Sealing a hole in the firewall for a throttle cable

[Alex Hodgkinson]

Hi all,

I've been pondering over how to this ever so often over the last few months while I pressed on with other jobs on my car. Now I need to get it done though so I thought I'd ask what everybody has done on here to seal the hole their throttle cable passes through in the firewall.

Here's a picture as it is right now:



As you can see I've pushed a gromet into the hole for now but it's such a thin panel it's not a real solution. Those two holes below the throttle cable are for brake and clutch reservoirs, and are providing me with the exact same problem.

Any input and photographs would be appreciated!

[Al Weyman]

a nice blob of black silicone mastic?

[VIVA GT]

Back in the day we used to use a non-setting, but sticky putty called Dum-Dum for this. (Way before silicone sealer Al!).

[dtype38]

If you want a simple mechanical solution, use a cable gland. Its a hard plastic panel seal for getting wires in and out of a control box but keeping it waterproof. They usually have a hex section and a threaded section which pushes through the panel and is held by a back nut. There is then a rubber seal ring and a threaded section which slides over the cable and screws into the gland. They come in various sizes and only need a hole a little bigger than the cable. You should be able to get some from any electrical wholesaler or possibly even B&Q

[MGDavid]

Originally Posted by VIVA GT

Back in the day we used to use a non-setting, but sticky putty called Dum-Dum for this. (Way before silicone sealer Al!).

Eldro Dum Dum (no hyphen) still made, available on the 'bay (of course)

[dtype38]

This sort of thing. I believe you can get metal ones as well.

http://www.adaptaflex.com/types.asp?ID=147

[Alex Hodgkinson]

Originally Posted by dtype38

If you want a simple mechanical solution, use a cable gland. Its a hard plastic panel seal for getting wires in and out of a control box but keeping it waterproof. They usually have a hex section and a threaded section which pushes through the panel and is held by a back nut. There is then a rubber seal ring and a threaded section which slides over the cable and screws into the gland. They come in various sizes and only need a hole a little bigger than the cable. You should be able to get some from any electrical wholesaler or possibly even B&Q

Great, that's just about exactly what I had in mind to make up so that's backed up what I was going to do. I will have to fab one either way because the throttle cable OD is ~8mm and those glands seem to be ID 10mm at smallest.

Regarding the putty/silicone solutions - I'm not a fan to be honest. I can see it will do the job but I much prefer mechanical solutions.

Now, time to start my next thread...

[dtype38]

That was just the first example I thought of. A quick google for "miniature cable gland" brought up this as the first listing: http://www.pro-term.com who's larger range are for cable sizes 6 - 9 mm dia. Or here's some nice brass ones in similar sizes: http://www.mossexpress.co.uk/mss/mss...T-82KKL2-51883 , I'm sure there are lots more. Why make something when you can buy it ready made :-))

[Dom]

I dont see what the problem is with a rubber grommet? never seen one fail - even on 20yr old cars, so why re-invent the wheel?

[Alex Hodgkinson]

Got some (free) cable glands on order, thanks for the pointer.

I tried a grommet but the panel is so thin it just didn't want to stay in place.

[jerryk]

square of fibre board drill hole right size in centre, cut in half through hole and fix each half with 2 screws . job done .

[RPD Motorsport]

A good question was asked earlier;
Why do you need to perfectly seal the bulkhead? If a grommet is a bit loose due to how thin the pannel is, find a washer with the same ID as your hole and use it to pack the grommet.
By making a more perminant seal you may be leading yourself for a fall in two ways-
Teams never make a tight seal as belive it or not the massive vibration and chaifing this can cause has been shown to lead to cable failure in the past. Secondly if you need to change any of those cables/hoses in a hurry you will find yourself cursing at the task of getting them in quickly!

Not kocking it, as i know it feels/looks good to have everything 'perfect', just think about if its needed.

[dtype38]

Good points RPD, but I can also see the case for a comprehensive bulkhead seal. On my own car I had a fuel hose split and spray fuel on the bulkhead. The first I knew about it was a strange damp feeling on my left ankle. Fortunately there wasn't any fire, but I quickly changed my mind about "simple rubber seals".

[RPD Motorsport]

For sure you need to think of the pros/cons both ways...
Look at it in your car, what situation are you in, if a 2mm gap could cause you danger in your situatuin, seal it! If not leave a bit of space.
It there room on the ends to get a few bits of heat shrink over the lines/cable? If so it could be a neat, tidy way to bulk the lines up a bit to make then snug.

[watty]

Don't know what your rule book say's, but here in NZ firewalls front and rear must be fume and liquid proof - so no holes at all!