I have a 1997 E300 with 184K mi and it runs good (no smoke, starts right up) except it has a small water leak at the back of the head. Water drips onto the exhaust pipes and about once a month the radiator low water light come on and I have to refill it. I have been operating this way for about 6 months now and since I have 2 weeks off for xmas I plan to do R&r the head gasket. I plan to check the head, check the injectors, remove and clean out all the glow plugs, then put it all back together again. I purchased alldatadiy so I have the instruction from that but I still have a few questions. Below is my current quesiton but will take advice from anyone that has done this and has some tips to "watch out for".

Can anybody tell me what exacetly to do with the chain tensioner (not talking about the guide rail). The one on the front left of the engine. Do I just pull it out? Can I reuse it or am I suppose to get a new one? How exactly do I fill it back up with oil and how do I install it. alldatadiy says to

INSTALLATION

• Replace chain tensioner only complete. What does this mean? Only install it assembled? Replace seal (8).
• Before installing, fill chain tensioner with engine oil. Place chain tensioner with the thrust pin facing down into engine oil until it extends over the collar on the hexagon. what does this mean? Are they talking about how to fill the tensioner with oil before installing?

Press thrust pin through slowly 7-10 times as far as the stop with the aid of a press or a column-type drill.

NOTE: After filling, it must be possible to compress the chain tensioner only quite slowly, evenly and with considerable force.

There's no reason to replace the chain tensioner, just remove and replace, making sure the metal seal ring is undamaged.

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"Buster" in the '95

Our all-Diesel family
1996 E300D (W210) . .338,000 miles Wife's car
2005 E320 CDI . . 113,000 miles My car
Santa Rosa population 176,762 (2022)
Total. . . . . . . . . . . . 627,762
"Oh lord won't you buy me a Mercedes Benz."
-- Janis Joplin, October 1, 1970

You will need to unscrew it prior to pulling on it. Yes, just remove it and pull it out. Pretty straight forward job. Do you plan on pulling front cover? How many miles are on it?

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Jim

Car has 184K mi. I think the answer to your question of do I plan to remove the front cover is no.

can't seem to find the engine block coolant drain plug. I found the one at the bottom of the radiator but according to the manual there is suppose to be a block drain plug.

Right side of engine (opposite side from starter), back near the block heater. Hose flange with hex socket -- put hose over fitting, loosen with wrench, coolant flows out.

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"Buster" in the '95

Our all-Diesel family
1996 E300D (W210) . .338,000 miles Wife's car
2005 E320 CDI . . 113,000 miles My car
Santa Rosa population 176,762 (2022)
Total. . . . . . . . . . . . 627,762
"Oh lord won't you buy me a Mercedes Benz."
-- Janis Joplin, October 1, 1970

I had the same coolant leak problem you describe on my 1996 E300D with over 250k miles on the odometer. The engine runs great and I really didn't want to open it up just for the leak and risk it not running as good after the repair plus I didn't want to lay out the cash to fix it ..... so a Mercedes mechanic I know suggested that I might just want to try a bottle of Bars Leaks in the coolant. He said that mechanics don't want to admit it but there are quite a few 90's vintage Mercedes running around with Bars Leaks in them. There are a lot of various Bars Leaks products on the market but he said use the $50 bottle that can be found at Autozone, the one you mix in with the coolant and leave it in. I was skeptical but I did it anyway .... I figured I had nothing to loose. I know it isn't the "right way" to fix the problem .... but guess what ...... it's been over a year and more than 10,000 miles and not a drip of coolant has leaked out. I've since drained and replaced the coolant in the system because the radiator was damaged in an accident and the seal has still held. So I admire you for wanting to fix it right .... but if your engine is running great then you might want to consider fixing it for $50 / 30mins and spend more time with the family over the holidays. Just a friendly suggestion.

You are the 2nd guy to recommend using Bars. I had always heard that stuff was bad for your radiator so thought I would just go ahead and fix it right. Actually it kinda too late now. I have the intake off, the exhaust is off, fuel lines are off, valve cover is off, drained the radiator, drained the block (using the bottom radiator hose) and will finish draining using the valve that you told me about.

I am waiting for some tools to come in before I can do much more. I have a precision 6MM drill rod coming from McMaster Carr (to insert in the intake gear and bearing cap. I am also waiting on a head bolt wrench.

When I got the exhaust off there is a bunch of white calcium all over the back exhaust area I attached a photo

In the fuel inlet photo what is that device in the center. Some kind of fuel pump. How do I take it apart? Just unbolt or do I have to take it all apart?

Any hints on how to disconnect the glow plug connectors? Push on the sides and pull? They don't seem to want to come off

Thanks so much for your help

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I'm not sure I understand the issue you point out with the exhaust. However, the "fuel pump" in the middle of your second picture isn't a fuel pump at all but it is a fuel heat exchanger to preheat the incoming fuel from the tank. Just unbolt it from the head and unhook the fuel line connections and it will come out. I would advise getting a new gasket for it before you reassemble so it doesn't leak coolant. As for removing the glow plug wires I believe they just pull straight off with a good tug if my memory serves me right. Good Luck!

This is a sign of a head gasket leak on the 606.

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Jim

It likely is silicate from the coolant. Mine looked like a bird roost in the same area. The splash from the rain has washed it all off now.

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'97 E 300 D

Back to work again. I have the valve train off and am stuck. The injectors are 22 mm and my deep sockets are not long enough. Can I remove the head with the injectors installed and pull them from the head later?

Yes. There's no reason to pull the injectors unless you're going to pull the prechambers.

Sixto
87 300D

Make sure you have some help when you start to lift the head off. It is somewhat cumbersome.

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Jim

Good to know I don't need to remove the injectors prior to removing the head so I can continue working.

I have all the head bolts off and have tried to gently lift the head. The right front corner seems to be hard down and the rest seems to want to wiggle.

Any idea what I might be missing? I have remove the 2 socket head screws located in the cavity where the chain sprocket is located and I don't see anything else that might be holding it down.

What is the deal with the oil water cooler attached to the oil filter Do I have to remove that? Not sure how to do that? See pics

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