AN LGT ACFT ON APCH DEVIATED FROM THE ASSIGNED ALT WHEN THE FLC WAS DISTR BY SEVERAL SYS MALFUNCTIONS.

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WHILE LINED UP TO LAND ON RWY 4R AT ORD; CLRNC WAS GIVEN TO DSND TO 8000 FT BY DEGAN INTXN. WE MISSED THE RESTR AND CONTINUED DSCNT FOR WESTN INTXN AT 5000 FT. DUE TO A NUMBER OF PROBS; WE ALSO MISSED THAT XING. ATC CALLED US TO NOTIFY US OF ALTDEV WHICH WE THEN CORRECTED TO 5000 FT TO CROSS WESTN AT 5000 FT. ALL OTHER RESTRS ON APCH WERE MET. THE MAIN CAUSE OF THIS DEV WAS ATTRIBUTED TO DISTRS IN COCKPIT CAUSED BY NUISANCE MAINT CAUTIONS WHICH DISTR BOTH CREW MEMBERS DURING DSCNT. WE WERE GIVEN A CAUTION FOR A PACK FAILURE (NEW PROB) AND ANOTHER FOR A HIGH PRESSURE BLEED VALVE FAILURE. DSNDING WITH PWR TO IDLE DEPRIVED THE SYS OF SUFFICIENT BLEED AIR TO OPERATE NORMALLY. ONCE CLRED; THE CAUTIONS KEPT RECURRING. THIS DISTR THE CREW ONCE AGAIN. THE FO WAS FLYING THE AIRPLANE WHILE I (CAPT) WORKED THE PROBS AND TALKED ON THE RADIOS. IN ADDITION; ADDING TO THE PROB; THE FO WAS USING DME OFF THE WRONG NAVAID WHICH LURED HIM INTO DSNDING TOO SOON AND; THEREFORE; BUSTING ALT. WE FINALLY ABANDONED THE CAUTIONS WHICH KEPT COMING UP AND FLEW THE AIRPLANE. IN RETROSPECT; WE SHOULD HAVE ABANDONED THE APCH SINCE WE WERE STILL A GOOD DISTANCE FROM THE ARPT AND TAKEN CARE OF OUR MAINT PROB SOMEWHERE OTHER THAN ON APCH.