B
badman gee
Guest
not sure? anyone?pete59 said:
Check your Vanos bolts!
- Thread starter Off Your Marks
- Start date
heath
Regular Member
I have read that the later models had the updated bolts fitted from factory & dont have the vanos problems the earlier models had.
Heath on Tapatalk
Heath on Tapatalk
Jonttt
Zorg Addict
So far as I know it was an S50 engined problem only.
wonderloaf
Dedicated Member
I won't start to panic yet then! Thanks for your replies :-bd
Off Your Marks
Regular Member
- Joined
- Apr 3, 2012
- Points
- 19
Following on from my concerns I thought that I would do a bit of a pictorial write up to help others do a bit of preventative maintenance
OK, first up is a shot of the part that makes our S50 engine such an addictive thing own. The S50 Rolls Royce VANOS (variable Nockenwellensteuerung) variable camshaft timing device.
There are two packs of twin solenoids that operate on the exhaust and inlet side of the cylinder head. This write up deals with the LHS exhaust solenoids, but the same applies to the RHS, only difference is you need to remove the fan to get the whole cowling out
To get to these its best to create a little more room and remove the radiator fan cowling. the LHS is secured by a push rivet and then it lifts up and pulls out
Now, below the alloy vanos is a black plastic cover secured by 2off 10mm nuts - remove these and remove the cover to give access to the plugs for the Solenoids
Here is the plug
So, pinch the metal clip and pull out the plug
Once removed we can now remove the cover, first up make sure you put some paper towel or cloth down under the cover as some oil will come out when the Solenoids are removed. If you get oil coming out when you remove the cover then this indicated oil seal/O ring failure.
Now,you need to remove the valves. There are fitted rather snugly so you need to tease them out. I used a pair of soft jaw grips. Note the position of them and mark/photograph as needed.
Now, there are four wires on the SV's, two on each and three on the plug - two wires are common
Use a contact cleaner to remove all the trace oil
Next is to check the coil resistance - This reading of 3.3 ohms is good. If there was no reading then this indicates a failed coil
A common failure is the soldered connections to fracture so I re-soldered them and bridge the solder to bypass the copper connection on the printed circuit board (copper link can fail too)
Its time to fit the replacement O rings on the valves now.
Once the O rings are changed, clean out the oil from the SV housing as there will be residue in there
Now pop the valves back in, taking care to fit them in the same place as before. The click home securely
Refit the cover along with new paper gasket and torque new bolts to around 8-10Nm
The refit is the reverse of removal, ie refit the plug connector and plastic guard.
Once you restart the engine, it will be a little lumpy for a few seconds whilst the oil pressure in the vanos builds up
Job Done
Hope that helps! Just do the same for the RHS now.
OK, first up is a shot of the part that makes our S50 engine such an addictive thing own. The S50 Rolls Royce VANOS (variable Nockenwellensteuerung) variable camshaft timing device.
There are two packs of twin solenoids that operate on the exhaust and inlet side of the cylinder head. This write up deals with the LHS exhaust solenoids, but the same applies to the RHS, only difference is you need to remove the fan to get the whole cowling out
To get to these its best to create a little more room and remove the radiator fan cowling. the LHS is secured by a push rivet and then it lifts up and pulls out
Now, below the alloy vanos is a black plastic cover secured by 2off 10mm nuts - remove these and remove the cover to give access to the plugs for the Solenoids
Here is the plug
So, pinch the metal clip and pull out the plug
Once removed we can now remove the cover, first up make sure you put some paper towel or cloth down under the cover as some oil will come out when the Solenoids are removed. If you get oil coming out when you remove the cover then this indicated oil seal/O ring failure.
Now,you need to remove the valves. There are fitted rather snugly so you need to tease them out. I used a pair of soft jaw grips. Note the position of them and mark/photograph as needed.
Now, there are four wires on the SV's, two on each and three on the plug - two wires are common
Use a contact cleaner to remove all the trace oil
Next is to check the coil resistance - This reading of 3.3 ohms is good. If there was no reading then this indicates a failed coil
A common failure is the soldered connections to fracture so I re-soldered them and bridge the solder to bypass the copper connection on the printed circuit board (copper link can fail too)
Its time to fit the replacement O rings on the valves now.
Once the O rings are changed, clean out the oil from the SV housing as there will be residue in there
Now pop the valves back in, taking care to fit them in the same place as before. The click home securely
Refit the cover along with new paper gasket and torque new bolts to around 8-10Nm
The refit is the reverse of removal, ie refit the plug connector and plastic guard.
Once you restart the engine, it will be a little lumpy for a few seconds whilst the oil pressure in the vanos builds up
Job Done
Hope that helps! Just do the same for the RHS now.
B
badman gee
Guest
Thanks matt, the job seems quite straight forward.
Mark
Mark
Matt,
That's an impressive write up :ymapplause: Do you mind if I copy the procedure to our Z Roadster Wiki, so it can join all the other technical procedures we are cataloging? I can see this one being referred to many times in the future!
Cheers, Gary
That's an impressive write up :ymapplause: Do you mind if I copy the procedure to our Z Roadster Wiki, so it can join all the other technical procedures we are cataloging? I can see this one being referred to many times in the future!
Cheers, Gary
Off Your Marks
Regular Member
- Joined
- Apr 3, 2012
- Points
- 19
Yeah sure Gaz 
Cheers Matt.
Wiki entry added - http://zroadster.org/wiki/bmw-z3/ma...mw-z3-m-vanos-bolts-preventative-maintenance/
Added to 'News' section on home page, Facebook & Twitter!
Wiki entry added - http://zroadster.org/wiki/bmw-z3/ma...mw-z3-m-vanos-bolts-preventative-maintenance/
Added to 'News' section on home page, Facebook & Twitter!
Wow, thanks very much Matt that is a fantastic writeup which has given me confidence to have a go at doing this one day.
I notice there are a couple of people on ebay selling kits for around £50 which includes o'rings and new bolts, does anyone know if these are OK or is it better to go to BMW or even Dr Vanos.
I notice there are a couple of people on ebay selling kits for around £50 which includes o'rings and new bolts, does anyone know if these are OK or is it better to go to BMW or even Dr Vanos.
B
badman gee
Guest
They should be the same Ian.
Just get them from Mr Vanos to be sure.
Just get them from Mr Vanos to be sure.
DangerousDave
Dedicated Member
- Joined
- Jan 7, 2012
- Points
- 36
Excellent. One of the best write-ups I've seen.
Whenever I play with the vanos (or after a long time without running), I remove the filter and fill the vanos with oil before replacing the filter. This means the vanos won't start empty.
Whenever I play with the vanos (or after a long time without running), I remove the filter and fill the vanos with oil before replacing the filter. This means the vanos won't start empty.
Z
zedonist
Guest
Thought I would have a poke around the threads on this, and when you look at what BMW fitted to later cars you understand what the failure was.
First off the bolts are Cap Head Screws, and these are usually 12.9 grade, more commonly now they are 10.9 which is still pretty hard but slightly more ductile, so in answer to most questions you wont get a stronger screw. You can obviously get these in A2 or A4 stainless steel, but again they will be of comparable tensile strength usually 970Nm.
Bolts are designed to stretch, the torque figure used when tightening the bolt should be roughly between 60 and 90% of yield, which means that the bolt will want to return to its original length and thus apply a clamping load to the joint, depending on the amount of torque applied.
Now when bolts are not tightened correctly and you do not have enough clamp load the bolts will vibrate and rotate loose and then fall out. In the threads i have read people have complained about parts being broken and shearing, this will not have happened as there is no axial loading to the bolts and therefore failure from fatigue will not occur. So the next clue that really identified the root cause of failure was the finish of the fasteners.
In the earlier threads the bolts being changed were of a bright yellow finish, which is characteristic of an electroplated zinc and passivate finish (BZP). in the photo's in this thread the bolts are a dull grey finish characteristic of an organic finish such as Delta or Geomet or Dacromet. It is this change that explains the failure mode, and the failure mode is attributed to Hydrogen Embrittlement, derived from the electro plating process. In low tensile steels the material (steel) is ductile enough to accomodate the addition of the atomic hydrogen molecule, however in less ductile, harder materials such as 10.9 or 12.9 the material is not capable of accommodating the extra addition and thus micro cracks appear at the grain boundaries, in severe cases the bolts snap on application, but in most cases the failure is delayed until the cross sectional area of the bolt is reduced enough due to propagation of the crack to cause the bolt to break.
Up until the late 80's early 90's it was the accepted method to have high tensile parts in BZP because they looked nice and negate the effects of Hydrogen Embrittlement the bolts are baked following plating to drive out the excess hydrogen. how ever the process has to be carried out immediately following plating and for a designated number of hours between 8 and 24 depending on grade. Unfortunately, manufacturing processes in those days was encumbered by over processing, panic jobs, breakdowns etc (sounds the same as today) and consequently some batches would not have the correct treatment.
In order to get round this problem, new finishes emerged that did not require the parts to be processed in Acid and the new dip spin finishes were born, which in essence are an aluminium and zinc rich paint that is applied to the parts by dipping in the liquid and then spun off in a centrifuge to give a thin even layer, the deeper the layer required the more dip spin steps you take.
The advantages of these finishes are increased resistance to corrosion and the removal of potential Hydrogen Embrittlement problems.
Therefore if you check your engines and you have the grey finish fasteners they will be ok and will not break, just check they are torqued up correctly, also I would point out that if you have bright yellow fasteners and they are original and they are not loose then they are not affected and will not fail.
These issues are always batch related and the recall notice would have identified all possibly affected VIN number ranges
8Nm is the correct torque for an M5 Grade 10.9 bolt.
Great write up BTW
First off the bolts are Cap Head Screws, and these are usually 12.9 grade, more commonly now they are 10.9 which is still pretty hard but slightly more ductile, so in answer to most questions you wont get a stronger screw. You can obviously get these in A2 or A4 stainless steel, but again they will be of comparable tensile strength usually 970Nm.
Bolts are designed to stretch, the torque figure used when tightening the bolt should be roughly between 60 and 90% of yield, which means that the bolt will want to return to its original length and thus apply a clamping load to the joint, depending on the amount of torque applied.
Now when bolts are not tightened correctly and you do not have enough clamp load the bolts will vibrate and rotate loose and then fall out. In the threads i have read people have complained about parts being broken and shearing, this will not have happened as there is no axial loading to the bolts and therefore failure from fatigue will not occur. So the next clue that really identified the root cause of failure was the finish of the fasteners.
In the earlier threads the bolts being changed were of a bright yellow finish, which is characteristic of an electroplated zinc and passivate finish (BZP). in the photo's in this thread the bolts are a dull grey finish characteristic of an organic finish such as Delta or Geomet or Dacromet. It is this change that explains the failure mode, and the failure mode is attributed to Hydrogen Embrittlement, derived from the electro plating process. In low tensile steels the material (steel) is ductile enough to accomodate the addition of the atomic hydrogen molecule, however in less ductile, harder materials such as 10.9 or 12.9 the material is not capable of accommodating the extra addition and thus micro cracks appear at the grain boundaries, in severe cases the bolts snap on application, but in most cases the failure is delayed until the cross sectional area of the bolt is reduced enough due to propagation of the crack to cause the bolt to break.
Up until the late 80's early 90's it was the accepted method to have high tensile parts in BZP because they looked nice and negate the effects of Hydrogen Embrittlement the bolts are baked following plating to drive out the excess hydrogen. how ever the process has to be carried out immediately following plating and for a designated number of hours between 8 and 24 depending on grade. Unfortunately, manufacturing processes in those days was encumbered by over processing, panic jobs, breakdowns etc (sounds the same as today) and consequently some batches would not have the correct treatment.
In order to get round this problem, new finishes emerged that did not require the parts to be processed in Acid and the new dip spin finishes were born, which in essence are an aluminium and zinc rich paint that is applied to the parts by dipping in the liquid and then spun off in a centrifuge to give a thin even layer, the deeper the layer required the more dip spin steps you take.
The advantages of these finishes are increased resistance to corrosion and the removal of potential Hydrogen Embrittlement problems.
Therefore if you check your engines and you have the grey finish fasteners they will be ok and will not break, just check they are torqued up correctly, also I would point out that if you have bright yellow fasteners and they are original and they are not loose then they are not affected and will not fail.
These issues are always batch related and the recall notice would have identified all possibly affected VIN number ranges
8Nm is the correct torque for an M5 Grade 10.9 bolt.
Great write up BTW
Thanks for spending the time to look into that, it's great that we have someone with your knowledge and experience to be able to put the science and reasoning behind the failures. Gives everyone the extra insight and more visual things to look out for which is always good.
Jonttt
Zorg Addict
Great write up matt. I particularly like the fact you have the perfect tool for everything, wear gloves so you don't get fingerprints on that engine and that little mirror is ace
Great explanation also re the reason for the bolts issue which confirmed it was the bolts vibrating loose that was the problem and not them shearing.
Great explanation also re the reason for the bolts issue which confirmed it was the bolts vibrating loose that was the problem and not them shearing.
Z
zedonist
Guest
Yes Jontt, the original recall would have been the plating issue causing breaking bolts, this issue is most definitely joint relaxation due to clamping onto a white metal casting as it is soft it deforms under the load and the bolt slowly unwinds over time, some times they get around this with a harder inserted bush material for the boss or using a thicker boss cross section, i expect in the design process they assumed the loss of the cover is not detrimental to the engine performance, In this case periodic monitor of torque is recommended.
I would also assume that some people will never see this issue if they have a cover made from a more robust cast of the alloy (top end of the chemical analysis spec), i.e. harder than a leaner cast.
Or buy a M44 1.9
I would also assume that some people will never see this issue if they have a cover made from a more robust cast of the alloy (top end of the chemical analysis spec), i.e. harder than a leaner cast.
Or buy a M44 1.9
Off Your Marks
Regular Member
- Joined
- Apr 3, 2012
- Points
- 19
Good stuff
glad you all find it useful
Just a note re the RHS - you have to remove the fan and cowling to get at it properly. The fan nut is a left hand thread!
Zedonist - fantastic detail there, very interesting indeed :-bd
glad you all find it useful
Just a note re the RHS - you have to remove the fan and cowling to get at it properly. The fan nut is a left hand thread!
Zedonist - fantastic detail there, very interesting indeed :-bd
We certainly have some very knowledgeable people on here :ymapplause:
Thanks everyone for a comprehensive explanation.
For my shame and embarrasment I got so distracted by the clean shiny engine pictures, I didn't really take the information in
Thanks everyone for a comprehensive explanation.
For my shame and embarrasment I got so distracted by the clean shiny engine pictures, I didn't really take the information in
Jonttt
Zorg Addict
I could not read it without quotingGazHyde said: