Slipping Fan Belt

[BOB-AUSTRALIA]

I Have A Problem With My Belt Slipping On The Vaccumm Pump Causing The Wastegate To Stay Open This Only Happens When
The A/c Is Turned On And Can Sometimes Take Awile To Happen
It Seems You Have Problems Getting Things Fixed Over There
Here In Australia Mechanics Tend To Lift The Hood Shake Their
Head And Shut It Again So Any Help Would Be Greatly Appreciated

[Hubert]

First off take note Diesel's have more stressful harmonics on the serp belt than gassers.

I'd check the belt quality and health first. Can't skimp here has to be OEM grade belt. Now thats not so easy to specify even GM has changed quality over the years. Compare belts side by side and get the best one possible.

Then in no particular order check:

The idler arm or tensioner arm assembly to make sure its not spread and actuates smoothly might need to be cleaned or replaced.

Then check main pulley hub and make sure the rubber hasn't started to fail and overstressing the serp belt with too much give with harmonics

Then check the vacuum pump itself and make sure its not going bad and too hard to turn.

If you turn it it builds resistance then releases twice in a rotation if you can imagine its internals kinda sorta pushing on a rubber diagraphm.

Then check all accessories pulley's A/C specifically as its a linked cause.

[simon]

look at the tensioner line up marks,if beyond marks,1/2" shorter belt could make the diff.
i had same problem, good vac pump, not enough traction

[mncguy]

G DAY BOB
iam having a similar problem,but my diaphrame in the vacuum pump has a hole in it causing the wastegate to remain open.very embrassing under hard ecceration.yours might have worn out on the shaft causing the not to get as much movement,hard to describe in text give me a call if you wish 02 65 668 257,0419 208 516
regards andrew