Engine Knocking

[phil_d]

Hi Guys,

I went to take my Zed out for a Sunday arvo drive today and when I started the car, I immediately noticed a distinctive knocking sound coming from the engine. First time I've heard this sound. I don't trash this car so it hasn't been driven hard so I'm trying to figure out what the problem is and why now. I will be contacting my dealer tomorrow to book it in and it will be towed in rather than driven, but I was wondering if anyone else has had a similar problem?

I originally thought the noise was coming from underneath the car, perhaps from the exhaust box, but it definitely sounds like within the engine to me.

There are no lights or cautions and the oil level is fine. There are no leaks of any kind. The car was driving perfectly fine a few days ago.

My car is 2.5si, built in 2006 and collected in Sep of the same year, 6 speed manual.

Thanks,

Phil

 

[Ski]

Odd, does not sound good though..good luck man..

 

[srhutch]

Did the noise go away after a while?

 

[cj10jeeper]

Almost impossible to diagnose the cause given the limited detail provided. Engine internal you suspect then the obvious initial reaction on a heavy noise is engine bottom end, but the car sounds too new for that. Since it's off tho the dealer you'll have the answer (and bill) soon enough

Let us know what it was.

 

[phil_d]

Dropped the car off today - trucked in - they started it but couldn't replicate the sound, bloody typical. Anyway, I've suggested they leave it overnight and try again in the morning as the engine was cold when I heard the noise. Luckily, the car is still under warranty (3 years).

Interestingly, I had to move the car from my basement carpark to the traytop and the noise was there - as soon as depressed the clutch, the noise dropped quite significantly but then heard it returned.

Anyways, I'll keep you guys posted.

Phil

 

[phil_d]

Well, turned out to be nothing at all wrong with the car. Apparently, when the car sits idle for a few days, the oil drains away from the hydraulic lifters, so that when the engine starts, there is some knocking until hey re-pressurise. The car seems to be fine now, so maybe that's all it was but I'll keep an ear out. They were going to charge me but decided to put under 'dealer goodwill'. Well, probably over cautious but at least I learnt something.

Cheers,

Phil

 

[srhutch]

Sound exactly like the issue I had, if it does it again like in my post below though it's going back as it sounded like a tank even though BMW resuce said it was fine.

http://www.z4-forum.com/forum/viewtopic.php?f=3&t=613&p=8989#p8989

 

[ZetaTre]

Here's a little litterature on the subject (from Wikipedia)

Hydraulic lifters

A hydraulic lifter, also known as a hydraulic tappet or a hydraulic lash adjuster, is a device for maintaining zero valve clearance in an internal combustion engine. The Conventional means of adjusting valve actuation always require a small clearance to be left between the valve and its rocker or cam follower to allow for thermal expansion and wear. It is vital that a valve must never be prevented from closing completely; this rapidly burns it away, especially in the case of the exhaust valve. The hydraulic lifter was designed to ensure that the valve train always operates with zero clearance, leading to quieter operation and eliminating the need for periodic adjustment of valve clearance.

The hydraulic lifter consists of a hollow expanding piston situated between the camshaft and valve. It is operated either by a rocker mechanism, or in the case of one or more overhead camshafts , directly by the camshaft. The lifter is filled with engine oil intermittently from an oil galley via a small drilling. When the engine valve is closed, the lifter is free to fill with oil. When the valve is opening and the lifter is being operated by the camshaft, the oil feed is blocked and the lifter acts just as a solid one would, oil being incompressible.

History
The first firm to include hydraulic lifters in its design was Pierce-Arrow in the early 1930s. Hydraulic lifters were popular on automobiles designed in the 1980s, but most newer cars have reverted to bucket-and-shim mechanical lifters. Although these do not run as quietly and are not maintenance-free, they are cheaper and rarely need adjustment because the wear caused by operation is spread over a large area.

Disadvantages
There are a number of potential problems with hydraulic lifters. Frequently, the valvetrain will rattle loudly on startup due to oil draining from the lifters when the vehicle is parked. This is not considered significant provided the noise disappears within a couple of minutes, typically it usually only lasts a second or two. A rattle that does not go away can indicate a blocked oil feed or that one or more of the lifters has collapsed due to wear and is no longer opening its valve fully. The affected lifter should be replaced in the latter circumstances. In extremely rare circumstances, a lifter can "pump up" and create negative valve clearance so that its valve cannot close. This is more serious as burnt valves will result. In all cases it is important to follow the manufacturer's recommendations for oil viscosity and quality.

 

[fionawilkinson]

Hi,

We have had a Z4 2009 model for 9 months. We are having problems with the knocking noise you describe. It began within 1000 miles and within 3 months. The knocking has been reoccurring ever since. We have referred the issue to the dealership and has been reported too BMW Germany, they proceeded to replace all hydraulic valve lifters as discussed above at a cost of nearly £500 under warranty. The noise still continues and appears to have worsened. The noise only disappears after about 15 minutes of driving. We are awaiting a 'fixing method' from the dealership in Bradford but they do not expect a quick resolve to this problem.

After speaking with trading standards we have been advised to see if this is a common problem and whether other Z4 owners have suffered with this problem to this extent. Any help will be appreciated.

Many Thanks

Fiona

 

[srhutch]

Fiona

From what I have read this is a fairly common problem on the Z4 and other BMW's with then N52 engine. If you have the old shape Z4 with 2.5, 2.5si or 3.0si then you have this engine.

I had a new head assembly fitted which I had been informed had a redesigned head with a non return valve fitted. This has cured my problem since it was fitted over 1 year ago. The warranty cost of this repair for £3.5k from memory.

From around September last year BMW just started replacing the Hydraulic lifters, now unless they have been redesigned in some way to include a non return vavle this will not cure the problem as you are finding out.

All I can say is keep on at the dealer and if you can drive the car to them whilst it is making the noise then do that to demonstrate the problem as that will help get it resolved.

Good Luck