W124 Wiring Loom Issues

[eyelight]

Is the whole disintegrating wiring loom problem which plagues mid 90's 6 cylinder cars, confined to these models, or is it an issue with 4 cylinder E class cars too ?

And is the probability of needing to replace the wiring loom based more on mileage or on the cars age ?

Thanks for any info.

 

[television]

Is the whole disintegrating wiring loom problem which plagues mid 90's 6 cylinder cars, confined to these models, or is it an issue with 4 cylinder E class cars too ?

And is the probability of needing to replace the wiring loom based more on mileage or on the cars age ?

Thanks for any info.

Its mainly the 90-92 cars as a bio cable was used,A new part harness is available from MB and not to hard to fit. Nothing to do with milage more age and hit the 124 and 129 the worst.

Malcolm

 

[eyelight]

Thanks Malcolm,
I had thought it was more a problem with the 94-95 cars.

Currently thinking of buying a 94 E280 with 110,000 miles. Haven't got a chance to go look at it yet, but the seller was unaware of this potential problem.

 

[television]

Thanks Malcolm,
I had thought it was more a problem with the 94-95 cars.

Currently thinking of buying a 94 E280 with 110,000 miles. Haven't got a chance to go look at it yet, but the seller was unaware of this potential problem.

All 94 cars are clear of this,so no worries, not a bad build year most models



Malcolm

 

[124coupe]

Sorry that's not correct. W124 up to 95 are affected. Many will have had new harnesses but all should be checked before purchase.

My own 95 E320 Coupe had a new harness (according to the receipts) in 2000 and the "new" one still looks like new (except where the installer broke one of the knock sensor cables).

 

[YoYo_Balls]

Is the whole disintegrating wiring loom problem which plagues mid 90's 6 cylinder cars, confined to these models, or is it an issue with 4 cylinder E class cars too ?

And is the probability of needing to replace the wiring loom based more on mileage or on the cars age ?

Thanks for any info.

the most common problem is caused by heat at the plugs causing the loom to break up.

 

[kth286]

eyelight

124coupe is absolutely spot on.

It is the 2.8 and 3.2 litre straight six (all electronic) engines. Called HFM.

These engines were introduced around 1992 and went until 1996 ish in the W124 and then contined in the later 210 range.

It seems as though 1992 to 1996 are the bad years.

These engines are found in most models across the Merc brand.

 

[eyelight]

Thanks all,

Are the 4 cylinder cars affected by this problem?
W124 E200 and E220.

We currently have a 94 E220 Coupe, but the recent arrival of a baby means 4 doors are better. Getting a baby seat into the back of a coupe gets old after a while, plus it means pushing the front passenger seat way forward.

So looking for an estate to augment the coupe. Actually that's what we were looking for when we bought the coupe, but other than an OVP relay right after we bought it, it's been very reliable over the past 18 months.

So should I contain my search to E200 and E220 estates. Budget for an estate is about £2000, give or take a bit, and currently see some N reg ones in that range, plus a 1991 230TE which looks in rather good nick too.

The E280 I had been thinking of is on eBay, but the wiring loom problem makes me wary.
http://cgi.ebay.co.uk/ws/eBayISAPI....MEWA:IT&viewitem=&item=190072793400&rd=1&rd=1

Same seller had a very nice E220 last week which i should have bid on.

 

[3146bj]

Its mainly the 90-92 cars as a bio cable was used,A new part harness is available from MB and not to hard to fit. Nothing to do with milage more age and hit the 124 and 129 the worst.

Malcolm

It's also '93 build cars.

 

[television]

It's also '93 build cars.

its almost as though there are two kinds of wiring problems involed

malcolm

 

[eric242340]

Well this is very interesting, glad im not the only one to confront this problem. We have found so far that the 104/119/120 engines fitted to the 92-95 range of ths S Class 140 are all affected by heat. Not related to mileage or car age. Certainly the 104 engine can be found in C and E class of the same era. Taking it a stage further, tests have proved that engine working at normal temperature does damage the loom, so its not an overheating problem it appears the looms made in the 92-95 period were not up to the job. If my memory serves me correctly, there was a modified loom on the market as early as 94ish.

 

[kth286]

eyelight

I see nobody has answered your original question regards 4 cylinder engines.

The main problem with the engine loom on 6 cylinder cars is the feeds to each coil which are buried under the top engine cover plate.

I do not know off the top of my head whether the 4 cylinder (all electronic engine) coils are buried under the cover plate and over the spark plugs in the same way.

If they are, then I guess a potential problem.

Under the engine cover the outer wrapping needs to be snipped open to reveal the actual wires inside which go to each coil.

It is the actual inside wires where the insulation has crumbled off and caused the individual wires to short out the coil/s that cause the problems. It can also then cause the output drivers of the ECU to blow.

Every time a spark plug change is done the wires have to be moved and more movement then causes more insulation to fall off the individual wires inside thus exaserbating the problem.

 

[television]

I have to go along with kth286 well written answer, it will not better,if left it could prove expensive.

Malcolm

 

[eyelight]

eyelight

I see nobody has answered your original question regards 4 cylinder engines.

The main problem with the engine loom on 6 cylinder cars is the feeds to each coil which are buried under the top engine cover plate.

I do not know off the top of my head whether the 4 cylinder (all electronic engine) coils are buried under the cover plate and over the spark plugs in the same way.

If they are, then I guess a potential problem.

The plugs on the 4 cylinder multivalve engines are under a cover, just like the 6 cylinder, so I'm guessing that they could well be plagued by the same problem. I've just never heard anyone mention it.
Maybe there are fewer 4 cylinder owners frequenting this forum.

Was this issue rectiified towards the end of the W124 model run ?
Quite a few N reg cars about.

 

[kth286]

well, my coupe is N reg and that loom had the insulation in bits and kept shorting the coils, so I changed it out myself.

The cost would be less than my £443+VAT (approx), for a 4 cylinder car. But if you sub out the work the labour is on top of that. Figure 2-3 hours depending if they ever changed one before. I actually allowed myself a day and it all worked out OK instantly, and has not missed a beat for over 13000 miles now.

 

[Hurm]

Recent price!!

well, my coupe is N reg and that loom had the insulation in bits and kept shorting the coils, so I changed it out myself.

The cost would be less than my £443+VAT (approx), for a 4 cylinder car. But if you sub out the work the labour is on top of that. Figure 2-3 hours depending if they ever changed one before. I actually allowed myself a day and it all worked out OK instantly, and has not missed a beat for over 13000 miles now.

I have recently aquired a 280TE and just joined the forum. The car was purchased very cheaply as it has a really bad missfire. Im absolutely certain that its the loom so I trundled down to the dealer to get a price....bl**dy hell £592+vat and labour at £88 per hour. I think not......having spent 18 years previously in the motor trade I will be repairing the existing loom myself, 592+vat buys an awful lot or wire,solder and connectors !!!

 

[Apial]

As far as I am aware the 300-24 fitted with the non-HFM M104 engine is trouble free, so contrary to what Television says, 90-92 engines have the older non-recyclable plastic insulation that came in with the 320s.

 

[kth286]

Hurm

I suppose it depends how much value you put on your time, and whether the car is a second (project) car.

Also whether it is a keeper, and whether you want to keep it's condition as original.

Also there is the risk element, of the repair not working properly , because the coil feeds shorting on this engine have a habit of blowing the main ECU.

That's £1,000 in round figures (just for the part) and the subsequent main dealer 'star system' programming of codes.

 

[Hibbo]

I have recently aquired a 280TE and just joined the forum. The car was purchased very cheaply as it has a really bad missfire. Im absolutely certain that its the loom so I trundled down to the dealer to get a price....bl**dy hell £592+vat and labour at £88 per hour. I think not......having spent 18 years previously in the motor trade I will be repairing the existing loom myself, 592+vat buys an awful lot or wire,solder and connectors !!!

Absolutely!

600quid for a loom?

We are not talking about state of the art electronics, or ANY electronics for that matter, we are talking about WIRES.

That is an absolutely astonishing price!

Whilst I can sort of understand where kth286 is coming from if you REPAIR the insulation damage on the old loom, but if you make a new one yourself then there is absolutely no danger whatsoever.

Having no experience of these engines, when I heard people discussing needing a 'new harness' and the prices quoted, I assumed it was a high-tech bit of kit incorporating all sorts off sensors and electronics.
Then I saw a home-made one and realised; no, it is quite literally JUST A LOOM OF WIRE. £592+vat??! Unbelievable!

 

[124coupe]

Good luck repairing the loom, you will need to cut apart a mass of connectors and binding on the old loom and then hack it all back together.

I hope you rate your time as "free" and are happy with a long time off the road.

A new loom takes a morning to fit DIY first time.