e320 (95) wiring loom

[gt-83]

checking under the bonnet today and i noticed my wiring is cracking and showing the copper in one or two very small places, ok so i knew when i bought the car this has been an issue with these models, my question is do i need to replace now with no running faults or is it good for a while and do i have to buy this loom from the dealers or is there an alternative

 

[moakesr]

If you want to keep the car long term, and you can afford it, then I would definitely get the loom changed.

Loom failure can have a cascade effect, which may lead to ECU/Coil failure which will turn out very expensive

 

[grober]

checking under the bonnet today and i noticed my wiring is cracking and showing the copper in one or two very small places, ok so i knew when i bought the car this has been an issue with these models, my question is do i need to replace now with no running faults or is it good for a while and do i have to buy this loom from the dealers or is there an alternative

Do it for the reasons above. Relatively easy DIY which can cut the cost.
http://www.mercedesshop.com/Wikka/M104WireHarness

 

[gt-83]

are there alternatives to main dealers for these,,,,,,just that ive seen some very steep prices thrown around 5-600 pounds!! seems expensive

 

[grober]

are there alternatives to main dealers for these,,,,,,just that ive seen some very steep prices thrown around 5-600 pounds!! seems expensive

Sorry no other source unless you are prepared to make one yourself. Try to negotiate a discount and shop around several dealers.

 

[gt-83]

Sorry no other source unless you are prepared to make one yourself.

mmmm, now you have got me thinking,,,,,cant be that hard can it?,,,,anybody else tried?

 

[nick mercedes]

mmmm, now you have got me thinking,,,,,cant be that hard can it?,,,,anybody else tried?

Imagine how many wires there are...

 

[normanr]

I have seen those spiders before Graeme they are called LOOM SPIDERS LOL.:bannana::bannana:

 

[imadoofus]

"How hard can it be?"

The war cry of the eternal (and prematurely demised) optimist...

 

[gt-83]

have you had to replace yours???

 

[imadoofus]

have you had to replace yours???

No, but I've a nasty feeling I'm about to...

 

[Mark300SL]

If you have the time and the patience you can do a very effective repair with heatshrink/insulating tape and cloth tape for about £30

Mine took about 8 hours but I KNOW for sure its now OK. I have ordered an ECU and coilpacks but I am completely confident in the harness

http://www.mbclub.co.uk/forums/showthread.php?t=51471&page=4


I did check resistance of every wire with a multimeter to check I didnt have a high resistance anywhere and I was fairly confident of my soldering abilities - though the actual soldering job is about as basic as it can be.

 

[kth286]

gt-83

It does not really matter that the wires are showing on say a connection to the coolant temperature sensor.

The VERY important bit is under the engine cover where the coil feeds are.

You need to carefully clip back the outer covering on the wiring to the coil feeds and you will see the hard insulation cracking.

DO NOT BEND THOSE CABLES AT THIS TIME.

One day, without warning, you will start your car and blow one of the coil packs and the engine will now be on 4 cylinders instead of six.

The problem is this fault can simultaneously blow one of the output drivers of the main engine ECU. That will have to be repaired at cost of say £300 plus cost of coil say £55.

The good news is that there seems to be a repair kit for the 3 coil feed wires at a considerable cost saving to replacing the complete loom.

Enquire at your local main dealer for info.

 

[Dieselman]

What about loom manufacturers.?

http://www.sbdev.co.uk/Engine_Management_Systems/Adaptor_Looms_GroupN/Ignition_Only_Wiring_Looms.htm

 

[Roger Jones]

There's also:

http://www.autosparks.co.uk/

For what it's worth, the MB E-class owner's bible suggests that limited bits of insulation breakdown can be dealt with:

" * Wrap a small piece of pliable plastic (cut from an empty factory coolant bottle, for example) between the touching wires.

* Tape and shrink wrap the wires and reseal the set."

Perhaps worth trying as a short-term measure, but, as suggested above, if you are going to keep the car then bite the bullet and get a good independent mechanic to do the job.

 

[Dieselman]

Thanks Roger. That's who I was searching for but I couldn't find them...Doh..!!

 

[gt-83]

thanks for all the advice here,,,this forum is amazing,,,gentlemen all round...(and ladies!).i think in summary i have to keep a close eye on the important bits, whilst waiting for a good price on a new loom (wonder if they will be cheaper as the model dies out or command a higher price!!)

 

[Dieselman]

Nothing to stop you doing what Mark's done before it gets necessary.

Remove the binding tape and seperate the wires. Cut the wires, slide heat shrink over the insulation, solder the cut wires back together and heat the tubing with an air gun then re bind the loom.

Not hard or particularly time consuming at this stage.

 

[Mark300SL]

Nothing to stop you doing what Mark's done before it gets necessary.

Remove the binding tape and seperate the wires. Cut the wires, slide heat shrink over the insulation, solder the cut wires back together and heat the tubing with an air gun then re bind the loom.

Not hard or particularly time consuming at this stage.

Not particularly difficult either - very little cost and a few hours of your time

I discovered the failings in mine just by (effectively) changing the plugs! When I removed the coilpacks for a cleanup I "folded" the wiring back and at that point all the insulation just seemd to turn to powder, but of course I couldn't see that happening - and my harness looked perfect so I wasnt looking for it!


My findings are exactly as mentioned above - the wires in the very close proximity of the head are the ones most likely to fail. Unfortunately these include the wiring to the coilpacks and the injectors. All of which have individual drivers in the ECU. If the coilpacks or injectors short then you could have a failure like mine where all of the injector drivers have inexplicably failed leaving the ECU as good as scrap. I will try a repair once its all up and running again but for now I am going on a S/H guaranteed ECU and new coilpacks just to be sure.

I would be looking inside the sheathing on the coilpack wiring for damage as an absolute minimum if you own an HFM M104 engine - regardless of its age or current good running status.



Mark

 

[Dave Lewis]

This appears to be a time-related issue, where the degradation is accelerated by high temperatures, although other parts of the harness documented to be at risk are the coolant temperature sender on the water pump, inside the throttle actuator, and the cable leading to the MAF. I've got a complete new harness, I justify it by calling it preventative maintenance. They're vin dependent, mine cost a whopping £600 so I'll be keeping this car for a long time.
Since the youngest of these cars is now 12 years old, I'd definitely recommend anyone with an HFM/SFI M104 to investigate the harness thoroughly.