cabin smell and injector hold down bolts

[jonta]

Hi all,
I hope someone can help with this, problem is the other day I decided to investigate fume type smell I have recently noticed within the car, (not always) after a look on here I decided to check for leaks/blowback on the injectors; and yup looks like I've got a MINUTE leak on no.4; no carbon build up or goo of any description just what looked like a very small damp patch of diesel and a TINY bubbling in this area which suggests a seating problem, thing is its so small a leak I am not sure it is the fume in the cab problem no chuffing noise either, anyway I loosened off the hold down bolt on the offending injector and in my opinion this bolt seems to be a little 'sloppy' and not the snug fit I would expect so didn't go any further at this stage just cleaned and replaced the bolt.Had a w202 with a similar leak and done well over 5k miles with no probs (or carbon build up) so I would normally simply leave this and keep an eye on it, but for the fume smell. any Ideas anyone?

 

[hmang]

the fumey smell is the first bit .
after that comes the bigger leakage and then black death nastiness.

looks like you might have caught it in time , so happy days .

those bolts are not really supposed to be refitted but if its holding and sealing then fabulous !.

next time it hints of leaking i'd suggest replacing the seal and bolt and clean clean clean the sealing faces on the injector and cyl head ...

hope you dont have to ....

oh yeah forgot ..... clean the bolt hole tooo....

 

[jonta]

Thanks for your reply hmang I appreciate the bolts are not supposed to be re-used this was only a temporary measure to get me going, I now know the injector needs re-seating, my concern is the bolt seems to be a 'sloppy fit' and although I will be replacing the bolt if the fit is anywhere near the same as the one that is in at the moment I am not sure if it would take the torque so it has me worried that I may strip the threads. just wondering if anyone has any advice on this

 

[M80]

Depends what you mean by "sloppy".
Do you mean the bolt is able to move side to side, in which case it can't be clamping and it will leak?
Or do you mean the bolt feels solid bit the clamp is able to move, in which case it seems you have clamped onto gunge in the bottom of the bolt hole? This will leak also.

 

[mersum1es]

Thread may be damaged if there is play sideways, time-serts have been used succesfully, helicoils have been some troubles occasionally. Long tool shafts needed...

 

[jonta]

thanks for replies m80 & mersum1es, yeh the 'sloppy bolt' is sideways movement which makes me feel a little apprehensive about the replacement bolt if I strip it then I am goosed at least it is running at the moment, so I feel I am going to need a back up plan and I am not afraid to admit it scares me somewhat to start drilling and tapping on a cylinder head, though if this is what it takes then its time to bite the bullet, any advice on re-threading (would prefer to go for an insert) would be greatly appreciated:|

 

[hmang]

inserts

the trouble with inserts
1/ the hole is really quite deep , so you'll need a long tap if you want to use the full length of thread....possible but not in most peoples tool boxes
2/ the length of thread on the bolt is longer than most standard inserts ..helicoil or time sert so for full length thread you may have to stack inserts or make a custom one
3/ theres only a certain amount of outside material available before you start to get close to other stuff.

its all possible with care

personally with yours at the moment ....if its working and not leaking ...i'd leave it alone.

if it does leak, i'd clean up as previously and change the seal and bolt , if youre nervous of the thread , get a long 6mm tap and chase it along to clean it up .
after that you're into the more involved work.

my 2 p worth .........if it aint bust , dont fix it

 

[Mark A]

Have a look here.

http://forums.mercedesclub.org.uk/showthread.php?t=124384

 

[jonta]

thanks I would leave this alone if it weren't leaking but unfortunately it is so I will go with suggestions of clean up and new washer & bolt, after first cleaning the threads with a tap,
I am gonna need a back up plan and the necessary parts in place as I have a feeling the threads won't hold up. Was wondering though if it was crucial to use all of the thread on the bolt when using an insert?

 

[Mark A]

The thread serts are more than long enough for the job. When you drop your new stretch bolt in, there is only about 8 -10 mm sticking up. If you do need to to an insert repair, look at the thread below. They aren't cheap, but I can thoroughly recommend a timesert.

Mark

 

[jonta]

Thanks Mark A, I had made my decision to use time-sert and you have just confirmed this.... Have you used these for this type of repair? I have sourced 19mm m6 x 1.00 inserts so with 19mm of thread: should be as you say, more than long enough

 

[jonta]

just looking at an earlier post and realised that that the thread is 40mm or so down the hole in which case it makes the job look a little MORE daunting.. This would also suggest that a 19mm insert may be too long and bottom out before it is fixed/seated. any thoughts on tapping out the top of the hole to accept a m8 time-sert an use a m8 allen bolt as I am sure more torque could be applied with a steel insert, or how about same method using an m8 stud with nut & spring washer (more torque?)

 

[mersum1es]

M8 replaces have been done (I've only read about them), in my opinion problem is that m8 allen bolt is not stretching so you'll lose ability of the injector attach adjust heat expansions. Some M8 repairs have been ok, some not.

 

[jonta]

yeh had thought of the bolt stretch factor (in my opinion this is the weak link) and again; only my opinion but more torque with steel inserts and spring washers of good quality... in theory! I feel would solve this problem. In all honesty I have no faith in stretch bolt applications in my mind these are weak points usually in the most vunerable locations heads etc, ................ bolt too small.... lets put some stress on it and stretch it to keep it tight and flex, I would rather use a bolt and thread system that could handle the job. any thoughts or suggestions ?

 

[Mark A]

Look at the link in my last post. I used time sert with stretch bolt and worked very well. Put 40 k on the ml before we got rid, and still no leak on the repair. As per other posts be careful, not much between hero and zero. 3 mm of alloy belie the standard injector hole and the water course.

Best of luck.

Mark

 

[jonta]

Thanks Mark A, read your earlier posts just didn't realise they were yours till after posting, Question now is don't suppose you can remember what length insert you used? as I am trying to get the parts in place before I attempt this repair: have sourced 12mm 17mm & 19mm normally I would have went for the 19mm but I now think this may be too long and bottom out....? did you manage to countersink the collar ok on your repair? not easy to check when its buried so deep within the hole!

 

[Mark A]

I used the 12mm insert. If you have a look online IIRC, the optimum length is 2x the diameter, so for an M6 bolt, that would be 12mm.

No countersink.

Best of luck.

 

[mercedes13156]

A word of warning from my own experience of removing the Nr 4 Injector, if it's not already out. There's a lump of metal on the head thet will easily smash the plastic electrical shroud if you twist it too far to the left.

I spoke to Steve@Avantguard about my chuffing injector when I popped in to see him on a visit to see my son in Yeovil, and he highly recommended a particular way of getting the threads redone. There's no-one in Scotland that does that, so I had to put an M8 helicoil in. Steve warned me that the non stretchy bolt wouldn't hold the torque because of expansion and contraction and he was spot on. It loosened off as he said it would, but a tiny wee bit of threadlock on the bolt completely stopped it from moving until I sold it many thousands of miles later.

 

[Steve@Avantgarde]

Using oversize steel bolts into an alloy head wont work because as the head expands with heat then a small amount of torque is lost on the injector and it causes the black death to reoccur. The injector bolts used are alloy stretch bolts designed to hold torque under heat and stress.

We have an engineering company local to us which drills out the existing M6 thread to M10, in goes an alloy insert which is then drilled and tapped to M6 allowing the correct M6 stretch fixing to be used.

 

[hmang]

Using oversize steel bolts into an alloy head wont work because as the head expands with heat then a small amount of torque is lost on the injector and it causes the black death to reoccur. The injector bolts used are alloy stretch bolts designed to hold torque under heat and stress.

We have an engineering company local to us which drills out the existing M6 thread to M10, in goes an alloy insert which is then drilled and tapped to M6 allowing the correct M6 stretch fixing to be used.

that'll be cylinder head off then steve ?

i think a lot of people are trying to avoid that