Strange noise on warm up from cold

[Wavesong]

Hi Guys. I have posted on this matter before but, now that I am able to pint point things, wonder whether anyone out there can shine some light on this for me? The car is a year 2000, 2.0 six. The car starts normally and sounds fine. Once the temperature reaches about halfway to normal operating temperature, there is a rattling or buzzing noise coming from the top on the engine in the area of the inlet manifolds. This only happens at a specific rev count at around 2000 revs and only lasts for a minute as with the engine temperature rising, is disappears . I have removed the two top plastic engine covers as it sounds like something resonating but its still there with the covers removed. Otherwise the car performs normally so the problem is specific to something coming into to play during the warm up process and even then, only at a specific temperature and engine speed. I have recently completed a 2700 mile road trip round Britain including the Scottish North Coast 500 route and the car performed faultlessly with the exception of this noise which I had at the start of each day from cold as described above. Any ideas anyone please?

[Del]

Sounds like the DISA valve

[Wavesong]

Sounds like the DISA valve

I googled that and I now know what it is in so far as I can identify the black box that houses it. I can see it has a rotor which I presume is rattling at a certain pitch. But, what does it do and is it linked to the warm up procedure/process? I wonder whether the rattle is there for a limited period whilst things reach operating temperature and that once warmed up, any play is taken up. Another forum suggested that this is in place of the VANOS. Is that right? I thought my car has a double VANOS but how can I tell?

[mrscalex]

It's a valve that opens/closes at different revs to lengthen/shorten the run in the inlet manifold to draw more or less air in and give the car a kick.

It's well known for making a racket when it wears.

These are expensive parts new £250 ish. And good secondhand ones are hit and miss, when available. There is more than 1 type and 1 of the types is rebuildable with a kit - probably yours I think.

There are worst things to waste your money on if you replace/rebuild it and it turns out not to be that.

[Wavesong]

Hugely helpful thanks. I have now read some horror stories about these if the spindle lets go and given the car's age at 16 years old and the symptoms described elsewhere, everything seems to point to the DISA unit. I gather a Vaico unit is half the price but not sure I want to risk an aftermarket unit given the havoc that complete failure can cause so inclined to bite the bullet and fork out for the OEM item. It at least looks easy enough to do.

[mrscalex]

I looked at the Vaico units and there was some debate on this forum as to whether Vaico was the OEM. It turned out not to be for the DISA on my M44 (11611438404) but if I remember rightly there was a possibility they might have been for other types. It's well worth reading up as much as you can on here, zroadster.org and via google. But no, personally I wouldn't use an non-OEM part for something like this.

There are horror stories but how often they actually break-up is open for debate. But all the same that's why I said you could do worse than replace it and then find out it wasn't that.

You will need a new sealing ring which may not come with the valve itself. I haven't got round to changing mine yet as it's got an electrical fault only and the bodywork was a priority. But my understanding is it's an easy job on an M44, helped if required by removing the ABS control unit (also easy - I've replaced that before).

BMW call them Adjuster Units. I'm sure you know about realoem.com. If not go there, put the last 7 digits of your VIN in and look up the exact part number. The sample 2.0 (Jan/2000) I entered came up with 1611440049 and is also used on the 2.8. This type is more widely available second-hand than the M44 one. I have to say I would be tempted to buy a second-hand one off Ebay (£25-£35) and rebuild it with one of the rebuild kits if it's available for your specific part number (remember there are various). Then you have your original to fall back on if the rebuild goes wrong.

[Wavesong]

Well a saving of £125 doesn't justify the risk, for me. The symptoms reported on this forum seem to fit and, given my car is sixteen years old but with only 62k miles on the clock, is a prime candidate for DISA failure. Even if it doesn't cure the problem, its something that can be crossed off the list and it does coincide with a lack of torque at lower speeds noticed recently. I have also had error codes relating to inlet cam sensor which apparently can come up as a result. So, a new DISA unit it is and fingers crossed all turns out well. Many thanks for your help which is much appreciated.

[Del]

Common for these to start becoming noisy after 60-80,000 miles. Because 6 cylinder cars are more common throughout the World - particularly in the US - there is a 6 cylinder version repair kit which will fix any physical fault (rattle) but not an internal electrical issue.

The Z3 4 cylinder cars also have a DISA although it is different to the six cylinder one and there is no repair kit. I replaced mine shortly after getting the car as mine was very noisy with a loud rattily buzzing noise.

Personally, I'd be happy with the Vaico one (I didn't know about this option when I bought mine) as this is such a specialist/unique item I would doubt very much that either BMW or another manufacturer makes them.

[mrscalex]

The original fit M44 DISAs have Bosch stamped on them. Well the few I've seen anyway.

[colb]

Had to change my Disa valve on my 1.9 M43TU after it started getting noisy, it had a clacking sound, replaced it with an oem part and all has been well since.

[Del]

The original fit M44 DISAs have Bosch stamped on them

Fair enough, it's just that they're such obscure items you can't imagine more than one specialist firm making them

[Wavesong]

Thanks to all for the advice, from the descriptions of noise, I am fairly confident that this is the source of the noise on mine and in any event, given the mileage of 63k and age, sounds like it should be replaced anyway.

UPDATE As of today (Friday) I have changed the DISA unit for a new OEM one. The car is smoother on take up, power maybe slightly up and I took the car for a good run but, the noise through warm up remains. The old DISA unit did have play in the spindle and was worth doing but the original problem is not resolved. I have the mot in a weeks time and will have a look underneath as I suspect a loose or misplaced heat shield may be the cause with possibly a bit of gravel caught up somewhere.