noisey condensor compressor

md

i have a general question on a 5 ton rheem ac unit,,, its in my church and is over 20 years old and its life is coming to an end,,, they have freon  added to it every 2 years and we cleaned the condensor and evaporator coils and fired up the unit this year, the issue we are having i never heard of,,, when the unit runs compressor sounds good, cooling is good, no bubbles in sight glass but when ever it wants to, [ maybe once a week  the compressor gets very loud and noisey the sight glass has bubbles flashing around, there are no freeze up on coils or  low side line like when gas get low,fan is running,, if you turn unit off for 5 min and refire it up unit is quiet and no issues,bubbles gone. we can not hook up gauge to high pressure side the valve is all corroded up, everyone checks charge from line temp and low side only, any ideas on noise, of course no funds for replacement yet.thank you

Techman

noise

Why can't a BPV (Bullet Piercing Valve) type of access valve be put on the liquid line just outside of the cond unit? Knowing the hi side press during the noisey time would help. What type of metering device?

md

valve

i know their is no txv just an orfice at the A coil area. also i did not mention the unit ran last year all night long with the fan motor burned out and the comp was really hot and roaring then,,,, but has been ok since last seasons fan replacement.. thanks