Richard's pair of nightmare W124s
 

My neighbor Richard had a very nice '90 W124 300E until about a month ago, when he attempted to remove most of the sheet-metal on one side of the car with a utility-pole.
So he acquired a nice, straight, solid-body '92 300E replacement with serious issues. The '92 engine has a serious oil-leak and apparently has been run low on oil numerous times, until now after warm-up, the oil-gauge struggles to reach maximum unless it's revving 3000 rpm or better.
The other problem is the '92 car was towed about 200 miles with the rear-wheels on the pavement. Richard claims the tranny seems to be working OK but he's barely driven it since he got the car home. So now the questions are (If anyone here would be kind enough to provide an answer, opinion, or point me in the right direction) Is the tranny also toast? And will the good engine & tranny from Richards wrecked '90 300E, easily swap into his '92. Or will there be serious compatibility issues with wiring, plumbing, sensors, emissions equipment and/or computers?
Both engines are the M103 3.0. I don't know what part# the two automatic trannys are.
Thanks in advance.

Happy Motoring, Mark

As you have both cars side by side you should be able to see any discrepancies. You can check part numbers on computers and other bits if necessary. I would expect it to be a straight swap.

If you know that one transmission is definitely good I would most certainly fit it (with new fluid and filter if it hasn't been done recently) rather than risking the "knackered" one.

In my experience (with out a lift and a transmission jack) the best way of doing an engine swap is engine and transmission out and in when they are mated.

For now, the wrecked one is in a lot somewhere, the 'knackered' one is in Richard's driveway, and I'm 200 miles away from both.
Last time I did a swap like this was 25 years ago, putting a '70 250C engine & tranny into a '72 250 sedan. I think there was one sensor wire that had to be moved and the coupe-engine carbs were messed-up so I wound up installing the ones from the sedan. Wiring & plumbing have become too complicated since then. Even one model-year difference can create a big hassle.

Happy Motoring, Mark

There could indeed be a whole load of very irritating plugs that don't fit - but I doubt if a wiring diagram or people's experiences could pre-warn you of that.

I can say that the whole wiring loom for my W201 (1992 vintage) can be unravelled from the electronics boxes hidden behind the battery - I can then make a very big assumption and guess that the W124 is probably arranged in a similar way; assuming the worst happens then you should be able to unhook the engine loom from one car and transplant to the other.

Have you got EPC? If so you can see specific data for the specific VINs

Looking at the EPC parts diagrams on EverythingBenz - Mercedes-Benz Forum and Web Search Using Google might also yield a warm wet feeling!

You can pull these cars all year long, they have a secondary pump driven by the prop shaft. You can even pullstart them.

I DONT THINK YOUR CAR WILL BE DAMAGED BY TOWING IT WITH THE REAR WHEELS ON THE FLOOR, LAST THURSDAY I SPOTTED A W124 BEING TOWED ALL THE WAY FROM LAREDO TEXAS TO GUATEMALA OR ANOTHER CENTRAL AMERICA COUNTRY.

WISH YOU THE BEST LUCK WITH YOUR ENGINE SWAP AND IF YOU'RE WILLING TO SELL A SET OF FUEL PUMPS AND THE PROTECTIVE "BOX" FOR THESE, I WILL BE HAPPY TO MAKE AN OFFER.

Geez. Parts vultures already? :rolleyes:

It should be fine. If both are M103 3.0 like you say, they are both 722.3. You should be in good shape. Not sure so much about that 1990 300E though. ;)

Good luck to you and Richard!

I AM MAKING A POLITE AND RESPECTFUL COMMENT ABOUT FUEL PUMPS THAT RICHARD WILL NOT NEED AND I DO, I DONT THINK IT GIVES YOU THE RIGHT TO MAKE OFFENSIVE COMMENTS LIKE "PARTS VULTURES"

I knew Mercedes had a rear pump on the W114-115 cars. I even tested the 'push-start' on my '72 250 many years ago (actually had to get it going about 20-25 mph before it would crank over). But my owners manual still says to limit the speed and distance if the rear wheels are on the ground. Plus I didn't know if the rear-pump feature had been eliminated on the later models. Richard will be pleased that his '92 300E tranny may not have been ruined by the 200-mile tow.

Happy Motoring, Mark

Well, I didn't mind your comment. But unfortunately, Richard's '92 also acts like it has an intermittent fuel starvation problem. (plus his son has a '90 190E 2.6) So I think for now, he'll be hanging on to the fuel-pumps and anything else he can salvage from the wreck.

Happy Motoring, Mark

Ok, I apologize. That was nasty sorry! Sorry to offend.

I may eat my words, but the engine/transmission from the 1990 should drop right into the 1992. There were no major differences between components or wiring between those years. Its easier to R&R the engine with transmission attached IMO.