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Old 03-04-2006, 09:34 PM
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Found my oil leak. Now a couple Valve Cover Questions.

I've got a '82 300SD w/ about 250k mi. Had it for a month now. Past owner didn't give it much love. I'm going thru a quart of oil every 150 miles or so and I'm pretty sure that its coming from the valve cover gasket. I tried giving the valve cover bolts a bit of a tighten to help remedy the problem and found that one of the 4 nuts was stripped. The threading on the bolt itself looks dubious as well. Also, regular washers were used as opposed to crush washers. I found another nut that seemed to fit, I tightened it down, but its still leaking. I guess I should try replacing the gasket next. A couple questions:

1. i'm new to foreign cars. Let me restate that. I'm new to most cars in general. Will I be able to find replacement nuts at a hardware store? Do I need to worry about thread pitch or count?

2. should I try to re-thread the bolt or is this an easily replaceable part? Judging by some pictures i've seen on the dieselgiant site, it doesn't look like something I'll be able to replace easily.

3. what torque should I tighten the nuts back down at?

Thanks for the help.

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Old 03-05-2006, 12:20 AM
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I am not familiar with this engine like I am with mine, but I have some experience with MB valve covers/gaskets:

1. The "bad" way to stop a leak (which sounds like someone has been doing) is to keep tightening. This will probably eventually warp the valve cover. If it is similar to mine, the cover is a thin aluminum alloy, and once warped, it's not going to ever stop leaking, new gasket or not, unless you get very lucky.

2. By all means, replace the valve cover gasket. Put the removed cover on a flat surface and see how flat it is. If it isn't flat, it might be a good idea to boneyard a flat replacement. Milling is tricky and expensive; new ones are really expensive.

3. The torque is critical (and of course, cross-tightening is too); on my engine, torque (with crush washers installed) is 3 Nm; even fairly good torque wrenches of 3/8" and 1/2" sizes are not very good on the low ends of the scale. I bought a 1/4" torque wrench just for this job, possibly overkill, but I had just put in quite a few hours on polishing a set of covers.

I have no advice on the nuts/bolts; however, 3 Nm (the value for a 117 engine) - about 27 in-lbs - isn't around for the crush washers. The dealer wanted $1 ea!!!
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Old 03-05-2006, 06:20 AM
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You may be better off getting a new vavle cover and bolts. Take the valve cover off and you'll see how the tightening mechanism works. It is very hard to explain. If I remember correctly you can take the cover off and install a new gasket but on the underside of the cover you can bend some tabs so you don't have to tighten the bolts as much. It has been a while so forgive the vagueness.

A quart every 150 miles is an awful lot to lose through the valve cover. I think you have a little more than that going on somewhere.
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Old 03-05-2006, 02:44 PM
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Ok, I got the valve cover off. I've got some good news and some bad.

The good: The gasket had a small piece broken out of it on the inside near the #1 cylinder. I consider this good news because its an easy fix and could be the source of my leak. Check the pic of the gasket damage below. You're looking at it as if you were inside the cover

The bad: My valve cover has a slight warp. I placed it on a couple of different "flat" surfaces. On the worst (an old kitchen table), I can slide an x-acto blade (wish I had more exacting tools) underneath one end while putting pressure on the other. On my kitchen countertop (perfect place for an oily cover), I was barely able to get one end to pop up at all while putting pressure on the other end. Is there a set of tolerances I should be aware of? What do you guys think? Should I replace the cover too?

One more question. If I decide to adjust my valves say 6 months down the road, will I need to replace the gasket again?

Thanks much.

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Old 03-05-2006, 02:50 PM
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Join Date: Nov 2002
Location: Milford, CT
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You should adjust your valves now, if you have no record of when they were last done. In 6 months you could probably use the gasket again.

Give that engine a good cleaning I suspect you have a large leak somewhere else.
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Old 03-05-2006, 04:57 PM
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Is it pretty standard procedure that i'll need a breaker bar (or a long 22mm) to turn the power steering pump bolt in order to turn the camshaft to adjust my valves? I just gave it a good amount of umph with a pair of vise grips (I know, bad idea) and I'm worried i'm gonna stretch and/or break the belt connected to the power steering pump.
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Old 03-05-2006, 07:10 PM
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Location: Lafayette Indiana
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i would check the

valve cover with a straightedge. the table and counter top arent reliable for this. then if it is warped more than lets say 1/32" i would take it and get it planed at the local automotive machine shop.

actually i doubt it is warped. the way the hold down studs are designed it is impossible to tighten it all the way down. a new gasket normally is all that is needed.

and yes you should be able to get nuts at the hardware. check diameter and pitch of threads.
the studs if stripped will have to probably be replaced with factory parts.

tom w
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Old 03-05-2006, 07:20 PM
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On the side of the cover where the bolts/studs come through , the four bosses are correct length to prevent you cranking down on the nuts to cookee-cutter the gasket. ......they allow for just enough gasket crush. If you machine the vavle cover gasket face you will decrease the pressure on the gasket unless you maintain the hight difference..

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Old 03-06-2006, 12:21 PM
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Be Careful with Valve Cover Studs

You need to be very careful with tightening down the valve cover bolts. It does not take a lot of tourque. Start with a clean surface and a new valve cover gasket then evenly tighten them down with a 3/8" ratchet. If you break one of the studs it is very difficult to replace. I have had several MB's with the same 5 cylinder engine as yours. once a year I would adjust my valves and always used a new valve cover gasket (they are cheap at around $10).
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Old 03-06-2006, 12:35 PM
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My 0.02, I'd replace the gasket, torque properly with new washers (if used on this engine), and see if it leaks.
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Old 03-06-2006, 03:49 PM
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Ok, I just bought a new valve cover gasket, valve wrenches, air filter housing mounts, and a new breather hose.

My final question.

When adjusting my valves, should I turn the camshaft via the crankshaft or via the power steering bolt? I am slightly nervous that the belt around the power steering pump is old and may break! I would prefer to turn the crank, but from what I understand it isn't easy to get to. What do you guys recommend? In yall's experience, how hard do I need to tug on the power steering bolt? I know its not an easy thing to describe.

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Old 03-08-2006, 01:27 AM
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Location: Los Angeles, CA
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should I turn the camshaft via the crankshaft or via the power steering bolt?

an option is to turn the ignition key ever so slightly and of course be careful not to start it up.

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