maxprimus

I have a 2012 W166 ML350 Bluetec.
The front and back windscreen washers do not work. I can hear the pump.
the Headlight washers works well.
Because both front and back are not working I don't think it is the nozzles.
Is there a check valve in the system that could be clogged.
Does each nozzle have its own check valve.
Will I do any damage by using a needle in the spray jet holes.
Any advice will be welcome.

pcy

I don't believe there is any check-valve in the windshield water system.

There is a screen/filter that is attached to the pump where the water gets pumped in to the system. It is possible that screen/filter is clogged. There is a separate pump for headlight washer and a separate pump for the windows cleaning.

If I were you, I'd pull out the pump and check the condition of the screen.

maxprimus

Thank you for the info.
The next query would be:
How to get at the pump as it is hidden way down somewhere below the left headlight and water bottle.
On YouTube there are only different and older models and on each they seem to want to pull half the car apart to get at it.
Is there a solution I could use to dissolve any gunk that may have built up without damaging any components (and Paintwork).

ItalianJoe1

Nothing to clean it without removing it.

Pull the wheel and fender liner, you should see it there. Not that bad to get to, take it out, clean the screen or replace it (they are cheap at the dealer), and it will work like new again.

pcy

^ +1.

Removing the left front wheel helps if this your first time accessing washer fluid pump.
It's not absolutely necessary [to remove the wheel]. What I do is turn the steering all the way to the right so the front wheels are pointing to the right, then remove the pins and screws holding the plastic liner for the front left wheel well - you only need to lift up the liner that is towards the front. You should see the washer tank. These pumps are usually attached to the side of the tank. You just need to pull the pump straight up. Use a screwdriver as leverage, if necessary.

RA112623

fyi, i have a 2016 gle (USA). i have determined that the rear wiper washer feed takeoff from the reservoir is higher than the windshield takeoff. the rear washer stops far ahead of the "check fluid" indicator. this is now consistent since purchase (kept an eye on it). figure more important to see ahead than behind (but i thought that was Italian road-racing rules ) don't know if any of this pertains, just wanted to provide some info. good luck, ron

maxprimus

Thanks everyone, I will have a go at it with the wheel on. If unsuccessful I will go up to my son-in-law's who has all the good gear including a heavy duty jack and an air compressor. As he likes me so much, I might even get him to wash the car. And, Italian Joe1, I have 2 Alfa Spiders for my own toys. The Merc is for the missus and towing the camper trailer.

odin101

this is my scenario

Etienne Lau

Whats your problem. It's not clear from you pictures. What kind of WW fluid you put in? I hope it's not the RainX stuff......

odin101

walmart sale it , Color of liquid is blue

Etienne Lau

Don't matter if fluid is from Walmart or otherwise. My experience with WW fluid is anything that leaves some sort of film that is similar to RainX will cause issues with MB, VW and probably BMW WW systems. The only fluids that work well are your standard WW fluid that just evaporates and does not leave a water repellent film on the windshield.

Barry45RPM

There is a filter in the bottom of the WS Fluid Tank that gets clogged periodically. They have to remove the fender liner to get to it... that is your problem. I primarily use the green bug type fluid (whichever is cheapest) but will substitute the blue when I can't get it.. (Which is an irrelevant fact).

The filter will solve your problem.

ItalianJoe1

What he's showing is the "filter", it is part of the grommet that the pump sits in. We usually replaced them, you can also rip off the slotted end and it won't plug up in the future. I've never seen a pump actually clog up, only that rubber filter, so I don't know how that will go for everyone but we never saw it be an issue.

petergusa

Thanks for explaining the tank grommet with built in filter is what's shown in the pictue. Its upside down with the filter end going down into the tank. If any one has taken a garden sprinkler apart you'll notice there's something similar inside - looks more like a course filter with holes in that case. This has really fine holes so easily blocks. Mine was blocked with blue gunge too. Easy to clean to like new again under hot water. No need to replace. No more additives for me, just clean filtered water from now on!