GTV6 footwell leak: source partially identified but not entirely... - Alfa Romeo Bulletin Board & Forums

 
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post #1 of 11 (permalink) Old 03-02-2017, 09:38 AM Thread Starter
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GTV6 footwell leak: source partially identified but not entirely...

Hello,

I've got leaks in my GTV6 footwells when it rains. Which I'd like to avoid, especially on a car prone to rusting out...

I have identified the main source of the leak, but cannot find how to stop it.

I experimented by covering up the two black plastic air vents between the bonnet and windscreen with duct tape (obviously not whilst driving) during a period that we had a bit of a wet spell.

During that whole time: no leaks, footwells dry.

So... Does anybody know the routing of whatever piping is under there; how it's getting from the vents to the footwells?

I had a similar problem with my Giulia. Turns out the same culprit - rain drainage between windscreen and bonnet - had a pipe that was routed directly down, through the firewall into the cockpit, then bent back outwards, through another hole in the firewall into the engine bay then straight down. In that little section that was within the cockpit, the pipe had perished and the water was dripping down. I'm not usually a duct tape bodger but in this case it has worked very well.

Back to the GTV6 - any ideas?

Thanks,
Dan

1975 Giulia GT1300 Junior, 1981 GTV6, some modern German stuff, and a 1958 Messerschmitt KR201.
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post #2 of 11 (permalink) Old 03-10-2017, 07:08 AM
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The two intake grills feed into a common plenum which has a drain tube. The drain is accessible in the engine bay, it's a corrugated pipe connected to a plastic spigot which is riveted to the plenum and central in the upper part of the firewall. Check if there's a blockage. The other unfortunate possibility is that the all metal plenum has been attacked by tinworm.
If you have any difficulty locating the drain , advise and I'll post a photo.
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post #3 of 11 (permalink) Old 03-10-2017, 07:38 AM
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Thanks for that input, Dermot! I have the same leakage on the US passenger's (starboard) side of my GTV6. Will be taking it into the shop this Spring to have that addressed. So, any fotos you can offer may help focus their time in diagnosing the source of the leak.

Cheers,
Peter
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post #4 of 11 (permalink) Old 03-10-2017, 08:13 AM
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If you find a clogged drain you're likely going to find some rust. Hope for the best!

Rob
Alfas first, then everything else.
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post #5 of 11 (permalink) Old 03-10-2017, 09:50 AM
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From Dermot's fine description, I'm thinking this may be the drain pipe in question, with the yellow pencil pointing to it. Mine looks to be broken. But I should have an extra in my stash. At least now I have a better idea of 2 or 3 places to investigate. Exit port, beneath the cowl grilles, and behind the dash. Please look past the damage varmints have done to my firewall insulation. Rust and squirrels are not my friends.
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post #6 of 11 (permalink) Old 03-10-2017, 12:06 PM Thread Starter
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Excellent! Thanks for this info. I'll check that out tomorrow - the engine is currently out of the car so should be easy for me to get to it! I didn't realise this pipe was linked to the two plastic vents. I'll find out when I check it out, but I hope that if it is blocked, it's easy to free up. I might pour some water down the vents intentionally to see how fast it flows out of the corrugated pipe.

If I'm not mistaken - this design, like on my Giulia, does appear to also go straight down from the vents into the cockpit, then out through the firewall to evacuate down the pipe in the engine bay - is this correct? And if so, would the 'inside' part have anywhere it may leak? Or if it's all metal is that unlikely? Hoping I don't need to start dismantling the dashboard...

1975 Giulia GT1300 Junior, 1981 GTV6, some modern German stuff, and a 1958 Messerschmitt KR201.
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post #7 of 11 (permalink) Old 03-11-2017, 10:36 PM Thread Starter
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Hmm unfortunately it seems like the whole draining system is pretty much inaccessible... Removing the plastic vents didn't really gain anything; no *visible* clogging... Likewise the pipe at the bottom seems free. How odd, no water comes in when the vents are covered over. Is there nowhere at all it could possible be coming into the cockpit from the plenum? I'm not sure what route it takes and not very easy to see under the dash.

1975 Giulia GT1300 Junior, 1981 GTV6, some modern German stuff, and a 1958 Messerschmitt KR201.
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post #8 of 11 (permalink) Old 03-12-2017, 10:19 AM
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Somewhere between stealing insights from above and a spitball guess, it sounds like there is a metal chamber on the interior side of the firewall that collects air from the two cowl vents. Since there is only one drain tube, it may be a single air box almost the width of the dash (and not split into two)? As Rob and Dermot had mentioned, if any clogs were preventing draining the excess water... moisture + leaves + pine needles would be collecting in a wet pool inside. Then the 'tin worms' have permission to start making some unrequested drain holes on the interior side of the firewall. Draining into the footwell, and not outside of the car. I'm either stating the obvious, or way off the mark. So when I take mine in to have that issue reviewed, I guess that will be our starting point. If others with more experience have a different take on this, we're happy to be steered in a better direction. The carpeting has a thick rubberized layer on the underside, and the puddle seems to be above my carpet. So this may suggest a rust hole(s) may overhang the carpet. And not drooling down the interior side of the firewall to get under the carpet. Fingers crossed on finding no rust in the floor boards too!

As the puddle in my case is solely on the passenger's side... this may suggest there is a low spot in that chamber on that side of the car?

That means the dash will have to come out to get in there. Only half a pain for me, as the dash in my car (with the foot bath feature) has had a nice dash cap installed. I have another dash in 'A-minus condition' that could be swapped into this car. And save the one with the dash cap for my project GTV6.

Could be another month+ before that repair gets going. So, still interested in any news in the meanwhile.

Last edited by planetmojo2; 03-12-2017 at 11:08 AM.
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post #9 of 11 (permalink) Old 03-14-2017, 11:49 PM Thread Starter
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OK, I'll let you know how I get on - it's something I need to address but at the moment lower priority than the other jobs (good weather is starting again here). The mechanical overhaul is nearly finished so at the moment I'm more interested in getting it all back together and just driving it again!
But yes I will at some point have to start dismantling the dash to find out where the leak is coming from. There's also a very annoying rattle coming from behind there which I want to find and muffle.

1975 Giulia GT1300 Junior, 1981 GTV6, some modern German stuff, and a 1958 Messerschmitt KR201.
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post #10 of 11 (permalink) Old 03-15-2017, 06:04 AM
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Just to help visualization here's a photo of a US GTV6 '85 with the dashboard stripped out. The plenum enclosure includes most of the metal visible under the bottom of the windshield; observe how the heater box is fixed to the plenum , making the lowest point. The visible ( in Peter's photo) front panel from where the drain is taken more or less mirrors the heater box. The car in the photo is fitted with tropicair and a blocked drain from from the parcel shelf evaporator has caused the corrosion that can be seen in the lower left - this is why the dash is out. Another potential source of water you might check are the drain pipes from the sunroof - if you have one; there are 4 , 2 F and 2 R. The front ones travel down thro the A pillars and into the wheel well where they are sheltered by the rear splashguard. All kinds of things happen to these drains which might result in spillage into the footwell.
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post #11 of 11 (permalink) Old 03-15-2017, 06:06 AM
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Correction to my previous - the corrosion is visible in the lower right of the photo
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