SL 350 Instrument panel going crazy!!!

[W1Z]

Well would you believe it, I FINALLY found my leak! Actually two leaks, I'd never bothered checking the driver foot-well because it wasn't causing me a problem, but it was wet there as well.

I started to suspect water coming in from under the car, even though I couldn't see anywhere it could come in when looking under the carpet. I decided to try and inspect the underside of the car and luckily a friend of mine knew the manager at a local Kwick-Fit centre who let me put it up on the lift for a few hours.

I removed the underside panel, which is held in place by a number of plastic 10mm nuts and a few 8mm bolts. Under the panel are LOADS of rubber drain bungs, I mean, there must be more than 10. 6 of them were along the sill and then various others in other positions.

Unfortunately, these rubber bungs can perish. There are four very big ones, about 30mm across, two at the back of the car (you can see these from under the carpet) and another two just at the front of the foot-well, which cannot be seen from inside the car and are much harder to see from underneath, even with the under-panels removed. These front two bungs are on the front edge of the foot-well and so they are under constant attack from road spray. In my case, the drive side bung was perished and spilt so that the centre part opened like a flap (see below), the passenger side bung was missing altogether, most likely it’d come out when I went through some standing water at speed once.

Enclosed is a picture of the hole and the split bung. Why it’s necessary to have quite so many places water can get in I have no idea, but there they are. With the front bungs out (or damaged) water from the road goes through the hole and collects in the foot-wells, eventually casing all manner of electrical malfunctions etc.

So, it seems there are many places water can get in, rubber bungs in the floor is definitely one more to add to the list

 

[blaser24nig]

Well, I got to the bottom of my "crazy dash/warning lights" problem, but haven't quite finished fixing it yet.

I striped back part of the passenger carpet and it was soaking wet, so in the end I removed the passenger seat, removed all the trim I could easily remove and lifted the carpet up as high as possible. The floor-pan was FULL of water, I mean, there must literally have been a bucket full in there. The electrical conduit was actually sitting under water, no wonder I've had this problem, frankly I don’t know how it’s been working at all.

So, I mop up all the water and then dry the floor-pan completely with a towel. Then I open the conduit, vac out the water, dry it meticulously, open the connectors and blast them dry with an airline; then I reassemble them using a little electrical silicon grease which is designed to give a good contact and repel water. The thing that most struck me was that this water ingress looked new and very sudden. There was no corrosion and barely any green oxidization of any of the copper contacts which would be a sign of a persistent leak. So next to inspect the drains...

I get the wheel off and in the interest of getting a really good look, I removed the liner completely. I poured some water into the bonnet vent and saw it pour out of the drain hole in the wheel-arch. The drain was completely clear. There seems to be a very soft rubber nozzle at the bottom of the drainpipe which has a kind of corrugated exit hole. It this lines up with a funnel that is part of the moulded plastic wheel-arch liner and directs the water out of the wheel-arch. It seems to me the function of the rubber nozzle is to slow the speed of any water coming down through the vent and stop it from splashing back up over the edges of the funnel. If it does splash up and over the edge, it can enter the passenger foot-well.

Anyway, the whole system for mine was completely clear with no obstructions. So, how the hell did all that water get in my car! Well, eventually, the answer dawned on me. The water in the car had been slightly soapy, as I wrung out the cloths and sponges there was some foam on them. I thought this might be old residue in the sponges, but in hindsight it couldn’t have been as some of them hadn’t been used before. I have no doubt the water in my foot-well was from a jet-wash. I get my car cleaned every week or two at a hand carwash and during the jet-wash part they often blast any bits of debris from the grills with the water. There is little doubt that the “drip-funnel” arrangement Mercedes use for draining the grill can’t cope with the high water flow coming from a jet-wash and it all ends up flowing over the edge of the funnel and into the passenger foot-well, a pretty crappy bit of design to be honest

So the good news is that now all my electrics work perfectly, including the remote roof module I fitted, which had stopped working and there are no more warning lights. The only problem I have is that the sound-proofing foam under the carpet is still sodden and drying it out is going to be a nightmare. I think leaving the seat out and running a small heater in the car with the carpet held up for a few days might be the only option.

I’ve seen quite a few people with this problem in my searches, many say the warning lights come on when they brake hard and now I know this is because under braking, all the water under the carpet runs to the front and floods the connector blocks. So the answer is:

DO NOT JET-WASH YOUR SL! Or any Merc that has those bonnet air intakes. I’d say don’t even rinse it with a hosepipe unless you can avoid the passenger side grill. The drainage system just can’t hope with high water volumes.

It looks like it would be fairly easy to make a flat plastic cover for the grill which I can place under the bonnet and block off the vent all-together whist washing the car. I think this is probably a must for SL owners

Thanks to all the posters who take the time to share their knowledge here, without your help this would have been a very slow and expensive fix!

Hi everyone, I have a 2006 facelift sl350, could I have this problem aswell as I jet wash my car every week??

 

[W1Z]

Hi everyone, I have a 2006 facelift sl350, could I have this problem aswell as I jet wash my car every week??

For me, I think that was a red-herring and I jumped the gun with my solution I'm afraid, sorry for the miss-information. I think as far as the top grill is concerned, you'll be ok so long as the drains are completely clear of debris (they can block up). If they get slightly blocked, then it is possible to get water in the car especially when jet-washing, but if they are clear you should be fine.


My post directly above yours was definately my problem in the end, if you are getting water in the car, then checking the underside bungs is definately something else you need to do because I found three that were missing or damaged, which shows it is not rare for them to come out.

 

[vauxhallmaniac]

Hi W1Z glad you finally solved it...... i will keep an eye on mine over the winter thats certainly a new one on here!! Simon..

 

[RHARRASS]

Was this ever sorted

Hi Guys. First post on here but have been following this thread as my SL350 has gone mental. As described on here, dashboard flashing, lights dancing etc etc. Checked under the NSF carpet and sure enough water has got in as expected.

Thanks to all on here who highlighted this problem.

Can anyone confirm what the proper fix is - is it the drainage bung behind the NSF wheel arch or is it the rubber bungs under the car - both i expect.

Can anyone confirm that these two fixes have solved the problem as i'm off to local MB dealer on thursday with these specific fixes in mind.

Many thanks (praying no more rain!!!)

Rich

 

[television]

Yes you have to remove or slacken off the rear section of the wheel arch liner and you will see the end of the spout, many cut the end off so that it can drain.

Its a simple job to get the seats out

 

[RHARRASS]

Thanks Malcolm - taking the seats out - now that does look simple!! Do you think i need to worry about the underside bungs? Dont suppose it will hurt to have them have a look... (apart from the wallet)

 

[television]

You cannot get under the carpet with the seats in,,that is the problem and they are very heavy,,if water has got in although it may dry and be OK you just never know. there are only wires under there nothing else, mainly CAN and wakeup wires

 

[vauxhallmaniac]

Hi Rich, i can confirm removing the N/S/F wheel arch drain bung cured my water ingress to the n/s/f floor pan over a year later i have had the carpet out for a different fault and it was bone dry even some dust about!!!! you would be wise to have the N/S seat removed if the water has travelled back as far as the CD multi changer there are some plug connectors there that will corrode, are you sure you want to pay Dealer prices for this repair there are many Independents on here who will do it at a fraction of the price??? seat out is not too bad 5 bolts, one vac pipe and a couple of plugs just another Sunday afternoon for an SL230 owner:lol::lol:!!!!!!!!!!!!! regards Simon..

 

[W1Z]

Further to this thread, I've found two other leak areas on my SL: One was probably unusual, the bottom seal of the windscreen was leaking - found that out when the screen was changed (insurance). Then I started getting water in the boot due to a blocked drain at the base of the rear pillars. Found that and cleaned it out thanks to Malcs excellent guide.

Now I'm water free again, shame that leaks tend to wreck the PSE pump, I've fixed mine about 6 times now, which would have been very expensive if I hadn't been able to do it myself

 

[television]

You should really do the C pillar mod where the seals are glued down on both sides. I never had one drop of water in my SL since doing that mod.

Water is a killer in our cars

 

[Marrijon]

Instrument panel malfunction.

Hi. I've just seen your post from some time ago in connection with water ingress damaging the electrics. I've just had an almost identical problem. My car was parked outside my office in Sheffield on Friday July 6th 2012 which was the worst day of the recent unrelenting heavy rain. It was on a slight incline with the front end about 4" higher than the back. When left a 5pm to go home the bell noise sounded after about 100m and all the dials dropped out. Virtually all of the warning indicators were flashing. I stopped for a minute or so and switched off the engine. When I restarted the fault had cleared. Someone I know from the local Merc dealership told me about the grommet in the receptacle just below the air intake on the top of the bonnet at passenger side. Sure enough it was full of decayed leaf matter and there was about 6" of water in it. We removed the grommet and the water drained out.Over the next week or so the weather improved gradually and the car has been in full sun for at least a day. However the instrument panel has gone completely out of control now and is bleeping with all of the lights flashing etc. Ive had to take it to a local German auto specialist to have it looked at but from reading the posts it's sounds like it will need the front passanger seat out to check the cabling. Do you know how long this
takes?

 

[television]

The seats come out in 20 mins each side, the passenger side should be the one though both sides have CAN wires in them and connectors. It a matter of checking the Can and wake up connectors, applying a non drying switch cleaner to them all and then drying off the carpets. you should not pay for the drying time

 

[Marrijon]

Spot on thanks. The garage have confimed as much. The SAMs are still functioning and they've advised about £200 charge to remove seats, dry the carpets check for corrosion and re install the seats. They've been really good and agreed a courtesy car at low cost even though I'm well out of warranty.

 

[television]

Thank goodness I do not have to walk around any more with those seats, I had the comfort ones and they are very heavy, this is what your car is looking like right now. I never had water damage, just a wiring fault from new

 

[Marrijon]

Crikey. Looks a bit of an upheaval!
Now that the grommet has been removed from the air intake on the bonnet, do you know if there can be certainty that there will be no recurrence of this fault? I'd hate to
have water get down the bulkhead again say, in the winter time? Cheers. Jon.

 

[television]

You need to cut off the spout on the heater box drain that comes out under the rear section of the passenger side wheel arch