Aaaargh - Bosch Dishwasher will not drain again!

Hi, I'm hoping someone can help me....

I have a Bosch dishwasher, it's about 6 or 7 years old. Water started being left in the bottom at the end of the cycle, so I did the usual, checked the waste pipe, unscrewed the cover in the sump and checked the propeller, removed and checked the rubber valve flap. All ok. Tried again, it worked, then a few days later the same.

This problem has been going on for a couple of months now. Sometimes it will work ok for 2 weeks then it will return and usually after double-checking the propeller is not inhibited a couple of cycles through rinse and quick wash and it has been resolving. Today I cannot clear it. I've had the outlet hose into a bucket, some water dribbles out and I can't get it to clear. I can hear the pump running so either there is a blockage somewhere or the pump is in some way faulty - not sure hiw to check the outlet pipe for a blockage and the appliance end?

Given its age and our intention to replace is next year anyway if the kitchen refurb goes ahead, I am reluctant to spend much on it, but wasn't planning ob buying a new machine this year.

Suggetions very welcome, thanks

Best thing is to remove the drain pump and check for any obstructions that bob in and out.
Otherwise these pumps can get weak and intermitant or the impellor can actually break off the shaft/the vanes break

Thanks Leccy758 - the impeller seems fine, it turns as I would expect it to and has a little resistance, so suggests it's all attached ok. How do I get to the pump, do I have to take the top off the appliance to get to the back and I wasn't sure what you meant by seeing what bobs in and out?

Sometimes bits of crud can jam the impeller and they can move about so they block it for a while then get dislodged, then fall back in etc etc.

Drain pumps on Bosch D/W are accessed by a removable base if lucky or by removing the front kick strip and going in through a little access panel (easier to remove the metal door outer if going to do this though.

A quite common one I have found is a blockage in the waste pipe especially if it goes onto a spigot (I usually push though a pulling wire or a piece of three core 2.5 mm flex down the waste hose after checking for grease and gunge in the end of the pipe and the spigot or down pipe)

Thanks again Leccy. I haven't tried to get to the pump as yet, so having to go through a cycle of starting a program, rest, starting reset about 5-6 times. This starts the pump and by putting the outlet into a bucket I can see when the flow goes from a trickle to a proper flow and I know that if I run a full cycle it will then work. Observing that suggests that the pipe isn't blocked as it will flow normally but that periodically (and increasingly) it seems the pump will just not push the water out other than a tiny trickle. Does that suggest the pump has had it rather than is blockled, it surely can't keep blocking and clearing by starting it multiple times?