OMG, where to start. I am new to the world of working on MB and I feel as if I may have bitten off more than I can chew. I have an 85' 300SD that is running incredibly slow up hills, no power in higher gears, and rock hard brakes at slow speed. I think that I have exhausted all my options and am at my wits end. I changed the check valve coming off vac pump, to no avail. I tried to chase all vac lines I could replacing rubber fittings and inspecting thoroughly the ones I didn't. Most recently I capped off all vac lines, leaving only main line to brake booster to see if that would change my brake performance, which it didn't. Might have been major mistake but as I said, am the biggest novice there is. Have checked numerous sites and I can't find out how much a vac pump should pull at idle speed. Also forgot that engine will not shut off with key. Can anyone enlighten me on what my next step should be?

 

Thank you for your input. While having vacuum connected to brake booster only, with accessory legs capped off, I put a vacuum gauge on one of the accessory legs. I only pulled 1"Hg at idle and roughly 6"Hg at 2000rpm. Would it be safe to assume, as much as I abhor that word, that my vacuum pump has given out on me, or is there something else that could be giving me woes? Would a malfunctioning vacuum pump cause transmission to flutter, for lack of a better choice of words, as to make it seem as though the engine were losing power when on inclines or when extra power is required from engine? thanks again. forgot to include that am 1000' above sea level.

 

Plugged booster hose with finger only to have same result. I guess that I am off to buy a vacuum pump. I greatly appreciate your help in narrowing this down for me. Crossing my fingers with high hopes, as they are not the cheapest replacement parts by any means. Thanks again.