Mildew Smell after rain & car wash

Since spring I’ve been experiencing a mildew smell in the cab after rain/car wash. I first noticed it after a lengthy detail I did in early spring, and it was something I didn’t put much thought into being that we were going into summer with little to no rainfall expected for the next few months. Well, the issue was brought to my attention again after a rainfall we recently had in Oregon, lone behold the cab smelled like mildew the next day.

The first thing I did was investigate around the cab to try and locate any standing water or damp spots, no luck. Everything was dry including the carpet and seats.

After visually inspected the outside of the truck (window/door seals, etc.) I decided to try and isolate sections of the truck I thought could be problematic. First order of business was 3rd brake light, even though I had the TSB completed late last year. Hoses that area real good for about 10 minutes, gave it 24 hours, and no mildew smell.

Next place I went to was the windshield cowl, which is where I think I found my issue. The attached picture shows the cowl drain holes that were blocked up with all kinds of debris. I vacuumed that area really good, and cleaned everything around it too. Did a flush to make sure it drained quickly, and so far things look good.

The unknown, is how backed-up water in the cowl found its way into the cab. I had checked the cabin air filter many times and it was never damp or had signs of getting water in there either.

 

Update. After a good rain the other day the smell is back, not sure where to go next. Any ideas would be welcomed

 

Any of the headliner areas wet? I’m not sure if you have a roof rack or not but the holes for roof racks are present on all our 3rd gens. Maybe there isn’t a good seal but it’s just an idea.

 

3rd brake light TSB?

 

I believe part of the 3rd brake light TSB, was determining how much water damage there was. In some cases, great lengths were taken to- the interior was removed, for a team like ServPro to come in and clean the interior sheet metal, after sound deadening was removed. Seats were stripped, headliner was replaced. This was a large job.
I would investigate and see if the dealer didn't properly diagnose this repair, and covered up mold. You may have to investigate yourself, if you leave it up to them. they conveniently may not be able to find any mold.

 

Mildew doesn't form instantly after a rain or wetting.

You're smelling something that's old, and 'reactivated' when it gets wet again.

 

Under your cowl vents is areas where water and debris can lay and stay wet. Remove your plastic coal panel and clean in there

 

TSB was completed last December, and we had rain for a handful of months afterwards, with no smell present in the truck. But, it could still be the culprit, maybe it started off working fine and got worst over time?

 

I appreciate your reply, what you’re saying makes sense. Seems like a heavy lift to take all of the trim panels off along with the headliner, etc. Do you know if anyone else on the forum has done that and made a thread?

 

Good point. This makes me more worrisome now. Where do you recommend I take my next step?

 

Already did this, cleaned it out really good a few weeks back. Mentioned this in my initial post above, thanks though.

 

try a search, I am on my phone, I think there is more than one.

 

I took a second look at the 3rd brake light, and one of the sides looks off (Photo attached.) It almost looks like there are gaps between the plastic cover and the rubber surround.

 

here’s the other side, a lot more clean looking. Maybe the 3rd brake light could actually be the culprit to water getting into the cab. Thought I had gotten around this since the TSB was done last year, but thinking that might not be the case any longer. Taking it to dealer this week to have them take a closer look and inspect the work they previously did

 

I would bet on that

 

very likely!
@Clearwater Bill is absolutely right, mold doesn't grow in minutes or even hours, more like weeks and months.

 

Welp, Toyota inspected the 3rd brake light TSP they previously performed and said everything looks fine there. Wanted to charge me $770 to spend 4-hours to diagnose other areas. Told them to kick rocks. Any ideas where to look next?

 

The slight gap doesn't matter. They use a marine grade sealant. They run a bead of it around the light, and use a special squeegee to make sure there is the right amount, and covers everything it's supposed to. The black plastic trim has 3m tape that holds it to the body. The sealant is trapped between the light, trim and body to make a complete seal.

I have done over a hundred of them. Never once has one come back leaking.


EDIT* you can actually see some of the sealant on the light in this picture

 

Idk, that passenger side bead looks pretty messed up compared to the driver. Looks like something more going on than 'sealer on the glass'

 

Re: mildew smell: Does the smell get worse/stronger when you turn on the heater/ac blower? If it does, it might be the a/c evaporator behind the dash, since it's wet when the a/c is running, and mold and mildew can grow and build up on it: especially when the fan is off after shutdown.

There is a Toyota two part kit to service it and clean it out. Search YouTube for: "Toyota ac clean out kit"