Causes of fractured/exploded prechambers?
 

Ok, this is sort of a continuation of a different thread I started when I noticed the balls on the PC's in 2 cyl were missing. I removed the offending PC from the head today. What I found has me baffled. The hole in the side of the PC for the glow plug to enter is completely blown apart. The top of the hole is normal but the lower portion of the hole is all missing with pieces missing all along the wall of the PC. The best way I can describe it is that it looks as if someone tried to ank the PC with the glow plug was still in place and the glow plug shattered the PC. However, the GP look original and are undamaged. Even more strange is that there arent any pieces anywhere! Compression is good and even across all 4 cyl and I see no damage to the top of the piston crown. What could cause this type of catastrophic PC failure, yet leave no debris? Anyne who has had a PC out will understand why this is so strange. For the pieces to enter the piston area they would have to fit thru the tiny holes in the portion of the PC that extends into the normal combustion chamber. There is no other way. So, anyone have any ideas??

Could this be an example of what starting fluid can do?

Len

The genius tried to pull the prechamber with the glow plug installed. Couldn't do it and finally realized his error. Removed the broken glow plug, pulled the prechamber, cleaned all the debris, and, naturally, reinstalled the prechamber because he certainly wouldn't buy a new one. Then, he put a new glow plug back in.

Then he sold the vehicle to you.:D ;)

BTW, the shafts that the glow plug ball is mounted on will eventually loosen in the prechamber walls and you'll lose the ball. It's not that uncommon. On my 617, with 180K, all the shafts were a bit loose and the general opinion was that they would never go another 100K without a failure.

the prechamber probably self destructed.it can happen.starting fluid or ether can also contribute to an early demise.i had one go in my 80 300sd.the ball pin was bouncing around and destroyed the nozzle tip.your PO may have removed the debris while attempting to diagnos poor running

I am going to take a photo and post it is a few mins. I really want you guys to see the destruction. I know I always love to see the mangled mess that poor maint can leave behind :)

Here it is! So does anyone think 2 prechambers that look like this could cause a shake?? Or am I going to replace these and find out that the idle shake is just cause this car is cursed??

looks exactly like what i experienced on my 80 sd.no starting fluid was used.:)

One way pre-chambers shatter, assuming it was due to a small crack growing til it did shatter is poor spray pattern which results in powerful shock waves, depending on the spray pattern, per se, and how long the condition existed. The cracks then start at the weakest point, glow plug hole, the small holes which allow the pressure into the cylinder, per se. Poor spray pattern shock waves can also cause glow plug with loop filament to fail early.

this makes sense to me.

tom w

Pc
 

How did you remove the prechamber?:confused:

There has got to be some debris somewhere.:confused:

Michael Cole, what running symptoms did you have with your busted PCs? Was rough idle one of them? I have looked all over for debris and there is none. probed the cyl with a magnetic probe...nadda. I drove this car for 2 weeks before the idle got to me and I decided to dig deeper. It never made a rattle or metalic noise as long as I have had it. This tells me the debris was removed by someone. At some point there was debris in there however since the botton of one injector is dimpled and eaten and the other cyl had the shattered heat shield. But, all the mess was cleaned up at some point and it was put back together without replacing parts. Either someone thought that the pieces meant dead motor and tossed it back together, or it was some Bubba Benz mechanic who figured it would be fine with the frags removed. As far as yanking the PC's, I did it with a 14 dollar bike crank puller and some sockets and some steel angle iron. If I geta chance Ill post some pics of the rig I made. Isnt a long term tool since it took a beating getting these out, but its still functional enough that I could do the other 2 if need be. Best part is it cost me 14 bucks so the tool shark E-Pay people didnt get a dime!!

i would think if the bits were small enough to get into the combustion chamber they would go out the tailpipe.

or be lodged in the exhaust system.

tom w

You've seen the holes in the bottom of the prechamber, correct?

No possibility of any debris lodging anywhere but the inside of the prechamber.

That's why I'm sure that the PO removed it and cleaned it out before reinstalling it.

I decided to take a peak at the seats in the head where the PC's live. On #4 there was almost 1/8th of an inch of carbon baked on the bottom. There is no way the PC was seated. It was sitting on a little caron throne. Took me 20 mins of scraping to remove it all. So, Im sure there was some odd combustion characteristics on that cyl. Im just hoping it was odd enough to make her shake!