Breville Bes 920 no Crema and bad tasting coffee issue fixed

Just a quick service note on a Breville Bes920 that came in recently. The pressure gauge was not working at all and the customer was complaining that the coffee no longer had crema and did not taste good.
It turned out to be multiple factors contributing to the issue so I thought it worth going over them, these will be of interest to Breville owners.


Poor quality coffee from a Breville Coffee Machine

I happened to have an identical Breville BES920 in the shop and it made great coffee. It had the Breville buzzing valve syndrome which I will blog about later. Anyway I conducted a flow test, as this unit has a nice timer function, I timed how long it took to fill a shot glass. This included the infusion time that is programmable. The good unit filled the glass in 17 seconds, the unit making the poor quality coffee took 30 seconds. So clearly a flow issue. Note temperature of the water was perfect.

breville pressure gauge

replacing a Beville pressure gauge

I firstly checked that the pressure gauge was receiving water. It was, so I removed it and tested it, it was faulty. A common problem on these machines. I replaced it (not expensive from Breville) and it was registering very low pressure.
Because the pump sounded loud I checked the supply line and cleaned the flow meter. Water supply was a little slow, possibly some crap in the line which was removed after my inspection. Note there are restricters in the flow meters which accumulate crap. Flow meters can be cleaned by removing the top and flushing them out. Don’t just buy a new one.
As pumps are expensive and customers do not like paying for new ones, I left this to last, in case something obvious and cheaper was the cause. I checked the valves and water lines. The water line did have a leak. Again this is common in the Breville, so I replaced all the o-rings in the line. Cleaned the shower screen and other obvious things.
Note on some Breville machines scale in boilers is a cause of low flow rates. I injected these boilers and blocks with acid and gave them a descale like they have never had, this flushed a lot of scale out. Note as the steam boiler distills water, scale accumulates in the steam boiler on the hot surfaces. This scale can break off and travel into valves and jets, blocking them. and the coffee line goes through the steam boiler and collects scale, so scale is a probable cause of low flow rate.
Next I checked the pump bypass. These appear to be adjustable, although my experimentation revealed no obvious change in pump pressure with adjustment. These bypasses I know from experience are a cause of low pressure. They fail and bypass too much of the water flow. This one was ok, I know as I tried a new one, same pressure.

920 pump bypass

pump bypass bes920

So finally the pump, an Ulka. It looked fine but after replacing it, the pressure was up at 11 bar with the blind filter in place. So in summary, a blocked pump was the main culprit, but scale, a leak and blockages in the flow meter contributed.