help needed

[silverarrow]

had blowing diesel injectors again
new washers and cleaned up but i need the torque settings for the w202 cdi 2151 cc 2000 v reg
asap please help main agents said will ring back ?????

 

[silverarrow]

re torque settings


rang diesel injector service company
very helpful the answer on cdi w202 is 7 nm and extra 1/4 of a turn ie 90 deg
also special mbz only injector compound should be used most people just fit new washers and tighten up

car fine at present :bannana: :bannana:

 

[Brian WH]

rang diesel injector service company
very helpful the answer on cdi w202 is 7 nm and extra 1/4 of a turn ie 90 deg
also special mbz only injector compound should be used most people just fit new washers and tighten up

car fine at present :bannana: :bannana:

I know that is what they said - but a quarter of a turn on top of a Torque setting seems illogical to me??

If the torque setting in itself is not enough, then you should increase it surely???

If they had said tighten by hand then apply an extra quarter turn, then that would have made more sense?

 

[Dieselman]

I know that is what they said - but a quarter of a turn on top of a Torque setting seems illogical to me??

If the torque setting in itself is not enough, then you should increase it surely???

If they had said tighten by hand then apply an extra quarter turn, then that would have made more sense?

Using angle tightening is deemad a more reliable method of touquing than applying a full torque load to a thread.
The reason is that the thread creates variable torque, so the torque is kept low but constant then extra turning is added by using angle tightening.

 

[silverarrow]

power up and no leaks

 

[Brian WH]

Using angle tightening is deemad a more reliable method of touquing than applying a full torque load to a thread.
The reason is that the thread creates variable torque, so the torque is kept low but constant then extra turning is added by using angle tightening.

This would only apply to low torque applications. In my opinion this defeats the object of torqueing for that application. A nip up by hand then a quarter turn will give the same result.

For High Torque applications only the torque setting should be used or the whole setting will be over tightened.

 

[glojo]

Using angle tightening is deemad a more reliable method of touquing than applying a full torque load to a thread.
The reason is that the thread creates variable torque, so the torque is kept low but constant then extra turning is added by using angle tightening.

Hi Dieselman,
I always read with great interest and respect your very informative and most helpful replies.

If a DIY person tightens the bolts/nuts to the required specifications, then give that little extra 'required' quarter turn. I would be more than slightly gutted if that very sick 'ear shattering, heart breaking little 'pling' is heard and the thread is stripped!!!

Your explanation certainly makes good sense, as does the query.

Have a nice day,
John

 

[Dieselman]

This would only apply to low torque applications. In my opinion this defeats the object of torqueing for that application. A nip up by hand then a quarter turn will give the same result.

For High Torque applications only the torque setting should be used or the whole setting will be over tightened.

Why does this create any problems? Nearly all manufacturers now use angle tightening as the metod of setting final torque settings.

If a thread it tightened to a high torque the drag of the thread creates torque of it's own so the setting becomes unreliable. If the torque setting is kept low the thread doesn't create resistance so all fixings can reliably be set to the same value. Then a certain amount of angle tightening is brought into use to give the final torque setting.

For example most head gaskets are now set using a combination of torque settings and angle tightening.

The advice given is not to "tighten the injectors to the required torque then add a bit of a turn for good measure", it is to "torque to a low setting then finish with angle tightening", in the case mentioned this is 90 degrees. Angles can be any given setting.

This is factory spec settings.

 

[Brian WH]

Why does this create any problems? Nearly all manufacturers now use angle tightening as the metod of setting final torque settings.

If a thread it tightened to a high torque the drag of the thread creates torque of it's own so the setting becomes unreliable. If the torque setting is kept low the thread doesn't create resistance so all fixings can reliably be set to the same value. Then a certain amount of angle tightening is brought into use to give the final torque setting.

For example most head gaskets are now set using a combination of torque settings and angle tightening.

The advice given is not to "tighten the injectors to the required torque then add a bit of a turn for good measure", it is to "torque to a low setting then finish with angle tightening", in the case mentioned this is 90 degrees. Angles can be any given setting.

This is factory spec settings.

I don't disagree with what you say but,quote: -

"Then a certain amount of angle tightening is brought into use to give the final torque setting".

The final setting is not a torque setting? If it was it would have a value that you could use, surely???

The problem of torque feedback on threads is not new, and only proves that torque settings are now a misnomer, if extra part turns are then used.

 

[Dieselman]

I don't disagree with what you say but,quote: -

"Then a certain amount of angle tightening is brought into use to give the final torque setting".

The final setting is not a torque setting? If it was it would have a value that you could use, surely???

The problem of torque feedback on threads is not new, and only proves that torque settings are now a misnomer, if extra part turns are then used.

It's still a torque setting as the thread of the fixing is an exact value the stretch / pull down force of that fixing can be accurately calculated.

The fixings will have a given torque, it's just that that figure isn't reliably achieved so a more reliable method has been used.

At the end of the day the pull down force or tension in the fixing is what is important not the amount of torque in the thread.

 

[Brian WH]

It's still a torque setting as the thread of the fixing is an exact value the stretch / pull down force of that fixing can be accurately calculated.

The fixings will have a given torque, it's just that that figure isn't reliably achieved so a more reliable method has been used.

At the end of the day the pull down force or tension in the fixing is what is important not the amount of torque in the thread.

I agree that the ultimate aim is to ensure the correct tension.

If you set a torque wrench to 200 lb.ft and pull it up, then add a quarter of a turn, the resultant torque is probably nearer 210 lb.ft. The manufacturers are just covering themselves to ensure that the bolts are tightened to at least 200 lb.ft all round, without overstretching the bolt.

If I was teaching someone to pull an accurate 200 lb.ft. I would make sure they set the wrench lower then gradually working up to the required setting, thus achieving the necessary torque , overcoming thread resistance, but not overtightening.

 

[silverarrow]

very interesting comments however i would still like to know why so many cdi engines are having new copper washers on the injectors my mechanic is aware that several cars with various miles on the clock have had blowing injectors
and a mbz tech has confirmed they do a 90 deg as per mbz policy

 

[Dieselman]

I agree that the ultimate aim is to ensure the correct tension.

If you set a torque wrench to 200 lb.ft and pull it up, then add a quarter of a turn, the resultant torque is probably nearer 210 lb.ft. The manufacturers are just covering themselves to ensure that the bolts are tightened to at least 200 lb.ft all round, without overstretching the bolt.

If I was teaching someone to pull an accurate 200 lb.ft. I would make sure they set the wrench lower then gradually working up to the required setting, thus achieving the necessary torque , overcoming thread resistance, but not overtightening.

Sorry Brian, I obviously haven't made my description clear enough.

If we use your example of 200 lbft then adding an extra quarter turn will increase the torque well past 210 lbft, but will still be an irregular tension.

If we use the 200 lbft as the final torque then the sequence might be; tighten to 60 lbft, tighten to 100 lbft, tighten to 160 lbft, lastly add 180 degrees of rotation.
This gives the required 200 lbft.

The manufacturer doesn't want to "add a bit for good measure" as this can be harmfull.

 

[Dieselman]

very interesting comments however i would still like to know why so many cdi engines are having new copper washers on the injectors my mechanic is aware that several cars with various miles on the clock have had blowing injectors
and a mbz tech has confirmed they do a 90 deg as per mbz policy

AFAIK these injectors are clamped in place, not screwed in. The torque is applied to the clamp bolt not the injector.

I believe it's the clamping that's causing the problem as obviously the injector cant be a tight / interference fit so that allows some space for blowby to occur.

 

[silverarrow]

umm makes sense are the new injectors screw in
i am aware that some fords have 2 bolts

 

[glojo]

AFAIK these injectors are clamped in place, not screwed in. The torque is applied to the clamp bolt not the injector.

I believe it's the clamping that's causing the problem as obviously the injector cant be a tight / interference fit so that allows some space for blowby to occur.

Hi Dieselman,
Does this appy throughout the CDI range?

Why do you think they have gone down this route if there are the problems you have listed?

What are the benefits?

Regards,
John

 

[silverarrow]

mbz part number for special compound to lubricate injectors is a001989425110 and you also need a new washer and bolt.

NOT MANY PEOPLE KNOW ABOUT THE SPECIAL COMPOUND AND NEEDING A NEW BOLT I PRESUME THEY EXPAND LIKE CYL HEAD BOLTS

 

[Dieselman]

Hi Dieselman,
Does this appy throughout the CDI range?

Why do you think they have gone down this route if there are the problems you have listed?

What are the benefits?

Regards,
John

Yes.

Probably because manufacturing is easier thus cheaper.

 

[glojo]

Yes.

Probably because manufacturing is easier thus cheaper.

If there is this alleged problem then surely this will be a false economy. Mercedes-Benz would simply not be allowed to sweep it under the carpet and make the consumer pay.

Now that CDI engines (at present 270CDI in Sprinters, 320CDI in E-class) are being imported into the US, lawyers would have a field day and the rest of the world would simply jump onto the 'gravy train'.

Regards,
John

 

[silverarrow]

all i can say is top gear and customers who i know and have seen in the stealerships
and jd power merc bad results
reduce profits to build up quality
ummm charge more per hour for repairs i think