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Best way to fix this? It came out pretty easy using my Torx socket as I didn't realize someone had changed it out. So it wasn't that tight. And there was some sizeable metallic debris in the hole after I got the bolt out. Doesn't seem like it was doing much and the injector seems pretty stuck. In fact it look like it might be held in with JB weld...
My thought was to get the injector out and then properly fix the hole so I can use the proper sized (metric) bolt rather than the 1/4" one that was kind of in there.
How big can I drill the hole to effect the repair??
There was a small roundish chunk of metal in the hole when I removed the bolt. I assume it was in there already but tough to imagine there was enough room for it and the bolt. I removed it with a magnet. Remnants of a broken bolt perhaps?
I'd like to get the injector (#2) out to further investigate but it's pretty stuck. I had #5 out and it was able to pull it out by hand. This one will be more difficult.
Any number of possibilities for previous shoddy workmanship. Could very well have snapped it off, got the new bolt in and jbwelded it since it looks like it was only held by a couple threads. If that ones larger ya wont ever get the original smaller one to work correctly.
IMHO I would try and clean it out best as could, if necessary or possible do the extractor for the broken off part. Then tap and either do the larger threaded bolt if it works or do the helicoil insert to get back to original. Looks to me that the old broken off part is in there so you wont ever get past a couple thread engagement which isnt great.
A few things to consider:
1. They are stretch bolts, so tighten to yield. I imagine this is to try and keep constant tension over heat cycles.
2. They have relatively low torque requirement, so it does give options on repairs, but you want to try and clean up the mess first.
3. There is very little metal at the bottom of the thread, so be careful. If you drill too far you will go through the cover and the cover is matched to the head.
2nd pic really does look like it's been drilled out and an insert spun into it - looks like the insert isn't all the way home.
Likely the previous owner used whatever insert he could put hands on and went SAE on it.
The good news:
Looks to me if you have a set of small pliers with sufficient grip you can turn the outermost edge of the insert up and pull on it.
(It looks like a wire insert rather than a solid one, so the wire should untwist away from the head casting!)
The bad news:
Since they drilled out (and tapped?) for a 5/16 insert, the hole likely is too big for a 6mm insert to screw into securely.
These insert kits provide a specific drill bit and tap for the particular coil/insert.
But, I've seen the wire-type play funny when you go to twist them home.
It's possible the Time-Sert kit (
) is thicker than the wire one they tried.
But the outer threading on it almost certainly won't be the same as what's already been cut.
With a Time-Sert the stretch bolt won't really be stretching over it's full length. Only the length of one insert (1/2 inch or so).
Not sure how that will affect overall injector installation.
Might be best to take pictures to a nearby machinist for advice. This is a puzzle.
I imagine the engine had black death at one point on #2. Someone tried to remove the injector hold down bolt and it broke off. Rather than removing the broken bit, they helicoiled the top portion of the hole for a 5/16" bolt (which is about 8 mm). The engagement wasn't great, so they used JB weld to help seal/hold the injector. Or at least that's my theory.
I've had no luck with a small slide hammer so I have a bigger one. And I'll put some heat to it. Once the injector is out, I will work on hole repair. The bolt wasn't that tight so I think the JB weld is largely holding it in place and will need heat to release.
I have a short 5/16" bolt with a pilot hole. I'll screw the bolt into the helicoil, and then use the bolt to guide left-handed drill bit to drill into the broken M6 and start the extraction process.
Once it's all said and done, I have a feeling I'll end up with a Timesert.
I assume the M6 hole in the head is threaded right from the surface? How deep is it approximately?
If I replace the threads with steel, then 10mm of engagement should be sufficient. If the threads start at the same spot, then the distance from the first thread to the clamp will be the same, so the clamp load/spring should be the same as OEM. Mercedes added an extra 90 degrees of torque to the bolts so it wasn't very well engineered from the start anyway.
PO JBWelded the injector??!
When I first read, I had impression JBWeld was used to hold the coil insert.
Yeah, hook up the fuel return lines again start it up and crank the AC throw a blanket over the hood maybe even block radiator for a bit.
IDK if engine operating temperature will be sufficient to soften it but maybe so / best of luck!
+++ left handed bits, they are really the best way to extract a broken-off bolt!
With the 5/16 bolt out, JBWeld or whatever is the only thing holding the coil insert.
PBBLaster or whatever you've got...
If motor heat can soften it and you can get purchase on the tail end of the wire, pulling on it and unwinding should be possible.
Once it starts to pull out you'll see - the wire has good tensile strength and won't break into bits.
Hopefully you have a center punch narrow enough to put a center on the remaining original bolt, getting the reverse drill centered helps.
If that is the top of the old bolt showing under the coil, I wouldn't bother with an insert after you get everything cleaned up.
I put a heat gun on it for about 30 minutes and then used a larger 5 lb slide hammer. It moved on the first blow. I started the heat gun on low and creeped up to 300C. Warmed everything up nicely. A 2lb slide on a cold engine was fruitless.
Sure looks like JB weld. Grey and glossy and brittle.
Turns out the helicoil hole was not square to the head. I replaced it with a E-Z LOK Self Locking Thread Insert: M6 x 1 Internal Thread Size, 10x1.5mm external threaded insert from Grainger. I then put in a stud and bent it so I could align and install the injector and hold down clamp. Runs great now.
Turns out the helicoil hole was not square to the head. I replaced it with a E-Z LOK Self Locking Thread Insert: M6 x 1 Internal Thread Size, 10x1.5mm external threaded insert from Grainger. I then put in a stud and bent it so I could align and install the injector and hold down clamp. Runs great now.
did you reuse that injector? Looks in terrible shape!
I put in a Bosch reman. The ugliness on the injector is probably just the JB weld.
The copper seal area in the injector bore needed a bit of cleanup but the new injector slide right in. No Black Death.
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