Water Leaking into B4 Trunk (not your typical source though)

Hi,

I have a strange problem with water leaking. Only after a heavy rain my trunk will host a nice little puddle of water in the back part behind the bumper, for a moment I thought meh easy fix! assuming it was the tail light seals. I cleaned my sunroof drains a couple months ago and verified that they are draining to the bottom of the car so that's not the issue.

Earlier today after a light rain I figured maybe I can find the source this time since it wasn't a downpour which causes everything in the trunk to get wet making it difficult to trace the source, well I was right when I went to look inside my trunk I saw exactly where it was dripping from before everything else got wet. Low & behold it seems to be coming from the sheet metal, not the trunk seal or the tail lights, literally coming from the cavities in the metal behind the trunk lid hinges.

Has anyone come across this? how is it leaking into the bodywork? how do I fix it?

I have a pic of the location but not sure how to post it since photobucket no longer works for 3rd party links!

I’m sure there are spot welds there, where 2 or more body panels are meeting. If so, sounds like you need an application of seam sealer.

More readily available products would likely also work, although it wouldn’t be their intended purpose... plastidip, liquid electrical tape, flex seal... ymmv.

-Todd

I looked closer & began to arrive to a similar conclusion, just behind the trunk seal there is a small flat spot in the corner where water pools a little before draining down and around the trunk lid. In that area there is a hairline seem where sheet metal meets and joined together, that joint is likely compromised.

I think I'll try to find some sort of hardening liquid to pour in there so that it flows into the crack sealing it for good, if I'm lucky I'll find something clear so it doesn't look horrid, some kind of resin most likely.

Cars of this age are starting to have issues with seam sealer. My wagon leaked from the roof seams until I applied more sealer under the black strips where the panels meet. These sorts of aging issues will become more troubling but are not insurmountable.

I caution against using a rigid 'hardening' liquid because it will expand and contract at a different rate than the metal or original sealant. What would probably serve you better is a flexible sealant, like silicone, that you can inject, or push, into the existing crack to help fill the void yet would be flexible enough to move when the panels expand / contract.

Steve

Good point, I found myself struggling with the resin idea too.

Honestly it's starting to feel like the best idea might be to get the masking tape and wire wheel out, strip the area down to metal, body fill & seal it then let the body shop paint over it when I take the car in for a spray, likely before the end of the year.

This will also motivate me to take the wire wheel to the surface rust inside the trunk that was caused by this leak and strip it all off then silver spray. Shortcuts of any sort will all be just temporary solutions, strip & reseal is the only permanent method.

Look to marine stores for products that serve this very purpose. They also act as bonding agents to lock the panels together.

Someone pointed out that the little plates on the outside of the C pillars can be a leak source then he showed me pics of his without the plates on and sure enough he had thin rusted cracks there, any idea how I can pull those things off without breaking them or the clips that hold them on the car?