ACFT ARR FM THE NE, CROSSED OVR THE ARPT IN IMC CONDS & CONTD TWD THE SW TO THE INITIAL APCH FIX (IAF) FOR AN ILS RWY 4 APCH. THE IAF WAS OVR THE OUTER MARKER (OM), 4.2 MI SW OF THE ARPT. AS THE ACFT DEPTD THE IAF, IT CONTD OUTBND TWD THE SW ON AN IMPRECISE TRACK FOR APRX 1 MIN, MADE A PROCEDURE TURN (PT) BY TURNING RGT (WEST), THEN BACK LEFT (EAST) TWD THE LOCALIZER (LOC). INBND HDG FOR THE LOC WAS 045 DEG. RADAR CONTACT WAS LOST DRG THE PT. AS THE PT WAS COMPLETED, THE ACFT ANGLED TO THE EAST OF THE LOC & INTERCEPTED THE 045 DEG RADIAL OF THE MONTEBELLO (MOL) VOR. SUBSEQUENTLY, THE ACFT HIT A MTN TOP WHILE IN LVL FLT AT 2400' ALONG THE MOL 045 RADIAL. CLD BASES WERE AT APRX 2000'. NO PREIMPACT PART PRBLM WAS FND. ACFT RDO INSTLN WAS NONSTANDARD, NOT FAA APPROVED; 1 ADF & 2 NAV DISPLAYS WERE IN UNSUIT LOCATION FOR COPLT. RDO TRANSCRIPT INDCD PLTS WERE UNCERTAIN OF GEOGRAPHIC PSN BFR IMPACT. COMPANY PLT EXP REDUCED BY RECENT PLT TURNOVER. BOTH PLTS HAD LMTD EXP IN RESPECTIVE PSNS. HI NOISE LVL IN COCKPIT MADE CONVERSATION DIFFICULT. LACK OF FAA SURVEILLANCE