Just bought a '78 300cd w/ 145,000 mls. In good one owner condition except that "accelerate" on cruise works but cruise won't lock in. Also sunroof needs to be "bumped" w/ the switch to open and close (sticks). Also rear windows only go halfway down unless helped. Bought both the Chilton's and Haynes books but no help on these matters. Any suggestions? Thanks, Marvin

Marvin:

The sunroof needs MB sliding sunroof paste applied to the sliding surfaces. This is the best stuff, by far, and is only available in 500 gram tins -- get it done at an indy shop or find one that will sell you what you need -- the whole tin is a waste.

Don't use ordinary grease, it isn't the same!

The regulators on the rear windows need to be lubricated, and check the channels the windows slide in -- when these get old, they shrink, and the window will jam slightly sidways rather than straight up and down -- I think the rear channel can be adjusted.

I don't know if you have the vacuum operated cruise control or the electric one -- it will be obvious when you look at it. If vaccuum, check the vaccuum lines for integrity -- if they are leaking, it can prevent proper operation. If electric, probably the amplifier.

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!

Marvin,

I just repaired the amplifier on my cruise control by heating the connections with a soldering iron and then letting the set up again. It took about 1 1/2 hours all together, but it salvaged my otherwise defunct cruise control--works great now! It wasn't difficult, just time consuming.

If you're not familiar with this method, search the archives. Otherwise, let me know and I'll forward it to you.

Thanks for the information. I don't know if I've got vacuum or electric Cruise control. The thing that looks like it might be the cruise is a soup sized can, mounted on the driver's side, with a black tube running to the throttle and other tubes running to the firewall, also several wires. I'll try to eaxmine it more carefully tonight. Also, what is the best way to lubricate the rear window regulators in my 300cd? Can I shoot some lubricant down in through the seal with one of those wd-40 tubes? Do I remove the rear inside panels? If so any tricks or pitfalls in doing so?
Thanks, Marvin

Marvin:

Hard plastic hoses with rubber ends = vacuum control. Check the rubber parts -- they tend to get soft and leak, or get rock hard and crack from the engine compartment heat. Either way, the CC won't work. The plastic is usually ok, just brittle, so be carefull when attempting to remove the rubber ends. Rubber parts can be replaced with standard vacuum line from the autoparts store -- any "y" connectors should be MB replacements so they fit properly.

Check carefully for little plastic double-ended inserts in the lines, too -- these are filters or resctiction orifices and need to stay where they are if you replace the rubber bits.

Don't use WD-40 to lubricate anything -- it isn't lubricant, it is water dispersant. Turns into rubber cement with age. You need to take the rear side panels off and check the alignment of the window tracks -- if there is too much clearance between the window and the channel, it will jam. The gear mechanism may also need some light grease on the center pivot. Usually slow windows are worn channels -- if the motor itself is slow, it will need to be replaced.

Also, check the switches -- if the windows got used a bunch they may have high resistance.

My bet is that the window channels are shrunk, allowing the glass to get cocked and drag. I had the same problem with the 220D -- the "repaired" regulator on the driver's side broke (manual windows) -- got a replacement at the junkyard, and tightened up the channels a bit when I put it in. Window works much better now!

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!

Thanks, psfred and Bill_Greenwood, I've replaced most of the vacuum connectors, but still no cruise, I'll work on it some more this weekend. Also, in a problem I believe to be vacuum related, the passenger door now won't close properly unless the motor is running, or has just been shut down!. I'm sure in my replacement of connectors, I messed up something. Is there a good vacuum diagram out there somewhere to help troubleshoot vacuum problems? I've got the chilton's and Haynes books..no help.
Also, I removed the passenger side rear panel and lubricated the rear window regulator..works great now. Then I attached a WD-40 red tube to a spray can of White Lithium grease (It doesn't freeze here in the Lowcountry) and carefully positioned it through the inside of the driver's side rear window between the rubber seal and glass so that I could lubricate the regulator..worked like a charm! Now have 4 fully functional windows! Thanks, Marvin
PS what is that black plastic box about the size of a Tom Clancy novel mounted on the driver's side front tire well? It has some circuits and an in line fuse in it. Thanks

I believe that your P.S. refers to the glow plug timer/ relay. Also I don't know of any vacuum diagrams available, so perhaps investing into a mity-vac would help. You could use this to troubleshoot your vacuum systems by seeing if they hold vacuum.

Adam

Thanks. where do I get a mighty-vac, how much? Marvin

Pep Boys or another auto supply store. Around $30 for a decent hand powered pump. On a w123 where everything is vacuum, they are worth their weight in gold!

Note: Pump must have a vacuum gauge (in. Hg. ) with it to troubleshoot, although I have never seen one sold without a vacuum gauge. After you draw the air out of a line or accessory, watch the gauge and it should keep that pressure for several minutes without changing much (10%). If not, you have a vacuum leak in that part. Be systematic, and try to test just one thing at a time by removing or stopping other lines and connections. May be more difficult, but really saves time in the long run and makes it easier.

Best of Luck and have fun!
Adam

you said you had to bump it by using the switch right? when you say bump do you mean that it slows to a stop, or that it suddenly stops on you while trying to use it? if it suddenly stops, check the switch. MY sunroof was doing the same thing, very intermittent and i had to press the button many times to get it to close/open. Turned out the contacts inside the switch were all carboned up, i cleaned it up and now it works like a charm. When it stops the next time, try helping it by hand and see if it starts to go again, if it doesn't i'd check the switch.
R

__________________
83 300SD.......sold
96 integra SE....sold
99 a4 quattro....sold
2001 IS300.......sold
2002 330i.........current.
2004 highlander limited....current.

Marvin:

Sounds like a bad lock actuator on the driver's door -- if it doesn't properly unlock, it may be causing the latch to jamb. Could also be a leaking plastic or rubber fitting.

Quick guide to vacuum lines:

Brown and brown with blue stripe are engine shutoff.

Green is AC. check vavle on firewall.

Yellow, yellow with red stripe, and yellow with green strip are vacuum locks. Locks are switched by a valve in the driver's door. Check valve on firewall

White is for the transmission modulator control. There is a restrictor at the connection to main vaccuum line.

There are two vacuum reserviors -- one for the locks (big) and one for the AC (small).

There is a vaccum diagram posted in this discussion group for the vaccuum modulator system, I don't remember which one.

Hope this helps!

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!

Thanks everyone again for the help on my '78 300CD. Ryan, the sunroof motor continues to run when the roof stops (sort of seizes, actually), so I think maybe the switch is OK. Helping it manually doesn't really seem to help it move. I'm still planning on getting some sunroof paste from our local (Hilton Head Island, 45 miles away) MB dealer and trying that. Does the sunroof have some sort of cable or pulley that could be too tight or loose? PSFRED, thanks for the color coding and door advice, I'm going to get one of those mighty vacs (Thanks ATLD)and check everything out. There appears to be a vacuum line running from the bottom of the oil filter housing to the firewall..is that transmission related, or some oil pressure thing? I don't see one that goes to the valve cover. Also the worst looking vacuum connection left under the hood looks to be the rubber manifold type octopus thing attached to the driver's side firewall, w/ several connections (or maybe pass-throughs) sticking out of it, one much longer than the others. What is this part called so I can order it's replacement? Thanks to all, Marvin

Marvin:

The "octpus" thing is a seal -- all the vacuum lines and such from the dash and etc run through it. To replace it you will need to disconnect everything!

All the vacuum lines should attach to something except the vent line (black) that goes under the dash or somewhere like that -- lets air in to vent vacuum when required.

Vaccuum line to oil filter housing? That's new to me -- what color is it, and is it actually attached? There is an oil pressure line (thinner than the vacuum lines) that goes to the gauge, but I think that goes to the main oil gallery, not the filter!

The modulator control valve may be on the IP rather than valve cover.

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!

The one from the oil filter housing to the firewall is the oil pressure line to the instrument cluster on the dash.

__________________
Jim