EastCoastMojo GRM+ Memberand Mod Squad
9/10/14 10:11 p.m.

Hey gang, I'm getting water in my truck after heavy rain. The door and windiw seals all look good, I'm thinking it's coming from the vents at the wipers. Gets mostly wet on the passenger side, but the driver's side is damp too. Definitely coming from under the dash area somewhere. Haven't used the a/c, so I don't think it's condensation.
Any suggestions on what I should check? When I wash the truck I do see water run out of the drains when I squirt it in those wiper vents, so I thought they were flowing ok. It only seems to happen during a hard rain. Any advice is appreciated. I want to nip this in the bud.

Swank Force One
Swank Force One MegaDork
9/10/14 10:24 p.m.

Driving in hard rain or just sitting in it?

JamesMcD Dork
9/10/14 10:39 p.m.

GD body mazdas (88-92 626 & MX6) had a recall or service bulletin for leaky cowl boxes. They had to re-seal the area under the cowl vent where the wiper mechanism is, which the HVAC system pulls air from. You may have a similar problem.

EastCoastMojo GRM+ Memberand Mod Squad
9/10/14 11:03 p.m.

Good info, thanks! It's just been parked for the worst of the rain. Mine's a '93.

JamesMcD Dork
9/10/14 11:15 p.m.

Could also be a rusty windshield pinch-weld or previous botched aftermarket windshield install.

Lancer007 HalfDork
9/10/14 11:31 p.m.

If you aren't seeing any water running on the inside of the windshield I doubt its that, but it could be.

I have no idea how to clean out the drain box under the cowl but if that get full of dirt or leaves then it definitely can overflow into the blower motor and cabin air intake system. I've seen that many many times before.

EastCoastMojo GRM+ Memberand Mod Squad
9/11/14 7:34 a.m.

There's no dirt or leaves in there that I can see through the vents, and I am constantly picking leaves out of the vents to try to keep that from happening. Is it easy to remove the wiper arms and take that vent panel off? I would love to check under there for debris.

rcutclif GRM+ Memberand Reader
9/11/14 12:13 p.m.

MGB's do this when the check valve on the drain in the bottom of the cowl gets clogged. Sometimes there will not appear to be any leaves or debris in the cowl area but the check valve is still plugged. Maybe yours is draining some water (as you can see when you wash) but after a while of heavy rain a partially plugged valve can't keep up and the excess flows into the cabin?

A long metal skewer (think roasting a marshmallow) fixed my issue with my MGB without even removing the cowl cover.

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