Air Con Sloshing noise

EnzoBlack · Post by **EnzoBlack** » Mon Jun 16, 2025 3:01 pm

Hi, I bought a Z4 E85 2.5L (2003) about 2 months ago. Today I got into the car and the air con wasn't blowing as per usual. I stopped the car, and just fiddled with the dials a bit and it started working again, however it should already have been working on the setting I had left it on...

But the worrying thing was a liquid sloshing noise that I could hear literally behind the air con controls on the dashboard - it was quite noticeable upon braking throughout my 30 minute journey. Does anyone know what the problem could be?

Many thanks!

enuff_zed · Post by **enuff_zed** » Mon Jun 16, 2025 3:26 pm

Welcome to the forum.
There is a drain from the HVAC unit that runs out through a hole in the top of the transmission tunnel. Possibly that's blocked so the condensation isn't running away?

EnzoBlack · Post by **EnzoBlack** » Mon Jun 16, 2025 4:14 pm

Thanks for the info!

I took out the passenger floor mat to clean it and noticed that the carpet underneath is damp - it's not awful but definitely noticeable.

When I ran my hand over the carpet the damp liquid had a bit of a greasy feel to it but there was no smell to it.

It appears to be most damp closest to the transmission tunnel. There is no dampness on the driver's carpet or anywhere else as far as I can see.

Does this all sound like the HVAC unit drain hole you mentioned?

Many thanks.

bigwinn · Post by **bigwinn** » Mon Jun 16, 2025 4:17 pm

That sounds more like your heater matrix has sprung a leak

EnzoBlack · Post by **EnzoBlack** » Mon Jun 16, 2025 4:23 pm

Thanks, would that be an expensive job to fix?

bigwinn · Post by **bigwinn** » Mon Jun 16, 2025 4:35 pm

Dashboard out… sadly that will be expensive

enuff_zed · Post by **enuff_zed** » Mon Jun 16, 2025 4:40 pm

bigwinn wrote: Mon Jun 16, 2025 4:35 pm Dashboard out… sadly that will be expensive

If you are good with your hands it need only be expensive in time. Separating the HVAC assembly to get the matrix out requires it to be in the bench so then it is simpler to fit another one.
You may find someone on here with a replacement to sell you.
But.................. it is a huge job to take everything apart if you've not done it before.

However, the heater matrix leaking should not affect the aircon? So I think further investigation is needed.

You may not fancy doing this, but if you get some of the fluid on your finger and dab it on your tongue, does it taste sugary? If so then it's antifreeze and your matrix is leaking.
If it's bitter then the cat has peed on your carpet.

EnzoBlack · Post by **EnzoBlack** » Mon Jun 16, 2025 4:48 pm

Thanks guys. I'll do that sugary taste test.

I've had the car 2 months and the only thing I've done differently was lower the soft top yesterday. But there is no damp on the carpet behind the passenger seat or under the passenger seat. So am I correct in thinking it doesn't have anything to do with the roof motor and water ingress in that area? Therefore strictly a HVAC/ heater matrix issue? Or could it be the windscreen cowl drainage system? I'll crank the car up here again, see if the air con is working. Cheers.

EnzoBlack · Post by **EnzoBlack** » Mon Jun 16, 2025 5:02 pm

enuff_zed wrote: Mon Jun 16, 2025 4:40 pm

You may not fancy doing this, but if you get some of the fluid on your finger and dab it on your tongue, does it taste sugary? If so then it's antifreeze and your matrix is leaking.
If it's bitter then the cat has peed on your carpet.

[/quote]

I did the taste test - it did not taste sugary, it just tasted like nothing, therefore water. What does this mean?

enuff_zed · Post by **enuff_zed** » Mon Jun 16, 2025 5:22 pm

EnzoBlack wrote: Mon Jun 16, 2025 5:02 pm
enuff_zed wrote: Mon Jun 16, 2025 4:40 pm
You may not fancy doing this, but if you get some of the fluid on your finger and dab it on your tongue, does it taste sugary? If so then it's antifreeze and your matrix is leaking.
If it's bitter then the cat has peed on your carpet.

I did the taste test - it did not taste sugary, it just tasted like nothing, therefore water. What does this mean?
[/quote]
Firstly, it means the car is cat proof.

Sounds unlikely that the matrix is holed then.
So I come back to a possible blockage in the drain from the base of the HVAC unit if you are certain the sloshing noise is there.

EnzoBlack · Post by **EnzoBlack** » Mon Jun 16, 2025 6:00 pm

Thanks enuff_zed. I just started the car up there after about 2.5 hours from the last journey and the air con was working fine.

Do you think it could be water getting in from the windscreen cowl area? Although, that wouldn't have stopped the air con working that time, would it?

Also, forgot to say - coolant level seems to be fine.

enuff_zed · Post by **enuff_zed** » Mon Jun 16, 2025 6:04 pm

EnzoBlack wrote: Mon Jun 16, 2025 6:00 pm Thanks enuff_zed. I just started the car up there after about 2.5 hours from the last journey and the air con was working fine.

Do you think it could be water getting in from the windscreen cowl area? Although, that wouldn't have stopped the air con working that time, would it?

Also, forgot to say - coolant level seems to be fine.

Thing is, if you can hear sloshing then there's a lot of water somewhere.

Are you 100% sure its from behind there?
It is possible for water from the roof drains to escape through the join in the drain and fill the inner sills. When you brake it all sloshes about.
If you get a screwdriver and prise the rubber jacking points to one side you may find water runs out.

EnzoBlack · Post by **EnzoBlack** » Mon Jun 16, 2025 6:32 pm

Ok, I just moved the rubber jacking points on the passenger side (front and rear) and water dripped out!

But could water in the inner sill (passenger side) make the passenger side carpet wet? Because it isn't really damp close to the door - it's more closer to the transmission tunnel, middle, and back, but it's not awful.

Also, I checked the driver's side just in case. There was no water leaking from the front jacking point on the driver's side, so I went to check the rear rubber jacking point on that side, and there wasn't one! Is that normal?

Thanks for your help!!!

enuff_zed · Post by **enuff_zed** » Mon Jun 16, 2025 7:28 pm

EnzoBlack wrote: Mon Jun 16, 2025 6:32 pm Ok, I just moved the rubber jacking points on the passenger side (front and rear) and water dripped out!

But could water in the inner sill (passenger side) make the passenger side carpet wet? Because it isn't really damp close to the door - it's more closer to the transmission tunnel, middle, and back, but it's not awful.

Also, I checked the driver's side just in case. There was no water leaking from the front jacking point on the driver's side, so I went to check the rear rubber jacking point on that side, and there wasn't one! Is that normal?

Thanks for your help!!!

The water in the car could be getting in elsewhere.
If the slushing stops now the water is out of the sills then you’ve resolved that.
Not unusual for a jacking point to go missing.
Maybe the AC was just a glitch?

EnzoBlack · Post by **EnzoBlack** » Mon Jun 16, 2025 8:20 pm

Ok, I'll keep an eye on the AC and the dampness on the passenger footwell carpet.

I'll take the rubber jacking points off and drive up and down a couple of hills to get the water fully out. Is there a method to taking them off or do you just jimmy them off with a screwdriver?

Do you know how to take the windscreen plastic cowling off? I have to see if there is any blockage to that drain.

Thanks very much for your help!

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