I have an older Expobar Office Lever (E-61 HX style machine). Recently it has begun over-pressurizing intermittently, to the point of activating the safety relief valve. Any ideas what I may need to replace/adjust to remedy this?

Well, its going to be one of two things: the pressure stat or the relief valve. Whats your gauge reading? Over 1.5 bar?
PRVs do wear out, as do p-stats.
If it was me, firstly, take a flat blade screwdriver and turn the adjustment screw on the p-stat up and down, sometimes they get sticky. See if that alleviates the issue. Otherwise, replace the PRV and the p-stat.

RNAV wrote:I have an older Expobar Office Lever (E-61 HX style machine). Recently it has begun over-pressurizing intermittently, to the point of activating the safety relief valve. Any ideas what I may need to replace/adjust to remedy this?

Replace the pressurestat.

My Expobar was doing this as well. I needed to replace the pressurestat. It was an easy operation and all is well afterwards.

Thank you for the guidance. I'll attempt adjusting the pressurestat first, then opt for a replacement if that doesn't bring resolution.

UPDATE

I'm befuddled. Adjusting P-stat didn't make a difference, so I ordered and installed a new P-stat.

Now I have a new problem: the machine will cycle as designed between 1.0 to 1.1 bar for a while (amount of time varies), then it will randomly not kick on the heating element at 1.0 bar, and the pressure will slowly drop to and remain at zero.

Summary: old p-stat causes intermittent over-pressure; new p-stat causes regular non-activation of heating element.

Any ideas?

Also, not having a function espresso machine BLOWS.

You should contact whole latte love. They'll know whats up. And then post what they say here for future reference.

For what its worth, my expobar is designed to be around 1.3bar steam pressure, and this is what WLL suggests in their pressurestat videos as well. Maybe you could turn it up a bit.

I contacted WLL because I ordered the replacement p-stat through them. My initial assumption was that I'd received a bad p-stat.

After a few emails back and forth, Danny sent over the following: After going through that, I was able to determine the high limit was bad. My machine is so old it didn't have a resettable high limit. So I ordered a new one and now the machine works great.

FWIW, in the video the guy states that HX expobars should be around 1.1 bar; dual boilers should have the brew boiler set to 1.3 bar. I think I may up mine slightly . . . the temp will sometimes dip below 198 in the last 1-2 seconds of my pull.

Ah, I'd forgotten the different limit for HX machines. I'm glad you got it worked out!