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1978 300d
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Discussion Starter #1
i haven't had a problem starting my 300d on cold morning yet (knock on wood) but i would still feel a little more comfortable with a valve adjustment. is this an difficult procedure? i'm 17 and my brother is a mechanic, but i think it's time i start learning how to work on my car myself. is it something i could do myself? does anyone know of a good guide on these forums that could help me out?

thanks!
 

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1984 300D
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5,070 Posts
Adjusting the Valves is not difficult. However, it is easier with the special bent 14mm Wrenches. To see what the Wrenches look like you can go to eBay and do a searche for Mercedes Valve Adjustment wrenches.
The Diesel Giant Web Site has a pictoral on Adjusting the Valves and a buch of other Mercedes repair jogs. (This is not an endorsement to buy parts from that site.)

The Job can be done with regular 14mm or 9/16 wrenches; you may have to grind the heads thinnner. The special Hazet Valve Wrench Head thickness = 0.242; so a 1/4 inch thick Wrench will be OK.

Adjusting the Valves is not difficult. However, it is easier with the special bent 14mm Wrenches. To see what the Wrenches look like you can go to eBay and do a search for Mercedes Valve Adjustment wrenches.
The Diesel Giant Web Site has a pictorial on Adjusting the Valves and a bunch of other Mercedes repair jogs. (This is not an endorsement to buy parts from that site.)

The Job can be done with regular 14mm or 9/16 wrenches; you may have to grind the heads thinner. The special Hazet Valve Wrench Head thickness = 0.242; so a 1/4 inch thick Wrench will be OK.

But, if you do it that way it is easier if your remove the Fuel injection Lines coming from the Fuel Injection Pump and attaching to the Injectors.
When you re-install the Fuel Injection Lines it is OK to tighten the ones attached to the Fuel Injection Pump but the ones attaching to the Injectors should be screwed on hand tight and backed off a turn or so.

After that you crank the Engine until Fuel comes out from under the lines (this bleeds the Air out of the Fuel Injection Lines). Stop cranking and tighten the Line Nuts and you should be able to start with no problem.
I will PM you some more info.

Your Brother being a Mechanic may or may not help depending on what he works on. Most modern Cars have Engines with Hydraulic Valve Lifters and there is no routine Valve Adjustment on them.
So He may not have had to do many Valve Adjustments working at his job.
But, he will have a better idea of what needs to be done.
 

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1981 240D
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185 Posts
Another piece of advice: TAKE YOUR TIME! Only do one valve at a time. Print off a diagram of the valves and mark off each valve after you adjust it. Remember that you should be able to pull your feeler gauge out with a little resistance, but it should not be bound up. Also remember that you have different tolerances for exhaust and intake valves. You also have different tolerances for a hot or cold engine. Make sure you keep them straight. You should adjust your valves annually.
 

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2001 Volvo V40
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2,954 Posts
Here you see the special wrenches, two bent ones and a retaining wrench.



You also need a set of feeler gauges:



Here you see how the wrenches in use, I use clips so I know which valve I've done (so I don't enter into an endless cycle of valve adjustments).



A 300D has of course an extra cylinder.

Intake or exhaust valve corresponds with a pipe of the intake or exhaust manifold.

When you tighten the lock nut, the valve clearance sometimes lessens, so adjust the adjusting nut, give it a little more clearance and then tighten the lock nut.

Also read what the Service Manual has to say on the subject:

05 Cylinder Head, Timing, Oil and Injection Pump - OM617
and there 05-210

First time takes some time, after you've done it a couple of times, you can do it very quickly.
 

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1967 300
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494 Posts
Valve adjustments are crazy easy. I can do it now in 30 minutes. The first time it took me 2 hours because I was crazy nervous about making sure everything was ok.

I do my valve adjustments during my Thanksgiving break once a year. First time I did it they were all tight since I was about 45000 miles out of adjustment. Next time I did it only 3 of the valves were tight.

I've been in Chalfont before!

There is a very helpful gent who lives in Montgomeryville who goes by the name of Chad300TDT. Find him on this forum and send him a PM if you truly get stuck.
 

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I dont mean to hijack this thread, but since we are on diesel engine valve adjustments I would also like to know what are the correct valve clearances for my 200d 615 engine.

Thanks and happy holiday motoring to all.
 

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1978 300d
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Discussion Starter #7
Valve adjustments are crazy easy. I can do it now in 30 minutes. The first time it took me 2 hours because I was crazy nervous about making sure everything was ok.

I do my valve adjustments during my Thanksgiving break once a year. First time I did it they were all tight since I was about 45000 miles out of adjustment. Next time I did it only 3 of the valves were tight.

I've been in Chalfont before!

There is a very helpful gent who lives in Montgomeryville who goes by the name of Chad300TDT. Find him on this forum and send him a PM if you truly get stuck.
great! that makes me feel a little more confident, thanks.

on another note, would anyone mind telling me exactly what adjusting the valves does? i'm almost clueless when it comes to motors, what exactly is being accomplished when doing this? :confused:
 

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1984 300D
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I dont mean to hijack this thread, but since we are on diesel engine valve adjustments I would also like to know what are the correct valve clearances for my 200d 615 engine.

Thanks and happy holiday motoring to all.
My book shows a 615 Engine as being a 220D; you said you have a 200D?

If where you live has a Library with the large Hard Cover Chiltons or Motors Imported Car Manuals for your model year the Valve Adjustment spec will be in there.
 

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2001 Volvo V40
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My book shows a 615 Engine as being a 220D; you said you have a 200D?

If where you live has a Library with the large Hard Cover Chiltons or Motors Imported Car Manuals for your model year the Valve Adjustment spec will be in there.
OM615 can be 220D or 200D. Valve specs are 0.10 mm intake and 0.30 mm exhaust with cold engine.
 

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2001 Volvo V40
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on another note, would anyone mind telling me exactly what adjusting the valves does? i'm almost clueless when it comes to motors, what exactly is being accomplished when doing this? :confused:

Valves are opened by the camshaft, lobes on the shaft push against the top of the valve stems when the shaft rotates. When the cam stops pushing, a spring will close the valve again. Here you can see a picture of a valve:



This is a valve of a big diesel engine, the valves of a car engine are not longer than your hand. You can see the valve stem and at the bottom where the valve comes into contact with the engine head.

Valve clearance is the clearance between the camshaft and the top of the valve stem. This clearance is measured when the lobe doesn't push against the valve.
By increasing the valve clearance the valve will:

- open later in the combustion cycle
- close sooner in the combustion cycle
- open less

By decreasing the valve clearance the valve will:

- open sooner in the combustion cycle
- close later in the combustion cycle
- open more

The timing of the opening and closing of the valves are critical to the good running of the engine. Valve clearances are calculated to provide the best timing. Imagine if the valve is still closed whilst the piston is moving downward, trying to suck in air, because it can't, more stress is placed on the engine and more fuel is consumed. Also when a valve is open whilst the piston is moving upwards, trying to compress the air, less compression will take place, reducing the amount of diesel that can be ignited.

During normal operation of the engine, the valve is opening and closing against the so-called valve seat on the engine head. The valve seat will wear down, so valve clearance will be reduced slowly. This is why you need to check the valve clearance regularly. In extreme cases the valve will stay open, which can cause a burnt valve or lack of compression so that the engine will not start.

Most wear will occur on the exhaust valve, because hot exhaust fumes will stream past. Valve clearance on the exhaust valve is therefore bigger (0.30 mm on NA engines and 0.35 mm for turbos against 0.10 mm for the intake valve) so that the valve will stay closed longer. By staying closed longer the valve can pass the increased heat to the engine head (which in turn passes the heat to the coolant).

Adjusting the valve clearance is done by adjusting a nut which is screwed on top of the valve stem. The adjusting nut is locked by a locking nut. The valve clearances are tiny, only tens of millimeters, but they are critical for the good running of your diesel engine.

You might want to look at howstuffworks.com or wikipedia to get some more knowledge about engines and how they work.
 

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1978 300d
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Discussion Starter #11
Valves are opened by the camshaft, lobes on the shaft push against the top of the valve stems when the shaft rotates. When the cam stops pushing, a spring will close the valve again. Here you can see a picture of a valve:



This is a valve of a big diesel engine, the valves of a car engine are not longer than your hand. You can see the valve stem and at the bottom where the valve comes into contact with the engine head.

Valve clearance is the clearance between the camshaft and the top of the valve stem. This clearance is measured when the lobe doesn't push against the valve.
By increasing the valve clearance the valve will:

- open later in the combustion cycle
- close sooner in the combustion cycle
- open less

By decreasing the valve clearance the valve will:

- open sooner in the combustion cycle
- close later in the combustion cycle
- open more

The timing of the opening and closing of the valves are critical to the good running of the engine. Valve clearances are calculated to provide the best timing. Imagine if the valve is still closed whilst the piston is moving downward, trying to suck in air, because it can't, more stress is placed on the engine and more fuel is consumed. Also when a valve is open whilst the piston is moving upwards, trying to compress the air, less compression will take place, reducing the amount of diesel that can be ignited.

During normal operation of the engine, the valve is opening and closing against the so-called valve seat on the engine head. The valve seat will wear down, so valve clearance will be reduced slowly. This is why you need to check the valve clearance regularly. In extreme cases the valve will stay open, which can cause a burnt valve or lack of compression so that the engine will not start.

Most wear will occur on the exhaust valve, because hot exhaust fumes will stream past. Valve clearance on the exhaust valve is therefore bigger (0.30 mm on NA engines and 0.35 mm for turbos against 0.10 mm for the intake valve) so that the valve will stay closed longer. By staying closed longer the valve can pass the increased heat to the engine head (which in turn passes the heat to the coolant).

Adjusting the valve clearance is done by adjusting a nut which is screwed on top of the valve stem. The adjusting nut is locked by a locking nut. The valve clearances are tiny, only tens of millimeters, but they are critical for the good running of your diesel engine.

You might want to look at howstuffworks.com or wikipedia to get some more knowledge about engines and how they work.
great! thanks so much for the help. i have a little experience with fuel systems and cooling systems, but i've never worked with valves before; that's why i'm so lost. so it's .3 mm for the exhaust valves and .1 mm for the intake valves? this is measured with those gauge tools? i read some tutorials, and it seems simple enough, so maybe i'll order those tools and take care of it within the next months :D
 

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-1985 300d (champagne/palomino 133k) -1979 300d (dead parts car)
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you don't need the bent wrenches if you take off the hard injector lines, as i did. i had never done the valves before, and it took me about 3 hours with straight wrenches...
 

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1967 300
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great! thanks so much for the help. i have a little experience with fuel systems and cooling systems, but i've never worked with valves before; that's why i'm so lost. so it's .3 mm for the exhaust valves and .1 mm for the intake valves? this is measured with those gauge tools? i read some tutorials, and it seems simple enough, so maybe i'll order those tools and take care of it within the next months :D
HowStuffWorks "Diesel Engines vs. Gasoline Engines"

Scroll down until you see a slow motion cutaway video. That's the best example of what the valves do. :cool:
 

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1982 300D Turbo, 126xxx miles
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you don't need the bent wrenches if you take off the hard injector lines, as i did. i had never done the valves before, and it took me about 3 hours with straight wrenches...
I recently did this job for the first time with straight wrenches (I'm cheap) and decided not to take the hard injector lines off (I'm lazy). Ended up taking me an entire day to finish the valves, and then an hour the next day to get the new valve gasket properly seated again.

Needless to say, my back was not happy with me for the next few days, and I plan on either bending my own wrenches or just buying $$$ ones before doing this again.
 

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2001 Volvo V40
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so it's .3 mm for the exhaust valves and .1 mm for the intake valves? this is measured with those gauge tools?
Indeed, 0.10 mm for intake and 0.30 mm for exhaust with the engine cold.

If the engine is hot, it is 0.15 mm intake and 0.35 mm exhaust. Best to do it with the engine cold, it is easier.

You need the feeler gauges, I hope you can find metric ones, otherwise find the nearest inch-size ones.
 

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@300Dman: yes sir, it is a 200d.

@Govert and everyody:Thank you as always for the replies and tips.

Happy holidays.
 

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1984 300D
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I recently did this job for the first time with straight wrenches (I'm cheap) and decided not to take the hard injector lines off (I'm lazy). Ended up taking me an entire day to finish the valves, and then an hour the next day to get the new valve gasket properly seated again.

Needless to say, my back was not happy with me for the next few days, and I plan on either bending my own wrenches or just buying $$$ ones before doing this again.
Even with the Bent Wrenches the fist time takes longer.

I waited until I had the Bent Wrenches before I did mine. My though was that if I had the right tools (or homemade ones) I would be more likely to get out there and get the job done than to postpone it.

While the real 3 wrench Hazet set cost a lot it also retains value pretty well if you had to resell the set.
 

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1982 300D Turbo, 126xxx miles
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Even with the Bent Wrenches the fist time takes longer.

I waited until I had the Bent Wrenches before I did mine. My though was that if I had the right tools (or homemade ones) I would be more likely to get out there and get the job done than to postpone it.

While the real 3 wrench Hazet set cost a lot it also retains value pretty well if you had to resell the set.
I finally decided to to tackle this job since I got tired of having to constantly crank the engine to get it to start, so I paid $5 for two wrench sets at Lowes and just went to town. I'm glad I finally got it done, starts up easily now.

I think you're right though, the Hazet wrenches do hold their value, so maybe I'll just buy those next time around.
 

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1977 300D, 1980 450SL, Genuine Buddy 125cc Scooter
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252 Posts
Im cheap too, and lazy. Ive no true record of when they were last adjusted, Ive owned the car since August 2010. Runs great, daily driver, starts up always on the first try with minimal starter cranking. Smokes alot, has alot of injector nailing as well.

Ill probably adjust them in the nest week or so as I wanna know its been done, plus its january..a good month to mark time with lol..
 
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