WJ Jeep Grand Cherokee 2.7 CRD Mercedes engine

[Geoffjake]

Looking for advice ,I was checking the injectors for ' black death ' when I noticed one of the injector clamping bolts had been replaced with a bigger bolt ,I know these bolts are stretch bolts and you must use new stretch bolts ,my question is should I re-use this bigger bolt or replace it , these bolts get stripped out if the bolt hole is not properly cleaned out and the new bolt can bottom out on rubbish at the bottom of the bolt hole

 

[m80]

I'm assuming you don't have issues at the moment.

Is the bigger bolt of a larger thread?
Is there chance the thread has been stripped and the replacement bolts are to over size and repair?

Tbh I would only consider removing the bolts if i was confident the new stretch bolts will go back w/o issue. You may be looking at a replacement head otherwise.

Are you aware that the rear injector wont come out w/o removing the head on these?

 

[Tuercas viejas]

There are repair techniques we use regularly on that engine.
Often we use a Timsert repair method to bring it back to standard
The other a field service method I developed using a S/S grub screw, introduced into parent head holes.
Threaded 7/16 UNC on the exterior, the injector hold down bolt hole is repaired by drilling out to 3/8th's & thread cut using an extended length 7/16 x16 tpi UNC thread tap.
Once cleaned out the grub screw insert being about 1 inch long, is introduced into the head pocket and locked.
Since the inside of the hollow grub screw is threaded to 6 x1mm, It will now take the original new MB bolt and be torqued to 7 NM plus 90 plus 90 of torque to yield.
Many in service in the US prepared/repaired by yours truly, Old Nuts .
Hasta la vista baby!
Tuercas viejas
p.s a new head is $3500 exchange if you can find one .
Incentive enough to fix it all propah like

 

[Geoffjake]

I'm assuming you don't have issues at the moment.

Is the bigger bolt of a larger thread?
Is there chance the thread has been stripped and the replacement bolts are to over size and repair?

Tbh I would only consider removing the bolts if i was confident the new stretch bolts will go back w/o issue. You may be looking at a replacement head otherwise.

Are you aware that the rear injector wont come out w/o removing the head on these?

Yes it most likely the threads have been stripped out ,if the threads in the bolt hole have not been cleaned out properly the new stretch bolt can bottom out on rubbish Bush that's fallen in,what I need to know is weather to reuse the bigger bolt and what to torque it up to as its not a stretch bolt

 

[Geoffjake]

There are repair techniques we use regularly on that engine.
Often we use a Timsert repair method to bring it back to standard
The other a field service method I developed using a S/S grub screw, introduced into parent head holes.
Threaded 7/16 UNC on the exterior, the injector hold down bolt hole is repaired by drilling out to 3/8th's & thread cut using an extended length 7/16 x16 tpi UNC thread tap.
Once cleaned out the grub screw insert being about 1 inch long, is introduced into the head pocket and locked.
Since the inside of the hollow grub screw is threaded to 6 x1mm, It will now take the original new MB bolt and be torqued to 7 NM plus 90 plus 90 of torque to yield.
Many in service in the US prepared/repaired by yours truly, Old Nuts .
Hasta la vista baby!
Tuercas viejas
p.s a new head is $3500 exchange if you can find one .
Incentive enough to fix it all propah like

Yes it would have been a much better job if it had been repaired with thread insert

 

[Tuercas viejas]

I have seen that form of what I would call a quick back yard field repair more on Sprinters than Jeeps. which of course share the same engine family..
Some will go the distance others will blow out in the shorter term.
Much depends upon the scope of the job !.
This quicky repair often relies upon the overlap of the valve cover casting around the injector hold down location forming a circular lip.
The thread is marginally tapped and a 3/8 allen bolt remedy I have often seen is usually a Russian immigrant jobbie from cargo expeditors based in the Chicago & the Midwest cities.
More often than not, the threads are cut more so into the the thin valve cover than the head below it, & consequently it fails in the long term usually on a long journey stranding the driver.
Van comes in huffing 'n chuffing like my late aunt Ethel's old ex MOD wartime BSA M21!
The last one I did was for someone at Christmas time past, stranded in a lonely Kansas agricultural township who was trying to get home to Dallas some 500 miles away.
After all, who wants to be stranded in the middle of a huge flat central plains wheat field that stretches from Oklahoma to the borders with Canada and east to Ohio, some 500.,000 sq miles.
OMG ! So lonely you can hear your beard grow!
Tuercas Viejas

 

[91dm]

What did you do in the end, re-use the bolt?

 

[Geoffjake]

What did you do in the end, re-use the bolt?

No ,I just wanted to find out if I would need to replace the bolt and what torque it would setting would it have to be ,I know the injector seals are prone to leaking and wanted to be prepared

 

[Geoffjake]

What did you do in the end, re-use the bolt?

Thanks for your reply

 

[Tuercas viejas]

I would think a Zummerzet or Iowa farm boy approach is best in this situation.
If it ain't broke don't fix it! Or just leave it alone and don't poke the Pitbull !
Tuercas viejas

 

[91dm]

Thanks for your reply

Yes I would leave it alone and just keep checking if every few months to monitor and make sure it's not leaking. The first give away is a smell into the cabin.