Proper 555 return line hydraulic pressure?

Here's my question: What should the pressure be at the inlet of the filter? When I run the engine, the indicator gauge pegs to the max, meaning that I'm getting greater than 60 psi at the inlet of the filter. This may be normal for this hoe, but I don't know. The guys at NH said that they "thought" the OEM filter housing was designed for 38-42 GPM and had a 50 psi bypass on it, but they weren't sure of the operating pressure. I thought return lines ran at very low pressures, though, hence the typical 60 psi "filter change" gauge, where it indicates "service filter" at anything over 15 psi. The gauge port doesn't appear to be relaying a pressure differential, but merely the inlet pressure, itself.

I would like to know if anyone knows what the actual operating pressure in the return line should be for this hoe, just to make sure I'm running safely. (BTW - a refurb OEM filter housing was close to a grand, so that's why I went with the Zinga).

I'm going to post this in the Ford board also, in case anyone there may know as well.

Thanks,
JB

There could also be some restriction near the reservoir that is causing the higher pressures, but it could also be designed to have higher pressures at the filter. After all, the OEM filter housing seemed to be pretty robust (it was a bowl with drop-in filter -- not a spin-on), but that could have simply been to protect it from rocks etc., since it's right in front of the rear wheel & prone to getting dinged.

I'd like to find the "typical" 555 operating pressure at the filter in order to determine whether I need to tear apart the return lines looking for a restriction, or if the high pressure is nothing to worry about. I'd like to filter the fluid (as opposed to the straight pipe that was in place before, but that's another story), and I also want to make sure I'm running safely and not overpressurizing a filter that's rated at 250psi operating pressure.

Thanks! JB

Joe

Thus, I have a head-scratcher. But, as you indicated, the return line pressure could still be higher than 25psi by design. I know that there is supposed to be some sort of screen/mesh filter on the inlet of the pump to screen out large chunks, but I wouldn"t think that filter would cause a return line pressure like I"m having.

Thanks for the help, and any more insight would be greatly appreciated!
JB

Hope I helped some

Joe

I also told him that the previous owner had plugged and subsequently crushed the pump inlet filter screen in the reservoir. The previous owner replaced it and made the appropriate repairs, however, the NH guy told me that the cooler could have gotten gummed up from packings(?) when the screen got crushed. He said that it"s possible that the cooler is causing the restriction, and that it may be good to "boil" it at a radiator shop to remove any gunk. He also said that the high pressure would subside after the fluid warms up (it was about 20-30F when I got the high pressures), but that it would also increase at higher RPM (I had the 60+psi at idle, and never revved it up). Makes sense to me.

I know that the relief valve is properly installed, since it"s integral to the filter housing, and the flow direction on the housing is correct. I think my next step is to check the actual pressure (as opposed to the idiot gauge I have now), and see what I get. I think that if it"s anywhere under 200psi, I"m not going to worry about it. Otherwise, I think a cooler cleaning may be in order.

Thanks,
JB

Joe

I worked the hoe for a half hour (sometimes at higher engine RPM), and when I checked the gauge with the engine stopped, it stayed at 40psi, indicating that I may have oversprung the needle, and had a pressure higher than around 200psi.

At least it seems to be lower than the max psi for the spin-on filter, but I'd still like to know if my pressures are normal.

JB