M111 to M104 conversion (e220 to e320)

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sagesingh

Active Member
Joined
Jun 12, 2007
Messages
111
Car
'95 W124 E220, '96 W124 E320 Cabriolet
I have the e220 cabrio but it lacks powers so i changing it to a m104 320. i have considered several other options but i think this would be the best.

I consider myself an experienced DIY mechanic, but without a doubt i have lots to learn still, i am carrying out all the labour myself to keep costs down.
I recently purchased a e320 coupe (£700) to use as a donor car and over the past few weeks have stripped both cars down. The following part have been/are being changed:

  • engine
  • gearbox
  • propshaft
  • front brake calipers (pads+disks also)
  • exhaust
  • Radiator
  • intercooler
  • the 320 also has a oil cooler pipe that runs across the rad
  • all the air ducting and water pipes
  • ecu
  • engine wiring harness --- i only removed the wiring connected to the chassis, the rest remained on the engine.
  • gearbox wiring ---- this connects just above the passenger foot well, just as simple and unpluging and plugging in the new one.
  • brake pad sensors wiring --- open the connector in the engine bay and slide the old wires out through the gromet, then thread in the new wires and put the connector back on and plug it in.
  • maybe the left head light, or just the covering behind it as the air intake has something to do with that. didnt really look at it properly.

For ease i didnt remove any of the engine accesories, e.g. altenator, a/c comprossor etc... this saved a lot of time and all i have to do is connect up the pipe work afterwards instead of bolting everything back up to the engine.

there are 2 main differences in the body harness wiring,
  1. on the m111 the lambda sensor is on the exhaust manifold, whereas on m104 its on the exhaust, to do this i cut the wires from the e320 and threaded through the fuse box into the driver side under the carpet and then had to drill a hole into the body of the e220 (where MB has done on the e320 already). I then cut the connector block off the spare sensor and used this to attach the wiring to the original connector block of the e220 making it look original.
  2. on the m111 on sensor, not sure what it is is conected to the left of the engine block whereas on the e320 its on the right. I transferred this wire over too. It is hard to explain how i did it so i will take pics this weekend to show you how i maintained factory look. (in short i cut open the e320 wiring loom and transferred this one wire and placed it into the connector block where the old one was).

There is also a difference in the centre propshaft bracket so that needs changing over also.

Regarding the suspension, i have the bilstein b12 kit that was orignally designed for the 300ce, so that is staying the same.

there is a second wiring loom coming out of the ecu, and there are three differences in the 220 and 320 wiring, I have a copy of the ecu pinout and pins, 9, 22 and 23 are different, the rest of the wiring is the same.

Pin 9 is the transmission overload protection switch, 320 has it 220 doesnt.

Pin 22 is different on both cars, for the m111 it is the cruise control on/off but on the 320 it is the clutch pedal switch. (i 99% sure i am asking a stupid question now, but are clutch pedal switchs only on manuals?) Another question i have is: i do not have cruise control so why is this pin there and not blank in my harness?

Pin 23 is CO potentiometer, i have it on the 220 but not the 320.

Instead of changing the looms over i plan to modify the harness i already have in the 220, i will use this my creating a 'converter box' which i will make from the 220 ecu female socket and the 320 male plug from the donor car. All the wires will be the same apart from these 3, i will block out pins 22, and 23 and wring in pin 9. This will make it look more original, or alteratively, i could just open the 320 ecu and solder onto pin 9 the wire and remove pins 22 and 23, i have not decided yet.

All in the wiring was actually alot easier than i had first anticipated.


The hard bits:

I know i have only really done the easy bits of removing things and the hard bit of putting things back in are still to go, but in all honesty i dont think the work has been hard, just labour intensive. The hardest bit was removing the 320 out of the bay, which i couldn't actually do, so i just ended up cutting the cross member on the coupe, but i cant do this on the cabrio.
so does anybody have any tips on how to get the engine into the bay???

Another question i have is do i need to change the rear dif?? the couplings are the same and the propshaft can just bolt up but are the ratios different?

i will post up pics of the car soon, at the moment i have a few on photobucket.

Merc Carbio pictures by CarPCCustoms - Photobucket

Also change a few broken vacuum pipes, which explained the aggressive gear changes.
On a side note, i have a jenhert install, wald body kit, (did have a custom exhaust, but wont fit on m104 engine so i putting it my brothers e220 coupe) among lots of other little things.
 

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Also have to change over the battery, but thats not really too hard in the grand scheme of things.
 
The car looks nice but I do think the alloys let it down a bit
Change the diff and the speedo to go with it.Also don`t forget to change the brakes as the 320 has bigger 4 pot ones
 
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The car looks nice but I do think the alloys let it down a bit
Change the diff and the speedo to go with it.Also don`t forget to change the brakes as the 320 has bigger 4 pot ones

I agree with you about the alloys, and i already have done the brakes, well almost, painting them black this week and putting them on.

Why go i need to change the speedo? what is different about them?
 
Is best to change the diff as the ratio is different and the speedo works goes with it.
 
Dash - you wouldnt by any chance still know anyone who has a m104 TT kit for sale? did ask you a little while back but pockets were not deep enough then.
 
Aka$h has a brand new one and I think he wants 2k for it
 
Other things that need to be changed are the gearbox lever linkage, and driverside headlight surround.

i have finished connecting the engine up, and the rad, i/c, wiring etc. basically everything at the front of the car is finished, however i am having issues starting the car. the car is on is respect to all the electrics, but it does not crank.

I had a quick look around and everything seems to be ok, and im not sure why to doesnt crank. anybody have any ideas?
 
Is the earth strap connected?
 
Gearbox inhibitor switch? You said that you need to change the gear linkage, maybe the car thinks that it is in gear?
 
afternoon all,

the earth straps are connected.

and i am just about to look at the gearbox switch.

thanks
 
I have check the continuity of pins 3 and 4 on the switch and they are ok, this indicated the NSS is good. im going to start to look at the starter soleniod to check if im get any current to it. but in the meantime, any other ideas would be great.
 
Shes alive. didnt really do anything apart from take the air intake off, and she started. connecting everything back up and it has started 6 times in a row, but on the 7th the battery ran out of juice.

Done for this week, next week i will have the following to finish off: (engine wise)

  • change rear diff and speedo
  • propshaft
  • exhaust
  • drill hole for lambda sensor,
  • mount the brake system, i.e. pads, calipers and hoses

In summary so far the hardest bit is getting the engine into the bay, wiring was relatively simple. I havent changed the ecu wiring as i discussed above, and it seems ok, but i have only turned it over to 10 secs or so.

i will give a full overview next week when if finished.
 
Sagesingh, as a complete non mechanic myself, I admire your courage and perseverance. I hope the rest runs smoothly for you.

One thing, regarding the exhaust. I think I am right in saying that the rear section is specific to the cabriolet, due to the floor pan being deeper to accommodate the workings of the roof mechanism, but I stand to be corrected.
 
so i charged the battery and now it doesnt start. slightly annoying, but thats the way it is with these things. my money is on the starter motor because it sounds as though there is power going to it and it clicks but the solenoid does not engage. i will change this over next weekend and fingers crossed it will rectify the problem.


MD5 -- thanks for the info on the exhaust, you might be right but as i had a custom on previously (now on my brothers coupe) i cant compare them next to each other. i guess i will find out on sunday.
 
i have now changed the rear diff and rear axle drive shafts (after much aggro), the exhaust is going on tomorrow morning then i can take it for a spin, troubleshoot any problems and then finish it up on sunday. :bannana:
 
I got the car mostly finished off today (in the 3 hour lunch break i had). she runs well, the exhaust is on. took it for a spin around the round cul-de-sac i live in.

I never realised how much the car weighs, i done have any power steering atm, ,or brakes really. Need to add all the fluids tomorrow, or maybe next week as i have my volvo to sort out also.

A complete list of what needs to be changed is:

  • engine
  • gearbox
  • propshaft
  • front brake calipers (pads+disks also)
  • exhaust
  • Radiator
  • intercooler
  • oil cooler pipe that runs across the rad
  • all the air ducting and water pipes
  • ecu
  • engine wiring harness
  • gearbox NSS wiring
  • brake pad sensors
  • left head light inside covering behind it as the air intake
  • rear diff
  • rear axle driveshafts
  • speedo cluster

i had a few other bits that i needed to sort out though also, so i changed a fair few other bits too.

I took me 5 weeks to complete the conversion working on average 2 days a week, so about 10 days work in total. there was not really anything too difficult apart from getting the engine into the bay and removing/installing the rear axle drive shafts.

As a quick guide this is what i did:

starting with the e220,

  1. remove ait intake pipes
  2. fan should
  3. remove the cooling pipes
  4. remove intercooler and rad
  5. remove all wiring from the alternator and starter motor etc...
  6. remove exhaust
  7. remove propshaft
  8. remove rear diff
  9. remove rear axle drive shafts
  10. remove front brake calipers
  11. remove engine and gearbox

do the same on the e320 and reverse the process.

the add all the fluids and bleed.
 
I have been driving around for a few days now and a few 'small' issues have arisen.

The main one is the fact that the front brake disk was hitting the backplate on one side and the actual wishbone on the other. as such i have also now changed over the wishbones and the hubs on the front of the car. The car now runs better, without funny noises.

apart from that it is just small little things that tbh are of my own doing.

One downside of the engine in the cabriolet is the fact that is is slower than the coupe, book values state 1.5sec difference, and i really do feel it. During acceleration i definitely remember it being faster but when you get moving its around the same. in comparision to the m111 e220 engine there is so much between them, then ride is smoother, faster and it requires alot less effort to drive now. I would definetly recommend the conversion to anyone but it is very time consuming and i do understand why some many of these conversion get stuck in the middle and abandoned.

On another note, insurance, i got the car insured and there was an increase in my premium but around 300ish pounds which i am happy with. I was expecting alot more but happy days. :)

:bannana:

Now i just have to wait a for the weather to pick up so that i can enjoy it with the hood down.
 

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