6-cyl double vanos problem assessment

[loach1]

I think Rajaie would agree that the inner elastomer o-rings are the ones that fail. The outer teflon rings probably don't change shape or size very much, so if the inner supporting/compliant o-rings could be sourced this might work fine. I have a VANOS o-ring that I keep meaning to measure and guess what size it used to be. One difficulty is that removing the teflon rings is tricky without damaging them since they have tobe stretched quite a bit to get them out of the groove. Teflon does have a good 'memory' though so they will probably be fine if they don't get any nicks.

I think Viton would be a good material given the heat and oil, but I'm not expert - does anyone know what would be best?

[edjack]

of BMW NA. The executives of this August organization must undergo injections of periodic Teutonic hubris.

How can they stonewall something as well-thought-out as this?
Ed in San Jose. BMW CCA member since 1980 (Nr. 62319).

'97 540i 6 speed. Build Date 3/97. Aspensilber over Aubergine leather.

[rajaieq]

I thought about your reference some more and realized you might be speaking of a post we put out a year back. As I noted the replacement of the valve seemed to initially work, but failed again within a day. The post was premature. Here’s a link to it. Elated only for a day! :)
Rajaie
528i 5sp 06/00

[ToddR]

it even had pics of the part that was changed. Sorry, if I can locate it I'll post here or email it to you. It may be of interest. Surprised no one here remembers it but, it was back in 2002 or 2003.

[chivas]

[RMedure]

[RMedure]

[RMedure]

I'm not sure I'd be worried about the "dynamic" piece of this application. Is it really moving alot? It seems it is prolly lubricated too.

[RMedure]

log the temp for a while?

[2000blk540i6sp]

Good info.

[rajaieq]

Rajaie
528i 5sp 06/00

[rajaieq]

The movement range is about an inch. The DME is constantly modulating the valve to maintain oil pressure in the compartments, so I'm not sure what kind of vibration is involved. You also need to take into consideration that the piston is attached to the camshaft. Thus it's constantly spinning inside the cylinder at half the crankshaft speed.

This is an unusual application for seals; both rotation and plunging. Loach has mentioned that this double criterion is likely what influenced the double seal configuration.
Rajaie
528i 5sp 06/00

[MikeD635]

Good idea, if you could determine operating temperature range, get some accurate dimensions, I think it would be possible to source the O-rings somewhere. It should not be difficult to identify the right material (Viton might be a good choice)

What could prove difficult is if one (or both) of the rings do not have a round cross section although with some more research, you might be able to find just the right part.

Just visiting this board from the E24 group, seems like a great bunch of people here!

Mike

[rmedure]

Cheers!
Robert


'99 540i sport, 6 spd
3.15 differential
Stop Tech front big brake kit, SS lines
Eibach front/rear sway bars
Dinan strut tower brace
Hamman HM2 18" wheels w/Potenza SO3 tires
Rogue Engineering short shifter
Zionsville Autosport aluminum radiator
Resonator delete
ACS exhaust
ACS front & rear body kits
ACS 3 piece trunk spoiler
ACS pedal set and e-brake handle
CDV delete
EVO Sport under-drive pulley kit
M5 Grills
Hella Xenon AE, auto leveling, clear corners
Clear rear tail lights
Clear sidemarkers
Pre-wired V1 radar
Traction control default "OFF"
Homelink (lighted)
Icelink w/ID tag display
35% titanium tint

I am a BMW Car Club of America member, are you? http://www.bmwcca.org/

[KirtKoeller]

Is there any way for someone to send me the bad piston seals the Teflon and rubber o rings. I can get Teflon seals made to spec and same with the o rings. I will also look to see if I have some of them (vanos) laying around to see if I can find a more reliable solution.

[NorCal05]

[NorCal05]

a teflon encapsulated viton o-ring?Nate

1993 325i
2000 528i

[NorCal05]

Getting the government involved may just succeed in putting the car on the gross polluters list, forcing all of us (in California at least) to go to a special test station. If we didn't pass, then they would make us fix the car - sending us all to the mechanics for new vanos systems.Nate

1993 325i
2000 528i

[NorCal05]

[NorCal05]

I used to sell seals for a few different companies.

The reason for two different materials in this situation is that teflon (are we 100% sure it's teflon?) doesn't have a very good memory (depending on the grade, there's PFTE, PFA, FEP, and other materials that DuPont calls Teflon). It 'cold flows', which means that it will deform under pressure. However, Teflon has one of the lowest coefficients of friction available, which is very desireable in a dynamic sealing application. There are a couple ways to combat the tendency to cold flow: you can mix it with fillers, which greatly improves its characteristics, but reduces its lubricity; or you can use a spring back-up. In Vanos case, the rubber o-ring is providing the spring force to keep the Teflon seal tight against the ID of the cylinder.

A much better seal, although more expensive (probably the reason BMW doesn't use them) is a teflon filled spring energized seal. These seals are machined out of a cylinder of filled teflon. The cross section is more or less a C shape. A metal spring is then etched and placed inside the C shape. Whereas regular teflon would deflect after a short period, the spring energizes the seal and keeps it intact for a very long time.

Here are some good pictures:

http://www.tamshell.com/spring-energized-seals.htm

There may be reasons other than cost that BMW chose the o-ring backed teflon seal, however. And there are more options than this, such as teflon encapsulated viton o-rings.

I have a friend that is an expert in seals (His job is to design seals, from torpedo propeller seals to massive oil rig seals). I'll see if he has any input.Nate

1993 325i
2000 528i