Windscreen washer pump diagnosis

[jeffremj]

A little challenge for the TR7 cognoscenti !:D

Over the past 2 years I have had to replace my windscreen washer pumps for every MOT as they seem to fail after a few months. When my 3rd new pump 'failed' I decided that perhaps it wasn't a pump issue. It wasn't, but what was it ...

Final failure mode - pump will spin at full speed but water would only dribble out of the nozzles. Water pickup filter is clear.

[FI Spyder]

Apply a small pressure to the hose going to the washer nozzles. See if you get a good spray. You don't want to much pressure or you could blow something out. You could even blow on hose using your mouth first. My weak spray was due to a clearish slime that built up on the hose screen over the many years. Worked fine every since (8 years). If it can build up on the plastic screen it might block the nozzles etc. as well.

[whitenviro]

I'll be interested in what you found. I've had several of the pumps do the same thing; even when I pulled them out of the system they spin but won't move any fluid. So I was able to eliminate clogs in the tubing or squirter jets as the problem. I have even opened them and looked over the impeller, but saw nothing obviously wrong.

[sonscar]

I had trouble similar to this and I resolved it by fitting a one way valve in the bottle as I thought that the water drained out of the pump and the pump will not self prime.Just my 2pennorth,Steve.

[nick]

If the pressure is inadequate, I'd be looking at the impeller. I had one that was spinning well, looked fine upon inspection but wouldn't move the water. After countless hours of futzing with it I changed it out for a new unit and it worked fine. I'd be tempted to put some Vaseline on it to see if that shores up any bypass.

[jeffremj]

In my situation, it was the one way valve in the water pickup! It became a 'no way' valve. I have just removed the valve (but keeping the filter) and it works as good as new, but with a slight delay as the feed pipe to the pump fills up.