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35i/is Exhaust Rattle (Vacuum/Flap) FIX

Maniac
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35i/is Exhaust Rattle (Vacuum/Flap) FIX

Post by Maniac » Thu Apr 18, 2013 3:40 pm

Well I've been running with a disabled exhaust flap in my 35i for some months as last summer it started the dreaded flap rattle just like the 335i etc.. A very common issue on x35i cars when they start to age a few years.

While the extra drone on the motorway is acceptable, and overall there are some louder pops etc that are quite nice. I was getting a bit fed up with the loud noise at cold start up as the flap was disabled, those initial high revs for 20 seconds or so made the car sound like it had a broken silencer.

So, thinking cap on, I determined that the issue was the fact that the vacuum actuator on the exhaust flap was simply not closing the flap fully and this caused the flap to rattle against the exhaust pipe internally on each exhaust pulse. You can't adjust the actuator and you can't easily replace it, you have to replace the entire muffler/silencer on that side.

Well I'm not about to replace half my 3 year old exhaust so after more thought I came up with the idea that, if the actuator cannot reliably hold the flap fully closed under vacuum (perhaps due to a leak/tolerance issue or whatever) then perhaps it can hold it reliably closed around 80/90% or so, enough to make it louder generally but quieter on those cold starts.

More thinking required on how to do this, one option being to place a small self tapping screw through the exhaust where the flap rests against the tube to stop the rattle. Problems with this were a) drilling in a confined space b) the toughened metal ring around the flap mechanism and c) the flap may still rattle against the screw.

So, the next idea was Jubilee clips.. and I'll get some pics on here when I can, but this has done the trick. I placed two clips around the rod from the vacuum actuator, so that, when the actuator pulls the rod up to close the exhaust flap, the clips prevent it from pulling it closed to 100% but instead leave the flap a few mm away from the wall of the exhaust so it closes say 80/90%. This is enough to make the car much quieter on start up, while reducing the rattle to near nothing at all.

Having tested it on the way to the office this morning, the car exhaust is now somewhere between normal and loud (GolfT) mod. Quieter on cold start up so I don't annoy the neighbours/sound like a ricer(chav), but still louder than stock to make me smile a bit.

Job done for mere pennys... Given the number of 335i's out there with this issue, I think I may patent it lol...

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Re: 35i/is Exhaust Rattle (Vacuum/Flap) FIX

Post by Stark » Thu Apr 18, 2013 4:00 pm

Please show me what I need to do. Mine started doing this for the 3rd time

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Re: 35i/is Exhaust Rattle (Vacuum/Flap) FIX

Post by Maniac » Thu Apr 18, 2013 7:22 pm

It still rattles a tiny bit on start up but its nowhere near as bad as if left alone and lasts a few seconds. You also can no longer hear it when driving around as you could just before. I'd rather have a couple of seconds of tiny rattle over the full on BOOOOM for 30 secs when starting the car. Prob just needs a little more adjustment to make it silent...

Pic...

Image

There are two to ensure the top one can't move when bumped against the actuator. The placement takes a little experimentation but they're easy to move around and tighten back up.

To make this completely quiet, my next test is to put a small spring between a hole on the actuator bracket (holes are there already) and the bottom clip I've put on. This should assist the vacuum actuator in pulling the flap 100% closed as it seems the spring inside the actuator overwhelms the vacuum part which is why the rattle exists. If I can take some pressure off that internal spring by putting an external spring on the clip, that should do the trick totally.

A cack design by BMW. The actuator has no seal where the rod enters the unit, crap gets in, the rubber actuator diaphragm deteriorates and leaks. This has been an issue on BMW cars for years and still they don't address it.

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Re: 35i/is Exhaust Rattle (Vacuum/Flap) FIX

Post by Paul c » Sun Apr 21, 2013 4:40 pm

Is there no way of stopping the crud from getting in there by putting a thick layer of grease round were the rod goes in or does it get to hot. :!: :thumbsdown:
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Re: 35i/is Exhaust Rattle (Vacuum/Flap) FIX

Post by andysat » Sun Apr 21, 2013 6:52 pm

Glad you have sorted it for pennies rather than hundreds of pounds :thumbsup:
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Re: 35i/is Exhaust Rattle (Vacuum/Flap) FIX

Post by Brasseye » Sun Apr 21, 2013 8:58 pm

Paul c wrote:Is there no way of stopping the crud from getting in there by putting a thick layer of grease round were the rod goes in or does it get to hot. :!: :thumbsdown:
So problem caused by dirt ingress?

Silicon grease might stand the heat ?

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Re: 35i/is Exhaust Rattle (Vacuum/Flap) FIX

Post by Maniac » Tue Sep 10, 2013 4:56 pm

So the rattle fix only lasted a while and the noise returned. After another assertive (cough) conversation with the dealer & BMW UK they've agreed to replace the part, if I pay for fitting. I can live with that. Still annoying that this keeps going on the car (this is the second one to fail in 4 years).

Still... Here's the interesting bit. The vacuum actuator that fails, is part of the exhaust box for that side, its welded on. The next most interesting part is that both back boxes are welded together as one unit as both pipes get to the middle of the car to connect to the front exhaust sections. So, to replace a tiny vacuum actuator, that has been an issue in BMW's for many many years and you'd think they'd make it a replaceable component by now, you must replace the entire exhaust system from the middle of the car back. That's over £1000 for the part alone, and a near perfect exhaust going to the scrappers because of a faulty vacuum actuator. I'll be paying the fitment cost, which at stealer prices is £250 :cry: Nice new shiny exhaust system, no more noise, and hopefully this one will last longer.

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Re: 35i/is Exhaust Rattle (Vacuum/Flap) FIX

Post by inkey$ » Tue Sep 10, 2013 8:10 pm

The 335i issue is mainly to do with the turbo wastegates going loose. Fixed only by new wastegate arms, a software update that keeps them semi open or new turbos.
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Re: 35i/is Exhaust Rattle (Vacuum/Flap) FIX

Post by flybobbie » Tue Sep 10, 2013 8:13 pm

Shame..same setup on the MGTF. My 10 year old when sold didn't have a problem, other than me having to reconnect it back to vacuum solenoid :D

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Re: 35i/is Exhaust Rattle (Vacuum/Flap) FIX

Post by Stark » Tue Sep 10, 2013 8:42 pm

My last one lasted 14 months, and is due to have another replaced under warranty thankfully :thumbsup:

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Re: 35i/is Exhaust Rattle (Vacuum/Flap) FIX

Post by dario » Tue Sep 10, 2013 8:50 pm

Maniac wrote:So the rattle fix only lasted a while and the noise returned. After another assertive (cough) conversation with the dealer & BMW UK they've agreed to replace the part, if I pay for fitting. I can live with that. Still annoying that this keeps going on the car (this is the second one to fail in 4 years).

Still... Here's the interesting bit. The vacuum actuator that fails, is part of the exhaust box for that side, its welded on. The next most interesting part is that both back boxes are welded together as one unit as both pipes get to the middle of the car to connect to the front exhaust sections. So, to replace a tiny vacuum actuator, that has been an issue in BMW's for many many years and you'd think they'd make it a replaceable component by now, you must replace the entire exhaust system from the middle of the car back. That's over £1000 for the part alone, and a near perfect exhaust going to the scrappers because of a faulty vacuum actuator. I'll be paying the fitment cost, which at stealer prices is £250 :cry: Nice new shiny exhaust system, no more noise, and hopefully this one will last longer.
What sort of mileage are talking. i'm just over 13,000 miles in just under 3 years and just wonder if i need to start worrying.

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Re: 35i/is Exhaust Rattle (Vacuum/Flap) FIX

Post by Maniac » Tue Sep 10, 2013 8:52 pm

My first one went at year 2 with 12k miles and it went again six or more months ago at around 20k. Rubbish.

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Re: 35i/is Exhaust Rattle (Vacuum/Flap) FIX

Post by Maniac » Tue Sep 10, 2013 8:54 pm

inkey$ wrote:The 335i issue is mainly to do with the turbo wastegates going loose. Fixed only by new wastegate arms, a software update that keeps them semi open or new turbos.
I have the same engine as the 335i. It has both waste gate and exhaust flap noise on this engine setup whether 335i or 35i. Quite common and quite crap really.

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Re: 35i/is Exhaust Rattle (Vacuum/Flap) FIX

Post by Stark » Tue Sep 10, 2013 8:55 pm

First thing you will notice is a slight rattle from the driver side exhaust at start up.....and then it gets worse over time...and at it's worst, can be heard at slow speeds at up to 20 mph

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Re: 35i/is Exhaust Rattle (Vacuum/Flap) FIX

Post by dario » Tue Sep 10, 2013 9:03 pm

I will have to listen closely!

Better them paying for replacement than me!

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