Leak behind blower motor - what to tear apart next?

[Jetson105]

Left a hose running on the roof and finally saw my leak in person. Stream of water running down the passenger side firewall centered behind the blower motor housing. Took off the cowel pieces and I don't see where it might be coming from from the outside . Don't want to waste time taking apart more than I have to. Any suggestions on what to dig into further? Outside or inside? Thanks!

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[90halfton]

Under where the heater hoses enter the cab under the hood there is a little plastic drain nipple thingy that sometimes gets plugged up and doesn't allow condensation to drain as it should be. Id check that first.

 

[delta_p]

see if this thread helps.

http://www.gmt400.com/threads/help-finding-leak-from-rain.37102/#post-951170

 

[Jetson105]

Thanks for the replies and suggestions. I thought I would get off easy when I investigated down the fire wall and found that the grommet around the antenna cable was pushed out of the hole. But the passenger side wiring channel at the bottom of the door frame was wet after the next rain, so looks like that was only part of it. Maybe I'll check out that body seam next.

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[Bob L]

If you have access to a compressor soap the outside anywhere you suspect a leak and blow air from the inside with someone watching outside. It will bubble when you hit the spot. If not dry up everything inside and start low with the water hose outside and slowly move up till water shows up inside. Let the water run for a while at each spot before moving up as it takes a while for the water to come in sometimes. I start with just a light trickle of water as it is easier to control where you are letting it flow.

 

[someotherguy]

If you have access to a compressor soap the outside anywhere you suspect a leak and blow air from the inside with someone watching outside. It will bubble when you hit the spot. If not dry up everything inside and start low with the water hose outside and slowly move up till water shows up inside. Let the water run for a while at each spot before moving up as it takes a while for the water to come in sometimes. I start with just a light trickle of water as it is easier to control where you are letting it flow.

If you don't have serious leaks in the door weatherstrip, just turning the fan on full blast and soaping it up at the car wash will produce bubbles. You should see how many pop up on my 2016 F450SD work truck if I leave it running/air on while at the car wash. Strikes me funny for some reason to see it bubbling around the door handles...anyway.

After all the usual suspects have been addressed like the cowl screw over the air inlet (not present on all year models) and the seam sealer around the metal cover on the cowl above the air inlet...I would begin suspecting some failed urethane adhesive on the windshield.

Richard