This is on my '76 240D, 115 chassis. I'm well aquainted with the injection primer pump (why do my kids always try to use the lower half of the fuel in the tank instead of the upper half??), but what is that OTHER red cap further back on the injection pump?? Looks like an oil filler port, but there's nothing in the owner's manual about putting oil in there. I always thought the injection pump was lubed by the engine oil system. Any clues?

Thanks!

The red cap is probably the oil filler cap if you have the M-series injection pump with the pneumatic governor. The M-series injection pump with the pneumatic governor came on some 240D models. My official M-B engine manual says this type of IP needs to be serviced regularly because it has a separate oil supply whereas the other series of IP with a mechanical governor (type M/RSF) is oiled by the engine's oil system and does not need servicing. However, the M-B manual does not specify how to service the M-series IP (typical short-coming). My Haynes manual also does not cover this series of IP. I do recall a thread where a member wrote that this series of IP had a small dipstick to check the oil level - perhaps this is the red cap that you are referring to. You will need to find out what kind of oil needs to be used (weight, service category, etc.), when it should be changed if it needs to be changed, and other related info. Sorry I can't help you more than this. Perhaps another member can provide more info to help you.

Good Luck!
Tom

__________________
America: Land of the Free!

1977 300D: 300,000+ miles

American Honda: Factory Trained Technician & Honor Grad.
Formerly:
Shop Foreman;
Technical Advisor to Am. Honda;
Supervisor of Maintenance largest tree care co. in US for offices in Tex.

My Chilton manual claims that you should change the oil and the filter in the pump. But it also claims that is on all the diesel models. Shows what they know. If you want to know exactly what the book says I should be able to find it. I don't use it anymore because of the mistakes.

OK, now I'm officially concerned. I've owned this car for 5 years and 50,000 miles, and never touched that cap. (Didn't even know it was there for most of that time.) I'd hate to have it suddenly expire over some little maintenance item like oil, especially since there's NOTHING in the owner's manual about it.

For what it's worth, it was picked up at the German assembly plant, then shipped over to the states. The numbers are:

Chassis: 115 117 12 124603
Motor: 616 916 12 030703

Thanks for any further replies!

Larry D,
It has been a long time (more than ten years) since my old 1975 240D returned to nature through corrosion of the body. The engine, however, was pretty strong the day my first new car got towed away with about 240,000 miles on it. Anyway, I do not remember every detail all that well, but I still have my manual. So, I just consulted the manual and it says to put the same oil in there as you would in the engine. It also shows a fill level plug and a really nasty sounding way to correct the level (the plug is on the driver's side, just aft of the hand pump - aft being toward the firewall). It also suggests the red cap has a filter in it. Well, I did not notice a filter in there, but I do remember a dip stick attached to the bottom, and I recall the oil in there was pristine after the car had about 30,000 miles. I never changed the oil, I just filled it up, too high as I noted in an earlier thread, as the oil was so clean I could not see it on the dipstick. Anyway, there is an overflow/vent on the IP, between the block and the IP, and the extra left via that port. I put Mobil 1 (which was a very light weight back then) in the engine as I was in Alaska and that made a big difference starting. So I put Mobil 1 into the injection pump too. The car never needed more of the stuff, the whole time I owned it, and the IP was in fine condition as far as I could tell when the body fell off (the engine ran fine) in 1992 or so. Hope this helps, Jim

__________________
Own:
1986 Euro 190E 2.3-16 (291,000 miles),
1998 E300D TurboDiesel, 231,000 miles -purchased with 45,000,
1988 300E 5-speed 252,000 miles,
1983 240D 4-speed, purchased w/136,000, now with 222,000 miles.
2009 ML320CDI Bluetec, 89,000 miles

Owned:
1971 220D (250,000 miles plus, sold to father-in-law),
1975 240D (245,000 miles - died of body rot),
1991 350SD (176,560 miles, weakest Benz I have owned),
1999 C230 Sport (45,400 miles),
1982 240D (321,000 miles, put to sleep)

when I got my 74 240 D I called the local MB dealer about red cap and they said to use the same oil that I used in my engine I topped it up and check it every now and then by taking the cap off and looking at the oil level with a flashlight ..............
William Rogers..........

Larry:

I pulled out my M-B CD-ROM service manuals, took the floppy drive out of my laptop and replaced it with the CD-ROM drive, and looked up the following info about the IP with a separate oil supply.

The manual shows two different IP, one for a 6 cylinder diesel and the other for a 4 cylinder 240D like yours. The 240 IP has a check plug to the right of the manual primer (looking from the right side of the engine compartment). M-B says to unscrew the check plug and if no oil flows out then unscrew the filter (located on top of the IP and just to the right of the fuel elements) to add oil. There is no info about what grade of oil to use (10W-40, or 20W-50, 30W, etc.) only that engine oil is used to fill up the IP, as Jim and William wrote. Also, if a mixture of diesel and oil comes out of the check plug, then keep adding oil until all of the diesel/oil mixture runs out leaving only engine oil in the IP.

How this info applies to your IP is uncertain since Jim wrote that his similar IP had a small dipstick to check the oil level. The M-B manual shows a dipstick for the 6 cylinder diesel IP (an engine that predates your 240). Also, the pictures on the CD manauls are not very good - so it was hard to see much detail and I cannot provide a better description than what I wrote above about where things are located and what they look like.

Good Luck!

__________________
America: Land of the Free!

1977 300D: 300,000+ miles

American Honda: Factory Trained Technician & Honor Grad.
Formerly:
Shop Foreman;
Technical Advisor to Am. Honda;
Supervisor of Maintenance largest tree care co. in US for offices in Tex.

Back again...

Thanks all, especially tcane with that handy CD-ROM! Well, the car is finally back from college for a weekend, so I took another look. There is no obvious check plug to the right of the primer pump, just a slotted-head screw that looks like it's for something else. Any chance of seeing those pix on the CD? Do they reveal size & shape of the check plug?

Everything else checks out. The red cap has the word "OEL" on it (under the layer of grime) which, as we know, is my ancestor's way of spelling oil. Under the cap, no dipstick but definitely some kind of breather/vent arrangement. From what I can see peering down into the IP with a flashlight (bifocals are such a cruel joke when working on cars...), there is a gear thingy and some liquid below that. Probing with a makeshift dipstick revealed this to be diesel fuel, which the CD says should be purged with new crankcase oil.

So then: What's that check plug look like, and what parts are supposed to be lubed by this IP "crankcase"? How often does it need checking, and why should the oil get displaced by diesel fuel during operation?

Larry D,

While my recollection of a dipstick seems to be questionable, the bent tube between the block and the injection pump should be there in any case because I clearly recall pouring a quart of Mobil 1 in the late 70's into the port covered by the red cap, only to discover it was running out the little tube. And on to my buddy's father's driveway. Made a mess that took me a long time to clean up.

Since I found no easy way to drain the excess out, and the car ran fine, I assumed the tube was intended to expell any excess fluid. In my old manual for the car the tube is called the "overflow pipe." In your situation, I would be inclined to pour oil in there and see if the excess ran out the overflow pipe. If it did, I would flush that way.

My old manual shows the intended level check plug as a small bolt about an inch or so aft of the hand pump, and about an inch or so up from the bottom of the pump. The instructions say to pull the plug and if the oil level is below the plug, add some in through the port with the red cap. If oil and Diesel leaks out, you are supposed to loosen the regulator cover and raise it slightly to let the stuff can run out. There is no identification of what the regulator cover might be, so I would get anxious at about this point and revert to pouring oil in until the overflow pipe started running. If Diesel fuel is mixed in and that is unexpected (my manual suggests this is normal) and you want to get it out, I would check to see if Diesel floats on your engine oil. If it floats, then you can pour some more oil in until the stuff coming out is clear oil.

Hope this helps. Jim

__________________
Own:
1986 Euro 190E 2.3-16 (291,000 miles),
1998 E300D TurboDiesel, 231,000 miles -purchased with 45,000,
1988 300E 5-speed 252,000 miles,
1983 240D 4-speed, purchased w/136,000, now with 222,000 miles.
2009 ML320CDI Bluetec, 89,000 miles

Owned:
1971 220D (250,000 miles plus, sold to father-in-law),
1975 240D (245,000 miles - died of body rot),
1991 350SD (176,560 miles, weakest Benz I have owned),
1999 C230 Sport (45,400 miles),
1982 240D (321,000 miles, put to sleep)

OK, I think I have it now.

This model does indeed have the bent tube between the IP and the engine block. Looks sort of like the tube you use to check start of injection timing, but no angled cutoff on the end. It is attached to the IP with a standard banjo fitting, and apparently remains open to atmosphere all the time. (Apparently there are other models that had the remove-it-yourself check plug.)

Not wanting to oil my driveway (again), I cobbled a little sluiceway from aluminum foil to route the anticipated overflow past the back of the IP and into a drain pan. Worked great, except that the vent port apparently isn't very big, and at just over 1/2 quart of new oil, the fill port began overflowing. (So much for good intentions!) I'll let the thing drip for a couple of hours, then put 'er back on the road, hoping that any unsuspecting motorcyclists know enough to avoid my oil trail...

Again, thanks all!