Greetings, last winter I noticed some water dripping in the cab while driving in the rain. I particularly noticed it at highway speeds. I have looked around a bit and have (temporarily ruled out a leak from the windshield as there is no leak while parked in the rain) My best guess is that the water is coming in from the steering column as it seems that is where the drip originates but not absolutely certain. I would like to try to correct the problem but not sure what to do assuming that it really is the steering column.

Can you tell if the water might be radiator fluid? Does it have a smell? Can you get a cat you don't like to taste it for you? If the water is coming from up behind the stearing column but a little higher, on the firewall, it could be from a leaky heater core or heater core hose. The core looks just like a very small radiator. with two hoses, in and out. Very rare for one to leak unless someone had reason to remove a hose and pulled it sideways a little, causing the hose attachment nipple to break lose and come unsoldered from the heater core. I did that once. Think it was a '73 Impala.

unlikely about the heater core but I will do some more checking. The reason I say that is the leak only occurs in heavy rain while driving on the highway so I think the water is being splashed up somewhere so the inside of the cab right around the steering column starts to drip. If I stop driving the drip goes away.

I had a VW Rabbit that had plugged up scuppers (don't know what they call them on a car) at the drain of the windshield. They backed up and leaked into the dashboard.

What year is your 4Runner? Where do you live? I found this while surfing. SNIP I think i found the culprit. As it turns out, it does not appear to be the windshield. It is the original windshield and has never been out. Underneath the dash behind some insulation on the firewall there is sum rust forming under a strip of seam sealer. It is very difficult to see because deep in the corner of the cab beside the fuse panel. It looks like it is from water coming into the cowl vent behind the hood. There is a chamber with drain holes where air is collected for the ventilation system. In that chamber there is a seam where the inner fender, firewall and cowl chamber all come together and are sealed with seam sealer. Apparently water doesn't drain as well as toyota planned and it sits in there and rusts that seam. You can't see it drip because the water goes through the rust in the seam and right into the insulation on the firewall. It runs down in the to insulation under the carpet and presto!, you have wet floorboards. this appears to happen on both sides. I don't know how to fix it bbecause you can't acess that area form the cowl chamber side because that part of the truck is all spot welded together. SNIP Keep us posted!