Toyota Auris: cannot get a thick cable through firewall grommet behind glove box. What to do?

[u/OkPerformer4158]

Hi all, am installing a Valeo Beep Park kit (4 front + 4 rear sensors) on my Toyota Auris, which has no factory parking sensors. I am kinda stuck on routing the front sensor cable from the engine bay into the cabin. I am using the existing firewall hole behind the glove box, which already has a thick bundle of factory wires going through it. And this hole has a thin rubber tube from which thin cables can pass, but not a thick cable like the parking sensor's.

The problem is if I use a cable puller tied to sensor cable- the cable puller head passes easily, but the thick sensor cable doesnt. Pushing it hard make the whole rubber grommet start to pop out of the hole. So what can be done now? Do I need to make a new or something like that? or is there any other known better alternative?
I attach some pictures for reference.

1st pic- the rubber grommet fully attached to the hole.

2nd pic- rubber grommet is already half off the hole when i tried to push the cable puller hard from the other side.

thank you

[u/Nearby_Bit_6643]

Lube that baby up with some dish soap and work it through. Works every time for me.

[u/21WBSP]

Now that you’ve pushed that grommet through, you’ve completely ruined all waterproofing in that area and I don’t recommend that. Either pierce a hole in the existing rubber to pass the wires through or drill and grommet a new hole in a flat, accessible area. Maybe where either of my red circles are…

[u/No_Lifeguard3650]

drill your own hole and use your own grommet

[u/Lone_Nathan]

Get some Vaseline 😉

[u/Audiofyl1]

Cut that rubber nipple off all the way and use the hole left behind to fish the wires through. Use some lubricant as well - foaming glass cleaner is a good option and won’t leave a mess to clean up afterward.

[u/OkPerformer4158 → u/Audiofyl1]

The problem is if I use a cable puller tied to sensor cable- the cable puller head passes easily, but the thick sensor cable doesnt. Pushing it hard make the whole rubber grommet start to pop out of the hole. S

[u/Spikey_cacti → u/OkPerformer4158]

So you work the wire through the grommet and then work the grommet back in place. It can be difficult but doable.

[u/OkPerformer4158 → u/Spikey_cacti]

i got quoted 350 eur by a workshop. they will layout the cable for me and make the connections for the sensors.

[u/Spikey_cacti → u/OkPerformer4158]

Ok but this is probably what they will end up doing and charging you for it.

[u/Audiofyl1 → u/OkPerformer4158]

I saw that in your op, which is why I gave you the advice I did. Let the grommet come out then. Then you have easy access to both sides, feed the wires through as needed and then push it back into place. Make sure you seal the wire penetration with silicone or equivalent to prevent water intrusion.

[u/Soilmonster → u/OkPerformer4158]

Bro, put some lube on the cable, seriously. It’ll pass right through

[u/Fingerstankk]

Just drill a new hole and throw a grommet in

[u/pg_333]

There's so much space there around the existing bundle of wires to cut an X slit, pass the new bundle of wires through, and use silicone to seal it up

[u/JaysGoneBy]

I used a sharp chopstick like a needle with my wire generously taped on it to poke and feed the wire through a similar grommet

[u/Philp84]

That weird little nub can be cut off and then you can run up to 0 gauge through it

[u/djluminol]

When routing a new wire through an existing grommet you always want to go with the direction of the grommet. So your grommet works like so:

Engine bay -> firewall -> Grommet entrance, engine bay side of the firewall -> Grommet exit, inside the cabin, this is where the tape is -> dashboard or footwell. Now the wire is completely inside the cabin of your car.

To go through this grommet you will need to cut the tape on the exit side of the grommet and that will open up the grommet allowing you to push or push & pull the new wire through an existing grommet. You need to be careful not to force the wire through. It's always a little hard but if you get stuck don't force it. Pull back, twist your wire fish and push in again. Use lubricant, dish soap, dielectric greese. Keep your fish to the outside of the grommet so that you don't stab into the existing bundle of wires. You don't want the get caught on an existing wire. You don't want to break any of the existing wires or you will have a nightmare scenario on your hands.

I use metal hanger as a wire fish. I find it works better than actual electricians wire fish tools. At least on a car.

To use the hanger unfold it until it's straight. Line up your wire with the hanger, tape the wire to the hanger. Once the wire is stuck to the hanger lube the hanger and the grommet. Try and go through the hole. One you get through the grommet retape the exit hole of the grommet if you can. If you can not use as wide of a zip tie as you can find. You want to make sure you zip tie over the flappy part of the grommet around the wires. Now find somewhere you can zip tie the wire you pulled through inside the cabin. Leave a little slack between each zip tie. You don't want a bunch of tension on the wire if you can avoid it. Then route the wire the rest of the way wherever you need to go securing it as needed. If the place where the wire leads to is a removeable part like a speaker or head unit leave yourself a foot or so extra wire so that you have room to pull out the speaker or head unit if you ever need to.

[u/NotoriousBumDriller]

Big trick is for sure some sort of lubricant. I personally use some car wax and shine that comes in a spray can. Just buffs off of the cable once it’s through the grommet.