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help!! Loud engine knocking noise... :(

Started by Ryan1980, 07 December 2008, 03:55 AM

TJ 450

#30
There is a knack to getting the fan off, I get second 10mm spanner and jam it between one of the bolts and the shaft to couter-hold it. Then you just crack the bolts one-by-one, turning the pulley as appropriate.
The radiator can even remain installed for this exercise, on the M117.

Tim
1976 450SEL 6.9 1432
1969 300SEL 6.3 1394
2003 ML500

oscar

how about leaning on the fan belt with one hand, that'll tighten it temporarily and stop the fan hub from turning whilst you crack those four bolts with the other hand.  It'll be much easier to turn the engine via the crankshaft once the fan's removed but like TJ says, you can turn the crankshaft from underneath with the fan in situ, but that makes watching the valve train at the same time impossible.

Re the PS reservoir.  It's a bugger that these earlier ones don't have a toothed adjusting bolt.  As you say Ryan, someone needs to lift it up whilst the other tightens the bolts.  A real PITA.
1973 350SE, my first & fave

Ryan1980

yeah tried that, no go. might have to give tj's method a go.

WGB

It's also safer to remove the radiator in case you slip with a heavy socket.

You can get around that with a sheet of cardboard.

Bill

s class

Quote from: Ryan1980 on 09 December 2008, 08:16 AM
by the way - i just realised my hair at the back is covered in automatic transmission fluid. im going really well here :P

This is a normal fringe benefit of working on old benzes.  I wash my hair twice afterwards.  No problems then. 


[color=blue]'76 6.9 Euro[/color], [color=red]'78 6.9 AMG[/color], '80 280SE, [color=brown]'74 350SE[/color], [color=black]'82 500SEL euro full hydro, '83 500SEL euro full hydro [/color], '81 500SL

WGB

Quote from: s class on 10 December 2008, 03:15 AM
Quote from: Ryan1980 on 09 December 2008, 08:16 AM
by the way - i just realised my hair at the back is covered in automatic transmission fluid. im going really well here :P

This is a normal fringe benefit of working on old benzes.  I wash my hair twice afterwards.  No problems then. 

Sort of like  pre-wash conditioner ;D

Bill

Ryan1980

ok i got the fan off, and am finally able to turn the engine!

ok looking at the engine , from the front of the car, i turned the engine to the right (clockwise) until the lines on the right hand side cam tower lined up. I then looked at the lines on the LHS, and they dont quite line up. Am i correct in saying they should?

Here's some pictures, i hope someone can tell me what's going on :)

http://i246.photobucket.com/albums/gg105/Ryan1980_photos/IMG_1450.jpg
http://i246.photobucket.com/albums/gg105/Ryan1980_photos/IMG_1451.jpg
http://i246.photobucket.com/albums/gg105/Ryan1980_photos/IMG_1452.jpg


TJ 450

Excellent progress, Ryan. 8)

However, it is the Right-Hand side you want to line up first, with the markings on the Harmonic Balancer near the region of zero (TDC). You then look at the left hand side and I think you'll find it appears the exact opposite of what you're seeing now. The degree of actual chain stretch can also be determined by observing the markings on the Harmonic Balancer.
This says to me that it is out by one tooth on the LH camshaft, although that will need to be confirmed as above.

Tim
1976 450SEL 6.9 1432
1969 300SEL 6.3 1394
2003 ML500

oscar

#38
What looks scary though is that I can't make out a TDC mark on you harmonic balancer.  Where is it?  With the RHS camshaft lined up at the TDC mark, your crankshaft should have its TDC mark under the timing pointer or very close to it . 



1973 350SE, my first & fave

TJ 450

#39
Yes, it seems that the TDC mark is way down behind the idler pulley bracket. Surely it can't be advanced to that extent?

Edit: Having reviewed the pics again, the RH camshaft is advanced past the mark, so if it was lined up, the TDC mark would be visible. However, if I'm perceiving this correctly, it would still be considerably advanced.

Tim
1976 450SEL 6.9 1432
1969 300SEL 6.3 1394
2003 ML500

Ryan1980

im running LPG, perhaps my timing is advanced for this reason?

anyways thats enough for me for tonight, ill adjust it again tomorrow night probably...



wbrian63

The timing you're referring to is ignition timing. The timing the other fellows are referring to is mechanical timing.

Ignition timing controls when the spark plugs fire in the rotation cycle of the engine. "Advanced" timing generally means that the spark occurs sooner in the cycle. The faster an engine runs, the sooner the spark must occur to allow sufficient time for the fuel mixture to ignite and the flame front to spread. In most engines, the spark occurs before the piston reaches the top of travel during the compression stroke, with the result being the maximum energy value being available just as the piston starts to travel downward. Advancing the ignition too far causes the fuel mixture to ignite too soon, and you get a "pinging" sound as the piston hits the "wall" of expanding gasses on it's way to the top.

Mechanical timing is the (theoretically) unalterable relationship between the crank (which connects to the pistons) and the valve-train, the camshafts. When the chain skips a link, that relationship gets adjusted. Generally, it results in the valves being open when they should be shut, and a piston on its upward stroke, can contact the valve and bad things happen. In some cases, it results in a mildly bent valve, and a cylinder that won't achieve meaningful compression. In some cases, catastrophic failures, like WGB mentioned occur, where something breaks in the camshaft area. In other cases, the heads of the valves themselves break off and bang around in the cylinder doing all sorts of damage, especially when they get into a place between the piston and the head where there's insufficient clearance - then you've got a busted piston, or head, or block or all 3.

Class dismissed.

All kidding aside - bravo to you for attempting this repair on your own. Hopefully the results are no bent valves and just a few replaced parts and skinned knuckles.

Oh - and when you're "folically challenged" like me, you know instantly when you've got tranny fluid on you...
W. Brian Fogarty

'12 S550 (W221)
'76 450SEL 6.9 Euro #521
'02 S55 AMG (W220) - sold
'76 450SEL 6.9 Euro #1164 - parted out

"Bond reflected that good Americans were fine people, and most of them seemed to come from Texas..." Casino Royale, Chapter V

koan

Quote from: TJ 450 on 10 December 2008, 08:13 AM

Yes, it seems that the TDC mark is way down behind the idler pulley bracket. Surely it can't be advanced to that extent?


It looks about 40 or more degrees out, I'm surprised the engine would idle with the valve timing this far out.

Is it possible the crank pulley / harmonic balancer is not on the crank correctly?

koan
Boogity, Boogity, Boogity, Amen!


TJ 450

#44
Now we're talking. :) 8)

So, it has now been established that the valve timing is out by 15 degrees due to chain stretch. The LH camshaft has skipped a tooth on the sprocket. This is my observation, anyway.

The LH camshaft now needs to be adjusted such that the marks are close to aligned, using the method Bill suggests.

BTW, I can see a recent genuine lower radiator hose with a NORMA hose clamp installed. I'm impressed.

Tim
1976 450SEL 6.9 1432
1969 300SEL 6.3 1394
2003 ML500