View Full Version : Wiring harness insulation

02-11-2011, 04:55 PM
Hi guys,

I'm in the middle of picking my engine compartment apart for various maintenance issues that need to be taken care of and as part of the disassembling I have to disconnect pretty much the entire engine wiring harness and move it to the side. I want to take the opportunity to fix/replace broken/cracked/rigid wire insulation. It seems that most if not all cables have wires pulled into the black insulation, so it should be relatively easy to pull them out of the old and pull into the replacement insulation. I've attempted to fix the cracked places before by removing the rigid parts of insulation and taping over, but what I really want to do is to completely replace the old insulation at least on some of the cables. Any suggestion on what kind of insulation tubing is suitable for this?


02-22-2011, 10:54 AM
It seems that the heat shrink type of insulation can be used, but I'm not so sure. I would rather stick with the type that is close to the original, but what is it and where to get it? Any suggestions anyone? Thanks!

02-23-2011, 04:47 PM
This looks good: Nylon Expandable Braided Sleeving (http://cableorganizer.com/nylon/).

Any thoughts anyone?

02-24-2011, 06:12 AM
If you use braided sleeving be sure to either cut it with a hot knife or put heat shrink tubing over the ends. Better yet, do both.

02-24-2011, 07:03 AM
There is only one thing I don't like about braided sleeving, that it does not protect the wires from the outside dirt and various liquids, which I would think should not be an issue for the wires, it just makes for a harder cleanup.

I'd like to go with something that as close to OEM as possible, here is a nice option: PVC Tubing Wire Conduit 1/4 inch (http://cgi.ebay.com/ebaymotors/PVC-Tubing-Wire-Conduit-1-4-inch-Black-10-ft-roll-_W0QQcmdZViewItemQQhashZitem3f0544325eQQitemZ27067 1295070QQptZBoatQ5fPartsQ5fAccessoriesQ5fGear). The problem here is that it's rated up to 105C, which seems too low for comfort. I read in several places that modern electronic components targeted for the engine bay should be rated up to 150C.

Anyone knows the source for the above, but rated for higher temperatures?

02-24-2011, 02:06 PM
105C rated tubing is going to melt or catch fire. Don't use it.

02-24-2011, 02:09 PM
105C rated tubing is going to melt or catch fire. Don't use it.

Agree. What do you think about the braided option?

03-08-2011, 09:28 AM
After some more research I've found this: Silicone Coated Fiberglass sleeving. It is braided on the inside and then silicon coated on the outside. Rated up to 200 degree Celsius, flexible, can be ordered in black and is available in many sizes. I think it would be perfect for the job, the only trouble is that it is not easy to find and is mostly sold in big spools. I've found one company that sells it in reasonable quantities (from 10' and up), but their pricing is higher then in another company that I've found, but I'd have to get 100' spool of one size and 250' of another and it adds up. If anyone is interested in this, we could share the spool and split the price.

03-09-2011, 01:58 AM
Sorry. I've been lurking but haven't had the time for a decent reply.

I've only used braided sleeving on indoor installations. Automotive I usually use a heat shrink that will stand up to automotive use. Most home stuff doesn't last in a car.

I did put braided sleeving on a cooling system hose on my pickup truck. The original hose was rubbing on a part and wore though. That was ages ago and I don't remember what I used.

Ummm you probably already saw this:


Mouser stocks or can get PIF200x line but as you already noticed it isn't cheap and you have to get a whole spool.

Parts Express might have something. http://www.parts-express.com -- I'd check PE's outlet and their eBay stores. I haven't really looked at their catalog since I moved to the UK. I've bought Techflex from Parts Express. That would be ok in some places in a car. Not sure about using that for a main wiring harness though.

MCM used to be good but they really aren't anymore.

Digikey might have something but like Mouser it won't be cheap.

03-09-2011, 09:20 AM
Thanks for the info. I believe the first link lists the same silicon coated fiberglass sleeving that I've found. I've just placed an order for 4 different sizes of 200C silicone coated fiberglass from KJCO (http://www.kayjayco.com/catPCCoverings.htm). Should have it next week.

03-20-2011, 08:34 PM
I got the new insulation in four different sizes and it looks and feels great (see the first photo).

I decided to take on the knock sensors as the first thing to restore. I started on it and the deeper I went the more frustrated I've become (see the pictures). When I got the rubber boot off the connector and exposed the wires, turned out that the insulation on the wires is no better then the external insulation. I then cut about 1/4" section off the black outside insulation to expose more of the wire in hope that the covered part of the wire preserved better, but it was the same, cracked and dried out. I have a used spare sensor that I could experiment on so I cut the cable on it close to the sensor to see the wire condition and discovered that the closer it got to the sensor, the worse it became (the closer you get to the sensor, the more you are subjected to the high temperature).

New sensors are at least $75 each and I don't feel like it's a good way to spend the money since it's going to be the same Bosch part, which will fail the same way and the thing that fails is the cable, not the sensor, and paying $150 for 3 feet of crappy cable is a bit much in my opinion. So I'm going to attempt a repair.

Overall I'm getting disappointed with the quality of a lot of rubber and plastic parts used in the car. I believe 13 years and 80k miles is way too young to have rotten wiring and falling apart trim pieces. This is my first BMW so I can't really tell if it's only this generation or not. Can anyone who has multi-generational experience chime regarding the quality? I'm just curious.