VANOS Answers!

Hope this info helps from learning the hard way and buying an late '97 E36 Evo coupe which ended up needing the VANOS gears replaced.

After a lot of research, I've found that the main problem with VANOS units is not failure, but they become very noise with vibration at the lower end of the rev range.  When the car is cold the noise isn't too bad, but as soon as it warms up, it sounds like a diesel at idle.

The engine has two overhead cam shafts, which have a gear assembly at one end of each, just under the cover of the VANOS (front of the engine).  Each gear is about 8cm wide and has teeth the whole way round the edge, which a timing chain fits over.  The teeth wear (even though not that apparent from the gears removed from my car) which causes the noise and vibration.

The reason for the wear seems to be oil starvation caused by the small oil filter in the VANOS getting partially blocked.  I think the oil filter only get replaced at Inspection 2 services and maybe inspection 1 services - not sure!

By replacing the two gears in the VANOS (just under £500 for each gear, which seems massively expensive for what they are) my car has been totally transformed and is now very smooth at all revs.  So hopefully problem fixed.  Performance is no different with the new VANOS gears, it went like stink before too.

I would strongly recommend that you replace the VANOS oil filter at each service - I think the filter is on the end of a bolt which fits in towards the top right of the VANOS unit and costs about £2, so minimal.  I would also strongly recommend you always wait for the oil temprature (not water) to reach standard temperature before thrashing the car.

The RECALL for the VANOS unit is not to replace the whole unit, but to replace the cover bolts on each of the two covers.  The original bolts sheared off, causing the covers to blow off.  The two covers are roughly 4 to 5 cm wide and stick out slightly from the surface of the VANOS unit.  Another recall part was to replace the 'VANOS pin' but I have no idea what that is (this was replaced on my car at the PDI when new), so I would imagine most post '97 cars had this done when new.

The gears are pretty specialist to replace, but I know specialist garages such as 'Munich Legends' can do the work.  All the parts from BMW for my car to replace the gears came to about £1,000 and I think the labour time is about 4-5 hours.  I had lots of conversations with BMW UK trying to get some kind of good will gesture, but they didn't want to know, which seemed to be due to the age of the car.

Good luck if you have VANOS problems and I hope this helps.

Apologies, just assumed it was the outer teeth that wore down, as you can tell, I'm no expert.  The helical inner part it is then. Anyway replacing both gears transforms the car and it's now how it should be, super smooth and goes like stink.

Regarding the comment above about replacing the whole unit.  This was not necessary with my car, the garage only replaced the two gears and a few other minimal cost bits.  The car still has the original VANOS cover, which I assume controls the variable valve timing.

From what I have read, the most common problem with VANOS units is the noise.  Regarding loss of power or a lumpy idle, then I guess that's down to the VANOS itself and however it varies the valve timing and not down to the gears, which just become noisy, with no loss in power.  If anybody knows anything about the loss of power problem, or could explain how the variable valve timing works in simple terms, I would be very interested to know.

I've found this site very useful for research, so hope by posting this I can help with the experince I've had with my car.

My next post will be "Braided clutch hose answers!" watch this space! Seriously though will be posting what I've learn't about replacing the braided clutch hose. Went to fit a UUC Motorwerks hose, but it didn't fit. Found out there are two different types, so going the more expensive route, which I wish I had done in the first place and getting the BMW modified part fitted - the car should be ready on Friday, so will advise if this fixes the problem of the clutch biting just off the carpet.

Guys small point - when I researched the subject around 12 months ago I found that the power loss comes from internal leaks in the pressurised vanos unit. The unit operates at very high oil pressure and when these seals go performance is degraded.

The noisy gears does not seem to affect performance in the main - my car is a little noisy when warm but was tested by the dealer and the vanos tested fine. (There is a vanos check that can be conducted for around half an hour lablour)

The problem is that people think noisy gears mean that the vanos is failed and many dealers will use that as an excuse to perform the work...