I have an Isomac Millenium which has given exemplary service for 8 years now.
I have recently completed a service on the E61 group head replacing valves gaskets etc. It's like new again.
I am curious about some of the main componentry (ie. pump, thermostats etc).
I have searched but cant seem to find any threads about assessing performance of an older machine plus subsequent strategies for overhaul/component replacement.
From various threads the critical areas are brew pressure and temperature. I am intending to procure some equipment to take a look at these.
Interested in hearing any comment or advice that you may have on the subject.
Thanks.

So I've put together my portafilter brew pressure measuring device. First test is topping out at 8 bar (closed circuit). OPV seems to be working.
I adjust the OPV a couple of times but the max I seem to be able to get is 9 bar. Certainly nowhere near the 11.5 to 12 bar that I was expecting. I observe water flowing back to the water reservoir from the OPV.
The pressure builds slowly to 4 bar (10 secs maybe longer) and then goes quickly to the end pressure.
My conclusion from this is that the OPV is faulty and opening at 9 bar regardless of the setting.
The pump may also be past its best given how long it takes to get up to pressure.
My current intention is to replace both the OPV and the pump.
Any thoughts or advice would be most welcome.
Thanks.

Do you want to brew higher than 9 bar? The ramp up time is normal for an e61 vibe pump machine. Unless you want to brew coffee at 10 bar, there is no need to replace the pump or OPV since it is producing the needed brew pressure.

When did you last descale the machine? Vibe pumps are relatively inexpensive so replaceing it would not break the bank if you really wanted to swap it out. Instead of replacing the entire OPV you could simply replace the spring that controls the OPV pressure. I am assuming you could get the spring, it has been a few years since I owned a Millenium. Scale buildup will also limit pressure.

I agree with Dave. Give your machine a descale if you haven't already and if it aint broke, don't fix it!

Your measured ramp up time to 4 bar is also likely largely influenced by your measuring device.

Been following this thread as I have been refurbing the millenium I picked up second-hand.

On mine I ended up replacing the vacuum breaker, shower screen, group head gasket, replaced the plastic plumbing tees with brass, and added teflon tape/cord to a few fittings to eliminate some leaks. I also did some serious descaling, backflushing, cleaning inside & out, and group head scrubbing with partial dis-assembly. Did all this with the case removed, waited until I was happy with the performance and the machine could be on 24/7 with no hissing or other weirdness.

I'd like to borrow a pressurefilter (?) to measure the pump, but as far as I can tell it's working fine... so I am not too concerned.

Just go to the hardware store and pick up a pressure gauge. Get a double female adapter, unscrew the spout on the portafilter, screw the adapter on and the gauge on. Instant portafilter pressure gauge. You will have to give the threads on the portafilter several wraps of Teflon tape. The threads on the PF are BSP (metric) and your adapter and gauge will be NPT but they are close enough to thread together but not seal.That is where the Teflon tape comes in.

Awesome info, thanks Dave! I will probably pick up a gauge today. I had researched this but was a little overwhelmed by the variety of information!

So basically, sounds like I am looking for pressure to build slowly to 4bar, then peak between 9-10bar.
Assume I use a standard single or double basket (empty) and no worries about brew water getting into the gauge. Please let me know if there's anything more to it! Thanks again.

With a closed circuit pressure test at 9 bar I am assuming that actual coffee brew cycle will be more like 7.5 bar (difference of 1.5 bar to that measured with closed circuit)? This is based on some of the posts I've seen in this forum. Any comments?
If it is at 7.5 bar is it worth aiming for 9 bar actual brew pressure which would require around 10.5 bar setup (again based on various posts). Perhaps not?
I descaled a couple of months ago so I'll probably do that and remeasure.
Anyway thanks for your comments.

The pump may also be past its best given how long it takes to get up to pressure. My current intention is to replace both the OPV and the pump.

My comments are made with the 8 years of service provided at the forefront. Lots of parts have paid their dues, including the pump, air release valve, and OVP. The pic below may or may not represent your machine but should be close.



Item 1 is the air release valve, also known as a priming valve. This should be replaced as it is a prime contender for your pressure buildup taking a couple of secs longer than usual.

Item 2 is the OPV. Yours may/may not be this large. Even though you don't need to, I would replace the entire OPV and "rebuild" the existing one for future use. Here is a separate pic of the one in the above pic disassembled:



The little part above the spring is what you would typically replace along with the o-ring (not clearly shown) on the adjusting "nut". When you replace the pump, also replace the rubber mounts for the pump.

Eric,
Many thanks for your advice, which I will definitely use.
I'm also seriously considering fitting one of your temperature probes.
There is some really impressive knowledge amongst the membership of this forum.
Thanks All!