When hooking up a mechanical gauge on my 1998.5 which pipe plug do I remove and where can I get a pressure tap that will thread into the hole. I want to keep the guage under hood with a hose that I can run into cab in case I want to watch FP. I do not have money for a pillar but I do want to be able to be able to check or watch my pressure once and a while to make sure no problems are on the horizon. Thank you.

 

There are two 1/8 npt plugs on the top of the filter, the one closest to the outside is prefilter and the other one is post filter. For a cheap setup, just use an oil pressure gage from the parts store, lowest pressure available. Compression fittings and air brake teflon line will work well, 1/4 is ok, or smaller if you want. Be sure to use air brake compression fittings though, they are different. Hang it under the dash and you are all set.

Many will come in and say that you can't use the plastic line in the cab, but I have run big trucks and hot rods with mechanical oil pressure gages in them for many years. Never had a problem. Big trucks also use this for the air pressure gages and they never leak.