w115 240d help - PeachParts Mercedes-Benz Forum

nachoman · #1 01-22-2021, 03:24 PM

hi all and happy new year ( i posted this in the vintage section as well, so please delete if inappropiate mods )
over the past 21 months ive been slowly restoring a w115 240d auto.
Mostly fixing rust issues., so firewall and floors have been repaired ( even had to pull dash out )
replaced windscreen shields , rebuilt auto transmissions

however now comes the motor , it blows smoke and the diesel blow by is a problem
so my options are to repair/rebuild the motor
or a swap
Id like to keep the original transmission in it , as it has just been rebuilt
so im thinking a om617 ( non turbo ) in keeping with the diesel theme. and there are plenty of w123 300d in my area ( the turbo never came to my country )
or
convert to a petrol motor, and something like an m130 or m114
the w115 has those two firewall to chassis strut braces , so i dont want to remove them and compromise the integrity/strength of the body.

Thanks for any feedback

resago2000 · #2 01-22-2021, 05:27 PM

check the air line running from the throttle body to the injection pump, if its cracked anywhere, replace it with std vacuum line.
also see if the vacuum pump output line is pushing oil into the intake. that line should be clear, never black.

adjust the valves.

t walgamuth · #3 01-22-2021, 11:11 PM

If you change motors the simplist is a 300d na. It should bolt right up to your tranny and the oil filter and battery will be in the correct place for you. I did one of these and it makes the car much more drivable with the extra cylinder especially with the automatic transmission.

Good luck with it.

nachoman · #4 01-23-2021, 01:34 AM

Quote:

Originally Posted by t walgamuth

If you change motors the simplist is a 300d na. It should bolt right up to your tranny and the oil filter and battery will be in the correct place for you. I did one of these and it makes the car much more drivable with the extra cylinder especially with the automatic transmission.

Good luck with it.

Will a w123 300d na motor fit ? these are plentiful in my area..

t walgamuth · #5 01-23-2021, 09:15 AM

There are a lot of similarities between the early 123 motors and the 115. The motor was changed around 1980 or so. notably the oil filter and ac compressor came to be mounted differently. I have not done that swap so cannot speak in detail.

Mike D · #6 01-23-2021, 09:55 AM

For a "straight" swap you need to source a pre-'76 N.A. OM617.910.

The engines used after '76 MY (W123) are the OM617.912 and other variants which have the oil filter mounted up high on the side of the block. An oil filter by-pass or conversion plate would be required.

ANY of these engines will require a modification to the engine shut down as the MW series injection pumps are used which use a vacuum system as opposed to the "Gorilla knob" manual shut-down and start type.

nachoman · #7 01-23-2021, 05:40 PM

Quote:

Originally Posted by Mike D

For a "straight" swap you need to source a pre-'76 N.A. OM617.910.

The engines used after '76 MY (W123) are the OM617.912 and other variants which have the oil filter mounted up high on the side of the block. An oil filter by-pass or conversion plate would be required.

ANY of these engines will require a modification to the engine shut down as the MW series injection pumps are used which use a vacuum system as opposed to the "Gorilla knob" manual shut-down and start type.

Something like this ?
https://www.doomsdaydiesel.net/product-page/om617-oil-filter-relocator

Sugar Bear · #8 01-23-2021, 06:16 PM

Yes to the link you provided. Good luck!!!

Screwdriva · #9 01-23-2021, 06:20 PM

I own a W115 240d 4 speed (now restored). I experienced similar symptoms to you which I was able to drastically reduce without a rebuild.

1) Perform an AUTO RX engine oil treatment (2 bottles). A quick google search will highlight that there is no safer way to remove sludge, carbon deposits or varnish from your motor internals, allowing for reconditioning of seals. It takes 5K miles for a treatment to be completed so make sure you follow instructions precisely.

During this time, I treated the fuel system with:

2) A Liqui Moly Diesel Purge (2 bottles).

3) Followed by Chevon Techron fuel additive (diesel). I use two consecutive bottles at first followed by one before every oil change.

IF Auto Rx does not solve your oil consumption/ blow by, then your only option left is to use Engine Restorer. This metallurgical chemical compound bonds to worn cylinder walls to undo damage due to past neglect.

Given that these cost <$150 combined, I highly recommend you attempt to rejuvenate the original motor vs. attempt a swap. I can assure you none of the above are snake oil and all of my 65 horses never rode better!

pj67coll · #10 01-23-2021, 06:32 PM

Nice looking car you have there Nacho. What country are you in? I'm guessing Australia?

- Peter.

nachoman · #11 01-23-2021, 08:50 PM

Yes in Australia.
the w115 3.0 om617 never came to australia. However the w123 300d did , so there are a few around

pj67coll · #12 01-23-2021, 09:30 PM

If it were me I'd keep it original, but your's to do with as you wish. It would give it a bit of a power boost with that extra cylinder. But there'd be less space to get in there if you ever have to do stuff.

- Peter.

nachoman · #13 01-24-2021, 01:58 AM

Quote:

Originally Posted by pj67coll

If it were me I'd keep it original, but your's to do with as you wish. It would give it a bit of a power boost with that extra cylinder. But there'd be less space to get in there if you ever have to do stuff.

- Peter.

Maybe the motor just needs some TLC

nachoman · #14 01-25-2021, 02:52 PM

pj67coll · #15 01-28-2021, 01:41 PM

Gorgeous car. Hope you have more luck with it than I'm having with my 81 at the moment.

- Peter.