40+ year old system. EFM oil boiler. Circulating pump has been leaking at shaft, then when running, sounded funny, thought pump was not working, partially working. Got taco pump; then found pressure regulator not letting any water through. Well pump supplies cold water to boiler for domestic, and then branches to closed loop by way of pressure regulator, then valve with bleed cap. Valve is open, and no water with bleed open. Then feeds to closed loop baseboard. Circulating pump pulls water down. (I think now systems push water up. Why?) Does it make sense that a old pressure regulator would completely stop flow. When submersible pump was changed a year ago it pulled up sediment. Should I also install a shutoff valve, then a check valve, then the new pressure regulator? Old pressure regulator is cash-acme, says inbuilt check, has about 1" hex plug on bottom with 6942RB on it. Probably won't find identical. What pressure does it let through? Am going to install filtering system from out of well. I have not installed the taco yet. I will make sure I run it wet. From what I understand, I open the drain valve at the bottom of the boiler, empty loop, change pump, pressure regulator, add shutoff valve and check valve, if you say. Then turn on water till steady water out of drain. Shut drain, run pump on separate temporary electric to bypass burner and thermostat. Crack open drain to let a little more air out. Thanks, Bob.

Sediment may be clogging the strainer on the pressure reducing valve. The hex nut on the bottom can be removed to check. If the valve is that old, replacement isn't a bad idea. Sounds like you have a pretty good grasp of what to do from there.

Circulating pump pulls water down. (I think now systems push water up. Why?) Should I also install a shutoff valve, then a check valve , then the new pressure regulator or the cleaned out one like you say? Thanks, Bob.

Also is there a standard pressure that is used for a hot water closed loop and does it make any sense to have a pressure gauge after the pressure regulator? Thanks, Bob.

Pumps for boilers can be either push or pull but usually the old term pump away (from the boiler) still fits today. Some manufactures for some reason may show it differently and if that is the case follow the manufactures instructions.

Usually single story at 12 psi static pressure. But I always run the least amount possible allowing for good flow and operation of the system. Why stress anything out if not necessary.

Pressure gauge is to be in the pipe or boiler itself. It is always after the water inlet pressure regulator/fill valve for accurate readings.