Loosing my head - need help - Mercedes-Benz Forum

 
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post #1 of 7 (permalink) Old 01-03-2007, 04:02 PM Thread Starter
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Date registered: May 2006
Vehicle: 1965 Mercedes 220 SEb Coupe (w111)
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Loosing my head - need help

Hi there,
I'm a fairly newbie home mechanic and would appreciate inputs and recommendations:
I recently did a compression test on my '64 220 SEb.
The numbers are: 90 / 100 / 100 / 110 / 50 / 80
From what I understand, this isn't very good; and the 50 is particularly worrisome.
The car had been sitting for almost 5 years before I got it 6 months ago.
It does smoke a lot when started, but otherwise cruises at 80 mph on the highway.

I removed the valve cover and checked the valve tappet clearance. It's very much off on all cylinders. But I haven't figured out how to adjust it.

I understand that a compression loss is either caused by
1. worn head gasket
2. valves sitting improperly - which requires a valve job
3. piston ring that is shot - which requires an engine overhaul

I have a few questions - and I'm not even sure they're the right one:
a. How urgently should I address the problem? What's the risk?
b. Does adjusting the tappet clearance impacts compression?
c. Is there any inexpensive fix I should try before taking the car to a mechanic for a valve job?
d. What is the best way to get the head/valve rebuilt?
e. What is the typical cost for a valve job?
f. Any recommendation for a mechanic in the bay area?

I guess my general question is what's the most cost-efficient way to address this?...

Thanks a ton in advance.
- David
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post #2 of 7 (permalink) Old 01-03-2007, 06:42 PM
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Help with Lost Head

I had a gas 220 of that vintage but never had to open up the engine. Here are some general comments.

There is a fourth reason for leakage and that being leaking valve guide seals. The oil smoke at start may be more valves than rings since oil doesn't run uphill. But still could be rings with the oil being sucked up by the intake stroke. I heard once on a 70s 4.5 engine that there were rubber guide seals, if so in your engine, 5 years of hardening could be your problem. I'm thinking little rubber "O" rings around the valve stems, but thats a guess.

The valve adjustments are probably on the side of the engine, look for a tappet cover. The adjustment mechanism was there in the early engines and moved to under the rocker arm cover later.

Any oil scum in the radiator or water in the oil? Sign of a blown head gasket or cracked head or block. Hopefully none.

Lastly, A mechanic will know several tests that can be run using compressed air in the plug holes to get a better read on where the leakage is. At top-dead center with valves closed where does the air escape? Things like put a measure of oil into the weak cylinder and retake the compression test. The oil runs down and helps to seal bad rings so compression goes up. It has no effect on valves and compression stays the same. Lots of judgement here. How much oil? How much air in and escape?

Good luck.

Last edited by Doubleclutch; 01-03-2007 at 06:44 PM.
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post #3 of 7 (permalink) Old 01-03-2007, 11:07 PM
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Quote:
Originally Posted by Doubleclutch
The valve adjustments are probably on the side of the engine, look for a tappet cover. The adjustment mechanism was there in the early engines and moved to under the rocker arm cover later.
The valve adjustments are under the valve cover. The finger followers are adjusted using a feeler gauge between the cam lobe and a wrench on the adjustment pin, all done cold. It's pretty easy to pull the head but you will have to remove the engine to replace the rings. Then there are the bearings and the oil pump tolerances too.

Watch the fuel injection. You must keep it clean and don't let dirt into the system, either low pressure or the high pressure side. Do not adjust the throttle stops to adjust the idle. There is an idle air bypass screw and a knob on the back of the injection pump which must ONLY be adjusted with the engine off.

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Not part of the in-crowd since 1952. It's BRAKES not breaks. You break a bone, use brakes to stop your car. /rant

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post #4 of 7 (permalink) Old 01-05-2007, 11:16 AM
cth
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Get the valves adjusted "right now". You can pay somebody to do it, or you can do it yourself.

To do it yourself, you need two special tools.
- Curved crows foot to grab the adjuster.
- Valve spring compressor.

You can get these off the internet pretty easily. The factory compressor is like 200$. However KD tools #3087 works "just fine". KD Tools. I have the hazet crows foot. There are others. Hazet's is #2770- something. Product Catalogue The straight 6 and v8 mercedes use different sizes. I don't recall at the moment if you need the 14mm or 17mm size.

You also need these tools...
28mm socket to turn the motor at the crank
small extension rod for the socket (like 3")
Big breaker bar for the socket
metric feeler gauges

The job is easier if you remove the plugs first.

-CTH
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post #5 of 7 (permalink) Old 01-06-2007, 05:23 PM
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A possible problem caused by the engine sitting unused for several years is the rings in the low cylinder rusted to the wall. I have seen this on other engines. The intake or exhaust valves which are open, allow moisture in the cylinder and rust forms. There is no short cut to replacing the rings and smoothing the cylinder wall at the point of rust. This is why it is important to prepare an engine if it will not be started for a long period. Unfortunately, we don't ussually know when we will not start the engine for several years.

Years ago, a company I worked for, had to take delivery for many trucks which they did not expect to need for several years. They enignes were 'pickled' to prepare them to sit outside 3 to 5 years. When they were unpickled, they worked fine as I recall.

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1974 280C W114 (Now running - driven off and on this summer)
1968 200D (Engine rebuild planned)
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1980 300D W123 (Parts car - engine runs, but trashed)
1981 240D W123 4 speed ( In sad shape when bought - many parts from '80 300D has back on the road. Needs work, but shows promise.)
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post #6 of 7 (permalink) Old 01-09-2007, 03:38 PM Thread Starter
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(Thread Starter)
Thanks All for the help.

Very enlighting. I have one more question:
So the first thing I should do is adjust the valve gap.
I tried to do that last week with a simple wrench - it wasn't moving at all and I wasn't clear whether I should push harder.

Is the spring compressor a must-have in order to be able to make the adjustment, or should a wrench with a larger torque work?

On the attached image, I'm basically trying to adjust (3) while measuring the gap where the red arrow points.


Thanks in advance,
-David
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post #7 of 7 (permalink) Old 01-09-2007, 08:43 PM
cth
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an open end wrench, given sufficent force to turn the nut might well slip off, bust your knuckles and damage the nut. Get the crows foot wrench I posted in the link, above, not the compressor. You need the compressor to remove the rocker arms (see below).

The picture you posted of the various parts is correctly marked in red. However, as the other picture points out, make sure the cam lobe points away from the rocker. Don't do it like in the picture.

If you're lucky, you need only adjust those nuts a bit to get the clearance you need. If you can't adjust the nut because it's too far down or too far up, then the next thing to do is replace the little metal pad at the top of the valve spring (item 7, I presume). Those pads come in various thicknesses in half mm increments. You would need to remove the rocker and then remove the pad with a tweezers. The pads are are something like 5$ each.

Another reason to have the spring compressor is to remove all the rockers prior to removing the cylinder head for a valve job. Lets hope we don't have to discuss that for a while, if ever.

-CTH
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