Author Topic: Replacing the Firewall Grommet for the Main Wiring Harness  (Read 4872 times)

doitwright

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Replacing the Firewall Grommet for the Main Wiring Harness
« on: September 27, 2019, 22:52:49 »
The one thing I was most concerned about when disassembling my SL was how would I get those wires back through the firewall and replace the totally worn firewall grommet. It is amazing what one thinks about at night when lying awake in bed. So here it is. My solution for fitting a square peg through a round hole.

Keep in mind I did this with the wiring harness removed from the car.

Go to Plumbing Section at your Home Depot or local hardware store and pick up one each a plastic 1-1/4" and 1-1/2" sink tail piece. Do not try this with regular PVC DWV pipe. The wall is too thick. Some petroleum jelly might aid in getting the grommet to slip onto the tail piece.

Make 4 cuts at the end of each tail piece (without the flange) at least 4" long and 90 degrees to each other. That should leave you with 4 cuts.

Start with the 1-1/4" piece and squeeze the cut end so the 4 sections of the pipe start to overlap each other.

While holding the overlapping sections tightly together, insert the cut end into the new grommet.

Once you have the tail piece through the grommet hole, push the pipe through until you get past the cut section and on to the uncut section of your tail piece. The rubber will expand to the larger opening.

I found that 1-1/4" was not large enough to get some of the larger connectors on the wire harness through the grommet so going to the next size tail piece (1-1/2") was just large enough.

The next step is to transfer the grommet from the 1-1/4" to 1-1/2" tail piece.

It was also easier to transfer from the 1-1/4" to 1-1/2" than trying to start with the 1-1/2".

Once you have your grommet fit to the 1-1/2" tail piece, trim the pipe to slightly more than the length of the grommet.

Now you are ready to pass your wires through the grommet.

Once you get the grommet to the same location where your old grommet was located, slide the pipe out of the grommet and cut the plastic pipe to remove it.

There you go.

Here is the link to my google album if you want to see the photos when I did this.

https://photos.app.goo.gl/NJg6gmEt5q6uL6M38

Frank Koronkiewicz
Willowbrook, Illinois

1970 280SL Originally Light Ivory - Now Anthracite Gray Metallic

dirkbalter

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Re: Replacing the Firewall Grommet for the Main Wiring Harness
« Reply #1 on: September 27, 2019, 23:15:14 »
Appreciated,
thank you.
Dirk
66 230 SL
70 280 SEL
53 CHEVY 3100
18 C300 COUPE
05 HD FLSTNI

ja17

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Re: Replacing the Firewall Grommet for the Main Wiring Harness
« Reply #2 on: September 28, 2019, 02:21:14 »
Normally done with all the connectors removed. Lots of work. Hope your new method works.
Joe Alexander
Blacklick, Ohio
1969 Dark Olive 280SL
2002 ML55 AMG (tow vehicle)
2002 SLK32 AMG (350 hp)
1982 300TD Wagon turbo 4spd.
1963 404 Mercedes Unimog (Swedish Army)
1989 flu419 Mercedes Unimog (US Army)
1998 E430
1974 450SLC Rally
1965 220SE Finback

doitwright

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Re: Replacing the Firewall Grommet for the Main Wiring Harness
« Reply #3 on: September 28, 2019, 03:48:14 »
The method works. Photos show the process and results.

Frank Koronkiewicz
Willowbrook, Illinois

1970 280SL Originally Light Ivory - Now Anthracite Gray Metallic

johnk

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Re: Replacing the Firewall Grommet for the Main Wiring Harness
« Reply #4 on: September 28, 2019, 04:00:25 »
Thanks Frank! This is my next step to complete.

John
John Krystowski
Avon Ohio
1968 Euro 280sl under restoration
2016 Jag F-Type R sold june 2021
1950 Alfa Romeo 6C 2500 SS For sale
2008 E350
2007 GL 450
2019 BMW 540

450sl

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Re: Replacing the Firewall Grommet for the Main Wiring Harness
« Reply #5 on: September 30, 2019, 06:55:38 »
I have these pliers , would gladly donate to forum.


mBdrvr

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Re: Replacing the Firewall Grommet for the Main Wiring Harness
« Reply #6 on: September 30, 2019, 17:53:32 »
The guy before me didn't bother with the grommet. Any suggestions on what to use with the wire loom already installed??
Paul Greenblatt
'70 280 SL
'66 250 SE Cabrio
'60 190 SL

Dave H

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    • Dave H
Re: Replacing the Firewall Grommet for the Main Wiring Harness
« Reply #7 on: September 30, 2019, 21:01:59 »
Cut through one side with a craft knife, fit it over and glue with tyre adhesive, possibly use a couple of cable ties to hold it together while the glue goes off, you won’t be able to tell it was ever cut if you do a neat job.

Its a similar job to replacing a CV boot only easier .
« Last Edit: October 01, 2019, 06:59:55 by Dave H »
Mercedes 250SL    1967
Mercedes 250SLK  2014
Alfa Romeo 166 3.2 Ti
Fiat 500

johnk

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Re: Replacing the Firewall Grommet for the Main Wiring Harness
« Reply #8 on: September 30, 2019, 21:13:17 »
I used Frank's method last night. Saved me a lot of time. Took about an hour to hour and a half slide the grommet onto the 1 1/2 inch pipe and then slide into place on the wiring harness. I only had to take a part a couple of the connectors at the end when I had too much wire already in the tube to also slide a connector through.
John Krystowski
Avon Ohio
1968 Euro 280sl under restoration
2016 Jag F-Type R sold june 2021
1950 Alfa Romeo 6C 2500 SS For sale
2008 E350
2007 GL 450
2019 BMW 540

mBdrvr

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Re: Replacing the Firewall Grommet for the Main Wiring Harness
« Reply #9 on: October 01, 2019, 18:13:48 »
Thanks Dave. I'll give that a try.

Paul
Paul Greenblatt
'70 280 SL
'66 250 SE Cabrio
'60 190 SL