So I just restarted my VBM after almost a 2 year hiatus (military duties, go figure) ((only had it for 5 months before issues started)). I have had the same problem with this machine since I mothballed it then: can't bring the temperature up to brewing temp. It peaks at 186F resting, though with a little coaxing by pulling a blank shot I can raise it to 197F. I have descaled it thoroughly twice in the last two weeks, pulled the mushroom and cleaned any debris. I have backflushed dozens of times, checked my water lines, and did everything listed on the past similar forum topics. My steam wand gets constant strong steam, hot water valve it steaming hot, so I know the temp in the boiler is right. What am I missing?

Is there a gauge to adjust the brew temp? It's been awhile, so it is quite possibly user error. One thing of note is I live in Colorado at 7K altitude, hence lower boiling temp. I still think I should get some steam out of the brew head. I have Erics temp gauge hooked up, hence my knowledge of the temp. What can you experts assist with?

Figured out the temperature brew adjustment at the top, but I don't think that is the answer (unfortunately). In order to get to a reasonable stable temp, it sounds like the boiler is going to explode. It is up to 192F stable temp, and can reach 202F after I flush it. I was thinking thermosyphon issues, but after descaling twice that seems unlikely. I am at a loss.

The first thing we need to know is how you are measuring the temperature. That is critical.
What is the range of the boiler pressure gauge when the pressurestat cycles on and off?
Do you have Eric's E-61 group thermometer? I HIGHLY recommend it.
The answers to those questions will help us give you more accurate advice.

I will guess that you are measuring the temperature of the water after it exits the group and with a thermometer in a cup... just a guess based on those "low" temperature readings.

I see you are in Colorado Springs. What is the altitude where your machine is located (and don't say on top of a 38" tall counter!).

And, most importantly, what has the espresso been like?

Hi Randy,

Great to see you answered my question(s) as you are a well known expert. Well, as I said I am using Erics thermometer, so it is not after it exits the group. Also, as I said, I am at 7K feet. Finally, I haven't made any espresso yet for fear of buying espresso that will go to waste since I can't get the temp up. I have a few local roasters (Pikes Peak roasters) that I will get some tomorrow to mess around with. This is really perplexing me. Thanks so much for the analysis so far...

Jason -

Firstly, welcome back home.

Although very unlikely, I will be more than happy to send you a replacement exchange thermometer to eliminate that as a problem. Just send an email to erics at erols dot com and, naturally, include your mailing address.

What is the on/off range of your boiler pressure gage? As but one example, if your maximum reading is 1.20 bar, that is ~ equivalent to 1.00 bar for operation at sea level and the thermometer should read around 204-205 F. All Vibiemme Domobar Supers sold in the US have a thermosyphon restrictor orifice located in the upper group tube at the boiler end of ~ 2.80 mm diameter and these machines are sensitive to obstructed orifices.

In addition, a small (potentially unnoticeable) leak at the brew valve in the grouphead would cause a thermosyphon stall and result in the dramatic drop in temperature you are seeing. When you lift the brew lever (empty portafilter in place), flow from the grouphead should be almost instantaneous. If there exists a couple of seconds of pump operation with no flow, this would be an indication of an internal leak which would play havoc with the thermosyphon action.

It was late when I replied, and sorry that I missed the details.. I even specifically looked for the details.. anyway:

First step is to check the thermometer's accuracy- things happen, you know. Mark the thermometer's insertion depth and remove it from the group. Check it in ice water and boiling water, keeping your altitude in mind.

While you have it off, pop the thermometer open as if to replace the battery and make sure that the thermocouple leads are still siliconed in place where they exit the electronics and enter the probe (mine had come loose once).

It was a good pull on Eric's part that thermosyphon stall is a possibility. I have a page on that:
http://home.surewest.net/frcn/Coffee/stall.html
I have experienced that.

You stated that you hit 202 after the flush, but what was the highest temp recorded DURING the flush? The temperature you are adjusting through the access opening in the inner divider, under the drip tray, is the boiler's pressure, which is an indirect measurement of the boiler temperature. Additionally, measuring the temperature without coffee in the portafilter is not all that accurate when just letting the water flow through, particularly at your altitude. 202 with no coffee is not bad. I would recommend getting coffee in the thing and worrying more about the taste and less about the numbers on the thermometer. All things considered, from what you told us, I think you are a lot closer than you are assuming.

For a data point, I am at +/- 2130 feet. I just turned down my boiler pressure to about 1.05 because at 1.1 it was overheating the machine at idle. The flush would hit 210 to 211. Now the highest it gets on flushing is 208. The steam pressure suffers just a bit, but I am wasting a lot less water in the cooling flush than I was before. I will say that the gauges are not exactly mil spec hardware, so there will be slight variances from machine to machine in these readings and the subsequent performance.

Additionally, you mention that you have turned up the temp and the machine is making noises "like the boiler is about to explode." That is worrisome. The machine does have an over pressure safety valve, and hopefully that is working properly. Please share the values on the boiler pressure gauge with us.

Once again, thank you so much for your feedback. Eric, I do not believe your thermometer is the problem but thank you for the offer. Here is what I found out by playing with it today: Bought some espresso at Pikes Peak and grinded it at my coarsest setting I usually start at; clogged the machine. Then tamped lighter, clogged again. Brew pressure on my gauge reads an estimated .7, not good I think. Turned the machine around to increase the brew pressure but this dang thing won't budge. It's relatively quick (1-2 secs) engagement of water out the brewhead when using a blank portafilter, so don't think that's the problem. I am really starting to think thermsyphon stall or pressure issue...

PS the boiler pressure gauge reads very low at (est) .2 bar. Isn't it supposed to be around 1ish? I still get lots of steam from the wand and water spigot.

If the brew pressure gauge is reading .7 with the machine choked, I think that you need to access the pressure relief valve and adjust it. Remove the adjustment screw in the body of the valve, remove the piston and spring and clean those as well as the bore. Use a small amount of food-safe silicone (Dow 111 or equivalent) on the O ring and reassemble. Use the blind backflush basket, and while doing a "backflush" adjust the OPV to about 9 to 9.5 BAR with the pump running.

.2 BAR on the boiler pressure gauge when the heating element light goes off is too low, indeed. 1.05 to 1.1 is more reasonable. iirc, it's clockwise for lower, counter-clockwise is a higher temperature. It's in the owner's manual.

If the gauges are responding normally (not jerky, sluggish, stiff, return to zero properly and smoothly, etc.) then there are adjustments that need to be made here.

Oops! No, when choked it kicks up to 12 bar and sometimes beyond. I will turn it down tomorrow as I think the problem is elsewhere (read ahead). I have read the owners manual, the one printed from the net, at least 5 times in the last week. I pick up something new everytime I read it. Of course, when you enlighten me as well. Now, I don't know if I can turn the boiler pressure gauge anymore, I really do think it's gonna explode! I do have the relief valve and it's working but when I turn it up too much it is working overtime. I can definetely tell just by hearing it.

Back to the actual espresso. So I played with the grind a little and made it coarser than I normally would. Forgot to mention that I bought my second Mazzer Mini, and was assuming the same gauging of coarsness would apply (NOT! Go figure). With my regular double portafilter, it kept choking. Then I changed to my bottomless. The first grind was too coarse, so it was spraying and was too fast. The second finer grind slowed the flow down, but still had sputtering of espresso. The last adjustment was just the right flow/time with very little sputtering. Tomorrow morning will fine tune it more. Taste? Well, I have had better but certainly worse. Tons of crema. When I pull the lever, the temperature shoots from approximately 192F to 200ish F.

This is all strange to me because the first 5 months I owned this machine, it heated up to 206-210 in 30 mins everytime with no issues. I lived at a lower altitude yeah, but its been a noticeable difference. I understand tweaking is what we love about the hobby, I just wanna put the cover back on and not have tools around my kitchen all the time, just when needed.

jherm77 wrote:Oops! No, when choked it kicks up to 12 bar and sometimes beyond.

I have read the owners manual, the one printed from the net, at least 5 times in the last week. I pick up something new everytime I read it.

You're welcome!

Now, I don't know if I can turn the boiler pressure gauge anymore, I really do think it's gonna explode! I do have the relief valve and it's working but when I turn it up too much it is working overtime. I can definetely tell just by hearing it.

The machine has two relief valves, so to speak. One is the pressure relief valve which is the largish brass part under the water reservoir's platform area, that has the big brass slotted screw in it. That adjusts the maximum allowable brewing pressure of the water from the pump through the heat exchanger during extraction (and backflushing, which is the same function as far as the pressure relief valve is concerned).

The other is the boiler pressure relief valve. That is mounted on top of the boiler. When that operates, it open to relieve pressure in the steam/hot water section of the boiler (not the heat exchanger and not related to brewing espresso). When it opens it vents steam inside the machine with good force, or at least the potential for good force. The boiler pressure regulation by way of the pressurestat adjustment screw, under the little black plastic cover under the cup warming tray adjusts the pressure in the boiler, and that, indirectly, controls the boiler temperature. Boyle's Law I think... but don't quote me, I was an art major.

I am trying to clarify these three separate devices and their functions because I am unclear about the sounds you are describing.

When I pull the lever, the temperature shoots from approximately 192F to 200ish F. This is all strange to me because the first 5 months I owned this machine, it heated up to 206-210 in 30 mins everytime with no issues. I lived at a lower altitude yeah, but its been a noticeable difference.

This definitely sounds like an altitude elated problem. I think Eric or one of our resident scientists (or someone who lives at a similar altitude) can assist more with that then I can.