sqeeky belt

[blicata]

So it looks like the belt from the smog pump to crank pulley to water pump is squeeling and getting hot. The crank shaft pulley is also hot. Is there more to the problem than just changing the pulley. 79 Coupe 425 with smog pump. Thanks

[Scot Minesinger]

Start with a replacement belt after verifying tension in existing belt is adequate.  After removing old belt, be sure the water pump and smog pump pulleys turn freely.  It could be that one pulley is not and that slows the belt causing heat build up and squealing.  If they all turn freely than install the belt and see if problem is cured. 

[35-709]

Yes, pay particular attention to the smog pump that it turns freely with the belt removed, a common failure mode for smog pumps is the bearing goes bad and it seizes up. 

[hornetball]

BTW, a good smog pump will sound "crunchy" when turned by hand -- but will turn easily.  It should be quiet when running.  The dry-lube vanes are flung out by centrifugal force.

[fishnjim]

I recommend to change all engine rubber wear parts; belts, & hoses on a 5 year schedule, even if not running much.   Simply, rubber ages.   Make sure it's the right belts for the car not just what might "fit".  Groove angle and thickness are prerequisites for proper force transfer.   They used to sell "belt dressing" but I don't like that, temporary fix.
Look at the belt, and if it's shiny and cracked it's probably the cause.   They eventually wear down and if not re-tensioned*, run loose and slip causing friction making noise and heat which turns them hard.   Lost it's grip, so to speak.   If you have a belt measure, also can check stretch/correct size.   There's only so much slack you can adjust out.   Sometimes oil, grease, or coolant gets on them causing to slip, leaks need attention before new belt.
Do the other checks noted.   Bearings usually howl or grind/wobble more than squeal.  A bad bearing induces drag and that pulley not turning same speed as others.  I suspect if pulley was "frozen" it'd have burnt belt by now and/or flung it.  Would be pretty obvious looking under the hood.   Unless you don't drive it, just start up and idle and squeals when you gun it, might just be loose.
But smog pumps were notorious in more ways than one.   We just did away with HP thieves like that.   Talk about a poor excuse to pass emissions, dilute with air under the guise of final combustion?   Even the EPA didn't fall for that one long.   
* - should be rechecked after a ~month of operation.   But who does that?   Cranking them down too tight isn't good either => will cause bearing wear.

[TJ Hopland]

With this setup the alternator is driven off the water pump which is driven by the smog belt so if the alternator was dragging that could be causing the smog belt to slip on the crank.    Smog pump failures are much more common than alternator tho.   Smogs usually fail because the check valve up on the smog rail fails which then lets the exhaust gases into the pump which kills em pretty fast.