How F am i? Cross threaded injector threads in prechamber

[JHZR2]

Originally Posted by betito123

How hard is it to remove the prechamber?

Thread in the slide hammer, after removing the glow plug, and hammer out. Not a big deal if the threads are ok. Thing is, even the slide hammer can damage the threads. The angled injector setup isn’t great for removal. The threads are weak.

I’d chase the threads on the prechamber. And be prepared to have to cut new ones and use some kind of adapter to hammer it out.

[Diesel911]

Originally Posted by JHZR2

Thread in the slide hammer, after removing the glow plug, and hammer out. Not a big deal if the threads are ok. Thing is, even the slide hammer can damage the threads. The angled injector setup isn’t great for removal. The threads are weak.

I’d chase the threads on the prechamber. And be prepared to have to cut new ones and use some kind of adapter to hammer it out.

One would think that there is a Mercedes special tool out there for the stripped thread issue. But maybe not.

It is hard to pick what to do when you are not there.

In theory if the threads were nonexistent if your adapter has long enough threaded area someone could get a skinny arc welding rod and weld it to the lip of the prechamber.

The other option is to rethread the inside of the chamber and make a puller adapter to thread into that.

Another option is removing the cylinder head and driving the chamber out.

[JHZR2]

Originally Posted by Diesel911

One would think that there is a Mercedes special tool out there for the stripped thread issue. But maybe not.

It is hard to pick what to do when you are not there.

In theory if the threads were nonexistent if your adapter has long enough threaded area someone could get a skinny arc welding rod and weld it to the lip of the prechamber.

The other option is to rethread the inside of the chamber and make a puller adapter to thread into that.

Another option is removing the cylinder head and driving the chamber out.

Any cross thread or thread damage would require change of the prechamber anyway.

I have the OE MB slide hammer. Its threads are somewhat weak themselves.

When I had an un-removable head shield, and it ruined my prechamber, I didn’t have a great ability to get the hammer threaded on. I forget why but the prechamber threads weren’t great. It all worked out. If not, rethreading the prechamber would have worked. Then the new bolt thread would just need to be adapted to the slide hammer.

[qualified-merc]

I remember growing up; my father was a master auto mechanic. However, once in a while he required a full service automotive machine shop for a particular repair. In those days some of the NAPA auto parts stores also had a full service auto machine shop. They had expensive specialized auto machine shop equipment on the ready and they could perform just about any service you might need.

I don't know if NAPA still has these machine shops because I haven't seen them for awhile, however it might be worth inquiring about. Also, you will probably need a flat bed to tow your car to the machine shop and be prepared to leave it for a week. One thing about it, you could screw this one up to the point of no return which means you would have a very expensive boat anchor on your hands. At least a competent (check out their trust pilot and yelp.com reviews FIRST) machine shop could get you back up and running.

[JHZR2]

Originally Posted by qualified-merc

I remember growing up; my father was a master auto mechanic. However, once in a while he required a full service automotive machine shop for a particular repair. In those days some of the NAPA auto parts stores also had a full service auto machine shop. They had expensive specialized auto machine shop equipment on the ready and they could perform just about any service you might need.

I don't know if NAPA still has these machine shops because I haven't seen them for awhile, however it might be worth inquiring about. Also, you will probably need a flat bed to tow your car to the machine shop and be prepared to leave it for a week. One thing about it, you could screw this one up to the point of no return which means you would have a very expensive boat anchor on your hands. At least a competent (check out their trust pilot and yelp.com reviews FIRST) machine shop could get you back up and running.

A machine shop is a great resource, but this is being overthought. Those prechambers are robust. Not much of anything can fall from the bottom due to the design. Retread the prechamber, make or weld a tool to attach the new thread size to a slide hammer, and remove the prechamber IAW the FSM. No boat anchors here. It’s pretty simple.

The hardest part of one does not weld, would be making a tool that fits. I would look at the right new thread size and see if a piece of rod or a big bolt could be turned down and then threaded to a slide hammer. Or else weld two together.

[qualified-merc]

Yes, if someone feels confident in their abilities I say go for it. Since the price of a remanufactured cylinder head isn't cheap, it might be worth finding a competent auto machine shop.

My father was a trained diesel engine mechanic. Anyone who witnessed his mechanical magic knew that there wasn't too much he couldn't fix or repair when it came to cars, trucks, SUVs or heavy diesel powered equipment, i.e. Caterpillar tractors, etc. And yet, there were a few times along the way he towed his machinery over to the NAPA machine shop. In those days, NAPA machine shops always delivered.

[Diesel911]

Originally Posted by qualified-merc

Yes, if someone feels confident in their abilities I say go for it. Since the price of a remanufactured cylinder head isn't cheap, it might be worth finding a competent auto machine shop.

My father was a trained diesel engine mechanic. Anyone who witnessed his mechanical magic knew that there wasn't too much he couldn't fix or repair when it came to cars, trucks, SUVs or heavy diesel powered equipment, i.e. Caterpillar tractors, etc. And yet, there were a few times along the way he towed his machinery over to the NAPA machine shop. In those days, NAPA machine shops always delivered.

I think the issue is there is no easy way for a typically equipped and adperson someone mechanically skilled to do it at home.

A regular automotive machine shop is not going to have the large taps or a means of making an adapter to attach the slide hammer.

In order to weld something to the prechamber someone needs to be a skilled welder to get down in there and not damage the head and only weld what needs to be welded. Once it is welded it is already hot.

I regular machine shop can re-thread and make an adapter to attach the slide hammer but that is expensive.

[Diesel911]

Originally Posted by JHZR2

Any cross thread or thread damage would require change of the prechamber anyway.

I have the OE MB slide hammer. Its threads are somewhat weak themselves.

When I had an un-removable head shield, and it ruined my prechamber, I didn’t have a great ability to get the hammer threaded on. I forget why but the prechamber threads weren’t great. It all worked out. If not, rethreading the prechamber would have worked. Then the new bolt thread would just need to be adapted to the slide hammer.

I have a metal cutting lathe assuming it is still working I can drill down the center of something like a bolt and get a tap stated into it straight if not doing the whole tapping job on the lathe. Few have that.

The next best option is putting the bolt in a drill press vice and using the drill press. That does not guarantee the hole goes down the center, but the hole will be parallel to the sides of the bolt even if it is off center.

If I had to drill into a bolt head with a handheld drill motor to tread it for a slide hammer for sure I would not get it straight down the middle. How much that would effect it in use I don't know.

Next is that most people don't have a 5/8x18 tap and proper sized drill hanging around their workshop. That is the size the autosome free large slide hammers used to be threaded for.

If someone cannot do any of those it is pulling the head off or towing the car to someone who can do the job.

I don't know if it possible to get something down in there to hook onto the ball pin. Not read of anyone exploring that idea.

[qualified-merc]

another idea; you could heat up the head/prechamber using a map gas torch before trying to remove it. After removal, it might be possible to literally weld the slide hammer tool to the prechamber. I'm not a welder however I have seen some welders work magic on various projects. If all else fails you could remove the cylinder head then work to remove the prechamber from the underside. Even then, laying down some MAP gas torching to the underside of the cylinder head might help.

Here is my idea in motion:

1. Cut heat shield material using a template to fit properly around the pre combustion chamber. The heat shield is to protect the cylinder head when using a welding torch.

https://www.amazon.com/Fireproof-Resistant-Retardant-Material-Plumbers/dp/B096LS732Y/ref=sr_1_10?adgrpid=1341404756023098&hvadid=83838036847828&hvbmt=be&hvdev=c&hvlocphy=97282&hvnetw=o&hvqmt=e&hvtargid=kwd-83838154234422%3Aloc-190&hydadcr=8431_13498573&keywords=welding%2Bblanket&qid=1706399613&sr=8-10&th=1

2. Take a one inch round steel rod (you will need to take a digital caliper and measure the interior diameter of the pre-combustion chamber so you can purchase the correct size steel rod) and weld to the end of your slide hammer.

https://www.amazon.com/Steel-Round-Diameter-Length-Rolled/dp/B0CJ1D9NSM/ref=sr_1_5?adgrpid=1346903217163823&hvadid=84181737580652&hvbmt=be&hvdev=c&hvlocphy=97282&hvnetw=o&hvqmt=e&hvtargid=kwd-84182401640438%3Aloc-190&hydadcr=26077_13566981&keywords=1+round+bar+steel&qid=1706398846&sr=8-5

3. Take the one inch round steel rod and insert into pre combustion chamber. Weld the one inch steel rod to the pre combustion chamber. Allow to cool overnight.

4. You can get a syringe from your local animal supply complete with needles so you could inject Kroil Oil directly around the pre combustion chamber. allow it to sit overnight and then put some more Kroil Oil in it the next morning.

5. next day use your MAP gas torch to heat up the cylinder head around the pre combustion chamber.

6. Use your slide hammer to remove the precombustion chamber.

7. Install a new pre combustion chamber.

this idea will involve some fitting and thinking. Also, it may end up costing you a slide hammer by the time you weld the one inch steel rod to the slide hammer.