I just bought a 95 E300 Diesel. 220k miles. Was shifting beautifully when I had the tensioner spring for the serpentine belt replaced. When I took it home it had a very hard shift to 2nd 3rd and 4th. A guy I work with suggested maybe the repair shop pulled loose a vacuum line. Is there anything up front they could have knocked loose to cause this hard shifting. If not what else could have caused it. I wanted to get some ideas before I hear back with the shops diagnosis.

Vacuum for the transmission might be sourced from a smaller nipple on the vacuum pump by the tensioner. I don't know what visibility is like under the intake manifold but there's a device hanging off the injection pump with a couple of vacuum lines. One line goes through a green cylinder to the transmission, the other finds its way to a vacuum source, either right at the pump or along the big hose to the brake booster.

Sixto
87 300D

There's a vacuum line connection directly by the top plastic mount for the tensioner spring, maybe check this to see if they disconnected it as the lines are kinda in the way when working on the tensioner spring.

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1993 320TE M104
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past:

1983 230E W123 M102
1994 E300D S124 OM606 (x2)
1967 250SE W108 M129
1972 280se 3.5 W108 M116
1980 280SE W116 M110
1980 350SE W116 M116
1992 300E W124 M103
1994 E280 W124 M104
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"music and women I cannot but give way to, whatever my business" -Pepys

Thanks guys! I took it in Saturday morning and the tensioning sprind was busted and the serpentine belt was loose. They replaced the tensioner spring. I bet you hit the nail on the head. I will definitely check it out and get back to you. By the way the shop, by the time I got done with the mercedes tech, had recommended a complete rebuild. But the owner of the shop drove the car with me and guaranteed that there was no need for the rebuild.

I recently went through a similar issue- post repair of my belt tensioner shock I had hard shifting - mine was resolved by a breech in the vacuum under the air filter. I looked for a bad line but not under the air filter (not the little can shaped vacuum thingy either) I was told the air filter housing need to be removed to see these. Also check the lines by your TPS
Good luck it was aggregating

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1991 190E 311K [Brilliant Silver/Black MBTEx] -retired
1996 E300 315K [Black/Grey MBTex]

Want to put a tank in the trunk for WVO/SVO in the E300 Need to find a place to store my OIL!
Still procrastinating about the biodiesel/WVO
Made some biodiesel but so afraid to pour it all in - I've added some and think I'll supplement my fuel to see how I make out

Made some biodiesel but the process scares me - methanol fumes are not your friend! Need to do this outside.

eng's rule of thumb

When vacuum issues come up right after a repair the first place to inspect are the vacuum lines that are close in the vicinity where the repair was made.

__________________
Jim

But they were fine. Definitely vacuum related though - or a mule in the back seat kicking. Oddly these were not near the work area but they are 13 years old.

Btw- that's aggravating not aggregating in my post above

__________________
1991 190E 311K [Brilliant Silver/Black MBTEx] -retired
1996 E300 315K [Black/Grey MBTex]

Want to put a tank in the trunk for WVO/SVO in the E300 Need to find a place to store my OIL!
Still procrastinating about the biodiesel/WVO
Made some biodiesel but so afraid to pour it all in - I've added some and think I'll supplement my fuel to see how I make out

Made some biodiesel but the process scares me - methanol fumes are not your friend! Need to do this outside.

I found it. Geez what a dummy I am. That one was mercedes diesel 101 really. There are 2 vacuum lines right above the tensioner and one was cracked in half. I took a piece if tube and coupled them together at work and it fixed the problem, It's not perfect like it was so I will inspect the rest of the lines. On my behalf, I attribute my miss to the spinning head that comes with a $2000 diagnosis when you go in for a $100 repair. Great Job and thanks for the diagnosis.