Well, the vacuum bug has struck my precious 300D. Everything worked fine (locks, engine shutoff) and then yesterday stopped. I've popped the hood and run the engine and felt for vacuum at the hoses and there is vacuum most places. The vacuum hoses have a little oil around them, like from oil vapor, but are not blocked. I don't have a vacuum gauge, but when I place the hoses on my finger there is a light tug.

I pulled off the blue/black check valves and made sure I could blow air through them and that worked OK. So I'm at a loss. The engine has 197,000 miles and for all I know has the original vacuum pump.

I've searched the forum but haven't found anything specific to this sort of problem. Any advice or links would be appreciated!

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Where there's a will there's a way
1978 300D

Do you have the vac pump that routes to the air cleaner?

Is it a diaphragm or piston unit?

If the former, and the diaphragm has ruptured, you'll need to fix it.

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83 SD

84 CD

My vacuum pump has two lines coming out of it. One goes to the air cleaner, and the other to all the vacuum hoses and the brake system. Don't know if piston or diaphragm? How hard is it to take it off and check it out. Looks like just a series of bolts around the edge, but are there any things to look out for when removing the unit?

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Where there's a will there's a way
1978 300D

WHOA !!!!!

YES , there are things to consider before taking it apart...

and they are listed in the archives with pictures....

Also there you will be able to tell which type you have...

if diaphram ....and that is split.. potential for in car fairly easy replacement... but you want to notice the position of some things as you go in.... and I don't remember what 7 years after mine broke....

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1980 240d ,

chain elongation, cam marks reference:
http://www.peachparts.com/shopforum/showthread.php?threadid=10414

http://www.peachparts.com/shopforum/diesel-discussion/305365-9-degrees-chain-stretch.html

evap fin cleaning:

http://www.peachparts.com/shopforum/showthread.php?t=156207&highlight=evaporator

A/C thread

http://www.peachparts.com/shopforum/diesel-discussion/297462-c-recommendations-mb-vehicles.html

you should start by getting a gauge at the pump before proceeding further.

i dont know if pump is the same on 79 300d as 79 sd,if they are,rebuild kit is expensive $275 , you might do better getting a good used one.new pumps for sd are insane

on the sd the pump has 2 lines emerging,one large one to brake booster and one smaller line going to all the other stuff(foors,pods etc) and one to air cleaner

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95 e320,87 sdl,79 300sd

Thanks folks. I've been scouring the web for pictures and info on my two line vacuum pump. Diesel giant only shows the one line pump. Can't find pictures or info here yet either. Sounds like I need to get a gauge to verify my vacuum, and then if the pump is the problem, like it is not hard to repair.

I would appreciate any links to any pictures or tutorials as I have not been able to find them myself after quite a bit of searching.

Thanks!

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Where there's a will there's a way
1978 300D

79 300d should have a single diaphragm pump. Replacing the diaphragm is a one hour job. Check the vent line going to the intake/air cleaner for oil.

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1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13

Island 300d, I returned your pm. I had to erase some stuff, because I went over 2000 words.

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"Knowing is not enough, we must apply.
Willing is not enough, we must do." Goethe

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1951 Chevy 3100

2003 Indian Chief Roadmaster

1983 GMC 1 ton Dually

1982 Chevy 1 ton Dually, service body (sold)

'90 GMC Suburban 6.2 "SS Veg-Burban"
(single tank WVO\diesel conversion) SOLD

'81 300D ~ Mama's car...my job (now my car)(but still my job) SOLD

'83 300sd ~ rescue car SOLD

2005 Ford Taurus (Mama's new car)(NOT my job!)

Just ordered a vacuum gauge and hand vacuum pump and appreciate the tips on checking for oil etc. I'm going to investigate and then get back on here and let people know what I am finding out.

Does anyone know if my vacuum pump is likely to be the type that has the loose ball bearings I've read about that everyone fears?

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Where there's a will there's a way
1978 300D

I don't think so.

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1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13

Clarification question: subject line says 79 300D, sig line says 78 300D. For the model-year change aficionados is that relevant to the question regarding potential vacuum pump parts?

As far as troubleshooting, I'd say isolate and overcome. If you can block off the "other consumers" like doors, reservoir, ACC from the shutoff/EGR/tranny lines I'd do that first since it could divide your potential problems in two.

There are a few vacuum threads with pics. Look for peterschmidtransmission for links to a vacuum diagram reference website.

Sorry Yak, it is a 78 but I had forgotten when I did this post! She's a gem, and I love her like a man can love a great car.

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Where there's a will there's a way
1978 300D

OK, I just got my vacuum gauge and hooked it up the big black line coming from the pump and it measures a steady 20 mm Hg. I think that is in the normal range. Good news I guess?

Bad news is I still need to find out why my engine shut off and door locks don't work anymore. Bummer is I snapped the little plastic "T" that combines the two big black lines between the gauge and brakes and had to cut off some of the black vacuum hose to free the broken "T". Business for Phil I guess!

Any suggestions on where I should look next? I do see light oil in the hoses, and have read that can only come from the vacuum pump. Should I check it anyway?

Any and all help appreciated.

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Where there's a will there's a way
1978 300D

Just went out and did a suction test on the lines using my new hand held vacuum pump, with the engine off, if that matters, and found none of them holding suction. The device works fine as when I cover the pump hold tube with my finger it quickly comes to pressure, but I tried each and every connection, every which way, and none of them held vacuum.

I even tried to isolate different colored hoses, and troubleshooted the rubber hose connectors, which held pressure. I made sure it had nothing to do with the connection of my hand held pump hosing, as connecting it to one of the rubber junctions and plugging the various holes held good pressure.

So, there must be somewhere that all those hoses have in common that has a leak. Could it be the main suction tank? A master hose connection somewhere???

Any vacuum gurus out there? I'm getting close!

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Where there's a will there's a way
1978 300D

It could be the grommet on the vacuum line going into the lock reservoir/vacuum tank in the trunk. But if you have some oil in the lines, you need to suss that out. I haven't had to mess with the vacuum system in our '79, so I'm basing this on my '85, which had a similar problem. I isolated the locking system from the engine system, and it was the grommet on the lock reservoir.

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1985 300D-189k The 'UD', Ivory and Pinkamino
1979 300D-211k Dark Gray, Parchment
A 1980 Harley-~166k and
A 1994 Ford diesel pickup-349k and
A 1990 gasser Volvo wagon-145k