Correct torque for C220 CDI injector bolts

[oulrichs]

Hi,

I need to replace the copper seal and retaining stretch bolt on one of the injectors on my 2000 (W) C220 CDI auto estate. Does anyone know the correct torque setting for the retaining bolt. I believe it's 70NM + quarter turn but I want to verify. I asked my local dealer but they refused to divulge the information...:-(

 

[jaymanek]

70?! Autodata says 7! plus the 90 degrees...

 

[oulrichs]

Just as well I checked then! - I've seen both the 7 and 70 figure quoted. Thanks.

oulrichs

 

[jaymanek]

70 is wheel bolts tight... i think you would have stripped your thread at 70

 

[oulrichs]

You may well be right. I'm picking up the parts (seal, bolts and MB grease) this afternoon and plan to refit the injector this evening. I'll let you know how I get on. Apart from an ocean of carbon gunk and a lot of WD40/patience the thing came out quite easily. The seat looks healty enough. I've gently scraped the carbon deposit of the copper seal seat in the cylinder head. Any hints on how to get this best cleaned up to maximise the chance of the thing staying tight for miles to come?

Thanks again,

oulrichs

 

[dava]

Hacksaw cut's(groves) down two sides of the old bolt and use it as a thread cleaner, also use a drill bit in your hand, to ensure there is no deposits in the end of the bolt thread. Most times people dont do this and the bolt gives an incorrect torque causing the inject seal to blow past again. MB recomend Mr Muscle oven cleaner to remove the carbon, dont laught it does work.

 

[Xtractorfan]

As dava says very important to clean out the bolt threads before fitting the new bolts..alloy wheel cleaner is used as well to clean off the carbon deposits......

 

[BlackC55]

If you don't clean the seat at the bottom of the injector this can happen (see pic)

You may also need to re-cut the seat so it seals again properly. Just replacing the seal does not always work.

The torque setting is 7NM and TWO angles of 90. The second angle of 90 has to be done with care and "feel" as they do snap. ONLY use new bolts.

 

[panason1c]

The torque setting is 7NM and TWO angles of 90. The second angle of 90 has to be done with care and "feel" as they do snap. ONLY use new bolts.

Are you sure about TWO angles of 90?...........if 2x90 is the correct procedure then surely there shouldnt be any risk of snapping a (new) bolt as torqueing a bolt using an angle guage is a more precise method than relying solely on a torque wrench.

I recently renewed one of my injector seals but only went to one 90 degree turn (after 7nm initial tighten)

 

[colechelle]

agree 100% with black, 7NM and two times 90 is the correct way, and yes as black and i both work on these things every day if try 70nm you will end up with a broken bolt before you get any where near 70nm,

 

[panason1c]

agree 100% with black, 7NM and two times 90 is the correct way, and yes as black and i both work on these things every day if try 70nm you will end up with a broken bolt before you get any where near 70nm,

Need to nail this, it's important to get this info correct to avoid peeps snapping bolts or stripping threads due to conflicting info........

I've just done a lot of 'searches' on the MB forums and i can only find references to the angle tightening of ONE 90 degree turn of the injector bolt.....(one example below)
Also, i came across a post where Dieselman made a reference to ONE tightening.
Two times 90 would explain why there is a risk of a snapped bolt.

All sorted now
I was surprised to be told by MB that the 6mm bolts should be tightened to 7N/M and then another 90 degrees. Had I not known I'd have probably stripped the threads.

http://forums.mercedesclub.org.uk/showthread.php?t=28154&highlight=injector+torque

 

[BlackC55]

Are you sure about TWO angles of 90?...........if 2x90 is the correct procedure then surely there shouldnt be any risk of snapping a (new) bolt as torqueing a bolt using an angle guage is a more precise method than relying solely on a torque wrench.

I recently renewed one of my injector seals but only went to one 90 degree turn (after 7nm initial tighten)

That is not tight enough. I would do it again before it leaks.

 

[panason1c]

That is not tight enough. I would do it again before it leaks.

Thanks, but i think i'll wait for a definative answer.....a leaking seal is a much easier fix than a snapped bolt or stripped thread

7 nm + 90 + another 90 seems excessive to me for a 6mm bolt.

 

[BlackC55]

Have a look on WISNET an it will tell you on there.

 

[colechelle]

did a set of seals the other day and trust me when i tell you WIS states 7nm + 90 +90, not gonna say where i work but trust me on this i should know what mb state for correct torque settings!!!

 

[oulrichs]

I did replace the injector seal earlier this week. Did the 7NM + 180 degrees as reccomended. Not a breath of (not so) fresh air has come out of the injector so far (after approx 6 hours and 300+ miles). Let's see how it holds up I've got a little collection of bolts and seals in my garage now so if I have to re-do the repair I'm prepared. Anyway, I noted the posts on how to clean out the threads of the retaining bolt hole. The way I did it was run the old bolt in and out a few times with copper grease on it. Then I cleaned the hole out with WD 40 and compressed air before inserting the new bolt. I also noticed that about 5mm of the lower section of the bolt had a resin applied to it. I suspect this is heat expanding and helps keep the thing in place over time. Very nice to get this job done - the engine is now cleaner and smoother running. Thanks for everyones input.

oulrichs

 

[kebo57]

Hi I also have done the injector seals
See http://forums.mercedesclub.org.uk/showthread.php?t=35511
A good test for leaking is to use diesel as a leak detector around the joint between the injector and the cylinder head
I had a leaking injector that you could hear with the bonnet down, but the others looked ok till I did the test and I had another 3 leaking, If you looked very closely you could see tiny bubbles coming up and showing in the diesel around the neck of the injector

Regarding torque setting of the clamping bolt, this would depend on the quality of the surfaces of the cylinder head & the injector the better the surface finish the less torque that is needed.
I have used some new original bolts but also have used couple of long series hexagon cap head which don't seem to be as spongy when tightening up as the correct bolts,
I didn't bother with the touque setting I just tightened & untightened & retightened till the spongyness was down to the minimum

Kevin

 

[oulrichs]

I had access to the MB WIS (2006 version) over the weekend and in there it clearly states 7NM + 90 degrees (although I personally don't think the additional 90 degrees do any harm). There is also a special MB tool for extracting the injector and one for cleaning the injector seat. However, they won't sell you any of these in the UK. Another point worth noting was that they specifically tell you to aviod applying the special grease to the seal and lower section of the injector. Too late for me unfortunately - but the thing is still not leaking (I did the leak test above using WD40).

 

[panason1c]

I had access to the MB WIS (2006 version) over the weekend and in there it clearly states 7NM + 90 degrees (although I personally don't think the additional 90 degrees do any harm).

Thanks for that.

Overtightening a 6mm bolt by an extra 90 degrees is actually quite a lot in terms of placing excessive stress on that bolt and very likely to result in either stripped threads or a snapped bolt.

 

[oulrichs]

Can't argue with that in general (particularly, as my experience is pretty limited). My comment was based on a) feel - 7NM + 180 degrees did not seem to stretch the bolt anywhere near breaking point and b) the actual accuracy of the the torque wrench - 7NM was right at the lower end of the scale of my torque wrench.