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Discussion Starter · #1 · (Edited)
Greetings everyone. I couldn't resist a low priced 87 300TD, advertised with a cracked #14 head. The paint and interior are in great shape, with only rust around the jack points and wheel wells, which I hope to repair once it's running proper. Engine had 250k on the (working) tach, so I assumed it was in decent health outside of the cracked head symptom.

Within the last year, the previous owner had installed new shocks all around, new tires, fresh fluids, new brakes, belts, r134a A/C recharge, and more.

One trip around the block and the engine temp starts to creep over 90*c, and it seems that the coolant hoses hold pressure well after the engine is running, although not "rock hard" pressures...

Before seeking out a new head, I figured an engine compression test made sense. The numbers below were done on a cold engine

Cyl 1 - 355 psi
Cyl 2 - 255 psi
Cyl 3 - 260 psi
Cyl 4 - 350 psi
Cyl 5 - 355 psi
Cyl 6 - 350 psi

The results worried me a bit, so I figured I'd reach out to y'all, for some input. I'm guessing a leak down test would be in order next?

Are these numbers a result of bad valve seals on the potentially cracked head? Or is it more likely I need to start searching for a whole new engine?

Looking forward to the response, and getting this benz back on the road!


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1995 E320 Cabriolet, 1994 E320 Wagon, 2007 E350 sedan, plus a brace of 124 diesels
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Let me know if you are interested in purchasing one of the later heads, I have one that I pulled from a W140, I don't remember if it is a #17 or a #20 or a #21, and I also think I have the inclined injectors to go with it. I'm down in Charleston SC, would be much easier for a local pick-up than trying to ship this to you.
 

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1995 E320 Cabriolet, 1994 E320 Wagon, 2007 E350 sedan, plus a brace of 124 diesels
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As far as concern about those compression numbers, I would not worry about the block at all, or the rings. Two cylinders that are low together and next to each other generally mean the head gasket or the head has failed between those two. Sure, you can do the leak down test to try to get a more definite diagnosis, but once you pull the head, you can look at the cylinder walls for those two and see if they are scored by broken rings or some other issue.

Pulling the head is not a lot of fun, and the 'while I'm here' temptation is strong to also change out the timing chain rails and the front crankshaft seal, and put in a new timing chain. My wagon is called "the White Whale" because it's white and when I did the head replacement, I installed a bad head first time around, so I found a 2nd head and installed that, and then I had a hydraulic compensator (lifter) that was over-filled and holding an intake valve open, and that took me a bit to puzzle out and fix. I think it took me over a year to get all that done, and I also did all the rails and the front crankshaft seal.
 

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1995 E320 Cabriolet, 1994 E320 Wagon, 2007 E350 sedan, plus a brace of 124 diesels
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Let me know if you are interested in purchasing one of the later heads, I have one that I pulled from a W140, I don't remember if it is a #17 or a #20 or a #21, and I also think I have the inclined injectors to go with it. I'm down in Charleston SC, would be much easier for a local pick-up than trying to ship this to you.
Also have the upgraded camshaft to go with this head. Basically you'll need to get it checked by a machine shop for the valve guides and replace the valve stem seals. You can also try to get it checked to make sure it doesn't have cracks, but that is a tough thing to find a shop that can do that work. If you get this head, and then find out it is bad, I'll refund your money if you return the head to me, along with the report from the shop that found it to be cracked or damaged in some other way.
 

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W124 300 TDT 1989
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In germany the latest turbo head #22 is about 1,000 € new.

 

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Discussion Starter · #10 ·
Thanks for the input everyone! I've already acquired a new head, #20, which included injectors. It was from a low mileage 1995 350sdl, and looked super clean, so hopefully it'll drop right in and be ready to go! One thing it didn't include was the camshaft, but I read the #14 cam was the same.

Starting the removal of my cracked #14, and just have the exhaust side to disconnect, before lifting off the head (with a hoist). Lined everything up at TDC, and I'm only off 2* at the harmonic balancer, so I think I'll leave the timing chain in place.

The car did come with a new water pump, so I may throw that in while everything is accessible too.
 

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1995 E320 Cabriolet, 1994 E320 Wagon, 2007 E350 sedan, plus a brace of 124 diesels
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Think about getting new INA hydraulic lifters. A few years ago, you could find them for about $12 each. Don't know what the price is now, but you can be assured of a nice quiet valve train. Also install new valve stem seals!
 

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Discussion Starter · #12 ·
Think about getting new INA hydraulic lifters. A few years ago, you could find them for about $12 each. Don't know what the price is now, but you can be assured of a nice quiet valve train. Also install new valve stem seals!
I've actually got a fresh set of INA lifters, ready to go! Are special tools needed to do valve stem seals? I hadn't planned to restore/replace any of the head components, but it's probably worth the effort, while the head is off...
 

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1995 E320 Cabriolet, 1994 E320 Wagon, 2007 E350 sedan, plus a brace of 124 diesels
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Well you need a tool to compress the valve springs and get the keepers off the stem, so you can remove the springs and valves. I fashioned a tool from a deep well socket that had a nice window in the side, and some plate steel and some big c-clamps. Socket pressed down on the top of the valve spring retainer enough so that the keepers came loose and could be removed with a magnet (through the window in the side of the socket), then you can get the valve spring off and you have access to the seals. Make sure you can find a supplier for the seals, I had a hard time getting them about 8 years ago, there are different seals for exhaust and intake.
 
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