Diagnosing belt squeal

[EastAustinSawdust]

All of my v-belts (I’ve got 3) feel tight. All are relatively new. Yet I get a squeal under certain conditions. Mainly when the engine has been running for less than 10 minutes and I’m accelerating from a stop. It’s worse when turning but doesn’t always happen when turning.

This is on a ‘78 big ten. Recently installed a vintage air system. The squeal didn’t start until several months after though. And the squeal isn’t affected by the AC being on or off.

Thoughts?

 

[Dave M]

Sounds like the power steering belt. I know others here have mentioned preferences for particular brands over others, because of belt squeal. Perhaps someone else might be able to elaborate.

 

[SirRobyn0]

Ok the usual applies, misaligned pully, worn pully, glazed belt or pulley ect. and if you want I'll elaborate on that stuff a little more in the morning but I don't think any of that is your problem.

I think in your case because it's in that first 10 minutes that your truck might be idling to slow at that time. Could it be idling lower than the normal warm idle speed? What I've seen happen is that the pulleys will turn to slow and then you hit the gas to pull out in to traffic or off the line and the driven pulleys can't speed up fast enough from an extremely low RPM.

 

[SirRobyn0]

Sounds like the power steering belt. I know others here have mentioned preferences for particular brands over others, because of belt squeal. Perhaps someone else might be able to elaborate.

The odd thing about belt brands is it seems like some rigs like one brand or the other, so it's hard to say running Gates belts will be better than another brand. It's true a lot of guys have good luck with Gates and they are our first choice at the shop for V-belts, but the formula we use at the shop is Gate first, if we still having issues, and everything else checks out pulley alignment ect, we switch to Dayco. Yea I know they aren't the best brand in belts, but they are the only manufacture that still makes a non-cogged automotive V-belt, like all these old rigs came with and used for years. And at that Dayco makes both a cogged and noncogged line so you gotta make sure to ask for the noncogged if you are trying to get away from that. I know the cogs help make the belt last longer but for some reason some rigs do not like them at all.

 

[EastAustinSawdust]

I think in your case because it's in that first 10 minutes that your truck might be idling to slow at that time. Could it be idling lower than the normal warm idle speed?

I recently adjusted the idle speed To be faster and the problem persists.

 

[EastAustinSawdust]

Sounds like the power steering belt.

The PS belt is relatively new. Think it could be the PS pump?

 

[Dave M]

The PS belt is relatively new. Think it could be the PS pump?

Hard to diagnose if I can't hear it, but I say the P/S belt because you mention it gets worse when turning. Tension it a bit more. If the noise is more of a "whirring" then i would check the pump fluid level.

 

[SirRobyn0]

The PS belt is relatively new. Think it could be the PS pump?

Unlikely. I can't remember ever replacing a Saginaw pump because it was locking up. A few alternators though.

Like Dave said maybe try a little more tension. If that doesn't do it, and everything else checks out, in other words pulley alignment, and wobble is ok, the pulleys aren't pitted from rust and they aren't glazed from squealing and the grove of the pulley isn't spreading or worn out, and oil isn't leaking on it. If all that checks out then try a different brand of belt. What brand are you running now anyway?

Chances are it's a cogged belt, with the cogs on the V part of the belt most are these days, but the thing is back in the day none of the belts were cogged, and I do think some vehicles / pulleys just don't like them. So try replacing it with a Dayco top cog. As the name suggests the cogs are on the top of the belt rather than in the V part of the belt where the belt needs to grip.