r129 diesel conversion - Page 9 - PeachParts Mercedes-Benz Forum

bkc · #**121** 09-07-2022, 04:58 PM

Guess it has been way too long since I posted any updates...

Here's a brief status update (since a more detailed one is why I kept not getting around to posting):

* The charge pipe is indeed custom exhaust piping. Made things nice and clean after the pressure actuator conversion.
* Car runs and drives. From the brief test drives so far (limited by the tranny issue, below) it seems to work quite nicely. Haven't been able to go on a highway yet because of the tranny problem. Wife enjoyed the brief test drives.
* Currently waiting on a replacement valve body for the 722.618 (since May, despite repeated promises from Marc at Sun Valley), since the 3-4 shift fails when cold - have only gotten to put about 10 miles on the completed car because of that.
* Got the car repainted (down to the metal) by a retired body shop guy (our "oops" guy - when we accidentally scratch or ding a customer vehicle) - discovered that the car had been repainted four times already (first well, then 3 poorly) and that it had covered up multiple collisions (I still shudder at what might have happened if the left rear had gotten hit again before we fixed that crappy repair). All repaired properly now.
* Engine is om602(.962), not om606 - rebuilt by Metric Motors
* Tranny is 722.618 - Rebuild from Sun Valley Transmissions who didn't charge a core even though swapping it for a 722.500 (i.e. not like-for-like)
* Using custom PCS 2800 TCU kit for the 722.618 tranny from Russell (whipplem104) and lots of good support from him for getting it programmed properly.

Summary of build:
* Radiator: 500SL/SL500 radiator to get hose connections in right places; using a Gates 22886 hose with a couple of inches cut off to fit upper hose connection (still looking for an MB hose fit); om602 lower hose fit perfectly
* Mounts: used om602 mount arm on left side, used m104 mount arm on right side; had to very slightly wallow out the mount bolt holes in the crossmember to rotate the engine a few degrees to line up with driveline, otherwise almost perfect fit; had to custom build tranny mount crossmember to fit 722.6 mount (did not have access to a later model r129 that came with 722.6, maybe that would be ok as is, although engine/tranny sits slightly further forward)
* Driveshaft: had to custom modify to have flanges to mate with 722.6 and length adjusted (cut down my w124 front half, attached r129 yoke)
* Lots of wiring, although probably nowhere near as much as I did if I were doing it again, knowing what I know now - still working on drawing diagrams for future repair/diag needs
* Preglow/Start: r129 ignition is same as w140, which had a diesel option, so there is already a circuit to use to enable preglow with key
* Shutoff: repurposed bowden cable from ignition to shifter to operate w124 ignition vacuum shutoff valve so engine mechanically turns off with key (didn't want to use a solenoid)
* Fuel Tank was usable as is, not galvanized, is stainless steel - had it steam cleaned by a radiator shop just in case, but was pretty clean to start with
* Air filter: currently using a Spectre filter local OReillys guy found to fit; hoping to eventually have an MB quality filter, since I expect Spectre has the same issue as K&N of letting too much grit through (please, no flame wars here)
* Fan shroud: 500SL

To do:
* still don't have tachometer working (data feeds to TCM fine, just not dash)
* still don't have oil pressure sensor registering on dash, need to figure out where my wiring is wrong
* still don't have reverse lights (light module is NOT wired as per diagrams)
* waiting on valve body to do more extensive test drives
* get A/C working
* better air filter option

I'm sure I left out other things, and obviously the devil is in the details. But I think I could redo this project in just a week or so (not counting any wait time for parts or machine shops) if I had to, now that I've done it once. Hope I don't have to!

Will try to remember to post pictures in near future. Plus will update once the tranny is working properly and I get some real test drives in.

Cheers!
-Bruce