Diesel injector clamp bolt

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Bob Monkhouse
Caddy2k Groupie
Posts: 7
Joined: Thu Oct 19, 2017 8:05 am
Engine size/power: 1.6 CR TDI (102bhp)

Diesel injector clamp bolt

Post by Bob Monkhouse »

Following on from last years debacle with injectors (I think I said at the time that I don't spend lots of time on the tinternet), a year has now passed and the van in question (a2011 1.6 diesel Caddy) has done 50,000 miles without problems- apart from having to have a reconned gearbox last week :? ) So, to the injector repairs (you'll have to look up my previous post on this matter). One of the reconned injectors dropped dead after only a couple of months forcing my son to buy a new Siemens one from Andrew Page's at a cost of £280+vat. This meant obtaining new clamp bolts, they are only £1.50 from VW ,don't whatever you do use the old ones.
On fitting the new injector and new clamp bolt I was tightening the bolt to its initial torque setting of 8NM (this is after blowing the thread out with an airline because the last thing you need in there is oil, as you tighten the bolt in any engine oil in the thread will hydraulic and strip the thread), this advice is immaterial because the bloody thing stripped at about 7NM.Before i had even got chance to try any angular torque .Grrrrr. That is the thread in the cylinder head,not the bolt.
I know this happens on an irregular basis because I have spoken with several mechanics who have all experienced it happening.(And the bolts break as well.This results in the whole engine out and possibly removing the head).. The only way to do this is by hand,gently, and that means drilling the offending M6 thread out by hand. I started by grinding flats on a 6mm drill, 6.3mm and 6.8mm ,this means that a chuck wrench will grip the drills properly, you have to go up in stages as the aluminium is quite sticky (it's probably a low silicon aluminium which means it flows better and is more suitable for complex castings), Run the 6mm dia.drill down to clear what is left of any thread, then the 6.3 one-or 1/4"dia- then run the 6.8mm dia.tapping drill down, be careful!! The next bit is even more stressful, get a set of three M8 taps,- most of us just use 2nd and plug taps but you are tapping blind into a hole and breaking a tap in there is not an option you want to consider.
Gently run the taper tap in, then follow up with the second and plug tap, I can't stress enough how careful you have to be, use tapping paste as well. When you;ve succeeded blow the hole out and measure the depth of the hole, the mistake I made next I wouldn't do again. I cut a capscrew to the correct length (it's been that long ago I can't remember the exact length) and then machined an old original bolt to make a dished washer. The bolts machine like chocolate ,there is no heat treatment on them at all which is probably why they snap when used twice. I've then Loctited the capscrew and tightened it up to 22lb/ft in 3 stages. As to the previously mentioned mistake, if I was doing this again I would make a stud with a shank on it, tighten the stud into the head and then use a nyloc nut. The slight problem I have had by using a capscrew is that I have nicked the rubber seal that the original bolt goes through ( the bolt has an 8mm dia. shank then tapers down to M6 thread, this eases the shank of the bolt through the seal) Hence we have a minor oil leak,I have cast some two part silicone casting rubber into the clamp well which has cured this.I really,REALLY don't want to take this bolt out again unless I have to. my excuses here are that I was doing all this in a car park and for the first-and hopefully last- time. My advice is to put some electrical tape over the thread on the stud when fitting the seal then pull it off before fitting the injector clamp.
One more thing associated with buggering about with injectors is the spill off/leak off pipes and more accurately the ******** clips. :evil: :evil: :evil: :evil: . I got some aluminium elbows at about £4 each and a new set of clips at 40 pence each. While the elbows are perfect I can't say much about the clips, the bloody things (imagine lots of four letter words here) are well, useless. Buy genuine VW items at £1.50 each. At this point I was going to give the VW part number but it looks like my better half has filed it in the bin.Bwaaaaaa. :roll:
Torpa
100BHP+
Posts: 134
Joined: Tue Feb 14, 2017 9:46 pm
Engine size/power: 1.6 CR TDI (102bhp)

Re: Diesel injector clamp bolt

Post by Torpa »

Helicoil is very useful when this happens.
https://www.stanleyengineeredfastening. ... ad-inserts
From Sweden
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