Is it safe to pull the pre-chambers without removing head? - PeachParts Mercedes-Benz Forum

lietuviai · #1 04-01-2009, 09:16 PM

I was wondering it was safe to pull the pre-chambers while the head is still on the engine. I want to examine the condition of the combustion chambers and the pre-chambers themselves on my 300D. I practiced removing a pre-chamber on a spare head. I did notice a little bit of carbon flake off onto a piece of cardboard that was under the head in the process. There were more carbon particles after reinstalling the pre-chamber. It might be OK to do so but I wanted to get some input from you guys.

daddi · #2 04-01-2009, 09:23 PM

I've done it worked ok for me.

bgkast · #3 04-01-2009, 10:34 PM

Yes, it should be fine.

Doktor Bert · #4 04-01-2009, 10:37 PM

Yes.

Blow the cylinder out with compressed air befor re-assembly to clear any particulate matter...Robert

lietuviai · #5 04-01-2009, 11:10 PM

Sounds like good advice. Can the metal O-ring be reused or is it a cheap replacement part?

Diesel911 · #6 04-02-2009, 12:40 AM

Before the removal have the piston up at TDC on the Compression Stroke. This way when you blow with the Compressed Air all the Valves are closed, and the Carbon cannot fall deep inside and leaving only 1 way for the Air+Carbon to go but back out.

I just picked up a $3 Air Gun and Big Lots that has 3 long Needles with it to go on the end of the Air Gun. The needles are sometims helpful to get way back inside somplace to make sure it blows out.

vox_incognita · #7 04-02-2009, 05:32 AM

I have a specific question-on a vehicle with an unknown service history,is it sufficient to measure the height of the rings used ?To what extend do they compress,given the PC locking rings are torqued to 150-180 Nm?
That`s the main reason I`m hesitant to pull mine...the rings OD is a bit wider then the PC collar diameter and there shoud be some place left unsqueezed to measure the original height I think..but I`m not that sure...

winmutt · #8 04-02-2009, 07:49 AM

The rings are one time crush washers and CANNOT be reused. They are cheap. Don't forget your heat shields as well. Just make sure you rotate the engine by hand through all the cylinder cycles before you start it up.

PS- I have the ring tool for loan on the cheap.

leathermang · #9 04-02-2009, 10:24 AM

The FSM says nothing about having to take off the head to deal with precombustion chambers...and I applaud your interest in them... the critical intersection between all the other factors in the design of a diesel engine which have to be correct to get the preformance out of the engine.

DO NOT USE COMPRESSED AIR TO BLOW INTO THE CYLINDER BORE....

Machinists know to use vacuum in cases like this because forced air can put carbon , machining metal, etc into areas which would require total teardown to remove... like between the piston and the bore wall in this case...

So figure some way to vacuum the best you can as compared to blowing it helter skelter inside that confined area...

When you pull them out there is going to be a relatively large hole to work with... as compared to the glow plugs for example....and we already discussed not using forced air there for the same reason..
So, duct tape a small tube to the end of your vacuum cleaner and do the best you can that way..

lietuviai · #10 04-02-2009, 11:09 AM

I don't have an air gun. That's one accessory I don't have for my air compressor. Makes sense about not wanting to shoot compressed air into the cylinder. It should be easy to use a vacuum. I have some ice maker lines that are rigid and are about the same size as the PC.
I have the PC removal tool along with the ring removal tool. There was a guy that made a high quality version without the high price. It worked really well on the practice head.

winmutt · #11 04-02-2009, 11:43 AM

Make sure you clean the head area surrounding the injectors VERY thoroughly before pulling them. I did the vac route, perhaps a plastic covered magnetic pen might not be such a bad idea either?

lietuviai · #12 04-02-2009, 11:52 AM

Good point. My head is clean. It got that way from my leaking injector lines and replacing them thereafter. It's been easy to keep it clean ever since.