I'm new to the HX world and the owner of a Bezzera Mitica Top for about 2 months. I'm having real trouble with off tasting shots so recently got Eric's thermometer to help me diagnose the issues.

After idle for an hr the machine grouphead temp is 200 fh.
I flush for approx 15 secs until the temp starts dropping around 207 and lock and load for flush n go the temp is steady 200.

As you can see in my video the temp stops dramatically to the 180s when I pull. Then it takes 15 mins to recover to 197.

I've tried dosing higher, grinding finer and asked Eric too who advised good to ask here. My pstat is 1.1 I believe I'm dosing at 18g.

Is it possible I have a leak or faulty pstat? If anyone can assist I can run some tests as machine is almost new.
I've searched the forums for low temp issues and causes.

Help I am confused adjusting my pstat setting may help recovery time is that right what about brew temp?

I think you are not working at the appropriate thermal regime for this machine;
it has some peculiarities: a special horizontal boiler type (less than 170 ml - ?) heat exchanger and it has as a kind of flow restrictor a 'union elbow' (p/n 5301521TR) of a smaller internal diameter (less than 4 mm) at the exit from the HX thermosyphon flow;
it has quite a 'thermal memory' and a slow recovery time;

so I worked (usind datalogging too) for 5 to 8 consecutive shots in a session, with only one initial flush, and no cooling flushes before shots; only respecting the recovery time between shots, of 90-150 secs!
the machine seems to work rather consistent if the interval between shots is around 2 min, and first shot at about 3 min after the initial flush to (somewhat) desired brew temp;
and these, after reaching full idle, with 201-207F (94-97C) in GH (depending on the boiler pressure and if the PF is on);
this method is not a flush and go/wait one, as there is only one cooling flush at the beginning; the shots are running based on the machine design/tuning;

there are differences in your case as Mitica has rotary, while my Magica had a vibe pump;
also I used as trigger points, not grouphead temperature as much as the 'near HX' temperature measured on the exit pipe;
there are some posts here where I've described these in rather more details;

Tighten up your grind. Shot seemed fast which would cause a temp drop on any machine.

Hi Darren, I watched the video. To clarify, in that video, was that 13 second flush after a full one hour warmup? Or, was it after you had already done some previous flushing or pulled some shots?

If it was the first flush after a full hour warm up, then something seems amiss. The thermometer reading shouldn't drop into the 180s in that case.

For readers, here is Darren's original thread from a while back before he got his Erics thermometer. For background reading and context:
Bezzera Mitica Top troubles with inconsistency

Also, by the way, Radu knows a lot about the Bezzera HX machines and he helped me immensely when I first got my Magica. So thanks again Radu!

So back to your Mitica. Did you buy it new or used?

As I mentioned before, my Magica behaves like this with a pstat at 1 to 1.1 bar. And I can only assume the Mitica, except for the rotary pump, should behave similarly.

After a full 1 hour warm up, my grouphead idles around 202F to 204F with portafilter locked in during warm up phase.

If I flush n' go, I can flush for about 13 to 14 seconds or so, and then lock and pull. And it won't drop to the 180s such as in your video. It will be around the 200F give or take.

Another routine I've fallen into, and I have no idea if it's the best possible routine for my machine, but it seems to work is... After a full warm up I flush for 12 the 13 seconds. Then I wait 45 seconds. Then I do a short flush for 2 to 5 seconds and thenock and pull. This gets me a thermometer reading of 200F give or take with a slightly declining temp profile, depending on how long my shot is. Again, this gets me in the 200F ballpark. Nowhere near 180F like you.

Wondering if there's something else going on with your Mitica. Is it new or used?

If you run the flush cycle past the point of 207 degrees will the temp drop into the 180's?
Seems like your boiler is running out of hot water rather fast. Could it be loaded with scale?

I still think before you start looking into anything else to get some fundamentals down. Proper warm up of at least 45 min, and then address your grind issue. Your shot time is 20 sec w/ preinfusion. up that to 30+ through a tighter grind and see what difference it makes.

He said he let it warm up for an hour. And even a fast shot and too coarse a grind shouldn't result in a temp drop that fast.

Perhaps but It's at least contributing to the problem and muddying the waters on what is wrong. This all started with him diagnosing an off taste. A 20 second shot generally won't taste that great.

I think your shots to fast which effects taste & temp. I have the same machine, I flush 10 sec's & flash steaming stops. Lock & load and pull my 30-35 second shot and they taste great.

why not trying the no-flush-and-go procedure from my previously post:

after an hour of warm-up, make a flush with 3-5 secs added after the stopping of the flash-boil, that is a 13-15 sec flush,
then wait for 150-180 secs (preparing the first shot) and only after, start the first shot!
the right moment for starting the (next) shot is when the group temperature which was descending, becomes steady for, say, 5 secs at least;
the machine is now recovered for the next shot;
if there are succesive shots, the intervals between them would be 90-120 seconds; no cooling flush;
I used to make a very short cleaning flush (1-2 secs) at the end of the shot;
here is the temperature profiles for such an initial flush and the first shot: