Looks like something you'd see on crownvic.net.

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Whoever said there's nothing more expensive than a cheap Mercedes never had a cheap Jaguar.

83 300D Turbo with manual conversion, early W126 vented front rotors and H4 headlights 401,xxx miles
08 Suzuki GSX-R600 M4 Slip-on 26,xxx miles
88 Jaguar XJS V12 94,xxx miles. Work in progress.
99 Mazda Miata 183,xxx miles.

My '82 240D, and the '79 or '80 Pick-N-Pull 240D I once pulled a temporary spare from, used piston pumps, with no vacuum exhaust line connected to the intake. Those pumps exhaust vacuum into the crankcase, via the timing-chain housing.

Happy Motoring, Mark

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DrDKW

Not all models apparently. My 1974 240D swapped with a piston pump from a early 300D. Venting was to the air intake. Some simple adapting to the line had to be made to fit into the 240D air intake. I can tell you the locks went up and down real quick with the higher vacuum. I guess in newer models the single vacuum inlet became the norm.

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1984 300SD turbo 126
"My true love"

God made me an atheist and who am I to question His wisdom

Hmmm...was ready to order...

But a simple test is recommended: to blow into the hose to tell if the diaphragm is still good.

Or swap pumps with a 300 type to get away from the diaphragm design.

But swapping pumps might require some modding - on an easy scale or ?

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1991 300E 124.030 103.983KE 722358 03 412178
207K

1979 240D 123.123 250K (Project car)

2000 Ford Ranger, 187K

2015 Dodge Ram 1500 EcoDiesel 37K

Sorry I didn't read your original post clearly which was plume of smoke shifting from 2nd to 3rd. Are you door locks working? Do you have power brakes? If so your vacuum pump is OK. Try to diagnose what caused the smoke instead of swapping out parts.

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85 300D turbo pristine w 157k when purchased 167,870 July 2025
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked

When my diaphragm started to rip and send oil up the pipe to the engine intake, my brakes were still fine. So that is not a great indicator of a torn diaphragm. If the tube between the vac pump and intake is black and contains oil, you need a new diaphragm. If it is not black, that is not your source of oil leak and you don't need those parts.

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1968 220D, w115, /8, OM615, Automatic transmission.
My 1987 300TD wagon was sold and my 2003 W210 E320 wagon was totaled (sheds tear).

Well in the OP, the car is a '79 W123 240D, and may already have a piston pump.
Need to verify before trying any blowing tests. Does it have two tubes connected, with one to the intake and the other to the brake-booster? If there's only the one tube to the booster, it's probably the piston pump.

Happy Motoring, Mark

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DrDKW

Door locks work like they have a leak. Not perfect. Brakes work fine.

My brakes, too, are ok. Yes, the air filter intake tube has traces of black oil.

BTW, did the test to force air into the (vacuum) tube (going towards the firewall) and was able to move some air.

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1991 300E 124.030 103.983KE 722358 03 412178
207K

1979 240D 123.123 250K (Project car)

2000 Ford Ranger, 187K

2015 Dodge Ram 1500 EcoDiesel 37K

Two tubes - one to the air filter and one to the brake (?).

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1991 300E 124.030 103.983KE 722358 03 412178
207K

1979 240D 123.123 250K (Project car)

2000 Ford Ranger, 187K

2015 Dodge Ram 1500 EcoDiesel 37K

If your vac pump has two tubes, one to the intake and one to the brake booster, you have a diaphragm pump.

Now, is the tube going to the intake black and wet with oil inside? If so, then your vac pump needs some parts, as previously discussed. If not, your problem has nothing to do with the vacuum pump.

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1968 220D, w115, /8, OM615, Automatic transmission.
My 1987 300TD wagon was sold and my 2003 W210 E320 wagon was totaled (sheds tear).

Looks like there is a vacuum pump from a 300D available.

Need to find out how much is involved when installing before I commit to order.

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1991 300E 124.030 103.983KE 722358 03 412178
207K

1979 240D 123.123 250K (Project car)

2000 Ford Ranger, 187K

2015 Dodge Ram 1500 EcoDiesel 37K

Am at this point but the fan is right in my way.

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1991 300E 124.030 103.983KE 722358 03 412178
207K

1979 240D 123.123 250K (Project car)

2000 Ford Ranger, 187K

2015 Dodge Ram 1500 EcoDiesel 37K

Was ready to buy a special tool because I could not access the screws to remove the housing.

Checked the garage again, and found the perfect item in my dad's old tool collection that did the trick (will post the pictures later).

Now that I have the 8 screws off, and I took off the front plate with the 2 smaller screws that cover the springs,

the housing is still stuck and won't come off!!!


How much do I try to pull or twist??? I'm afraid I'll break something!

Really reluctant to disconnect from the block.

Attached Thumbnails

   

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1991 300E 124.030 103.983KE 722358 03 412178
207K

1979 240D 123.123 250K (Project car)

2000 Ford Ranger, 187K

2015 Dodge Ram 1500 EcoDiesel 37K

Good news to report!
The housing finally came off with a lot of PB blaster and a chisel and hammer taps.

The rest was easy; took radiator off, moved fan blade a bit for more room.

What a job, but it was definitely worthwhile.

Parts ordered from Pelican came quickly, and very well boxed.

Thanks everyone for your help.

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1991 300E 124.030 103.983KE 722358 03 412178
207K

1979 240D 123.123 250K (Project car)

2000 Ford Ranger, 187K

2015 Dodge Ram 1500 EcoDiesel 37K

Another update: checked the air filter, very clean except for one (small) black spot from oil.

Locks work faster.