Continuous pressure increase

[letsdoit]

Guys,
I have a HP 1050 Quaternary valve Pump.
recently I have started haveing this problem ...
The pump pressure starts rising and the pump eventually stops.
Initially I thought that this might be due to the column...
But then the pressure keeps on increasing without the column as well.
However one more peculiar thing is that at low flow rates like 0.25 or 0.5 ml per min, the pressure remains steady altough a bit high like aroung 40 bar for 0.25 ml/min flow rate but the pressure goes on increasing at flow rates 1ml/min and greater.
the pump then eventually comes to a halt due to high pressure

Any suggestions why is this happening ??

[DR]

there are frits at the outlet check valves that are clogged (at least that's what I'd suggest if it were an 1100 - probably same w/ 1050).

[gbalock]

Another possibility may be a partially clogged flow cell.

[DR]

Flow cells tend to spring leaks well before shutting down pumps. I suspect a pump rebuild is in order.

[letsdoit]

Well I guess it is not the flow cell because I removed the column and just ran the line from the injector directly into the waste....without detector in connection...
And the pressure still kept on increasing.
I shut off the machine and went for lunch.
Now when I am back and just started the machine the pressure does not increase and stays constant at 21 bar just like it would do previously.
and now its running at 1 ml/min flow rate without the column and there is no increase in pressure

I am confused as to whats going on

So i do not know what the problem is....
I am sure if I run it overnight the pressure problem is going to begin