W124 Engine bay wiring looms

[Phileas Flash]

Hi all,
my new W124 has the dreaded insulation issue and I'm weighing up my options on getting it resolved. It doesn't affect the car yet, so I'll try and sort it before it does.

It's my only car so time off the road is crucial.

I've found a motorsport wiring loom company who told me they can take my old harness and sort it out for about a third of the price that MB have quoted me. Not a bad option, and the alternative is DIY. I'm handy enough with a soldering iron to think I could rewire it myself.
A good way for me to do that would be to take a harness and replicate it using the original connectors, and swap that out for my existing harness, giving me minimum off road time and less worry while doing the job.

Would anyone have a knackered old one lying around that I could use for this purpose?
The part number is 124 440 5332.
I intend to take photos as I go and if I follow that route would be more than happy to make a kind of how-to.
Thank you chaps,
Phileas Flash

 

[Tankman]

Hello fellow crunchy loom sufferers. Had my R129 5.0L MOT'd recently which showed up a problem with emissions and an intermittent misfire. The guy testing suggested coil pack or lead. The problem isn't affecting the car that much although I am now conscious of the imbalance this misfire makes on the normally silky smooth engine. Car is 1998 and has 150K miles now.

Haven't yet carried out any real investigation into the cause but whilst replacing the perished top breather hose witnessed first hand the crunchy insulation to the injectors.

Have seen prices of £500+ for new looms as a last resort in other threads but will check the MAF sensor wiring first as that is secured onto the cam cover and is most susceptible to heat degradation there.

 

[OKONJI]

What year is this w124 230E Vin No. WDB1240211B095611

 

[timshap]

Wiring loom

Just about to fit my new upper engine loom on the E320. Having tried to repair the old one which I was told by an engineeering firm who repairs such I managed to get a new one from inchcape delivered for £690

I am sure the delphi label states manufactured in 93 though?? so the parts dept did well out of me then....

In reality i need it on as the car is off to a professional paint shop on Monday.

 

[grober]

i was told ny a mercedes engineer when i was atending technician training in florida that the insulation on the wiring was a formulation by Delphi to make the wiring less palatable for rodents.. we called it SOY wire as it seemed an appropiate name for edible material lol

The story I heard was that the insulation was deliberately made biodegradable so that the wiring would decay in landfill sites. Such are the changes now in the world economy that people would be digging it up to recover the copper! Rumoured to be supplied originally by our own UK Joe Lucas

 

[grober]

Hello fellow crunchy loom sufferers. Had my R129 5.0L MOT'd recently which showed up a problem with emissions and an intermittent misfire. The guy testing suggested coil pack or lead. The problem isn't affecting the car that much although I am now conscious of the imbalance this misfire makes on the normally silky smooth engine. Car is 1998 and has 150K miles now.

Haven't yet carried out any real investigation into the cause but whilst replacing the perished top breather hose witnessed first hand the crunchy insulation to the injectors.

Have seen prices of £500+ for new looms as a last resort in other threads but will check the MAF sensor wiring first as that is secured onto the cam cover and is most susceptible to heat degradation there.

A 98 car should not be affected by the early 90's biodegradable wiring loom issues although all modern wiring in close proximity to the engine eventually runs the risk of going brittle as the heat of the engine accelerates the loss of the flexible plasticiser leaving only the brittle inert filler behind which will crack as soon as its disturbed by movement or vibration.
The motto should always be handle all engine loom wiring gently and avoid excessive bending if at all possible.

 

[super-muffin]

I've found a motorsport wiring loom company who told me they can take my old harness and sort it out for about a third of the price that MB have quoted me. Not a bad option, and the alternative is DIY. I'm handy enough with a soldering iron to think I could rewire it myself.

Not being handy with the soldering iron, could you let me know what company you talked to and roughly what the price they were quoting? My 320te loom as completely gone!

 

[Phileas Flash]

Not being handy with the soldering iron, could you let me know what company you talked to and roughly what the price they were quoting? My 320te loom as completely gone!

Sorry for the delay, I hope I'm not too late...
They're called Si-Leck.
Their website is here> Welcome to Si-Leck Motorsport Wiring

I can't vouch for them as I haven't had any work done as yet.

 

[Phileas Flash]

I've now removed the crunchy harness and posted it to Si-Leck today. The guy there was saying he replaces all the wiring with motorsport grade wire, and will fit all new connectors where possible and re-use the old ones where not. I posted the harness on the plastic tray as he said they'll re-fit it as it was. The removal job took longer than I'd hoped, but these things always do. About 3 hours or so.
I'll update to report on the results. Fingers crossed as the E280 is my only car and I need it for work!
And the key point that I forgot to mention earlier? £300 + VAT.

 

[inniminiman]

My 1992 320TE had started to suffer too from the dreaded cracked insulation problem, so much so that I was even afraid to change the plugs in case of disturbing the cable, and the engine would stall/race at times . After reading all the previous entries I bought a similar LHD 2002 loom from the USA , with import duty it came to just under £300. I mapped out which colour wire went to each plug on both looms , and the only significant difference was that the ETU wires were missing on the US loom. The new looms ECU plug cover was easy to open, as there was only a minimal amount of black silicon caulking round the neck, and this was teased out with a pick. The original loom's ECU plug was a dog, had to be sawn in half and sliced off as it was completely filled with araldite. I could not find a way to de-latch the 8 spare contacts I needed for the ETU cables,as there were none fitted to the new loom and had to resort to sawing spare ones out of the old ECU plug. It was then a case of adding 8 new colour coded cables from the ECU to the loom end of the ETU plug (I didn't open this plug as the old wiring insulation was good here, I spliced them all about 15cm away. I also spliced in 55cm of extra wiring to the MAF sensor so it reached across as normal..
At about the same time I also rewired a spare ETU (£80 on ebay) from its innards to inside the connector plug as I knew mine had shot wiring.
The replacement loom went on last December and 5k miles later, there have been no electrical faults with the engine. The new loom was 124 440 5632 (93/94 M104 engine) and the original was 124 543 8133. One thing I did before I started was to read all the posts on the engine loom issue, and I'd like to give a big thanks to everyone who's contributed here over the years. As I only joined the forum this year having moved up from the world of W123 estates after 12 years of running them, I hadn't quite expected the complexity of W124 problems that have faced me . You guys gave me the confidence to tackle this major issue , and its worked out very successfully..Thanks immensely,
Chris
(I've also read all the posts on stopping the head gasket oil leak,having done the top timing chain cover a couple of times. -I'm taking everyone's advice and getting a specialist to do the head gasket job)

 

[Phileas Flash]

I'm back with news.
I removed my harnessa and posted it off to Si-Leck (Welcome to Si-Leck Motorsport Wiring)
The guy there (Simon) advised it would take about a week. It was a little longer than that in reality but I would recommend him and his work He replaced all the wiring but reused the connectors. They are all still solid and don't feel at all fragile as a result.
The finished work looks good, he clearly knows what he's doing and knows these engines and could point out parts to me off the top of his head. He offered useful advice and was more than happy to take time to talk to me.
When I originally refitted the fixed harness the car wouldn't start and Simon was helpful and happy for me to return the harness which he retested and even put in a car to prove it. This gave me faith that the problem lay elsewhere, which it probably did. I don't know what it was but in all my checking relays and spark plugs, it's just vanished.
Conclusion:
I'd definitely send it off to him again and get it rebuilt for £360 rather than get a new one at upwards of £900.

I hope this can help some people and save a few of these cars from the scrappy.

 

[Oldandgrumpy]

Any old looms?

Very useful thread and site, awesome expertise.

Not sure if this is the right place to post so mods please move it if I have got it wrong ( old age and stupidity is a speciality of mine).

Does anyone have an old wiring loom For the M104 that they want to get rid off?

I want to DIY a loom but can't afford to have my car off the road.

 

[Williamwoo]

I would have thought that, even if you could get hold of an old loom, it may not be that helpful as looms can vary considerably depending on options fitted to the vehicle (I believe).

 

[trickk123]

mercedes 190e 2.5 16v

Hi everyone im new to this forum and i would like some help from you
i have mercedes 190e 2.5 16v 1989 automatic and i would like to convert to
manual dogleg gearbox is someone who done this and what sort of expenses
and maybe you now someone who selling parts to 2.3 16vor 2.5 16v in london or near,thank you for reading and waitin for responde

 

[tjamesbo]

Whils putting a new cat and lambda on the 124 I found this

and thats the good section
Its the Harness that runs to the MAF Now mines a 93 220TE with 4cylinder M111 Engine I didnt think they suffered like the 280 or 320's
Obviously this is the bit thats above the exhaust I was hoping I could renew just that bit It then goes behind the plastic covers by the wiper motors I have yet to work out how to get at this section and where it goes

Cursory look around shows most other harnesses look OK any others I need to look at ?
Boyd

 

[Druk]

On a 320 engine it goes all the way directly back to where the main harness exits the ECU. The maf plug on mine was a sealed unit and I had to Dremel it open to get at the wires then mastic it shut when repaired.






.

 

[hotrodder]

Obviously this is the bit thats above the exhaust I was hoping I could renew just that bit It then goes behind the plastic covers by the wiper motors I have yet to work out how to get at this section and where it goes

It runs all the way through the small gap between the engine partition and heater intake box. If you pull of the rubber weather strip the joins/clips and screws will be more apparent. Some are obvious, some less so... http://www.w124performance.com/service/Index/MiscFiles/83-140.pdf explains better than is possible with words alone but the various 'wiper how to' with pics should be clearer still. Don't need to take it all apart as the loom is just trapped between the partitions, once a few fasteners have been removed/loosened the loom can be got at. As Druk said it goes all the way back to the ecu, from memory on my 320 it rejoins the main loom shortly after it emerges from the other side of the engine partition.

Cursory look around shows most other harnesses look OK any others I need to look at ?
Boyd

The feed to the coils which are subjected to even more heatsoak due to their location. Back on pg1 the repair section for these was discussed along with part # for them. The plugs on these are clipped together but they're so cheap it's not really worth taking 'em apart to replace the wiring. These tend to cause problems after they've been disturbed during say a plug change and if they short have been known to spike the ecu. On the 320 they rejoin the main loom shortly after they exit the rocker cover

 

[kth286]

Don't know why, but the feed to MAF causes more problems on 220 engine than 6 cylinder engines.

It causes problems with diagnose of bad running for those that do not know, but cable easily replaced.

 

[harryk]

Gents, I'm in the middle of getting the harness replaced on my s124. It is being done by a friend who is in the auto-electric trade. He is also responsible for my v12 project in his spare time. We have discussed it, and rather than a repair of the loom where needed, he will create a whole new loom. He has done a few for local rally cars so has experience. I mentioned this thread, and got wondering if anyone here is in need of a new loom for a group buy?
Any thoughts/comments welcome!


P.S. Some of his past work is on his fb page-PM for info Will not post the details in case it breaks rules...

 

[tjamesbo]

On a 320 engine it goes all the way directly back to where the main harness exits the ECU. The maf plug on mine was a sealed unit and I had to Dremel it open to get at the wires then mastic it shut when repaired.

Thanks DRUK I was hoping to meet you and some others at the NEC Classic but by the time I arrived at the correct Lancaster Insurance stand I couldnt see any MB forum members
Thanks
Boyd