Help! Engine rattle round

[Olz]

Hi guys,

So, after washing my Z4 3.0si at the weekend I decided to drive it into the garage. While it was ticking over and I was checking my positioning I noticed a fairly loud rattling (hard to describe exactly) sound coming out from under the bonnet. I was pretty alarmed as it's not a sound I've heard before. I know people complain about the hydraulic valve tappets being a bit noisy when the oil has drained out of them but this was a different sound:

[youtube]HlQyvmHsQW0[/youtube]

I'm pretty keen to find out what's causing the rattling sound and get it fixed if I can. I initially thought it could be the water pump or alternator but I've done a bit of research and think it might be to do with DISA. So far I have:

- Disconnected the easy to reach DISA valve, no change in sound.

- Disconnected the difficult to reach (under the intake manifold) DISA valve, no change in sound.

- Removed the easy to reach DISA valve. Apart from a little oil, appeared clean with no play in the flap mechanism.

- Read the fault codes on the car. A few that were totally unrelated but an interesting one relating to the crankshaft position sensor.

- Started to try and remove the intake manifold to have a look at the other DISA valve, but then 1/3 of the way into the job realised how involved it is and called it a day.

Does anyone have any thoughts? Does it sound like a DISA issue or should I be looking elsewhere? Any suggestions are much appreciated!

 

[hopz121]

That sounds like a proper rattle, have you checked heat shields on exhausts? Pullys nice and tight with no play? Does the car have oil in it? Fan on front possibly? Water pump? Timing chain?

Sorry not much help just trying to think of places to start looking

 

[VRSteve]

Sounds like a marble in a tin can.

Take the belts off and start it up, that will rule out bearing failure on things like the alternator.

 

[Sky-drive]

Mine started making a very similar sound this week. Got the Zed towed to my local indie yesterday and it looks like its the DISA that's failed. Hoping I might be able just replace the flap with the upgraded metal version rather than have to fork out for a brand new unit ...

 

[Mike6]

Be careful how you remove the unit. I have heard that the pin holding everything together can sometimes drop out and end up going in the intake system requiring a fair strip down

 

[Sky-drive]

Be careful how you remove the unit. I have heard that the pin holding everything together can sometimes drop out and end up going in the intake system requiring a fair strip down

thanks for that advice Mike. Im dropping by mechanic on Monday and wondering if it might be worth jacking up the Zed off the floor on its front offside so that the pin is at least pointing downhill as and when the old DISA is pulled away from the engine. Certainly want to reduce any risk of the pin potentially falling into the intake!

 

[Chris1981]

I doubt that it's DISA related, the N52 engine has a far better DISA valve set up that the M54s which tended to get loose and make noise, if you have unplugged both and had no change in sound then i think you need to discount that theory.

Try seeing if it makes the same noise with the clutch pressed down, if it stops it's a well known DMF chatter and not too much to worry about, there are a few threads on the forum about it.

Other than that I'd follow the advice above and look for anything loose or the alternator.

Good luck and let us know what you find out to be the issue!

 

[coupedan]

Sounds like a combination of sounds to be honest, a mix of the DMF rattle and HVA unit.

As said above, depress the clutch peddle and see if the sound goes away.

Also, you can do a HVA bleed which involves either driving the car pretty hard for a while or letting the car get up to temp then revving it at about 3k for a set time limit (There is instructions somewhere online to do this)

Hopefully this helps..

 

[coupedan]

Just found this on another forum:


Update on n52 ticking: *>Important<* information
http://www.e90post.com/forums/showth...=13504&page=44

Ticking Noise SBSI B 11 09 07 -N52 Engine HVA System
________________________________________
The ticking noise is a known problem with the N52 (3.0L) engine fitted to e90 series vehicle. I have the problem with my 3 series wagon which now has 68K miles. I only get the problem if I travel short journey's, most of my driving is 30 mile min. so I don't here the noise very often. The real fix is to change the cylinder head, my dealer said because I reported it during the warranty period they would repair it if the SB fix does not work, so far it does.

This Service Information bulletin supersedes SI 11 09 07 dated April 2008.

designates changes to this revision

SUBJECT
Intermittent Hydraulic Valve Adjuster (HVA): "Ticking" or "Rattling" Noises


MODEL
All E82, E83, E85, E86, E88, E60, E61, E70, E90, E91, E92, and E93 with the N51, N52 or N52K engines


SITUATION
An occasional ticking or rattling noise from the HVA elements may occur during cold engine starts or frequent short-distance driving.

CAUSE
In these situations, the HVA elements may not yet have been supplied with sufficient amounts of air-free oil. This condition will not cause any damage to the engine, and usually remedies itself with a longer driving distance or operating times at full operating temperature.

CORRECTION
In the event of a customer complaint, please perform the following the HVA bleeding procedure.

PROCEDURE
Important notes:

The bleed time may take anywhere from between two minutes and (in rare cases) to a maximum of 30 minutes. This procedure is to be performed on a level surface with the vehicle stationary, and in a properly ventilated area.

Procedure preconditions:

Engine oil level correct – neither underfilled nor overfilled

Engine running at operating temperature

Bring the engine up to an operating speed (no load) of 2000-3000 rpm and maintain this condition for three minutes (bleeding procedure).

Let the engine idle for 15-30 seconds and reevaluate whether the noise is still present or not.

Engine quiet – procedure is finished.

Engine noise is still present – repeat the procedure; perform steps #1 and #2 up to a maximum of 5 times.

Only if the noise remains after performing the bleeding procedure 5 times: proceed by performing the procedure for a final time, also at an engine operating speed of 2000-3000 rpm, but for a total time duration of 15 minutes.

 

[Olz]

Time for an update. Firstly, thank you all for your thoughts and suggestions so far.

First to reply to some of the suggestions:

- Exhaust heat shields: unchecked so far. I think they would make a slightly different sound. Also, the sound seems to be coming from near to top of the engine bay.

- Pulleys and aux belt: possible. Only visual checks so far.

- Oil: the car did last time I was out in it (before the noise started). Problem with N52 engines (and probably many of BMWs other modern engines) is that they don't have a physical dipstick. Also, each time I've turned the engine off I've been able to hear oil dripping/running within the engine so I think there definitely is some.

- Radiator fan: wasn't running when the noise occurred.

- Water pump or alternator: possible, unchecked so far.

- Timing chain: definitely possible, given the difficulty of checking this I've held off so far.

- Dual mass flywheel (DMF)/clutch/gearbox: I have recently heard this sound a few times (it may have been there before but I just hadn't noticed it). From what I've read and what you've said this isn't anything to worry about. This noise only really becomes apparent when the engine is hot which leads me to believe it must be related to oil becoming less viscous and providing less damping and therefore the noise being more gearbox related.

- Hydraulic valve tappets (HVT): this is a very frequently discussed part of the N52 engine design and I've become familiar with what it sounds like. Nothing to worry about.

 

[Olz]

What have I done so far?

At the weekend I was keen to stick to my original thoughts and investigate the intake manifold further. As I said in my original post, I had already checked the easy to reach, large DISA flap with there appearing to be no problems. I thought I'd investigate the smaller one by taking the intake manifold off...what a complete pain of a job! There aren't many pictures of anyone taking the intake manifold off of a Z4 N52 so I'll include some:

Airbox and associated pipes removed. Sound enhancer removed (partially). Large DISA flap in place, about to remove the throttle body.

Throttle body removed.

Disconnecting fuel injector rail electrical connectors.

Pulling the intake manifold away from the cylinder head, only to discover a crank case breather hose still needs to be disconnected...and that the fuel line gets in the way!

Intake manifold removed.

Same as above, intakes stuffed with cloth.


The pictures don't show all of the steps but give an idea. There must be about 20 things that require disconnecting before the intake can be removed, BMW decided to use it as a mounting point for a lot of components.

At last the smaller of the two DISA flaps removed:



At this point it was a slight relief to see that the smaller DISA flap wasn't perfect. The overmoulded rubber seal has either disappeared in some areas (meaning it can't seal properly) or started to break away from the plastic in others.

I don't know at this point if this smaller flap is the problem, but either way it shouldn't look like it does in the pictures above so I've decided to order a new one. BMW seem to be the only source. List price of about £265 but I got one for £220 from Cotswold BMW (apparently there's a discount for cars over 3 years old).

It was interesting, the guy in the spares department said they sold 2-3 of the flaps a month which would suggest it's a common issue.

That's as far as I've got so far. Once I've got the new flap I'll install it and see what happens. I'll also take the old one apart to assess the mechanism inside.

I came across the video below which may justify my thoughts of the flap being the issue...at low, idle RPM the flap should be closed. If the rubber seal is broken it might not be able to seal properly causing some pressure sensor to activate the flap sporadically. Or, if the mechanism inside the flap is broken (like here) then it could be the flap is free to flutter in the intake flow (and make noise) - much like happens with the M54 intake manifold flaps.

[youtube]V8WV0-JmhOY[/youtube]

 

[jnwright71]

Hi Olz,

Did the new DISA resolve the problem ? Also, was the noise there when the engine was cold or only when warm ?

Thx, James