What is this knock... - PeachParts Mercedes-Benz Forum

DslBnz · #1 07-20-2008, 10:50 PM

Mysterious knock...prompted me to...
Replace all lifters (5 were gone), determine it was not vacuum pump...Noise seems to come from intake runner #2. Other than this, the car runs great! This noise came in and out over a period of two weeks. And now it's terrible. So, what could it be? Cranking the injector lines off on each cylinder makes no difference at all.

Guys, I've checked the timing; it's perfect...There is no excessive blowby...The engine has very strong compression....It just has a terrible knocking noise that is consistent at all rpms.

I will rev the engine in future video clips. So, if it isn't fuel related, it isn't the pump, it isn't the injectors, what could it be?

http://youtube.com/watch?v=JPFZIiT9bdk

I'm generally an optimist. I don't want to even think it's a bottom-end issue. The car does not burn any oil. It runs super. It definitely sounds like it's coming from up top, but the valve-train is super tight, now.

79Mercy · #2 07-20-2008, 10:53 PM

doesn't look there is much oil shooting out.

pawoSD · #3 07-21-2008, 12:22 AM

Quote:

Originally Posted by 79Mercy

doesn't look there is much oil shooting out.

Thats what I was thinking too....shouldn't the cam lobes be like....bathed in oil??

Where is all the oil????

79Mercy · #4 07-21-2008, 12:26 AM

I started my gasser up without the valve cover on and oil was splashing everywhere

Cervan · #5 07-21-2008, 12:27 AM

I think that sound is the sound of the rod hitting the crankshaft and spinning the bearing without any oil...

pawoSD · #6 07-21-2008, 12:30 AM

Quote:

Originally Posted by Cervan

I think that sound is the sound of the rod hitting the crankshaft and spinning the bearing without any oil...

Exactly what I was thinking.....it does sound very much like a bad rod knock....

JimmyL · #7 07-21-2008, 12:40 AM

I agree on the lack of slinging oil. And hold that camera still for a second!

compress ignite · #8 07-21-2008, 01:11 AM

Little or no Lubrication of Camshaft.
Knocking elsewhere.(Pray it's not a rod)

Weak oil pump...or clogged oil galleries.

I know it's not LOW on oil! (Please God?)

DslBnz · #9 07-21-2008, 04:59 PM

Quote:

Originally Posted by compress ignite

Little or no Lubrication of Camshaft.
Knocking elsewhere.(Pray it's not a rod)

Weak oil pump...or clogged oil galleries.

I know it's not LOW on oil! (Please God?)

No, it's not low on oil (your prayers are answered). Although it sprays that oil out rapidly with the v-cover removed, I'm careful to always keep it above the min mark on the stick.

Thanks guys. I will follow up when I find out what it is. Here's another clip where I vary the engine revolutions. This digital camera does not provide the best video or sound quality, I guess. Comparing one 603 to another, I also think there should be more oil getting to the top.

http://youtube.com/watch?v=nbcWMyM4p-w

Brian Carlton · #10 07-21-2008, 05:09 PM

I agree with the comments related to very low oil to the top end. Something is amiss there.

The knocking speed is at camshaft speed.........about 5.5 knocks per second.......giving you some potential for a low cost repair.

However, I'd disconnect each injector line in sequence while it's running and pray that the knock doesn't disappear when one of the cylinders comes off line.

DslBnz · #11 07-21-2008, 05:26 PM

Quote:

Originally Posted by Brian Carlton

I agree with the comments related to very low oil to the top end. Something is amiss there.

The knocking speed is at camshaft speed.........about 5.5 knocks per second.......giving you some potential for a low cost repair.

However, I'd disconnect each injector line in sequence while it's running and pray that the knock doesn't disappear when one of the cylinders comes off line.

Brian, I have done this. It doesn't seem to change the value of the knocking, whatsoever. On any cylinder.

Just to prove it, I'll post a video tomorrow of cranking the fuel lines one-by-one.

Thanks again.

Brian Carlton · #12 07-21-2008, 05:29 PM

Quote:

Originally Posted by DslBnz

Brian, I have done this. It doesn't seem to change the value of the knocking, whatsoever. On any cylinder.

Just to prove it, I'll post a video tomorrow of cranking the fuel lines one-by-one.

Thanks again.

Good job. That test more than likely rules out the bottom end. No need for further confirmation if you've done it already.

You've got an issue with low oil and some possible damage to the valve train due to the lack of oil. It could be as simple as a completely collapsed lifter...........even if brand new.

Cervan · #13 07-21-2008, 09:33 PM

Quote:

Originally Posted by Brian Carlton

Good job. That test more than likely rules out the bottom end. No need for further confirmation if you've done it already.

You've got an issue with low oil and some possible damage to the valve train due to the lack of oil. It could be as simple as a completely collapsed lifter...........even if brand new.

Why would this rule out the bottom end?... All he did was check to see if the injector was knocking, not if the rod bearings are coppered? The only other thing i can think it would be is a collapsed lifter, wich would go with the low oil theory as well....

Brian Carlton · #14 07-21-2008, 09:40 PM

Quote:

Originally Posted by Cervan

Why would this rule out the bottom end?... All he did was check to see if the injector was knocking, not if the rod bearings are coppered? The only other thing i can think it would be is a collapsed lifter, wich would go with the low oil theory as well....

Without the combustion pressures, the noise should be significantly reduced, if not eliminated. The noise exists at 1/2 engine speed...........so, either it's valve train related or combustion related on the bottom end.

I've discounted the possibility of an injector knock..........it appears to be too harsh for that situation.

pawoSD · #15 07-21-2008, 10:31 PM

Wow....the 603 is one sweet sounding engine when its revved up!

I never realized it sounded like that. Maybe I will have to consider one someday.