Boiler pressure dropping greatly while pulling a shot

[bigjp]

When I pull a shot on my Isomac Tea the pressure builds up to 9 bar, sits there for about 5 seconds, and then the boiler pressure starts dropping. The red light comes on when it starts dropping and it goes from 1.1 bar to about .5 bar before the shot is finished. As soon as I lower the lever it builds up again to 1.1 bar (where I set it). The brew pressure stays at 9 bars the whole time. I haven't had this happen when I back flush...only when pulling a shot.

Before this started happening I did some work on the machine. I descaled the HX and boiler, changed the power relay, and put a heavy duty OPV in it from Chriscoffee. The OPV is much bigger than the stock one, so I had to put a new piece of tubing on it to accommodate the size. The piece I changed is the one that is under the boiler and connects to the OPV. I can't find any leaks anywhere.

I checked the tube that sends water going back into the reservoir. When I backflush, water starts going back into the reservoir when it hits 9 bars, so I don't think it's the pressure relief valve. I got 6 oz. of water from the group in 25 seconds, so that might rule out the pump. I'm thinking since it doesn't happen when I backflush it shouldn't be an obstruction. I'm all out of amateur assumptions, so if anyone has an idea I'd love to here it. (edit: Okay, all this stuff I'm thinking of would be connected to brew pressure problems, not boiler pressure....I am tired.)

Just thought of something....I recently put in a new thermal fuse from Chriscoffee, but I didn't have any problems with it before descaling.

Any help you guys can offer is much appreciated. It's late here and I'm falling asleep at my desk, so if I can think of anything else I did in the morning I'll post it.

Chuck

[bigjp]

This morning I realized that in my sleep deprived state last night I made an error while trying to figure things out. When I back flush I don't let the water run long enough to get the pressure drop. So of course it also happens when I do a blind flush. I just have to let it run for the full length of time like a shot.

The red light will come on just as brew pressure reaches 9 bar. At about the 17-18 second mark after lifting the lever boiler pressure will start to drop. By 25 seconds it is on the .6-.7 bar mark, and at 30 seconds it is just under .5 bars. I haven't let it go any longer than that.

[another_jim]

Chances are there is either a leak in your HX (very bad) or the boiler refill valve is not sealing totally (bad, but not that bad). The second is more likely. The symptom you describe comes from cold water entering your boiler while you are making the shot. If this is the case, the boiler is overfilled. You can check this by running hot water. If the boiler refill doesn't come on almost immediately, after about 1 ounce of water has come out, the boiler is overfilled. This means the diagnosis is correct. If the boiler is not overfilled, I have no clue what is happening.

[bigjp]

Spot on once again Jim!!! I pulled 10 oz out of the water tap before the refill activated. So did this happen when I descaled you think? How can I fix the refill valve?

Thanks!!!

[bigjp]

I've been running it through some tests today and what I'm finding is this:

sometimes I can get a lot of water out of the tap before the refill kicks on >6 oz
sometimes I only get a little <1 oz
when doing a blind flush sometimes the boiler pressure drops a lot
sometimes it drops just a little under normal

So the refill valve probably isn't closing like Jim said because of the inconsistency with the symptoms, yes? I checked the wire connections for the solenoid under the boiler and they were loose (recent problem a member at CG had). I tightened them and the problem persisted. So could it be some debris that is stuck in there? Can I clean it out or do I need to buy a new part?

[another_jim]

I've been running it through some tests today and what I'm finding is this:

sometimes I can get a lot of water out of the tap before the refill kicks on >6 oz
sometimes I only get a little <1 oz
when doing a blind flush sometimes the boiler pressure drops a lot
sometimes it drops just a little under normal

So the refill valve probably isn't closing like Jim said because of the inconsistency with the symptoms, yes? I checked the wire connections for the solenoid under the boiler and they were loose (recent problem a member at CG had). I tightened them and the problem persisted. So could it be some debris that is stuck in there? Can I clean it out or do I need to buy a new part?

Hi, I hope the descale didn't create the problem -- but it sure sounds like the process knocked some debris loose and it lodged in the valve.

Unfortunately, you've gone beyond my knowledge -- I've never had this problem (my only source of espresso knowledge) -- and I don't know if the valve can be cleaned. You may want to post the question with a clear title like "how do I fix a refill valve" to see if anyone can help.

[bigjp]

Hi, I hope the descale didn't create the problem

Jim- I hope this statement doesn't suggest that YOUR instructions did something to create this problem. Nothing could be further from the truth. If the problem did develop because of the descaling then it happened with MY full knowledge that I am NOT a professional and I AM completely aware of what can occur during the process. I'm still testing wire connections on the chance that I knocked something loose while putting the new parts in.

Unfortunately, you've gone beyond my knowledge

Man, this statement gave me the feeling like the bad Terminator won the fight and Judgement day actually comes in T2.

After I do some more checking around my machine, I'll post a specific thread about the problem at CG. Honestly, I don't even know what the refill valve even looks like. I've done Google and CG searches and can't find an image of it.

Thanks for all your help so far Jim!!!!!

[HB]

Honestly, I don't even know what the refill valve even looks like.

I believe Jim is referring to the two-way solenoid:


Image courtesy of espressoparts.com (link)

There's also another pictured in Odd Expobar problem - no thermosiphon that Sean posted.

[another_jim]

Man, this statement gave me the feeling like the bad Terminator won the fight and Judgement day actually comes in T2.

Most amateur to amateur espresso advice is from people who've had the same problem and fixed it before you did. Unfortunately, I've been around long enough with unreliable enough gear to have had A LOT of problems. But there's always new ones, for you to solve, and then seem really clever when your turn comes to answer questions like these.

[bigjp]

LOL! That is so true Jim. I'm a complete amateur with all this and so clueless to many things discussed on these forums. However, I look back to what I was posting a year ago when I first got into it and just shake my head at how little I knew then. I've had enough things break on my machine so I can now at least understand the basic operations of it.

Thanks for the pic Dan!

The solenoid is something I do know and I actually have a brand new one sitting at home. I'm at work now, so don't have the machine in front of me, but if my memory serves me right I just have two main pipes I need to disconnect (and of course the wires) in order to get it out from under the boiler of a Tea. If looking at the machine from the back, there's one pipe coming from the boiler on the right and then one attached near the OPV on the left. If I disconnect both it looks like that whole section with the solenoid will slide out from under the boiler if I slide it to the right.

Does this sound right? Or is there something else I should disconnect to get it safely out? I hope that all made sense anyway.

[bigjp]

I pulled out the solenoid with no problems. Actually, it was quite easy to get out. Once I had it out I took some time to check wiring around my machine. I noticed some wear on some of them, so I spent some time on fixing that. I put the new solenoid in and put everything back together. I fired up my machine and........hmmmmmm....same problem.

I started checking other things I thought it could be like wires, clogs in pipes, and then the P-stat. I pulled it off and checked all the connections. No problems. So I thought to try the one I had on there before but took off because it was broken. With the old one I couldn't get my brew pressure to rise. I tried it out using a blind filter and while the brew pressure didn't rise, the boiler pressure didn't fall.

It was late when I tried this, so didn't do too much fiddling around. I should try and see how much water comes out of the brew head just to see if I'm getting the right quantity. If I'm getting less then that could explain when the boiler pressure if not going down on this one.....maybe? Anyway, I'm thinking it's safe to just go ahead and order another p-stat. The one at espressoparts.com looks like the right one. It's labeled for use with the Oscar (older model I guess), but it should be the same one that the Tea uses. I'll email them and make sure.

If anyone sees anything wrong with any of my theories or anything I posted, please post your thoughts on my problem (personal or otherwise. )

[shadowfax]

The thought occurs to me that if your wiring is OK and the refill solenoid is OK, the Giemme/Gicar unit that controls it could be malfunctioning. That would probably be pretty expensive to test via replacement, though.

[bigjp]

Yikes! Yes, it would be expensive. However, right now I'm at a loss over what is going on. After trying out the other p-stat again, it is working just as the first one was. I was getting some leakage from somewhere, but I couldn't find where. I could hear it, but couldn't see it anywhere. Now it seems to have cleared up. Haven't heard anything all day today. If it is the Giemme board then is there something that could have happened to it during the descaling, or would it just be coincidence? I can't think of anything that would affect it during the process, but when I make assumptions I'm wrong 90% of the time.

I'm going to give Chris a call tonight (his morning) and see if someone there can think of something. This whole situation is driving me nuts.

[bigjp]

Thanks to all you guys who offered advice for my problem. Once again, my machine problems helped me understand how things work much better.

My machine is now fixed and it had nothing to do with any of the parts. I ended up cleaning the wires with a file that were connected to my heating element and the problem went away. I guess there was corrosion on the wires that was keeping the heating element from getting enough power. Sounds strange, but it's now fixed so I won't question it.

Soon I'm going to change all the wiring in my machine as it's not looking so hot.