Low temperature grouphead idle on E61 HX Rocket

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spiffdude
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#1: Post by spiffdude »

Hi all,

It's been over a year since i've had my Rocket Evoluzione and figured it was due for a descale and some other general maintenance. I had noticed an intermittent pressure noise coming from the vacuum breaker area, which is what decided me to take action.

I first started by descaling the HX using a mix of citric acid and water per recommended concentrations on this site (30ml of powder per liter). I got some green tinged water that cleared out by the 5th flush so i figured i wasn't in too bad a shape.

Ran the machine for a week fine and then got to descaling the boiler. I did this by removing the vacuum breaker and siphoning acid solution in and out of the boiler with a clear plastic tube. The solution came out almost transparent, just a light green tinge, barely noticeable. I took this as a good sign that my water treatment and regular boiler flushes worked out all right.

While i had the machine open, i also cleaned out the vacuum breaker, water level probe and the steam valve that had a bit of a squeak to it. I tubed up the brew cam and follower pins and I also noticed two of the plastic water tubes inside the machine were a bit kinked so i gently moved then a bit to ease the kinks (one is the feed line to the pump and the other i think is the line from the expansion valve to the drip tray). Buttoned up the machine and turned it back on. Heard a slight pressure leak from the water probe fitting which i fixed by tightening said fitting by a 1/12 turn. I believe the probe is more or less at the same height as before. If it's off, it's probably 1-2 mm lower than before.



By the way, does anyone know why there seems to be a little plastic ball inside the tank vent line :?:

Anyway since then, the machine idles lower than before. It used to idle at 208-209 very steadily but now it seems to vary. I've caught it at 179 once (thermosiphon stall perhaps?), but most of the time it settles around 199-204. It will get back up to 208-209 if i flush water or even sometimes, just pull water from the water wand (why using the water wand would help is beyond my understanding).

Boiler pressure seems normal and cycling as usual, brew pressure is fine, i get water coming out the group as soon as i activate the lever as well. Since it seems to idle lower, i've had to adjust my flush since i am brewing too cold with the routine that has become a reflex.

I then proceeded to pull out the mushroom and clean out and descale the HX again (using a tube to push air and flush the HX lines 4 times completely). I didn't have a lot of scale at all, compared to pics i've seen posted on this site. My brew valve seal seems a bit more beat up than i expected, its like something ate away at it but it's not leaking at all.




Now, when i started up the machine after this clean up, it went up to 209 so i thought i had resolved the issue. Today, it's been hovering at 203-204 all day. :evil:

I am pretty darn sure that the HX loop is quite clean and although i thought my brew valve seal had seen better days, i have zero leaks from the discharge tube. Water comes out the group right away when i turn the pump on. I don't see water dripping out of the expansion valve outlet either once the machine has warmed up completely.

Anyone have an idea why i'm not back to 208-209 idle? I am a bit stumped.

My HX path is clear
Don't seem to have leaks in the HX that would cause a stall
Didn't touch the pressure stat settings
Boiler pressure seems stable at my usual range (0.9-1.1 bar)
Can't hear any pressure leaks with my ear close the boiler fittings
My water level probe could be lower than before, but wouldn't that give me a higher idle?
Damn this forum, I've had too m..muh...mah..mmmm..much caffeine!

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spiffdude (original poster)
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#2: Post by spiffdude (original poster) »

Update,

This morning, machine turned on at 7am. I checked the temp at 8:20 and it was at 199. There was water in the drip tray (i dried it last night and put a paper towel) i'm guessing from the water expansion valve outlet. This is normal i suppose?
Damn this forum, I've had too m..muh...mah..mmmm..much caffeine!

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sazerac
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#3: Post by sazerac »

Doesn't the plastic ball act as a one way valve once it settles within a solid housing. With flow in proper direction water just flows past it. Not sure where this would be.

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erics
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#4: Post by erics »

I did this by removing the vacuum breaker and siphoning acid solution in and out of the boiler with a clear plastic tube.
I would have filled the boiler with a baby funnel (available from any hardware store) and then siphoned the acid out as you did. As you probably know by now, you just need to be careful when filling the boiler and allow room for the water to expand.

A real nice mod to the vacuum breaker is to use the top half of one of these - the latest vacuum breaker from the LM GS3 & other models. "Tee" it into the line from your expansion valve to the drip tray.


By the way, does anyone know why there seems to be a little plastic ball inside the tank vent line?
I'm having a problem even knowing what that line is - can the ball move? BTW, the small white plastic reservoir can be rotated by slightly loosening the fastener on the bottom of the casing. Most definitely, you would not want a kink in the pump suction line.

I believe that your problem coincided with a leak (possibly intermittent) from the brew valve. Your pic shows a tired valve seal. That water is > 212 and any slight leak would easily be missed as the water flashed to steam - even more so if your PF is in the group. Get a new brew valve and some replacement inserts. Gently disassemble the old valve using a heat gun on the thread sealant.
Skål,

Eric S.
http://users.rcn.com/erics/
E-mail: erics at rcn dot com

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erics
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#5: Post by erics »

It will get back up to 208-209 if i flush water or even sometimes, just pull water from the water wand (why using the water wand would help is beyond my understanding).
The flushing process inherently fills the hx circuit full assuming there is a slight leak. The filled circuit allows the thermosyphon process to continue.

Removing a slight bit of water from the boiler via the water wand lowers the water level and would tend to increase group temperatures - see this - about 1/3 of the way down the page - Boiler Fill Level Impacts Shot Temperature Stability in PID'd Espresso Machines .
Skål,

Eric S.
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E-mail: erics at rcn dot com

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spiffdude (original poster)
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#6: Post by spiffdude (original poster) »

sazerac wrote:Doesn't the plastic ball act as a one way valve once it settles within a solid housing. With flow in proper direction water just flows past it. Not sure where this would be.
That could be. I think i will ask Rocket what it is.
erics wrote:I'm having a problem even knowing what that line is - can the ball move?
Yes it seems free within the tube. That tube is connected to the white cylinder which acts as the receptacle for water coming from the tank. It then runs back to the top of the machine and is open ended. In a review from Bellabarista they call it the vent tube. To somehow vent a possible pressure when the tank is inserted in the white cylinder i think. The cylinder to tank interface has a o-ring, so when that o-ring engages maybe it traps some air that needs to go somewhere. Not sure what the ball accomplishes though.
erics wrote:the small white plastic reservoir can be rotated by slightly loosening the fastener on the bottom of the casing
Aahhhh, that's a great idea :idea: , I will rotate it to relieve the kink some more.
erics wrote:I believe that your problem coincided with a leak (possibly intermittent) from the brew valve. Your pic shows a tired valve seal
That sounds logical. Would explain why i can get back up to 208 when i flush the machine and why it then slowly creeps back down to 199-200 like it did this morning; a small leak slowly emptying the HX circuit. i'll order a new brew valve AND some spare seals then.

Will update this tread with results. Thanks for the feedback guys, much appreciated.
Damn this forum, I've had too m..muh...mah..mmmm..much caffeine!

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erics
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#7: Post by erics »

Not sure what the ball accomplishes though.
Well, it could certainly act as a restrictive device should the free end of the hose inadvertently drop below the water level of the reservoir - after all, water does tend to seek the lower level - hello countertops :(

Additionally, as David said, it should travel to the port on the "baby" reservoir as the pump operation takes suction. It would prevent the pump from sucking air. That port on the small reservoir is used as a return from the OPV/pump priming valve on vibration pump machines and, in my opinion, simply capping the port off completely would have sufficed in your situation.
Skål,

Eric S.
http://users.rcn.com/erics/
E-mail: erics at rcn dot com

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sazerac
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#8: Post by sazerac »

Spiffdude...I noticed your comment by the picture that the tubing was kinked. I looked at my Cellini and noticed the same thing. I'm not sure how water has flowed for the past 2 years. I loosened the nut and took the copper rod out of plastic receptacle. On the bottom is a tiny nipple which must go into one of the three holes in the bottom plate. The rod goes into another hole. The potential problem is that when you reorient the receptacle it moves the position of the receptacle and when you try to eventually insert reservoir tank it just fits into the tank reservoir metal holder, with some pushing. Kink is definitely removed.

Even though my method of temperature testing is not indicative of "anything", I have noticed after a few hours that the temperature of water below the mesh is now 206 and then falls. It appears that the flushing of the HX unit did something. Now I would ask if I should lower my pressure-stat until 1.1 or so, from my 1.3.

I also noticed the little white ball in the line that is open ended and goes vertical for about 10".

Thanks again

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spiffdude (original poster)
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#9: Post by spiffdude (original poster) »

Eric, David, thanks for the info. What you are saying about the vent line and little ball makes sense to me.

Not sure why Rocket is letting machines ship with such a severe kink in the feed line! I will make sure to fix that quickly per David's observations.

Today, i let the machine idle for a good 5 hours (had to go out to one of our local shops to get a shot during this time :roll: ), It fell below the 200 mark, around 189. So i think this points to a small leak that flash boils and that i am unable to detect by looking at the drain tube outlet.

I will definitely try to find a local source for the brew valve or if not order it from Chris or some other US online vendor. Might take a week or two but be sure i will update once i replace this valve.
Damn this forum, I've had too m..muh...mah..mmmm..much caffeine!

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Randy G.
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#10: Post by Randy G. »

Check the parts listing for your machine. The tip of the valve (the square end that rubs on the cam) probably unscrews if you work it carefully, gently, and slowly. There is a little brass washer under it, and if you have some small tools (like thin dental picks, etc.) you can pry out the seal and turn it over and use the other side. It won't last a long time, but will do until the parts arrive. I keep three or four on hand to limit down time. be aware that it is possible to break off the threads on the seal side and that relegates the part to the dust bin.
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