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Discussion Starter #1 (Edited)
There have been several posts describing wet roof pump boxes. In fact, I checked mine after the first couple of posts but I was WRONG.:mad: I took off the lid, weighed it, held it under water, wiped off surface water then weighed it again with no appreciable gain in weight. In a spare moment I undid the plastic strap clip and waved my torch at the lower half of the box. I didn't see any water but there was a suspicious 'tide line' 25mm up from the bottom.

To undo the foam box strap, use a 40mm wide piece of plywood and push down very hard on the wide edge you can see sticking out. At the same time with a wide blade tool, push the vertical section of the strap inwards so the exposed edge clears the metal slot, see photo. You don't need to remove the clip bolts and clip to get the foam box out.

I fiddled out the lower half of the foam box from under the pump and immediately saw water lying in the recessed well of the trunk floor. This pressed 'well' and water it might hold is not visible unless you remove the foam box. The front section of the trunk floor was bone dry with no clues.:confused:

Do you have an EOS or are buying one? Do you park uphill in the rain? Get a multimeter set on high megohm resistance range, lift the spare wheel floor cover and set the meter probes about 1cm apart at the front of the foam box and about 1cm up from the floor. If the resistance is below 250K ohms, your pump box is saturated with water and your EXPENSIVE pump will eventually fail! If you push against the lower edges of the foam box you can probably squeeze out water.:eek:

Why didn't I pick this up before?:confused: Aside from water under the pump being hidden, the lower half of the box appears to be open cell Polyurethane foam able to soak up masses of water, whilst the top cover is closed cell and does not absorb much water. How much water can the foam box take? I tried to dry out the box leaving it in an oven at 70 deg.C whilst measuring its weight every so often. After 6 hours 'drying' and weight still dropping, I stuck the lower half of the box in a bowl of water and measured how much it could absorb. The foam box can absorb a whopping 1.5 liters of water and you cannot see it! I squeezed out as much water as I could, tried to repeat the drying process but eventually gave up. The foam box once saturated will need days of drying out.

I try to keep as much of the OE as possible, but the only solution for the EOS pump foam box is to dump it. VW should have used a closed cell foam, but then I am also unhappy the pump over temperature sensor (in the motor) can lockout during Summer. Do not think you can dry out a wet box!:(

My EOS was driveway parked slightly uphill during the recent U.K storms. There was no water under the spare wheel and it would have had to be over 15mm on the trunk floor to flood over and into the isolated well recess under the pump. Therefore my attention will go towards the water running off the sides of the trunk lid when it is opened and the seal along the rear of the trunk. Meantime I have to solve the foam box problem:

With the black plastic strap open (I left it bolted to the rear panel), I was able to rotate the pump assembly 90 degrees with all wires and hydraulics attached to look underneath. Water damage on the bottom surface of the valve body was immediately obvious. There was also some rusting of the bracket holding the bottom solenoid. I also spotted a body panel 'bung' in the recessed well under the pump which gave me an idea for a drain. I left a 1kW fan heater on for an hour, cleaned up the underside of the pump, then painted it with red oxide primer followed by Hammerite silver paint.

The EOS pump contains no sensitive electronics other than the over temperature thermistor. There is a 12 volt high current pump motor on the right and three solenoid operated valves which are the circular parts you can see on the left. I had no need to disconnect the hydraulics or electrics to explore the pump but I have always been curious as to how the expensive pump fails when wet, because water is an insulator for 12 volts. It would take 150mm depth of water to reach the motor armature and that is unlikely. However, the solenoid valves are close to the bottom of the pump and can get wet. The solenoid coils appear to be bolted to the pump body and can be removed. In ABS pumps, the moving part of the solenoid is enclosed by a stainless steel tube and the coil sends its magnetic field through it. If this pump uses this type of sealed solenoid I think water could be getting into the solenoid winding, corroding it (copper) and producing an open circuit. Easily tested with a multimeter. If the solenoid has an open moving plunger that can get wet - disaster because it will corrode and seize. Both problems are potentially repairable, without buying a new pump.

Here's my foam box fix: First I knocked out the sealing grommet (bush) immediately under the pump and fitted an open electrical cable grommet. Then siliconed in a 75mm length of 16mm o.d silicone hose to drop just behind the rear fender. I decided the pump could be supported with sufficient anti vibration absorbing just around the valve body (approx 80mm wide). This leaves the motor and solenoids open for better cooling and fewer water problems. The only material I had was 10mm thick sheet polystyrene to make a 'wrap' and I intended to keep the VW strap. Polystyrene sheet comes in different grades, mine was a fine grade and when tested by blowing through, it seemed pretty closed cell.

I cut a long strip of polystyrene 80mm wide and cut lengths for a fabricated open type box - top, bottom, front and back. The front, back and bottom requires two thicknesses (20mm) laminated using upholstery glue whilst the top is 10mm. I burned a hole in the top to align the pump release valve that sticks up. All the polystyrene parts were brushed with Evo Stick water based adhesive for extra sealing, dried until 'tacky' then wrapped in cling film. To ensure the bottom polystyrene did not block the new drain, I slid a couple of (red) 5mm thick glazing spacers underneath. My EOS pump now 'floats', held only around the central valve body by closed cell polystyrene and is sitting 20mm above the trunk floor well which is now drained.

I will check if driving in rain brings in water, although the under body slip stream might suck water out. I expected the pump noise to be unbearable now it is open, but it wasn't and how much time do you spend operating the roof pump anyway? My solution is incomplete because I need to nail the water ingress first, but I think I will be removing the rear light units. Remember, assume that once the foam box absorbs water it will never go away and will hold 1.5 liters!!
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Awesome, i was expecting something like this after your hints, and had already started planning what to do about mine, but i think ill clone your solution.

Oh btw, I opened the clip by pushing on top of the clip until it got pressed down, and then pushed at the marked point to release it.
 

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Vox - well done mate and thanks for posting the details.

Only suggestion I would make relates to pump noise - if it is objectionable, just get some plumbers lead flashing, roll it around the pump/motor casing and secure it with cable ties. Lead is a very effective sound absorber and used to line soundproof rooms such as recording studios - it also doesn't absorb water which is another benefit.
 

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Discussion Starter #4 (Edited)
I really didn't find pump noise an issue because there is the trunk floor cover over the top, but my EOS is diesel and any noise is lower than the engine background on idle.

I'm probably going to buy some black closed cell neoprene sheet to replace my polystyrene, but the principles don't change. The neoprene will look a bit more professional, but it isn't that visible to most anyway.

Lead is a very effective sound absorber and used to line soundproof rooms such as recording studios
I used sand to fill timber cavity structures. Cheaper, allows on site install and no lead hazard.
 

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Discussion Starter #6
Yes, but like everybody else if you park uphill in the rain and open the trunk lid quickly, you probably get a load of water coming from each rear corner of the lid and falling into the trunk space? The carpets won't hold water and it will run into that hidden well under the roof pump where it is soaked up by the foam, accumulates and stays stored forever. It adds a new meaning to 'memory foam'. I'll work on the lid 'water storage' problem when it gets dryer and warmer.

I noticed their foam box is marked OASYS. It is probably a manufacturer name, but over here flower shops use an open cell foam of a similar name which is very light with the highest water holding to foam volume ratio.:(

Do the multimeter resistance check on your foam box and repeat after driving the car in wet weather to be sure.
 

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Discussion Starter #8
Thanks, Yes I found some references. Let's take a guess OASYS designed the EOS roof system that although complex, is not that bad. They thought about noise and came up with the molded foam box as a way of reducing any pump noise, whilst giving support and anti vibration damping to the body. Perhaps ventilation and over temperature was a reason for using open cell foam, or they worried about tools in the wheel compartment crashing into the pump and lines?:confused:

Then it got fitted in an area of the EOS where nobody thought water would be. Perhaps no brief to OASIS that water could lie under the foam box and had they known, may have used a closed cell foam and chosen a location with clearance underneath the pump, to stop water wicking into the foam.

We don't have Surveys on this site, but it would have been helpful to all owners to see feedback stats of how many owners measured resistance near the bottom of the box and got low readings = water saturated.:eek:

Wouldn't it be nice if VW could be open, up front and clean to say 'We got this wrong causing EOS owners grief and expense to replace faulty roof pumps' and advise fitting an open clamp system similar to what I have done'? The problem for many with the foam box is how much water has already caused their pump to deteriate. There will be many who have not read this whose first post will be ' Water in the boot/trunk, My roof pump has failed, what do I do'? I suspect many will already have had their roof pump replaced, unaware they could have taken early action to prevent failure.:(
 

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Vox,
I did just take a look at my pump today. And there is no foam box in my trunk:confused:, which I never noticed. There is some styrofoam wrapped around and underneath it, but not too much.
Oh, and by the way, my resistance meter showed a full resistance, so it is totally dry.
I don't know why the box was changed. I know that my car was a VW operated lease car in the past, but that is it (it now has 187000 km/116.200 miles on it meter). And I know that it is pretty waterproof (just sometimes a drop of water along the rear side windows and a few warning droplets at the front when braking, to tell me to clean the tubes again...
 

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Discussion Starter #10
If you park slightly uphill and open the trunk lid after rain or test hosing, do you get a load of water falling off the right and left corners of the trunk lid as it is raised? I think some of that was falling inside my trunk and building up in the foam box. Since I got rid of the box, I've not seen any misting on the inside of windows.:)

The box is a mystery because what I have is shown on the diagrams of all the parts reseller websites I've looked at. But I don't know what you would get if you asked for the part today? Presumably your pump is now open at the right and left and just held by the wide plastic clamp like mine? I've now cut some black neoprene sheet which looks like a VW pro job! The neoprene foam is not so squidgy as the polystyrene I tried and holds the pump fairly firm whilst allowing it to float.
 

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I don't know if this is something done by the dealers or the car just started like this, but mine has normal sponge around the pump. I'm guessing there has been water there in the past, but only because the paper sticker with the VIN on it has nearly rubbed away on the bottom half.

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Discussion Starter #12
Whatever sponge it is and it looks like open cell, :( you have a lot underneath to wick up any water, check it is 'closed cell'. That means if you pour water on it it runs off and doesn't absorb water which you can then squeeze out (like a sponge).

The Neoprene I used is closed cell similar to that used for diving suits and doesn't soak up water. If the suits did that you would sink wearing them! :eek:
 

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I just took it apart to check again. I have the same, marked 1Q871863B.
It is open cell and can absorb a lot of water, you could use it as a sponge :D
Although mine is totally dry, there are rust marks in it anyway!
For precaution, I will also replace it with some closed cell type. Thanks again vox!
 

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Discussion Starter #14 (Edited)
Now you know where some of the rear window fogging and condensation comes from in Winter! :( Clean the pump body (and underneath) then spray over with WD40 before wrapping the closed cell Neoprene around. As I posted, you only need it around the central part and clear of the trunk floor. Their big clip holds it tight and the open pump body should help run it cooler.

Here's a link for 10 and 20mm thick sheet Neoprene, cut it to my sizes in the photo:
http://www.ebay.co.uk/itm/BLACK-NEOPRENE-PLAIN-SPONGE-FOAM-RUBBER-SHEET-VARIOUS-SIZES-1-5mm-25mm-THICK-/141115616908?var=&hash=item20db256e8c:m:m0ft2U6TPx3LelsYYVsHwOg
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