For the past few months we've noticed the washer nozzles on our GLK have lost most of their pressure. They now just barely push fluid to the bottom 20% of the windshield.

I'd like to avoid taking it to the dealer and paying $300 for them to look at it (out of warranty now).

Any thoughts?

On a SAAB that I owned I had a similar problem that was cleared up by disconnecting the rubber tubing and running the washers to free some gunk from the lines. The SAAB also had a series of check valves to keep the lines full and one failed,, not sure if the GLK has this feature. Also stopped water from draining out to the headlight washers.

I would sure check the filter and the lines before replacing the pump or anything drastic. Disconnect the tubing at both ends and blow it clean then check the filter in the reservoir for plugging.

It is not possible to disconnect tubes from nozzles, but you can easily check the pump, just remove left front tire, remove plastic liner and you will see the reservoir/container for the washer liquid...if you have also headlight washer nozzles there are two pumps...disconnect tubes from pumps and try it...check also the tube connectors to the pumps, I had problem with one of the plastic connector, I have heated tubes and nozzles, there was electrical shortcut which melted the connector on pump and plugged the tube...pump was working, but no water sprayed on windshield...headlight washer nozzles worked without any issue, the same for rear window...only windshield didn't work. The pump is very cheap part, more expensive is tube with nozzles, also more work to change it (need to remove wipers and plastic cover under the windshield)...but still easy DIY...