Mid-chassis tapping noise

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stahlgrau_hants
Joined: Mon 04 Jan, 2016 17:29
Posts: 8

  Z3 roadster 2.8

Mid-chassis tapping noise

Post by stahlgrau_hants »

Hi. I'm new to the forum. I've got a 1999 BMW Z3 roadster with the 2.8 litre straight six. I've owned it for nearly four years, although it has been in the family since 2004.

I have an unresolved noise issue. A couple of months ago the car developed a clattering/tapping noise which appeared to come from underneath the middle of the car. The noise only happens when I press the throttle, and not always. It is loudest and most noticeable when turning left, and is also typically more noticeable the harder the acceleration, if going uphill or carrying a passenger. The noise doesn't happen when the car is in neutral and the throttle pressed. As I said, it doesn't always happen, but is frequent enough to be a concern.

Having looked through the forums, I thought the problem may be a perished driveshaft centre bearing or guibo disc, so I took the car to the garage suggesting I thought this may be the problem. When the garage took a look, they suggested they found no issue with the centre bearing or guibo disc, but that the handbrake linkage was loose and touching the driveshaft. I think they made some effort to move the handbrake linkage out of the way, free of charge. The problem is not as bad now, but there is still a problem.

It's worth noting that I have problems with my handbrake. I did have issues with the handbrake not holding the car stationary very well, and one day when I pulled on the handbrake a little harder than normal it seized on, so I had to take off the wheel, loosen the adjuster and take off the drums to inspect them, which temporarily sorted the issue. When the handbrake is on now, when I come to lower the lever I can feel no tension in the cable until having driven about 100 metres, when the tension normalises. I suspect a partially seized component or possibly a snag somewhere. I'm planning on getting the drums and handbrake pads replaced anyway.

Has anybody else had this tapping/clattering issue, and has anybody discovered the handbrake linkage to be responsible? Would a handbrake linkage really make such a notable clattering noise only when pressing the throttle? I don't quite have faith in the garage, so would be interested for other opinions before my next move.
Del
Joined: Sat 19 Nov, 2011 18:35
Posts: 2136

  Z3 roadster 1.9

Re: Mid-chassis tapping noise

Post by Del »

Always hard to pinpoint issues on a forum. Your handbrake does sound problematic. The problem with these BMW systems is that the handbrake shoes can get neglected, they can delaminate with age and/or the retaining spring clips can rust or break - the result being that the shoes jam and don't operate properly. I have found that in this similar sort of situation on other cars, owners often believe there is a cable problem and make adjustments, they can also yank hard on their handbrake for some time and end up stretching and damaging the cable (sometimes to breaking point) when the problem was at the wheel the whole time.

Assuming there is no prop shaft problem it may be exhaust related. There is a steel shackle/bracket around the area of the gearbox which holds the system very firmly. These can simply disintegrate with rust and age. At this region in the exhaust the power and turbulence in the exhaust system is considerable and you will notice a metallic rattle upon revving the car. Other common causes for rattles when cornering and going over bumps can be the "droplinks" which tie the front and rear anti-roll bars to the suspension. The rears in particular often look dry and cracked (the rubber bushes) which means they are loosely gripping the anti-roll bar - eventually they can fall off.

Hope this helps.
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BonBon
Joined: Tue 08 Jan, 2008 21:10
Posts: 1227

  Z3 roadster 1.9

Re: Mid-chassis tapping noise

Post by BonBon »

Exhaust brackets are a good guess - but I'll bet on worn foam on the petrol tank supports straps.
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Southernboy
Joined: Thu 07 Oct, 2010 12:39
Posts: 6436

  Z3 roadster 3.0i
Location: Johannesburg

Re: Mid-chassis tapping noise

Post by Southernboy »

Sounds as though you have identified the source to the hand brake system. You will need to go through the entire length of it from the hand brake lever cables where they exit under the car to the back and each wheel. Probably best if you can raise the car on all 4 corners securely, and have someone to help you operate the hand brake from inside the car whilst you examine from underneath. Bear in mind that when you're seated in the car and driving that your head is closer to the rear wheels than the "center" of the car. So what you may assume is a noise in the center, is actually closer to the rear. :wink:
"Normal is overrated"
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stahlgrau_hants
Joined: Mon 04 Jan, 2016 17:29
Posts: 8

  Z3 roadster 2.8

Re: Mid-chassis tapping noise

Post by stahlgrau_hants »

Thanks for the responses. Perhaps I will carry out the works on the handbrake, and through replacing components I may be able to identify or rule out issues with the linkage.

If the issue were exhaust brackets I would be seriously concerned if the garage didn't spot the issue. Same goes for driveshaft centre bearing and guibo disc. A friend of mine wonders if universal joints/CV joints could be the issue, although he is unfamiliar with BMWs.

I think the main thing that caused issues for the car was lack of driving. Whilst it is now a daily runner, there was a period of two years where I only had it as a weekend car, and that caused a number of problems. That was when the handbrake issue started, but I also ended up having to replace the front brake calipers, pads and discs due to them seizing, there was a perishing tyre issue and non-regular driving killed off the original battery.
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Southernboy
Joined: Thu 07 Oct, 2010 12:39
Posts: 6436

  Z3 roadster 3.0i
Location: Johannesburg

Re: Mid-chassis tapping noise

Post by Southernboy »

The rear drive shafts have 2 cv joints - inner and outer - protected by rubber bellows type boots. The boots are held in place with steel clamps on either side onto the shafts and don't serve any other purpose than to keep the grease inside the boot and the dust / dirt out. It has been known, and from personal experience too, that the grease can "dry" up causing as in my case, an intermittent noise. The remedy is to remove the one clamp and inject a small amount of fresh cv joint grease into the boots. I did this, and the results were an end to the problem I had. I replaced the removed steel clamp with a decent cable tie of comparable width to seal the boot to the shaft again. The amount of grease you inject is critical, and should not be excessive. If you check in my posts under "rear drive shaft joints" you may find the specifications of both quantity and grease type to be used. Or, take the car to a reputable BMW serviceman who is aware of the requirements and has the correct grease. The entire job shouldn't take longer than 15 minutes and is easily performed.
"Normal is overrated"
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stahlgrau_hants
Joined: Mon 04 Jan, 2016 17:29
Posts: 8

  Z3 roadster 2.8

Re: Mid-chassis tapping noise

Post by stahlgrau_hants »

I've sorted my noise problem.

First of all, when I checked under the car, the bracket supporting the fuel tank seemed a bit loose, as if a rubber gasket had perished. I fitted a new gasket to prevent the bracket from rattling about. This did not solve the problem.

I replaced the rubber mount on the exhaust, thinking the old one may have stretched, although upon changing it the old one didn't seem too bad. At the same time, I noticed that the heat shielding around the exhaust back box was quite close to touching the spare wheel enclosure. I decided to bend the heat shielding back away from the spare wheel a little. After this, the noise was gone, so it was perhaps just the heat shielding.

I also did a near full handbrake component replacement as the old cables were completely shot.
Del
Joined: Sat 19 Nov, 2011 18:35
Posts: 2136

  Z3 roadster 1.9

Re: Mid-chassis tapping noise

Post by Del »

Well done and as is often the case with these "retro classics", some good renovation and preventative work along the way :D
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