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#1
10-24-2002, 12:22 AM
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vacuum repaired clunk still there
I had my vaccum line replaced (vacuum pump to brake booster) and system checked and I still have that "clunking sound" when the tranny downshifts just before I get to a stop. What is next to check? Tranny modulator? Can I leaking vacuum pump cause this problem? Thanks
1984 300D Turbo -260k 1999 ML 430 -40K 
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#2
10-24-2002, 09:21 PM
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Low vac at the transmission will do this, as will a bad flex disk. Check the vac line from the blue vac amplifier on the fender to the tranny for leaks -- you should be able to draw a hard vad (20" or more) with a hand pump and have it hold indefinitely. If not, check for leaking connectors.
Flex disk is between tranny output flange and front driveshaft flange. When they are bad, the driveshaft can rotate inside the disk, making it thump. Not too bad a fix, either. Peter
__________________
1972 220D ?? miles 1988 300E 200,012 1987 300D Turbo killed 9/25/07, 275,000 miles 1985 Volvo 740 GLE Turobodiesel 218,000 1972 280 SE 4.5 165, 000 - It runs!
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#3
10-25-2002, 08:52 PM
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Hey Danny, I share your woes...i even went as far as buying the mityvac but ended up returning it...anyway I'll try to look at that blue line from that contraption near the firewall tomorrow...i also bought a cd-rom manual for the w123 i heard it really has some good info...i live in huntington beach so maybe we can "eyeball" one of these days and compare our rides and see if we can get our machines runninng in top condition again...GO ANGELS!!!!
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#4
10-25-2002, 09:17 PM
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Gys:
Vac systems are real easy (at least for me!). What you have is vacuum rather than air pressure working things -- or to put it better, you remove the air pressure from the vac side of things and let atmospheric pressure do the work. Vac is supplied by a pump on the MB -- no intake manifold vacuum. Vac is supplied to all the other stuff by hard plastic hoses -- the one for the AC is green, for the locks is yellow, and for the tranny/EGR is white. Door locks inside have a yellow with green stripe (unlocks, I think) and yellow with red stripe (locks) -- vac shutoff supply line is brown, line to the shutoff is brown with blue stripe. You cannot troubleshoot vac systems without a supply of vacuum, and the MitiVac (or something similar) is the best there is. It is nothing but a hand pump with a vacuum gauge on it. You plug it into the line for a system you want to check after you disconnect it from the main supply line on the car, and pull a vac by squeezing the handle and letting go. If it is leaking, the gauge won't stay up. You may need to squeeze the handle a number of times for the AC and locks -- there are tanks that hodl vac so the work when the engine is off. Works very, very easy. There are a bunch of adapters that plug into the hose on the MitiVac so that you can connect any of the vac lines, and pretty good instructions. It also lets you keep pumping so you can listen for leaks -- the air hisses as it goes into the lines. It will supply the vac for the locks, shutoff, AC, etc -- lets you operate them with the engine off, for example. Don't be intimidated, it really is pretty simple once you get a handle on it. Peter
__________________
1972 220D ?? miles 1988 300E 200,012 1987 300D Turbo killed 9/25/07, 275,000 miles 1985 Volvo 740 GLE Turobodiesel 218,000 1972 280 SE 4.5 165, 000 - It runs!
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