(Please note: this post was placed elsewhere in this forum, and was suggested to be posted here. Since I can't apparently post the same photos twice, please see the pictures in the original post below).

300D conversion to 300 Turbo Diesel



My father is attempting to install a remanufactured 84 300 Turbo Diesel engine and transmission in his old ’81 300D. It’s a grand undertaking to be sure, but he has some questions, so I thought I’d post them here to see if there are any experts that can give him some advice. He believes the swap will be pretty straightforward, except for the following four items:


1. If you examine the first picture attached, you’ll see a “Turbo Pressure Switch”, labeled as item number 12. Since there is obviously no wiring for this setup in the 81, my father would like to know how to properly wire and fuse this item.

2. If you examine picture number 2, item number 7 is called a “Switch Over Valve”. There was no such animal on the ’81, so how exactly it will be hooked up properly on the ’81 is a mystery. It can’t be seen in the scanned picture, but the connections on the valve show the left connection heading “To Manifold” and the right one “To Aneroid Compensator”. I have no idea what an Aneroid Compensator is. Maybe you kind folks can help.


3. Looking at picture 3, you can see that the “Transmission Inhibitor Switch” is round. On my father’s 81, it is rectangular. The problem is this; on the reman 84 tranny the switch is round. Can the wires be simply spliced from the old switch and hooked to the new round one?


4. On the older 81, apparently there is a vent pipe that runs from the air cleaner to the oil pan, On the newer engine, it is eliminated. Is it necessary to hook this up? Does he need an air cleaner system specifically for the 84, or will the 81 work by simply closing of the air cleaner’s connection to the vent pipe?

Lots of questions, I know, but I hope you can help. If not, can you point me to any other MB forums which might be able to be of assistance? Thanks again.

PS Any other tips on this conversion would be gladly appreciated.

I've done the reverse of this swap, Turbo to NA....

3. Looking at picture 3, you can see that the “Transmission Inhibitor Switch” is round. On my father’s 81, it is rectangular. The problem is this; on the reman 84 tranny the switch is round. Can the wires be simply spliced from the old switch and hooked to the new round one?

Yes, You can splice the new connector into the car or as I did, cut the wires and I found red female connectors at Radio Shack which fit the male connectors in the neutral saftey switch. The pins are numbered on the plugs, 1-4 and they are the same wires on the round and rectangular connector.

4. On the older 81, apparently there is a vent pipe that runs from the air cleaner to the oil pan, On the newer engine, it is eliminated. Is it necessary to hook this up? Does he need an air cleaner system specifically for the 84, or will the 81 work by simply closing of the air cleaner’s connection to the vent pipe?

Use a correct Turbo air cleaner, they are bigger because Turbo engines consume more air....

Pay attention to the mounting of the engine shocks, Your NA engine should have a "U" shaped bracket bolted to the upper oil pan which holds the 2 engine shocks. Test to see if it fits the turbo motor... The crossmember which is welded to the car is set up differently for different motors used in the w123 chassis so the placement of the shocks using the turbo engine carriers (alum. arms bolted to the block) won't line up in the NA chassis...... read, you may have to do some fab. to make the engine shocks work in your chassis....

__________________
Over 21 years I owned several:
w108
w110
w111
w115
w116
w123
w124
w126
w212

There is also some good advise in your other thread....

I have a turbo intake/exhaust manifold in inventory if that is needed...