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1982 Mercedes 300TD wagon
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Discussion Starter #1
Are there any kits for rebuilding the head on my 82' 300TD?
Secondly, is this something a back yard mechanic should try to do? I've been doing a lot of research on this and the only thing I'm leery of is the timing chain. The car has 240k on the engine and I thought if it were affordable to do it myself, I might just have a go at it.

Thanks

Benzoid
 

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I don't know about the kits or parts but I do know you have to be extremely patient, careful, detail-oriented, and organized when attempting to do anything related to engine internals. And you should at the least be able to call on someone to help you who has done it before. If you can go spend time with someone while they do the job on another car, that would also be extremely helpful. There are a lot of parts to take apart and put back together.

I should mention I sent my W126 to the grave by fouling up the timing chain job (chain slipped, timing went off, couldn't find TDC, timing cover cracked, among other things). I've learned a lot since then, but it was one painful experience in failure. The poor car (my favorite) still sits out back of the workshop waiting for a new engine... or something.

So be careful.
 

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1984 300D
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Rebuilding the Cylinder Head takes Outside Micrometers to measue the Valve Stems. Something to measure the inside diameter of the Valve Guides like a Split Ball type Gauge.
A Precision Edge to check the surface for warpages.

But, most of all to do it right you need a Valve Seat Grinder and a Valve Face Grinder. If you are not sure what these are take a look on eBay.

If any of the Valve Guides need to be changed you will need a proper sized Punch to drive them out and install them.
To save money it is advisable to reuse the Valves if the Valve Stems are not worn and it appears there is enough meat left on the Valve Faces for themto be reground.
One new Exhaust Valve is in the order of $27 each.

If the Cylinder Head needs to be resurfaced the Prechambers need to be removed and later re-installed by some one with the proper protrusion. A special tool is needed to remove and install the Precombustion Chambers.

The only kits available are the Gasket Kit.

If you are not in a hurry to get the jog done I would take some classes at a Trade School where they have the equipment you need to do the job.
 

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Discussion Starter #4
Detail orientated eh? Yeah...I'm certified ADHD so that's a scary thought. However, if I VERY carefully remove, label, take pictures, document and put everything somewhere safe I could be ok. My guess is as optimistic as I am that I could do this, it would probably snowball into a bigger headache. I have a neighbor who is a retired MB mechanic and I might be able to get his cooperation. Especially with the timing chain stuff. Might as well replace it if the head is coming off. With that, I DO NOT trust myself considering the consequences. It's also recommended in the manual that it be a two-person job.


Or I could just buy a rebuilt head from metric motors for $790 + tax

Mercedes Rebuilt Engines
 

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"I'm certified ADHD" I am not sure what that is as when I went to Trade School there was no certification. Went Trade Shool, took Diesel Mechanics and worked a total of 18 years at it until I was involved in a traffice accident that messed me up for that.

If you know how to use and have access to the Valve Grinding equipment it is not a hard job.
However, when you replace the Timing Chain you are supposed to crimp/peen over the ends of the Master Link with the tool in the Pic I am attaching.
On the Peach Parts Forum there is a tool rental program. I do not remember if someone would rent this tool or not.
On ebay the tool is $220+ shipping.
 

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In your Mercedes Service Manual look up how to check the Timing Chain Stretch. You may not need to replace it.
 

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1983 300D
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Pat,

Just curious, what's the reasoning for the head work?

I know you did compression check, what's numbers again? If you have a low cylinder, did you perform a leak down test to find out where compression loss is coming from?





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Discussion Starter #8
First of all, that's some funny stuff regarding the "ADHD certified". ADHD is attention-deficient hyperactive disorder! I can see how it sounds like a certification program! Sorry for the confusion with that (but made my night).

Well, to be honest I'm due for a valve adjustment and just got to thinking about it. I heard that after 200k the heads on these cars tend to get a little tired. I was wondering if it might have anything to do with the shaking problem I have still not been able to fix. I didn't do a leakdown test nor am I sure how to do so. Someone said something about having a bad exhaust valve causing similar shaking symptoms on their car. I was just curious how bad it could be to remove the head, grind & inspect the valves, clean up, port & polish the head etc. After 240k I figured it probably needed it.

Compression numbers were:
1=360
2=380-390
3=360
4=370-380
5=350
 

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If it ain't broke, don't fix it! I assume you've followed all the easier shake arresting procedures including:
-Rack dampener bolt adjustment
-Injector return line replacement
-Motor mount and motor shock replacement/inspection
-Valve adjustment
-Injection pump timing

I did all but the last two, and my shakes have pretty much disappeared. I think the bolt adjustment and the injector returns gave the biggest benefit. You can get the cloth covered injector return hose at the local VW dealership (I told them it was for an old Rabbit diesel). My one motor shock was completely detached.

Digging into the head is a major undertaking.
 

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Discussion Starter #10
All has been done except the injection pump (IP) timing. The theory at this point is that the problem has to do with that. The engine vibration dampeners are toast but the consensus on that is that the excessive shaking killed them. Replacing them right now will help with the shaking but not the cause. The dampeners will probably end up wearing out prematurely. This topic is easily 2 years old on this forum and I still haven't figured it out. Car develops a shake at idle usually after the engine is nice & hot. But not always! A speedy freeway trip usually makes the car shake like a dog afterwards. But not always. On one day the car feels powerful and the next day it seems to be a slug. It's a very on & off and random problem that I could easily throw hundreds of dollars at (as I have) and still have the same problem.

How does an IP lose it's timing anyway?
 

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...... I didn't do a leakdown test nor am I sure how to do so. Someone said something about having a bad exhaust valve causing similar shaking symptoms on their car. I was just curious how bad it could be to remove the head, grind & inspect the valves, clean up, port & polish the head etc. After 240k I figured it probably needed it.
A leak down test would determine if the exhaust valve is leaking. A leak down test is when you pressurized the cylinder with around 100 psi of compressed air at top dead center. If the cylinder is leaking, then you'll hear or feel where the air coming from. If the exhaust valve, you'll hear or feel air coming out of the exhaust. If intake valve, you'll hear or feel air coming out of the intake manifold. If piston rings, then air will come out of the crankcase. If head gasket, then air will come out of the coolant tank, the crankcase or outside the engine block.

Here are some videos of a Leak Down Test.

This is a Harbor Freight tool but it too low of a pressure get an accurate reading. But nonetheless a good video to watch of how to do it.



This is a homemade leak down tester done on a VW Diesel. He does a good job of explaining the process.



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Compression numbers were:
1=360
2=380-390
3=360
4=370-380
5=350
Those numbers are pretty good except the fact that number 5 is at the upper echelon of the 10% rule of all cylinders should be less then 10% of each other. 390 to 350 could be cause it to run rough.



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