Water Leak - Air Con Condensation??

[JasonC]

I have noticed some drops of water underneath my 2004 TDI. I was wondering whether this was condensation from using my air con, but I haven't used the air con for at least two days?

When looking in the engine bay the water appears to be dripping down onto the near side drive-shaft joint where it joins into the gearbox. I think the drips are coming from around where the battery is situated - when I look in the battery compartment, there does appear to be a little water laying at the bottom.

I realise water can drip from underneath a car after air-con has been used, but is it normal for it to come from this area and still drip a couple of days after use?

Many thanks,
Jason
P.S. I am 90% sure it is not coolant leaking because the fluid doesn't smell and there is no drop in the expansion tank.

[Huweth]

Has it rained recently or have you washed your car?
There is a grommet under the battery that can become clogged. If this is the case, it may be dripping water very slowly rather than letting it through straight away. This might account for the small pool of water under the battery also.
The best thing to do is remove the grommet, it's overkill. The intention was to prevent road muck getting up into the battery compartment, but all it really does is cause water ingress into the car when it blocks (which they all do).
There is a guide how to clean it here http://www.weirdlittlebiscuit.com/passat/leak/index.htm

I found this overcomplicated. All I did was push the grommet up from underneath with my finger, you can feel it.
Once you've done it, you could try pouring a little water under the battery and you will be able to watch it drain out immediately.

I hope this solves your problem.
Huw

[guyg]

Nice call, Huweth.

I'd add that if Jason's plenum was blocked, he should check the passenger carpets and CCM to make sure they're dry.

Cheers

Guy

[JasonC]

Thanks for your reply Huw.

No, I haven't washed car lately and we have only had a very small shower. Does this area beneath the battery collect the majority of water that hits the windscreen?

Where does the water drain from this grommet? Mine seems to go straight down onto the undertray. It was parked on a downward slope and was therefore splashing onto the driveshaft first in this case.

Can you unblock the grommet without taking the battery out?

Sorry for all the questions!!

Thanks
Jason

[JasonC]

Crikey, all West Country folk - I'm from Cornwall too!!!

Jason

[guyg]

The whole area where the battery is located is known as the plenum and the grommets get clogged; the whole thing has been known to fill up like a tank with rainwater if the drains are blocked.

The Pollen filter housing on the nearside seals directly against the inner bulkhead and if this seal leaks, water can travel down under the passenger carpet and short out the electronic control module [Customer Convenience Module] that controls the alarm, windows and other bits and pieces. If this gets damaged, it can cost £500 to replace.

It sits in a plastic box in a recess in the floorpan below the passenger carpet [right under your feet]. It's worth checking the recess is dry...

Cheers

Guy

[guyg]

Crikey, all West Country folk - I'm from Cornwall too!!!

Small world sometimes

Guy

[Huweth]

Thanks for your reply Huw.

No, I haven't washed car lately and we have only had a very small shower. Does this area beneath the battery collect the majority of water that hits the windscreen?

Where does the water drain from this grommet? Mine seems to go straight down onto the undertray. It was parked on a downward slope and was therefore splashing onto the driveshaft first in this case.

Can you unblock the grommet without taking the battery out?

Sorry for all the questions!!

Thanks
Jason

Yep, most of the water from the windscreen will go through the grommet under the battery. If the car is parked on a downhill slope it will collect much water from the roof also! On my car, I can see a dirty stain on the bulkhead under the grommet where dirt from the rain is deposited. It runs all the way down the bulkhead, then drops onto the tray under the engine and runs out. It makes perfect sense that it will hit the driveshaft if the car is parked as you say.
Really, don't bother removing the battery. Just poke the grommet through with your finger from underneath (follow the dirty stain on the bulkhead up until you meet it). You might find it easier to remove the plastic engine cover to give you more room if you're a big chap. (A screwdriver and number 10? socket are all thats needed.)
I left my grommet loose under the battery as I couldn't be bothered to fish it out. Not a problem at all.
Good luck!

[JasonC]

Thanks for your very helpful response Guy & Huw.

Does the air con condensation collect in this 'plenum' aswell?

Do you get to the grommets from underneath the plenum?

Cheers,
Jason