Intermittent driver's side water leak (driving me crazy!)

[caribsailor431]

About a year ago, I picked up a 2004 LX470 for a family adventure rig. It's relatively low mileage (166k) and was a southern truck until 2021. I've gleaned a ton from this forum, but have come up short with addressing a pretty bad leak. Hoping somebody has seen something similar!

Basically, I have a leak on the driver's side, somewhere up high and behind the dash. The lower electronics (pic 1) are getting wet, along with the floor carpet, ultimately soaking through the floor. After a recent heavy rain, I felt further up the dash and found the gray box (pic 2) was wet, indicating the leak is somewhere even higher.

• I already cleaned the sunroof drains and confirmed these function correctly.
• I ran a hose extensively over the driver's side of the windshield and could NOT find any water inside the truck
• A recent rain when the truck was parked on a level surface left enough water under the carpet that I could soak it up with a sponge. Not good!
• After today's torrential downpour, the truck was completely DRY. The only thing I noticed was that it was parked on a slight upwards incline.

I know the windshield is prone to leaking, but I don't have any record of it being replaced. I've also confirmed it is OEM Lexus glass. When it has leaked, there is no sign of water on the A pillar or the exterior of the dash around the windshield.

The fact that it doesn't always leak has me really puzzled. Any thoughts or suggestions? Leaving for Michigan's Upper Peninsula in two weeks and would love to get this sorted.

Thanks for any insights!

 

[Trunk Monkey]

Spray something soapy along the outside perimeter of the windshield and then blow air from a compressor along the inside edge, see if you get bubbles.

 

[leveeguy]

Was sealant applied to the roof rack bolts when it was installed?

 

[OrionZodiac]

Just because the windshield is OEM Lexus doesn’t mean it wasn’t replaced at some point. Pull back the a-pillar trim cover and check thoroughly. Could be dribbling from up high somewhere. Pull back the rubber covering the rivets on the outside moulding and make sure those are secure.The roof rack may be culprit, but would expect headliner damage. Check the seal on the sunroof, it’s rubber and if it’s old, it may not be sealing properly

 

[BonS]

When we had our windshield replaced at Safelite I inspected their work and found that they had not replaced the OEM rivets that secure the side trim of the windshield. I made an appointment and brought them the OEM rivets to install. They said "We don't do rivets"! Okay, so they don't do things like they should and it's corporate policy. Ugh! I installed the rivets myself. If the rivets are left out then there are four holes in the A-pillar where water can get in and drip down onto your electronics. Not good! There is a thin rubber strip that is pressed in the channel of the trim that covers the rivets. Simply pull the strip out to reveal the four rivets and inspect. Inspect closely because they may have left the rivet heads in place but cut the rivets. Pulling on the trim sideways will reveal looseness if they did this. The OEM rivets are available from Lexus/
Toyota for about $1 each and you'll need eight.

 

[caribsailor431]

Thanks for all the feedback! Super helpful, especially the suggestion about soapy water and compressed air.

The Sherpa roof rack uses sealing rubber feet, so supposedly sealant isn't necessary. Also, there is zero water staining or wetness on the headliner or A pillar, so that doesn't feel likely.

@BonS, that sounds like a potential culprit. I'll pull off that trim this evening and take a look at it.

 

[caribsailor431]

Pulled off the rubber gasket on both sides of the windshield and was pleasantly surprised to find plastic rivets installed in the holes and zero signs of a leak point.

Next step is the soapy water test around the perimeter of the windshield.

 

[caribsailor431]

I pressurized the truck with a reversed shop vac and the truck's blower on Hi, then checked all over for bubbles in soapy water. Pretty amazing how well this worked! A few interesting findings:

• One of the 6 roof rack mounts was generating bubbles, but another turn on the bolts made it go away.
• All other roof rack mounts (and the other installed non-rack feet) were completely leak free. Gives me more confidence about the Sherpa rack design!
• Absolutely ZERO leaks around the perimeter of the windshield.
• Minor bubbling around the sunroof, which wasn't too surprising.

Considering the perimeter seal leaks, I took a water bottle and double-checked my sunroof drains. The driver's side drains (although slowly). The passenger side was not draining correctly, but that's not the side I'm getting water on, so not sure what to do with that.

After running several quarts down the sunroof drain, there was still no sign of water in the original areas.

It's great that the windshield doesn't appear to be leaking, but I'm still at a loss. Maybe the upper door mounting bracket?

-AB

 

[Nursebettty]

What about the loom in the Firewall. Could water be coming down and finding its way through there and dripping down?

 

[caribsailor431]

Interesting idea about the firewall. I'll start my own research on the forum, but at first glance under the hood, it didn't look super obvious to me.

-AB