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  #1  
Old 05-04-2003, 11:15 AM
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Ball Bearing in Pre-Chamber ?

I pulled out the Injector nozzles in my 81 240D and then removed the heat shield. I looked down through the hole with a flashlight and noticed what appeared to be a steel ball loose in the pre-chamber. I removed the steel ball with a magnet and it looks like a steel ball bearing. It is the same diameter as the hole. The other pre-chambers do not appear to have anything loose in them. Does anyone know where this ball could have come from ? Am I assuming correctly that it should not be there ? If it's not supposed to be there could it have caused problems ?

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  #2  
Old 05-04-2003, 11:30 AM
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sgoodhart, you assume correctly. It may be the tip of an old glow plug or the tip of an old nozzle (beaten round over time) or some goofball's idea cleaning the carbon from the prechamber with a ball bearing.
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  #3  
Old 05-04-2003, 11:39 AM
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I thought that this ballwas anintegral part of theprechamber. It is actually suspended and I believe helps the fuel pattern for burning. If it is floating around this is not good and means you should start looking into a new prechamber...

Double check me on this but I think I am right on this one...
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  #4  
Old 05-04-2003, 12:13 PM
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Ball Bearing

Fisherman & dabenz,

Thank you for your feedback. Although I can't see that well into the pre-chamber the others look the same. I wish I had a good picture of the inside of a pre-chamber. I'm hoping that perhaps it was just left in there from the last owner or mechanic. Do you think this could have caused any damage or running problems ?
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  #5  
Old 05-04-2003, 01:34 PM
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Oh! Balls.

sgoodhart,

That's not a ball. it's actually part of a pin that goes from one side of the prechamber to the other and has a ball like bulge in the center. I had one break off recently and rattle around inside the prechamber causing me to be very, very nervous.

I believe the ball becomes very hot while the engine is running and causes the fuel on entering to vaporize better before ignition.

Anyway, you need to replace the prechamber which is relatively easy if you have someone to borrow the impact puller from. Pull the old one first before buying the replacement so that you get the correct replacement. If you put the wrong one in and it's one of the longer ones, your troubles are just beginning.

Good luck.

Ben
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  #6  
Old 05-04-2003, 01:36 PM
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prechamber

sgoodhart,

I forgot to mention, don't lose the spacer ring when you pull the prechamber. Often they stick to the bottom of the old one and fall off without your seeing them and if you reassemble without the spacer, bad news.

Ben
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  #7  
Old 05-04-2003, 03:04 PM
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Balls

Thank you for the advice Ben. Interesting that the ball is part of a pin since it is perfectly round and not broken off in any way. It really looks like a perfect ball bearing. Anyway, I will check out the pre-chamber.

Thanks,

Scott
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  #8  
Old 05-04-2003, 04:09 PM
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Balls

Thank you for the advice Ben. Interesting that the ball is part of a pin since it is perfectly round and not broken off in any way. It really looks like a perfect ball bearing. Anyway, I will check out the pre-chamber.

Thanks,

Scott
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  #9  
Old 05-04-2003, 09:00 PM
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All the pre-chambers have a ball-pin in them, directly below the nozzle. If the pin has broken, the ball will rattle around in there, eventually breaking the tip off the prechamber, not a good thing.

You will have to pull the prechamber, as stated above, and replace the ball pin. If they are not present in the other chambers, they need replacing as well.

Peter
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  #10  
Old 05-04-2003, 11:08 PM
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sgoodhart,

Psfred is correct that you can just replace the ball pin if the part is available. It may only be available from your MB dealer.

Worst part is getting the prechamber out. You need the special prechamber puller. If it can't be pulled, you have to take off the cylinder head and press it out.

If you can't pull the prechamber out and don't want to take off the head, try running without the ball pin and see how the engine runs. It may just give a little more black smoke. But there is always the chance that the other 2 parts of the ball pin may come loose and you will have to remove them.

P E H
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  #11  
Old 05-04-2003, 11:17 PM
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Just wondering, but I'm having toruble visualizing it...how does the special prechamber puller get the prechamber out without making you pull the head?

Must be an interesting design
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  #12  
Old 05-05-2003, 01:28 AM
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Warden, the prechamber is put into the head from the top side.. so no problem taking it out that direction... two pullers are available... one impact ..like a dent puller... and the other a screw mechanism... one or the other will take them out fine unless something physical has happened to really damage them...

On the ball being really really round.... LOL... if you put something with small projectons on it in a container and heat it and turn it around and around a million times... it will come out VERY ROUND....and smooth... think of the process of making stones smooth in a tumbler....
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  #13  
Old 05-05-2003, 01:38 AM
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And everyone ALWAYS remember to remove the glow plug BEFORE pulling the pre-chamber.
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  #14  
Old 05-05-2003, 02:12 PM
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sgoodhart,

I noticed this thread is also alive and well in the Tech Forum, where it seems your description of the prechamber with the loose ball bearing piece also has an intact ball pin in it. So the ball bearing you have in your hand in fact is an extra part.

Extra parts in a place as unfriendly as the prechamber in one of these engines for any length of time has undoubtedly left its mark on the real ball pin, and the inside of the prechamber. The manual leaves little room for interpretation in its guidance for replacing the ball pin or the prechamber:

"Note: When the removed prechamber is again installed, check for perfect condition.

Ball should not be burnt."

While there is no discussion of random foriegn objects being discovered inside the prechamber, I would expect the present condition of the ball and prechamber to be less than "perfect" and would therefore replace the prechamber assembly with the ball pin. I would also be suspicious of the prechambers in the other cylinders. Good luck, Jim

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