Hi guys, long-time barista, first time poster, and it's cos I've got an Isomac problem.

I bought a second-hand Isomac Tea a week or two ago, I knew it needed a bit of tweaking and cleaning up and whatnot, and I don't mind that sort of stuff at all, so I descaled it, stripped the grouphead, cleaned it up, replaced the gasket and whatnot and put it all back together again.

Unfortunately, whilst it's nice and clean, it still doesn't want to work properly....

I switch on and it warms up, brew pressure wanders up to about 6 bar and doesn't go much higher, with the blank PF in it hits about 10bar before the OPV opens. On pouring a shot, brew pressure dips to 2bar, then slowly recovers to about 4 bar over the 25 seconds or so. Flushing the grouphead with no PF in drops brew pressure to 2 bar, and it tends not to recover, which makes pouring a shot impossible!!

I replaced the pump, I've stripped and cleaned the OPV and grouphead, I've descaled and back-flushed, I've cleaned out the copper pipe for the brew pressure manometer and now I'm scratching my head, what else is there??!? I know it's not me, I know how to tamp and whatnot from working as a barista.

Boiler pressure is absolutely perfect, plenty of steam and hot water, it's just the brew pressure...??

HELP!!

Wow - thanks!! I'll see how much water is pumped out of the return pipe in what passes for normal use at the moment! I had stripped down and cleaned the priming valve and it all appeared okay, but the spring might be a bit tired.

What puzzles me though, is that with the blank in the PF, it does get up to pressure.

Out of curosity, there's another valve between the priming valve with the reservoir return on and the OPV - any idea what that's for? I assume it's another priming valve but as it comes after the two way solenoid for the boiler feed it's another priming valve? I haven't stripped that one yet, as it seemed fine when I had it on the bench the other day - I guess that's worth checking now too.... but what does it do!?!

But thanks again, I really appreciate the help!!

Man, this is becoming epic....

So, I checked the flow rate, I was getting about 300ml/min, clearly something stuck somewhere. So I stripped the machine again, checked inside the HX and it was layered in scale still.... so, after a fun-filled afternoon of soaking in descaler, rinse and repeat, it's now clean and shiny again.

Put it all back together, and getting flow of about 620-630ml/min so I'm happy with that.... but still the brew pressure is poor!! I don't think that it can be the priming valve as this probably comes too early in the circuit to make a difference and it still has to feed the main boiler after that, I stripped the other 'thing' I eluded to above, that was a check valve, that's now stripped and rebuilt with a new seal in it.

Now I'm wondering if there's possibly a leak somewhere - not fluid, but it seems to me that maybe an air leak would drop the pressure and give the characteristics I'm getting - job for tomorrow is to remove, clean and refit all the fittings to the HX that I've messed about with!!

Anyone know if I can safely use PTFE tape on the plumbing? Thanks!!

I need assistance please, I also have an Isomac TEA.

I re-adjusted the OPV from 9 to 10 bar at the blind filter.

When i pull shot the pressure builds very slowly, the shot starts to flow before the gauge needle reaches full bar and highest it gets is about 8 bar.

But when i use the blind filter it reads 10 bar .

What could be the cause of low bar reading while pulling the shot that is properly ground and tamped ?

Thanks, WS

Hi Will, your problem sounds a lot like mine!

At the moment, I'm investigating the air bleed valve - the priming valve that Eric refers to above - as it seems a lot of water was being returned to the reservoir, clearly the OPV is working as we're not getting any pressure beyond 10 bar. Presumably you're getting a fair bit of water returned via the shorter of the two pipes into your reservoir too?

The air bleed valve is located after the braided hose from the pump and before the T junction that goes to the two way solenoid underneath the boiler.

At the moment, I've blanked off the bleed valve and put a stopper in the silicon pipe - I'm still double-checking the connections around the HX for a possible leak so I'll let you know if this makes a difference when I get everything put back together!

CSME9 wrote:I need assistance please, I also have an Isomac TEA.

I re-adjusted the OPV from 9 to 10 bar at the blind filter.

When i pull shot the pressure builds very slowly, the shot starts to flow before the gauge needle reaches full bar and highest it gets is about 8 bar.

But when i use the blind filter it reads 10 bar .

What could be the cause of low bar reading while pulling the shot that is properly ground and tamped ?

Thanks, WS

Grind finer. Coffee flow at low pressure is simply a grind adjustment, or your coffee is way beyond its service life, or you have massive channeling problems, or a combination of everything. The pressure never gets high because there is not enough resistance in the puck for the pressure to build. Normally, on a e61 machine with a vibe pump it will take around 5-6 seconds after the pump is turned on before you get the first drops from the basket, longer if you are using a spouted portafilter. If the coffee is flowing after 2 seconds, you have a coffee problem.

Adjusting an OPV with a blind basket on a vibe pump machine will normally give you one to two bar higher pressure than you will get with flow. So Set it at 10 bar with a blind basket and expect 8-9 bar with coffee. With that said, your max pressure does not sound bad but the early extraction does, if I am reading your post correctly.

Yay!! Sorted.

Lovely espresso now being produced again

The problem turned out to be a poor seal by the mushroom valve inside the group head and another slight air leak in the thermosyphon circuit. The problem was more to do with the mushroom valve than anything else.

The air bleed/priming valve appears to be largely redundant in every-day use, I blanked the bleed valve off to check it, and it made no difference whatsoever!!

So, in conclusion, if I had this problem again, I would firstly make sure the HX circuit and grouphead is thoroughly descaled (my HX was a mess, despite some hardcore descaling action in the preceding days), then I'd make sure that everything was snugged up nice and tight. I've used some PTFE tape to ensure the integrity of the joints.

Thanks guys for your help!! Really appreciated!!

Student Bob: Glad you were able to fix the problem.

This morning i pulled several good shots, not sure what happened but my machine seemed to work ok.

Cannonfodder: I understand the need to grind finer and the difference in pressure w/blind basket and without, since owning this machine a few years the difference has been approx .25 to .50 bar between using a blind and pulling a shot, i did not expect to see 2 bar difference.

I did notice today while flushing plain water thru the group without a basket the return hose was dripping steady water back into the tank. When i pulled a double shot at 9.75 bar the return hose to the tank had a steady stream of water....is that nornmal ?