A PIPER ARROW VACUUM PUMP FAILED IN IMC. THE PLT EXPERIENCED FLT ATTITUDE PROBS DURING VECTOR AND DSCNT COMPLIANCE. APCH CTLR INTERVENTION.

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I WAS CRUISING AT 9000 FT MSL 25 MI E OF MILWAUKEE; IFR. AS I WAS SCANNING; I NOTICED THE ARTIFICIAL HORIZON FLIP OVER AND WITH THE AUTOPLT ON; THE ACFT STARTED TO BANK. I IMMEDIATELY TURNED AUTOPLT OFF AND STABILIZED ACFT USING TURN AND BANK INST; VSI; AND MAGNETIC COMPASS. I CHKED SUCTION GAUGE AND THAT SHOWED ZERO. I CALLED MILWAUKEE APCH AND TOLD THEM I HAD A VACUUM PUMP FAILURE AND WOULD LIKE TO DSND DOWN TO 6000 FT. (FROM LISTENING TO ATIS; THEY HAD RPTED CEILINGS AT 6500 FT SCATTERED.) THE CTLR CLRED ME TO 6000 FT AND ASKED ME TO TURN TO A HDG OF 240 DEGS FROM 315 DEGS. I WAS FLYING NOW TO AVOID SOME LIGHT RAIN SHOWERS ABOUT 10 MI WIDE. I THINK HE WAS TRYING TO INCREASE MY CHANCES OF GETTING TO VFR CONDITIONS. I STARTED TO DSND AND TURNED L INTO A STANDARD RATE TURN TO NEW HDG 240 DEGS. THIS IS WHEN I STARTED GETTING PITCHED AROUND FROM TURB AND CLOUDS; I PULLED PWR BACK TO 15 INCHES MANIFOLD AND ASKED MKE TO HELP ME OUT WITH THE HDG BECAUSE THE MAGNETIC COMPASS WAS FLOPPING ALL OVER THE PLACE; AND MY DSCNT WAS GETTING A LITTLE FAST. I GUESS ANOTHER CTLR WHO WAS A PLT TOOK OVER MY SIT. HE ADVISED ME TO FORGET ABOUT HDG AND LEVEL WINGS AND DSND TO VFR MAINTAIN 3000 FT MSL; WHICH I DID. I BROKE OUT AT ABOUT 5000 FT MSL WENT DOWN TO 4500 FT MSL AND FINISHED FLT TO FLD; VFR. MY ADVICE TO ANYONE WHO EVER HAS THIS PROB IS TO DSND TO VFR AT PRESENT HDG IF POSSIBLE AND ADVISE ATC OF WHAT INSTS ARE OUT. IF YOU DO HAVE TO CHANGE HDGS; STOP DSCNT AND DO HDG CHANGE AT STANDARD RATE TURNS. IT'S VERY DIFFICULT TO KEEP EVERYTHING UNDER CTL WITH HALF YOUR INSTS GONE AND GETTING BUMPED AROUND IN CLOUDS.