bubbles around my injector 603 3.5 - PeachParts Mercedes-Benz Forum

t walgamuth · #1 04-30-2006, 10:03 PM

i know this has come up before, but what is the consensus on this, is it more likely to leak around the injector or is a prechamber leak more likely?

i dont have a good mental picture of the exact relationship of all of the above.

thanks in advance.

tom w

CSchmidt · #2 04-30-2006, 11:36 PM

Tom,

I was hoping my Indy could do a compression check for me, and didn't have the right fittings 8(. He returned the car with an injector return line leaking
8( 8( 8( . I just replaced a couple of the return lines tonight and have a small pool of diesel on the base of 2 injectors. I noticed the bubbles coming from the base of the injectors also. I think I have fixed the return line leaks, but I was too messy to get into the car and drive it and evaporate the diesel. I'll let you know in a day or so if the bubbles are still there.

My hypothesis... it appears there is a small vent hole of some type at the base of the injector where it screws into the head. Note the base of the injector is flush against the head for 355* of the injector base, but there is a small section that is purposely curved inward along the outside diameter. I'm guessing it is some kind of vent to allow air to move in/out while the injector moves.

Anyone else have a better idea?

Chuck

t walgamuth · #3 05-01-2006, 09:06 AM

so you are thinking a few bubbles around the base of the injector might be normal?

i wouldnt have thought so, but it sounds plausible.

what about it guys? bubbles normal? of course you need some fuel there to get bubbles, like when you have changed the bypass hose.

tom w

sixto · #4 05-01-2006, 01:54 PM

If you reused heat shields and there are bubbles then I'd say replace the heat shields. Even if the heat shields haven't been touched in a while I'd say change them on the chance they were fitted the wrong way.

If you have the right tool you can try retorquing the prechamber locknuts. Maybe there's a sealant you can apply to the locknut. Or a very fine copper thread.

gsxr provided instructions for machining 603.96 prechambers to work with -17- and later heads. I don't know how precisely a reworked prechamber can seal since there's no compression ring between the top of the prechamber and the head in 603s are there is in 617s. FWIW I didn't see bubbling around the prechamber in my 603 which had machine shop reworked prechambers in a -22- head.

Sixto

t walgamuth · #5 05-01-2006, 10:19 PM

now i am really showing my age, anybody remember lawrence welk?

i talked to my favorite machinist today and he said no, bubbles werent normal. so i have an extra metal seal for under the injector. tomorrow i will have my bro change that and see if it does the trick. if that doesnt work it will go to my favorite machinst's shop and he will pull the prechamber out from the top and check it out.

tom w

CSchmidt · #6 05-01-2006, 10:41 PM

Tom,

I may have mis-understood your situation. The reason I had bubbles was I had a pool of diesel sitting around the base of the injector from a leaking return hose. That dried up today and I have no bubbles or dampness now.

Was yours bubbling without fluid at the base of the injector?

Chuck

dieseldiehard · #7 05-02-2006, 01:21 AM

I wouldn't worry about a few tiny bubbles on a 603.
Removing the PC can be a real chore and theres the risk of damaging the split collars. Just removing the heat shields and cleaning the metal surfaces where the injectors meet the head is worthwhile I suppose. I use a Q-tip being careful not to leave any fibers.
I doubt that performance (idle) will change at all.
I've seen cars come in that needed new return hoses and when they are replaced some fuel drips onto the PC hold down collars and a few bubbles appear when the engine is started. Compression will be the same with or without the bubbles.

t walgamuth · #8 05-02-2006, 08:37 AM

ok thanks.

but it is also ignition knocking at idle. my machinist says a leak like this can make them knock at idle.

comments?

tom w

t walgamuth · #9 05-03-2006, 01:22 PM

bump

tomw

peragro · #10 06-27-2006, 06:09 PM

Bump again;

I just noticed that I've got the bubbles at the base of the injectors in the 300SDL also. My fuel return lines were crispy so I just changed them out today. Prior to the changeover they were weeping diesel onto the injectors and that's when I saw the bubbles. Pretty much all the injectors have the bubbles with the exception of one, maybe two of them. I still have bubbles, less so though, since the change out, but I'm curious as to what's causing them.

Any ideas????

t walgamuth · #11 06-27-2006, 07:22 PM

any 'spark knock' for you?

mine seems better now that the weather is warmer.

tom w

peragro · #12 06-27-2006, 08:18 PM

Quote:

Originally Posted by t walgamuth

any 'spark knock' for you?

mine seems better now that the weather is warmer.

tom w

Actually, there was a little bit before I changed the return lines. That seems to have quited things down considerably. As the day goes on when I check there seem to be less in the way of bubbles around the injectors as well. I guess this is merely the diesel evaporating; I would think that there is still something coming out from around the injectors even in the absence of the excess diesel. Have any idea why that might be?

jshadows · #13 06-27-2006, 09:05 PM

I had a line leaking on my 350 and it was bubbling around the injector. Might have been vibration, might have been air. Engine was nailing like crazy at the time, but has since disappeared with no intervention on my part.

I'm guessing it's normal

t walgamuth · #14 06-27-2006, 09:35 PM

well, i hope so.

tom w

amosfella · #15 06-27-2006, 10:55 PM

I had a similar problem with my 300 SDL, and I can't remember the technical terms for the parts there, but I'll do my best to describe the problem and how to fix it.
If you remove the injector, there is a housing underneath, basicly from a casual glance, it looks like a pipe with a slot cutout on each side. when you remove this, there is a washer underneath to seal it. If this washer is cracked, it will allow compressed gas to escape through the threads. This can cut the threads, causing a BIG problem. The washer was a $5 part from the dealer. Not too hard to change. All you need to take the housing out is a 1/4 flat iron that is the width of the housing, and a crescent wrench to turn it with. Just don't turn it back in too tightly when you're reassembling it.