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'00 ML 430
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Discussion Starter · #1 ·
Can someone please post a detailed routing diagram of the tailgate washer line. Mine seems blocked. Water will come out a drop at a time at best. And the pump is fine. Arrrrgh.....

Here is what I did so far:

I disconnected the rubber line from the spray nozzle in the tailgate to rule out any issue with the nozzle. I then connected a bicylcle pump to the other end of the rubber line (that normally connects to the washer pump)

I can pump up the pressure to about 60 PSI while blocking the end at the tailgate. Once I release the block the pressure goes down at a rate of about 10 PSI per second and some water bubbles out. This is way too slow.

My bicycle pump is a large volume floor version. Even without blocking the line with my finger I can build up the pressure to about 40 PSI just by pumping at moderate speeds. So there is got to be some serious blockage somewhere.

Now I wonder where the most likely spot would be for the blockage. I did check the feedthrough to the tailgate and the metal clips.

I didn't install or do anything to the car that would cause the line to get pinched. At least nothing that I remember. But I haven't used the washer in a long time. So I fear there is some deposit buildup somewhere.

My plan is to cut into the line somewhere along the way and them use male-male connectors rather than replacing the whole darn thing. What would be good spots.

Any pointers?

Thanks,
Ingo
 

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1999 ML320 Elegance, BMW R1150RT, SAAB 9-3
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282 Posts
not familiar with the details of the ML's rear squirter but i can tell you about my other car... it has a check valve for the rear gate squirter - the check valve broke and acted a bit like your problem. with the long run back to the tailgate on the ML i would expect some sort of check valve too (without a back flow preventer check valve the line would drain back into the reservoir and it would take long time for the squirter to work due to the transit time from pump to rear sprayer). maybe search the vehicle or the internet for "ml squirter check valve" or something 'along those lines' (hehe pun!). maybe checking the official parts fiche might yield some clues...
blocked hose is not very likely wouldn't you think?

good luck

hmmm - as an afterthought - why not try backwashing the pipe -with say compressed air -to see if you can dislodge anything ? that would really eliminated blockage as a likely cause.

did you do any thing to the vehicle since you last remember the rear squired working that might have pinched the hose?
i know you mention this... but it is a possibility - though my money would be on a broken check valve.

full of ideas as i had to troubleshoot my own system not so long ago.
 

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'00 ML 430
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Discussion Starter · #3 ·
I really don't remember anything I have done to the car that would even remotely result in a line pinch.

I agree that the check valve is a good guess. I have seen somewhere here a parts diagram and there was an item in it that could be the check valve. It was about half way between the reservior and the nozzle. I hope others chime in with more knowledge on where to locate that bugger. I don't want to rip the entire interior appart. Every time I take something appart on this car some of the plastic noses and hooks let go and it becomes successively harder to put it back together nice.

I was also thinking maybe to backflush the system. But if there really is a check valce in line I would pump against it and potentially cause the rubber line to disconnect. This is what prevented me from doing it so far.

Ingo
 

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'00 ML 430
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Discussion Starter · #4 ·
Here is the diagram I found in another thread. I would like to know what #8 and #11 is. I suspect #8 to be the check valve. Is #11 some sort of grommet or seal?

From the form of the rubber line I guess it runs from the reservoir across to the passenger side somewhere behind the dash/front firewall and then close to the passenger side rocker panel before it goes up at the c-pillar to the roof line. Is that correct?

So should I start taking the passenger side carpet away in an attempt to locate #8? Anyone?
 

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Check valve should be close to rear washer nozzle.


.
 

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1999 ML320 Elegance, BMW R1150RT, SAAB 9-3
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not to challenge the great witek:rolleyes: (as he nailed it with his post - both prooving the existence of the valve and providing you with the part #!) but if i were you i would start looking at the engine side first. makes way more sense for the valve to be at the start of the run. indeed the valve in likely to be accessible from within the engine compartment - albeit it with great difficulty.

i pulled the back of my saab (can i say that here? :D) apart looking for the cause of my inoperable tailgate squirter - have some badly fitting panels now as a result. the valve ended up being at the front - under the hood.... so the destruction achieved nothing.

imho: ** just start tracing from the reservoir output centimeter by centimeter ( where 2.54 centimeters = 1 inch ) ** ... you may have to remove wheel liner, adopt some interesting yoga poses, loose some skin on your forearm, etc in your search. good luck:thumbsup:

the only caveat - the picture (but not the parts listing) shows the firewall grommet before the check valve - so the check valve could be downstream of the firewall - which would place it NOT in the engine compartment. the parts list however has the check valve listed before the grommet. i dont have enough experience with ML documentation to say how these two factors could be used to draw any type of conclusion w.r.t the valve placement. imho the picture kind of has the valve floating in space... like the guy doing the autocad drawing didnt know quite where to place it!
 

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Rear check valve was installed to prevent post nasal drip on tailgate. There might be another one in front. I would look for it in air intake cowl. That's where front one is.

.
 

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Discussion Starter · #8 ·
Ha, now it seems we are getting somewhere. The TSB seems to imply there is another check valve somewhere (placement not optimal). And since I had my tailgate appart to disconnect the rubber line from the washer motor I know mine doesn't have the second one installed.

Now the question becomes how accurate is that drawing I attached in my previous post. It suggests #8 to be in the front passenger door rocker panel area after grommet #11.

I don't have much experience with MB parts diagrams. Any ideas?

Ingo
 

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Discussion Starter · #9 ·
The solution to the mystery: After ripping most of the interior appart I decided to cut into the washer line in the rear passenger door sill area. Fortunately, it was flowing well from the pump to that location. Next I took the C-panel interior cover off and finally found the check valve. See the attached photo. It was clogged with debris from what looks like hard water. I took it appart and cleaned it. All is well again.
 

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99 ML430, 00 ML320, 05 E500 4matic Wagon
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Success at last. I hate to think how many hours you had into that, but it is working.
I bet a dealer would have gone at least a grand on that.
 

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2001 ML430 Sport bought in very nice shape despite 156K miles in August 2010
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Nice work. Extra credit for the effort required to find the valve and restore it to operational state. Congrats!
 

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2003 ML500 Sport
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instructions for removing C pillar

Hello - I am now having the same problem with the rear washer. Can someone please help post the instructions to remove the c-pillar to get to the check valve? Thanks!
 

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1999 ML320
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The blockage of the windshield washer check valves is quite common, specially in a 15 year old vehicle.
It may be due debris, dishwashing soap hardened, or just the soft rubber tube inside the check valve that is getting a bit stiff as it ages.
The check valves can be replaced easily, any brand and model of windshield washer valve that fits the hose diameter will work fine. Actually an upgrade will be welcome, since the original design of these valves is not the best.
But you can dismantle the old valve and give it a few more months or even years of life.
I did it and it's working well for months.
It's a bit trick to open it without destroying, but with a thin screwdriver and some patience it can be done.
Sometimes a good cleaning is enough, but if the little rubber tube got stiff, there's a workaround. Just make four cuts on the rubber, turning the tube into four flaps, as shown on the diagram below.
During the reassembling position two oposite flaps over the holes on the center tube.
Blow some air to check if it's opening. If not, make the cuts longer, but do not cut through the sleeve, since it seals the valve when reassembling it.
Be carefull to not rip and destroy the rubber completly, nor just take it away, otherwise the valve may leak inside the vehicle.
If you have done it right now you get a working valve again. ;-)



Four cuts on the rubber tube inside the check valve.
 
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