E220 Cdi Injector Problem

[darrensbrooks0]

I have a problem with bolting down the injector to the head on a 1999 E220 Cdi, the problem is that it just won't bolt down tight enought to stop blow back (the puff puff noise and associated puff of smoke). I have used new bolts, washer sills, injector bracket and have cleaned everything up as much as possible but to no avail, it still does it, a experienced mechanic friend has also tried the same as I have but no luck. It has come to the point where we think the treads in the head are damaged though I loathe to take the head off and get it machined for such a minor problem (though I realise that the problem will only get worse, it's why the injector was removed in the first place!). Does anyone know any way around this? Will hellicoil treads work? Or is this a common problem? Any info would be fantastic as I'm really pulling my hair out and my boss is starting to moan about me using the company van!
Thanks

 

[colechelle]

you have carbon build up, run a bolt down a grinder to make a tap and clear it out, if all elase fails a couple of washers does the trick!!

 

[jimnybob]

id say get a decent engine builder/repairer to helicoil it should only be easy and much cheaper than removing the head!

 

[Xtractorfan]

As colechelle says you need to carefully clean the bolt threads as the carbon is stopping it from tightening..also ensure that all of the old copper seal has been removed from the injector seat.. one way to check the tightness of the bolt is to measure how high the other bolts are sitting in the head

 

[star]

also check the seating face as it may need to be recut and the injector face is square and that neither have been worn by blow past.

 

[BlackC55]

Seconded. The face needs to be re-cut. Tools are available for such a job. Are you doing up the bolt enough?

 

[darrensbrooks0]

Thanks for all your help and advise, have had the car looked at by a local engineering firm who has come up with drilling and retapping the head, reseating the injector plus making a stepped stud from a specification from someone who has in the past had the same problem (sorry have lost web address though have a print out if someone is interested). The engineering firm has said it can be done with the head in situ in 2-3 hours @ £30 p/h so fingers crossed! Will post the outcome in about a week and will recommend the firm if things go to plan!

 

[exeng]

Injector thread repair

I have done loads of these it can be repaired so you can still use standard parts injector screw and clamp and has a greater pullout strenth than original threads so correct torque can be used without the fear of stripping the threads, You can also do this after people have tapped out the original hole to m8 at the top which results in the lose of the stretch in the original set up.

 

[darrensbrooks0]

Just a quick note to give everyone an end to the story: The engineering firm that I took the car to drilled and retapped the head and used a 8m bolt (instead of the stepped stud I wrote about previously) and everything is fine! No blowback at all and no carbon depoisits around the injector after 250 miles. Cost me £125+Vat with the engine in situ so this has saved me a fortune with the car spending 2 days there. The engineering firm I used is called Sabre Engineering, West Pennard, Glastonbury, Somerset, 01749 890666. They don't usually deal with auto-engineering though will turn their hand to anything! Thank you very much to everyone who posted replies, the help was totally spot on!