Wire into engine compartment?

My usual way is to poke a straightened wire coat hanger from the engine compartment through a rubber grommet through which an existing wire bundle is routed from the engine compartment, through the firewall and into the interior. I then tape the wire to the coat hanger end, and then pull the coat hanger and wire into the engine compartment. I did it this on our 2012 Prius v and 2014 Sienna when installing rear fog lights. On these two vehicles, there were suitable grommets above the accelerator pedal and it took only a couple of minutes to do it.

 

Make sure you know exactly what your doing when you do this. Had a shop doing a electrical install on my car and when they 'poked' a coat hanger through, they also nicked a wire and the care wouldn't start. Took Toyota a couple hours to determine which wire they messed up and run a new one. $550 coat hanger repair.

Since then I have made sure that whatever i 'poke' through has no sharp edges. If you use a coat hanger, wrap the tip up.

 

You bring up a good point. It is a very bad idea to try to poke that coat hanger through the same grommet hole that an existing wire bundle is running through unless the existing wire bundle is very well taped. I usually aim for about halfway between an existing wire bundle and the edge of the grommet.

Some firewall grommets have extra nubs for routing wires through. Some people cut the tips off a nub to make it easier to push wires through but I've found that necessary only when running multiple wires or very heavy gauge wires.

The firewall grommets on our Prius and Sienna were exceptionally easy to push through and I've done this on a lot of vehicles.

 

Ok I'm bumping this old thread because I have no idea how to do this properly.

Pictures I have seen are piercing new holes through the rubber grommet as it seems like there is no clearance to run another wire alongside the main harness.

How do you propose piercing a hole in the rubber grommet if you don't use something sharp? Or do you just try to shove the coat hanger through the existing hole?

 

shove it through the existing hole. sand the end of the coat hanger till its rounded.

 

I've never had any difficulty staying away from an existing wire bundle when punching through a firewall grommet with my favorite coat hanger "tool". I suggest that you inspect the grommet from both the engine compartment and from under the dashboard so that you know what you are dealing with and how to avoid nicking existing wires running through the grommet. I'll be pulling another two wires through a grommet in the firewall of our Sienna in a couple of weeks through which I have already pulled wires for a rear fog lamp - this time it will be for an on/off switch for a Hella headlamp washer system so that I can turn it off when want to clean the windshield without using up fluid to clean the headlamp lenses when the headlamps are on. I expect it to be an easy task.

 

The secret to not hurting anything else in the grommet is to lubricate the penetrating first guide wire your pushing through the grommet. They make specific pulling lube but just use some Vaseline Ior grease or spray lube.Do not use god awful stinky WD40. I like PB Blaster CSP. NO stink high viscosity that stays where you spray it.
Just spray some lube on the entire assy going thru the grommet. Won’t hurt a thing.

On a G2 if your under the drivers side lift the rubber boot covering the intermediate steering shaft u-joint and lubricate that while your under that. Use the CSP.

 

The only reasonable suggestion I've seen in this thread other than mine is: "shove it through the existing hole. sand the end of the coat hanger till its rounded."

This isn't brain surgery and no lube is required. I've pulled wires through firewall grommets many times over the past 50+ years and it's usually taken no more than a couple of minutes each time.

 

but its normal to be a little nervous the first time...