belt slipping?

threebyfour

Registered User
so in my mind if I make a mark on the sc pulley and a mark on the belt im thinking that these marks will line up, after i run the beast, as of right now they dont. Can this be a sign of belt slippage? the car is boosting like the belt is slipping and I HOPE this is the problem. I,m guessing its a temp sensor or the likes but maybe I can get out lucky. any thoughts would help. thanks,,,,, Dan.
 
No. They are not set up like a timing chain set up. But my question is why are you marking the belt and what are you looking for?
 
Common signs of belt slippage are belt rubber will flake on to cam sensor and water pump also to check is go out for a few boost runs and feel sc and js pulley to be hot to the touch
 
what im trying to track down is a on / off boost condition. the boost jumps all over under WOT but runs perfectly without boost. Usually jumps around at or over 5psi. I guess I was hoping to tell by making" timing " marks. I will check to see if it is hot to the touch next time I drive it. And I am seeing black dust on the nose cone too.
 
Is the limit indicator on the supercharger belt tensioner within service range?

Get the right tools, swing the tensioner back and remove the belt - is it damaged? Then rock the pulley left/right and see how it feels...is there a bunch of play in the coupler? Then spin it to check the bearings.

Does the tensioner idler pulley spin smoothly with the belt off?

Have you inspected the bypass at the rear of the supercharger?
 
KMT...no I haven't checked any of these things, but thank you for giving me a starting point. I will do this weekend for sure. What am I looking for on the bypass valve ? As a side note,,,i did change all the IC tubing gaskets, with no change in condition.
 
what im trying to track down is a on / off boost condition. the boost jumps all over under WOT but runs perfectly without boost. Usually jumps around at or over 5psi. I guess I was hoping to tell by making" timing " marks. I will check to see if it is hot to the touch next time I drive it. And I am seeing black dust on the nose cone too.

It's not because of belt slip. Bucking under boost is one of the terms commonly used to describe this ignition problem. Engine is basically misfiring under a load and causing the boost gauge to be all over the place. 99% of the time it's because of a bad plug or plug wire. Easiest fix is to change plugs and wires with good quality replacments like Taylor wires and Autolite plugs.

David
 
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Thanks Dave, a mustang freak buddy of mine said the same thing, he told me to also check the coil packs. 150K and I have never changed the plugs and wires,,,,oops.
 
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