Re: DK motors DIY (archive)

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Bad DK motor is not due to to the fatique of the motor but merely due to bad contact. Bad motor will shut down permanently but bad contact will produce intermittent problems. I read several postings on this one and seems we all have the similar problems which is routed to bad contacts. Some mentioned about bad DK sync which suggested coast-down calibration....comment to this 'when your EML is on and DK shuts down, coast-down is not helpful at all'. Other menntioned about gummed-up in the throttle butterfly...my comment 'the DK motor is very strong, when DK is on try to push the butterfly to shift its position with your hand and you'll find it impossible unless you're really-really strong. So gummed at the throttle is unlikely to shut down the DK and don't waste your money for throttle cleaner which is supposed to be used for carburators.

So finally after reading so many postings this is what I did to solve my EML/DK motor permanently:
- Disasemble your DK into its three major parts, throtle housing, connectors/stator housing and rotor housing. Careful not to bend the feedback sensors in the throtle housing.
- Disasemble connector/stator housing by unscrewing the 3 philips screws. Take the one with the plastic housing with connectors and motor brushes attached and clean them with WD40 and spray them afterwards with strong air pressure. Make sure it is very very clean, especially the brushes.I wonder why BMW still use this conventional brush??? instead of a brushles motor. Assemble this unit back.
- Clean the rotor with air pressure. wipe the grease on the axle to the reduction gear box.
- Asemble rotor and stator unit back together. Re grease the gear at the bottom using high temp thick grease. Low temp grease will melt and drip to the stator which will create bad contacts again. Happen to me.
- Bend the feedback sensors attached to the trothle body as far as you can without breaking them so they will have good connection to the sensors plate attached to the stator unit.
-Assemble the whole thing...and thats it.

An alternative to this is replacing the stator unit with the plastic housing which should be not too expensive, but I cannot find a supplier...please let me know if you managed to get one.

I have a bad dk from last year when the dealer suggested me to change it due to EML problem. I apply this and it is back alive again. So now I have 3 DKs and all in working condition.

A good DK will sound smooth when you hear it very closely. A bad DK will sound loud due to drawing too much current...and will blow up the white relays in the E box next to the DMEs..(so don't forget also to replace them if you have them for too long, cost only about CHF 40 a pair, about $25).

I will try to take some picture when I havd the time. Anyway when you disassemble the DK you will know what I mean and there is no risk of breaking the components if you're careful. The most sensitive one is when you careless about the feedback sensors (drop them or accidently push them and they will bent beyond repair), which looks like a propeller. When you dissasemble the rotor from the stator the brushes will stick because there is a connector spring, just pull them through no problem and no damage done. But the tricky part is when you want to put them together, when you have no experience dissasembling an electric motor like this. To do it you have to push the brushes back as far as possible so the spring will be inactive and after you half way putting them back , use a tiny allen key or anything with L shape to push the spring back to the brushes until you hear a click.

Altoghter it sounds complicated but actually is fairly easy. I did it in 20-30 minutes or so and it save tons. No reason to be scared if your dealer says that you have to replace the DK, it is a nothing to lose proposition and believe me it works. So far I never hear a permanent problem and a 100% dead DK, people always say after shut down and restart it will work again for some time and usually happen when the engine is cold. This is a typical bad contact issue. Perhaps one day the rotor will be really 100% dead which usually due to lose insulations of the wire, then you need to buy a new one. If you live in Switzerland, Zurich area I will be gladly to help you.

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