Oil Pressure sensor wiring

[tewfiks]

So... I just finished replacing what I believe to be the original oil pressure sensor on my 94 E500. I was shocked on how the wiring to the sensor just disintegrated with minimal manipulation. I now have a bare wire going to the sensor. I wrapped it in electrical tape for the time being, but would like some suggestions on how to repair this in a more permanent fashion.

 

[Duh_Vinci]

Ideally, you should be replacing the entire lower harness, as all but 1 wire (starter wire) are usually crumbling. You can certainly re-do the harness yourself, it is a little time consuming, I did this on SL500, but really, not that different from your E500, here are some details of what's involved for the visuals SL500 progress and thank you all! | Member Roadtrips and Project Journals Alternatively, you can purchased a rebuilt one or have one rebuild by someone (Jono rebuilds them)

Regards,
D

 

[tewfiks]

This is what I am dealing with

 

[tewfiks]

I would gladly replace/ rebuild the lower harness

 

[LWB250]

Replace the lower harness. You're only going to have more issues as time goes on. If you're relatively comfortable with soldering you can rebuild it yourself in an hour or so. R&R will take longer than the rebuild.

I've rebuilt several over the years for M119 powered cars, and it's not a major undertaking.

Dan

 

[tewfiks]

Dan
Did you reuse the plugs/terminals or replace them?
My 95 E420 has been plagued with the same issue now for a year.
Where can I source the correct wires?
Thanks in advance

 

[gsxr]

All the pin bushing housings (plastic connectors) should be available new if needed, *except* the one for the oil level sensor at the engine block... that one has been NLA for a while and I don't know a source for it.

Another option is to buy the "rebuild kit" from Kurth Klassiks overseas, they supply the smaller wires with connectors on each end, and you re-use the main/large cable. The 034 and 036 harnesses are different, btw, if you buy their kits make sure you get the correct ones.

 

[tewfiks]

GSXR

I see four different lower harness repair kits for the 124s.
Would you have the part numbers of the 034 and 036 specific harnesses?

 

[LWB250]

Provide a VIN and we can look up the number...

Dan

 

[tewfiks]

 

[gsxr]

Part numbers are in this thread:

lower/starter harness compatibility | 400E / E420 Discussions

I was curious to see if anyone has noticed any major changes of the lower/starter harness from an e420 and a 400e. It's rather difficult to find a lower harness for a 400e, because I believe they are discontinued. However, I've seen that e420 lower harnesses are still available. I know they're...

www.500eboard.co

 

[kegmankipp]

Another option is to buy the "rebuild kit" from Kurth Klassiks overseas, they supply the smaller wires with connectors on each end, and you re-use the main/large cable. The 034 and 036 harnesses are different, btw, if you buy their kits make sure you get the correct ones.

I order a 034 harness from Kurth last Wednesday and had it shipped to a friend in Germany. It arrived yesterday! He’s adding to a package of parts and sending my way on Monday. I’ll post closeups of harness when it arrives.

 

[LWB250]

The "Positive cable" for your E420 based on the VIN you gave is a part number 124 540 31 30.



I sourced wire locally and got silicone jacketed stranded copper wherever I could. It means you may have to buy a small spool of the stuff, but it's still cheaper than buying a new harness (if that's even an option.) I reused the heavy stuff if it was in good shape. It's been my experience, albeit limited, that the larger cables are usually fine when it comes to insulation. it's the smaller signal and low current leads that seemed to be the most affected by insulation breakdown.

If it was sockets or pins that were soldered, I desoldered them from the old harness, cleaned them up and reused them. No reason not to, they're quite sturdy. I have a pile of pins in my parts collection, so I had spares in the event one was damaged. Depending on the application, there were usually some large ring terminals for the connections to the starter, which I just got from the "magic boxes" at my local Ace hardware. Besides crimping these I soldered them, too.

Also get an assortment of heat shrink tubing for covering terminals when required. If there was a jacket/sleeve along a length of the cable, as there is on the W140 harnesses, I got some high temperature wiring harness jacket material from the Island of Large Wimmen. Good stuff to have on hand, too.

Take the old harness, lay it out on the bench, and lay out your new wires next to it to match length and configuration. Move terminals from the old harness to the new one one at a time. This can be tedious, but it assures that you don't mix anything up. Be careful to recover any grommets or brackets and assemble them into the new harness in the proper location as well.

It's not brain surgery, you just need to be meticulous and take your time.

If you're doing an 034, it's a good idea to tie a piece of string or light wire to the old harness when removing it so you have something to "fish" the rebuilt harness into the holes in the chassis. Otherwise, it's a real pain to wrestle the new and usually quite rigid new wires into the opening and down into the chassis.

Dan

 

[tewfiks]

Dan,

Thanks very much. I look forward to repairing both lower harnesses. I also contacted Kurth and they informed me that both of the repair kits they sell are applicable to both 124s with the m119. They seem to be a good resource as well.
I appreciate everyone that has shared their knowledge and experience.

 

[tewfiks]

Received the lower harnesses and a few other items from Kurth a few days ago. Very high quality at first blush.

 

[LWB250]

Received the lower harnesses and a few other items from Kurth a few days ago. Very high quality at first blush.

Pictures?

 

[tewfiks]

 

[gsxr]

Looks nice! That is for the .034 harness.

Did you also buy their .036 harness repair kit?

 

[tewfiks]

Yes. According to Kurth the repair kit for the .036 and .034 utilize the same kit.
I hope to start the project tomorrow on the 94 E500.

 

[gsxr]

Yes. According to Kurth the repair kit for the .036 and .034 utilize the same kit.
I hope to start the project tomorrow on the 94 E500.

The 034 and 036 use different connectors. They should not share the same kit. Also, the routing is different and I'm not certain if the wire lengths are the same, although if long enough that shouldn't be an issue. The kit you posted photos of is for the .034 specifically.

 

[tewfiks]

Dave is correct, once again, regarding the differing harnesses between the m119 applications. The two Kurth harness repair kits I receivedwere identical. I didn't understand what was being discussed that the 034 and 036 were different. Once I started removing the lower harness from my E500 I quickly realized the difference. The proximal end of the harness differs between the two cars. I contacted Kurth, and they have promptly shipped the proper kit for the 036. Thanks to Dave for being such a tremendous resource to the Mercedes community.

I will update this thread once I have the correct harness kit.

 

[tewfiks]

Still awaiting the delivery of the 036 lower wiring harness repair kit. Original harness has been removed without much issue. I started dissecting the protective sleeve/jacket and was shocked that the three smaller caliber wires were basically bare the entire length of the harness, not just the portion outside of the sleeve/jacket. Any recommendations on replacement sleeves/jackets for my rebuild? So much for the German eco friendly insulation. Stupid idea.

 

[kegmankipp]

Still awaiting the delivery of the 036 lower wiring harness repair kit. Original harness has been removed without much issue. I started dissecting the protective sleeve/jacket and was shocked that the three smaller caliber wires were basically bare the entire length of the harness, not just the portion outside of the sleeve/jacket. Any recommendations on replacement sleeves/jackets for my rebuild? So much for the German eco friendly insulation. Stupid idea.

I received and installed their 034 harness last week. I’d recommend puttin a piece of tape on old harness next to the two metal support brackets so you know where those are spaced as all the split loom plastic will disintegrate when pulling the harness out.

I used this awesome tape

Tesa's Most Advanced High Heat Harness Tape 51036 Mercedes, BMW, Audi, VW https://www.amazon.com/dp/B01I2MLN2Q/

And needed maybe 3’ of 1” split loom and maybe 2’ of 3/4” split loom

 

[tewfiks]

Received the 036 harness repair kit. Very nice!
Of note, the 036 lower harness is longer than the 034 lower harness, so if I had try to modify
the 034 harness it still would be too short.

Looms and tape ordered.

Thanks to all.

 

[LWB250]

Still awaiting the delivery of the 036 lower wiring harness repair kit. Original harness has been removed without much issue. I started dissecting the protective sleeve/jacket and was shocked that the three smaller caliber wires were basically bare the entire length of the harness, not just the portion outside of the sleeve/jacket. Any recommendations on replacement sleeves/jackets for my rebuild? So much for the German eco friendly insulation. Stupid idea.

This is pretty typical. it also gives you an idea why things start to get wacky with gauges as these wires short out intermittently.

Again, look for the high temperature split loom braided jacket for things like this. Here's one possible example:

MGI SpeedWare: Wire Loom

I try to keep a few different sizes on the shelf for whatever needs I have. It's easy to use and is rated for the temperatures that are present in the engine compartment. I haven't used this particular brand, but I've used other similar products with good results.

You can source solid plastic tubing for the job, too, but the split woven tubing is so much easier to work with, accomplishes the same task, and give you the ability to separate things in the future should you need to get into the harness for whatever reason.

Dan

 

[tewfiks]

Finally getting back to the lower harness repair and reinstall on the E500. I am embarrassed to ask but I have forgotten where the brackets and the small wire that comes out near the starter connects. I have been away from this long enough that I have forgotten what I thought I couldn’t forget!

 

[tewfiks]

This is the wire in question

 

[gsxr]

Starter has 2 wires attached, the huge one, and a small one with a ring terminal.

 

[tewfiks]

Thank you

 

[tewfiks]

Another request:
Where do the two brackets attach?
I can not remember nor does anything look obvious

 

[gsxr]

One attaches at the same bolt as the dipstick tube, the other goes at the top/rear of the engine IIRC?

Photos at the thread below should help:

HOW-TO: Replacing Lower Wiring Harness | "HOW-TO" Tutorial Articles

Re: Alternator/belt squeal MODERATOR'S NOTE: Thread for additional context and reference is located here. Alright, wow. That sucked. But fulfilling too... old lower harness is out and new one is in! I have taken some pictures and this is not a professional write up, but I hope it can help...

www.500eboard.co

 

[tewfiks]

Finally completed the reinstallation of the lower wiring harness. I appreciate the collective knowledge of everyone on this web sites' forums.
The bottom bracket's point of attachment is on the bell housing above the transmission fluid tube. The top bracket is on the top of the rear right of the engine sitting just behind the fuel rail.

Now onto the E420 and its lower harness.