Air box water leak issue

adi #2 · Post by **adi #2** » 18th August 2009 - 2:44pm

Iv had a water leak for a while, and now i got the garden hose onto the car and sat in it and found out whats causing it.

The air box thing under the dash (the big black plastic box) seems to be filling with water!

I saw it dripping from where a hose connects to it on the passenger side (one of the air duts) and when i pulled the hose off lots of water came gushing out,

Is this a common problem? Should the air box thing have a drain somewhere thats blocked?

Or perhaps, somewhere there is a device to prevent water getting into the air intake, which is somehow either damaged or missing?

Any ideas?

Post by **purplepeter** » 18th August 2009 - 3:24pm

viewtopic.php?t=2295&highlight=air+box+drain+tubes

Post by **Editor** » 19th August 2009 - 12:25am

There's a lip round the airbox intake, which can rust. The tray drains through a 1/2" rubber tube and out through the bulkhead - exit is masked by the fuel tank.
There is a 1/2" hose from bottom of airbox to same bulkhead. Either or both can get blocked. The long one blocks, then water can fill up and get into the airbox over the lip.

adi #2 · Post by **adi #2** » 19th August 2009 - 5:07pm

Well, thanks alot for your help!

I pulled tank out expecting to see all sorts of horrors underneath, and also set a side a whole day for this exercise since i was anticipating pulling the air box and half the dash apart.

Good news, to my amazement i was greeted with a nice rust-free bulkhead, and two very very blocked hose outlets!

I am very lucky that the dreaded rust didnt get to the bulkhead, its hot, the chocolate bar in my pocket melted, i got covered in under-seal and fuel (from disconnecting the fuel line without a clamp) and generally i was NOT in the mood to rebuild a bulkhead today.

So anyway, first i cleared the top tray thing. There was dirt backed up all the way up the pipe, the cheif obstacle being what seemed like a pebble right at the bottom. I filled the tray with water, and started poking a piece of wire into the hose (which was disconnected and hanging into a bucket in the saloon).

As soon as the pebble came out, about 500g of gunk followed, and then the tube ran clear.

Next was the airbox, same story, blockage right in the end.

I rand water through the system and poked the pipes with a piece of wire with some cloth on the end, to clean all the gunk out, and it now drains very well!

Yay. That was easier then expected.

cbst3 · Post by **cbst3** » 20th August 2009 - 1:45pm

You're very lucky - mine was blocked, but had rusted through in places, so the water was coming in through the rust holes. Hose is now unblocked and I have patched up the holes as best I can without welding, so I too am dry inside.

Colin

Chino · Post by **Chino** » 9th July 2016 - 1:53pm

Sorry to revive an old thread, but do you think it would be possible to clear the drain hoses without pulling the tank? Pipe cleaners maybe? I've discovered a little leak from my Airbox drain hose so I suspect there's s blockage further along.

cbst3 · Post by **cbst3** » 9th July 2016 - 4:43pm

Chino wrote:Sorry to revive an old thread, but do you think it would be possible to clear the drain hoses without pulling the tank? Pipe cleaners maybe? I've discovered a little leak from my Airbox drain hose so I suspect there's s blockage further along.

Hey Chino, fancy seeing you here too! It looks like I am still subscribed to this thread, so although I haven't logged in for ages, it still popped up in my mail, and I was (pleasantly) surprised to see it was you posting...

Anyway, my Fastback is long gone from me, but is still on the road, somewhere in the Bristol area I think. However,I do clearly remember the issues with the airbox, so hopefully I can help. I didn't remove my fuel tank to get at the drain hoses, but I did remove the actual airbox. There are, if I remember correctly, 4 screws or nuts that hold it, then it just drops down. I remember removing the cables that run to it from the controls, which was a bit of a hassle, but not too bad. Once that was off, the drain hose on the bottom of it is accessible easily, and the other one from the drip try is also sort-of accessible. I certainly managed to clear both of mine without too much effort.

Here's a picture of mine for reference:

This is looking up under the dash, the front of the car being at the bottom of the picture. You can see two of the mounting tabs on the right, and I think the pressing between them leads to the drain hose.

Hope that helps, good luck with it, and I do hope yours is not holey like mine was!

Colin

Chino · Post by **Chino** » 9th July 2016 - 10:09pm

Hi Colin, thank you for replying

was yours an early or a late? Mine seems to be weeping from the hole where the hose connects on the drivers side?

cbst3 · Post by **cbst3** » 9th July 2016 - 10:57pm

No problem, mine was a 71, so a late one, and the drain hose for the metal bit of the fresh air box was on the driver's side. I think it was just a rubber hose pushed over a tube fitting, so probably easy to replace.

Chino · Post by **Chino** » 10th July 2016 - 7:57pm

Ok so I got it all off... Issue appears to be it was only secured with two screws allowing water to slip down the back where a proper seal wasn't being made. So I have two of these:

And now need two more. Anyone know what they're called so I can get some more?

Also, does anyone sell a replacement seal for the Airbox? Mine is probably reusable I'm just thinking it may be worth renewing whilst it's off.

Post by **Editor** » 11th July 2016 - 12:33am

They're just wing-bolts - I suspect the correct screws had rusted out or something. The right screws are M6 x 15mm hex head.
The drain hoses are just weakly glued into metal tubes to carry the water away where it runs down the front bulkhead between it and the fuel tank. The long hose drains the tray, and the short one drains water from the airbox, if any gets in there. Leaves and rust tend to block the drain holes and leads to water collecting in the tray and rusting out the mountings. The only way to easily get to repair it is to slice off the top of the airbox and clean up and repair, then join the lid back on. I have heard of someone removing the airbox from the inside and trying to repair from below. The tray is spot welded to the bulge under the bonnet - you can often see where it is pulling away as the rust expands between. That's an alternative way, but you need to get a tray that's rust-free, which probably won't be possible in the UK! If you found one, the whole car would be worth saving!

Maybe it's something a flbreglass guy could make up - meanwhile, it's welder time or P40 Isopon!

Chino · Post by **Chino** » 11th July 2016 - 8:32am

Thanks Dave, got some correct bolts ordered...I've had the bulge under the front welded and patched, it's just a case of water from the passenger side vent overflowing down the back of airbox, the drivers side seems to drain correctly under the front of the car. Could this mean there is a blockage in the passenger side area somewhere? I looked and could only see one hose coming down from drivers side and the one that drains from the airbox at the bottom.
I think the leak from the tray stems from the aibox not being secured properly for the gasket to make a correct seal, as water is escaping out of the top of the airbox rather than dropping down to the drain hose inside.

Chino · Post by **Chino** » 11th July 2016 - 6:51pm

Looks fairly ok up there, you can see spot welds through the cavity where the patch was done on the bulge:

Post by **Editor** » 12th July 2016 - 11:42am

There's no drain on the left end of the tray. It's an aspect of RHD that is a nuisance, since parked on a normal camber, the water pools on the left. LHD vehicles don't have the same problem. I suspect the water is filling the left end of the tray and running over, getting past the rubber gasket that was (originally) inserted between the tray and the bulkhead bulge before spot welding them together. You might be able to get some sealant in there with the airbox off, or maybe squirt some Waxoyl in?
Try to park level or slightly right side down would help as well.

Chino · Post by **Chino** » 12th July 2016 - 2:22pm

Sounds about right Dave, my drive has a slight left hand tilt where it was parked during testing. I have the original rubber seal that goes between the plastic airbox and the body, I suspect I can make this seal properly once the correct bolts arrive as it's in quite good shape. I've got some aerosol waxoyl I can spray into the cavity and spread with a thin brush maybe.

Post by **Editor** » 13th July 2016 - 1:12pm

That's not the one I'm thinking of, but easy if that's where it leaks! There's a lip on the tray that should stop debris getting onto the top of the plastic box unless the corrosion is very bad - maybe that's the line of weld on your photo. The seal I'm on about is between the bulkhead and the metal tray - it's inserted before the tray is spot welded to the bulkhead. I thought it was rubber, but now I suspect it's sealant. Once that fails and rust starts to spring the joint apartm it only takes about 1" of water pooling to get over the lip and down between the bulkhead and tray. In fact, I think you can see rusty water staining from that joint in your photo.

Chino · Post by **Chino** » 13th July 2016 - 1:27pm

Ahhh I think I see where you mean...right...I'll try and get a bead of some sealant of some description in there...seam sealer or even silicone sealant maybe? If I try and get it into that cavity towards the back, where the join would be? My thoughts are clean/treat the tray with something like kurust (I can probably brush it in through the cavity), I have a spare container of zinc based paint (the grey stuff used on external steel structures like I coated my floors in), then try to use a seam sealer on the edge and a blast of waxoyl for good measure?

Chino · Post by **Chino** » 13th July 2016 - 8:18pm

You were right Dave, it's coming from the seam... Looks like I'll be taking a hacksaw to the bulge to clean up and seal it properly.. I considered seam sealing it in the cabin but that would never be a lasting repair, so hacksaw, clean, weld it is I think.

Also, I'm looking at recommissioning the controls for the air box. Can anyone tell me where this bracket should fix for the passenger side flap?

Air box water leak issue

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