Damaged injector bolt thread

[gammakeith]

2004 XC70 D5

I was servicing the car today and noticed some gunk starting to build up around the middle injector. My heart sank a little when I noticed an Allen bolt in one side rather than the correct 8mm hex headed bolt. My heart sank even further when I found it was not tight. Sure enough a slightly longer bolt has been used as the threads are damaged and will not hold a standard bolt. I've tightened it up as much as I dare (much tighter than before but still only reasonably tight) and its not blowing at tickover. I'm guessing it will last for a while but I am aware that this is likely only a temporary state of affairs. I'll need to pull the injector at some point and deal with the damaged thread. However, it looks very tight for a helicoil. Can anyone advise how best to tackle this please?

Thanks!

Keith

[IainG]

Hi
Helicoil or thread repair would be best but,
If a helicoil won't work, would fitting a stud to the head work. You could use the max thread length available and also studlock in place.
This would be quick and easy. Run a "plug" thread tap carefully down the hole to max depth, clean out with solvent, use studlock and install stud to max depth using double nuts on the stud to tighten it. Don't use too much stud lock or you could "hydraulic" the stud on the way down the hole.
You will then be using the undamaged thread on the stud for tightening.
Not OE but if you use a high tensile stud and nut should be a fairly sound repair.
If you ate very careful and want to get the full depth of thread you can file a very slight taper to the threads on the end of the stud to match the threads at the bottom of the hole and you can gain an extra couple of threads. The original tapping of the hole usually leaves the bottom threads slightly tapered due to the tap used.
Sometimes during manufacturemthe threads don't always go to the bottom of the hole and again when cleaning out the threads with a tap you can sometimes gain a couple more threads.
Only warning, if you do use a tap, take it easy and don't force it. You would be worse off with a snapped tap in the hole!
Photo might help to show space available.
Iain

[dingov70]

Morning , you need to remove the hold down bolt & injector . The bottom of the injector hole requires removal of the sealing washer and then reaming to provide a perfectly flat base to the hole for the seal to sit on . If you omit this , the issue will simply occur again with blow-by occurring .

The hole simply requires a heli-coil or similar insert installing , BUT ensure BOTH holes are helicoiled , if one has been damaged you can bet the other is likely damaged as well . The clamping bolts are very specific in that the are torque to yield . It is best to buy a genuine kit as it contains all the seal , bolts & spring clamps required . Make sure that each bolt hole base it clean bright metal with nothing that can stop the bolt reaching all the way down the threads and giving an incorrect torque setting , too little & everything leaks , too much and you are drilling out & heli-coiling

[gammakeith]

Thanks gentlemen! Some good tips there. I am gratified that you both think that a thread repair in situ is the best option and is viable. I will certainly buy a genuine kit to complete the job. I will, of course, be hoping that Volvo injectors don't put much of a battle to remove!

Thanks again, Keith