage prior to my short ownership....... :'(

SMOKEY · Post by **SMOKEY** » Tue Nov 04, 2014 2:48 am

Update, jacked the car up and it's coming from the bellhousing. Sounds like something is loose in there, flywheel, torque plate.....dunno. Can see score marks on the transmission to engine mounting bolts so obviously trans has come off at some stage.....

Here's a video closer to the source of the noise:

http://vid16.photobucket.com/albums/b25 ... s0verf.mp4

Riggie · Post by **Riggie** » Tue Nov 04, 2014 7:47 am

Does it change if you engage D?

SMOKEY · Post by **SMOKEY** » Tue Nov 04, 2014 8:18 am

No, Riggie. Sound is present in R, N, all forward gears, stationary, rolling in gear and rolling in neutral.......

Smeeagain · Post by **Smeeagain** » Tue Nov 04, 2014 2:37 pm

[quote="SMOKEY"]
Hi guys

I'll preface this by saying I'm new to diesel ownership and I've put only 100km on my car in the 3 days I've owned it. I know diesels can clackety clack and carry on, so I'm not sure if this noise is normal or not - but it doesn't feel right.

I guess normally I'm in the car with the doors shut so I haven't really noticed this noise before, but I'm somewhat alarmed. This sounds to me like a bottom end knock. The car has 115km on it and what I assumed to be reasonably sound dealer service history.

I've taken a video so hopefully someone can help.

Diagnosis so far: Have run BMW Scan 1.4.0 - no error codes. Car is at operating temperature. Oil levels ok. Sounds quiet at start up but then at about the 20 second mark the knock starts to amplify. Noise is louder under the car and with the oil cap off, I can't really link the noise to tappets.

Any help would be hugely appreciated. It's a public holiday here tomorrow and I'll be stressing until I can get it in to my mechanic!
[/quote]

Cant help with the noise but just to pick up on your comment regarding "what I assumed to be reasonably sound dealer service history". Thats all it means - it means the car has been serviced. It does not mean that they have gone round checking every single thing is is good working order or not making odd noises. Only those items that are on the servicing lists gets checked.

So im not sure what you were expecting from a 'sound dealer service history' ....???

SMOKEY · Post by **SMOKEY** » Tue Nov 04, 2014 8:17 pm

Ok. Thanks. Not that it is my main concern at the moment - but by 'sound service history' I mean it has a full book of BMW dealer service stamps - not some Backyard Johnny. I see your point, but at the same time, I don't.

Sent from my iPhone using Tapatalk

shadrack · Post by **shadrack** » Tue Nov 04, 2014 8:40 pm

i see his point a full service history means nothing other than the service items have been checked

SMOKEY · Post by **SMOKEY** » Tue Nov 04, 2014 10:12 pm

And if I didn't mention it someone would have piped up and said 'what's the service history of the car?' - just trying to give as much detail as possible.

I don't know what the MAINTENANCE history is. Unless you're buying privately from a very diligent owner who keeps receipts of every dollar spent on the car, who would know? The best I can offer in terms of how the car has been treated prior to my ownership is to confirm it has a FBMWSH.... it could reasonably be argued, that if P/O could afford to put up cash to get the car serviced at a stealer, they could probably afford to repair as required.

Apologies if this seems short, but I've got a small window for redress with the dealer who sold me the car, and nobody is actually offering anything constructive towards a mechanical diagnosis.

X5Sport · Post by **X5Sport** » Tue Nov 04, 2014 10:34 pm

I wish we could. Mine didn't sound like that, nor do the other two BMWs I have with the same engine. It doesn't sound right, but it could be any number of items. Its frequency sounds slower than the crank but it could just be one cylinder beginning to knock.

I would just take it back, or at least get it assessed by a BMW Dealer or an Independent engineer who knows about diesels.

Engine issues are rare with these cars, hence no real input from the Forum. There's probably no one else in here who recognises it?

Richard

SMOKEY · Post by **SMOKEY** » Tue Nov 04, 2014 11:08 pm

Thanks Richard

I took it past a trusted mechanic this morning. He and another guy spent about 20 mins with it up on the hoist with a stethoscope trying to diagnose, but were pretty baffled. Hard to isolate the noise.

He feels it isn't a bottom end knock as they're normally present from the moment the engine starts, where as mine comes on about 20sec after starting (cold or hot). Obviously there are no certainties without opening the motor, but he did feel that it was a top end issue, perhaps a sticking lifter that was perhaps echoing down. His advise at this stage is to drop the oil, inspect for metal, then put in an lifter additive (not his preference, but at this stage he said anything is worth a go).

I'd already planned to do an oil and filter change this weekend, so I guess we'll wait and see.

Has anyone done a hardcore engine flush before? Something like Liqui Moly Engine Detox? I don't generally like putting in additives as they're often bandaid fixes, and an all out engine flush could dislodge some nasty stuff and move it into places it doesn't want to be........but any feedback is welcome.

Riggie · Post by **Riggie** » Wed Nov 05, 2014 8:55 am

When I had a lifter problem, the noise was a much higher frequency knock, more of a tap than the heavier sound that you're experiencing. I tried using cleaning additives without success and ended up changing the faulty one.

Given the the guys who looked couldn't isolate the area the sound is coming from, I would be taking it back to the dealer and letting them sort it out before you lose the window.

SMOKEY · Post by **SMOKEY** » Wed Nov 05, 2014 9:20 am

Unfortunately the dealer is 1500km away so that's not really an option otherwise, trust me, I'd be throwing him back the keys.

I did a liquid moly engine flush, fully synthetic Motul oil 5w-40 change, filter and put in a liqui moly lifter additive. No change.

Tried unplugging each injector individually to see if I could isolate a cylinder. No change.

Only good news at this stage is there was no metal in the oil when I dumped it.

I think I'm going to have to bite the bullet and give it to BMW, if anyone can work it out, they can.

Steamyrotter · Post by **Steamyrotter** » Thu Nov 06, 2014 1:09 pm

Check the torque converter mounting bolts and the flex plate..
My flex plate had snapped at a bolt hole and caused the torque convertor to run out of true with a muffled knocking

Sometimes the bolts release a bit and can hit the webs on teh back of the engine block.

AVI-8 · Post by **AVI-8** » Thu Nov 06, 2014 11:03 pm

All I can say is that mine doesn't sound like that, by the frequency of the noise it sounds as though it's one cylinder, does the noise get quieter once the engine is warm?

XSeries-forum

XSeries-forum