Hey all. Stumped by an issue that's arisen on the 1988. After the 3G swap a few months ago we've been dealing with some really annoying belt squeal. It chirps a little at idle but when you get on the gas it starts a'screamin. A little back story: all the conversion parts came from a '96 Bronco that was in the local pick-a-part. Tensioner/alt bracket and alternator. Prior to the 3G swap/tensioner "upgrade" the serpentine system was quiet as a mouse. This leads me to believe that it isn't likely to be another part of the accessory drive causing problems. Also, I've spun each of the other accessory drive pulleys (PS pump, water pump, AC, air pump) and they all spin free. So for the time being I'm looking at the parts that were "upgraded".

I feel like it's partially my fault, we rushed the swap as a "proof of concept" rather than taking time to R&R the bracket and pulleys. I believe the problem began with a stiff idler pulley that couldn't keep up at higher RPMs. Additionally, I noticed a little bit of "tensioner jump" when the truck was running (in comparison to MY '96 where the tensioner is rock solid). I started to wonder if the tensioner spring was going weak. To that end, we located another bracket off a '94 which we hoped would have a stronger tensioner spring and definitely had a better idler pulley. No joy, same jumping tensioner and squeal. Borrowed grandpa's engine stethoscope and heard some nasty growling from the idler and tensioner pulleys, so we took a trip to Autozone and got two new pulleys. Same issue as before. Tried a new belt, thinking that the older one was damaged from squealing, lasted about a week before it started singing just like the fat lady.

At this point, I'm angry at myself for manning the parts cannon, and really annoyed that the problem hasn't magically fixed itself. I don't have a lot of experience regarding the serp. system so I thought I'd check with the collective Ford Oracles. All pulleys have been wire brushed clean and checked to the best of my ability, we have a new idler pulley and tensioner pulley, and a week old belt, and still have the same issue. Starting to wonder if I my first guess hasn't been right all along and these OEM tensioners are all starting to get a little tired. Maybe we just need a brand new one?

Open to any suggestions, and maybe I can learn a thing or two!

 

Take a straight edge and make sure the pulleys are in alignment. I had a Dodge that always had a belt squeal I couldn't get rid of. When I took it to a shop to have the AC serviced I asked the tech to see if he could find the cause of the squeal. When I picked up the truck, the squeal was gone. When I looked under the hood to see if I could see what he had done to fix it, imagine my surprise when I saw the seven rib belt was trimmed down to six ribs and was routed to the front on some of the pullies and to the back of the pullies on the remaining. Clever way to fix the misalignment. You could also loosen the brackets that mount to the block and try to pry them away from the centerline of the engine. Maybe there is enough slop in the bolt holes to pick up a little more tension.

 

Check out the RELATED threads below this. Especially the one about the 3G.

 

This is a common problem with the 3G swap. The way that the belt is routed on the trucks that come with a 3G from the factory uses almost the entire surface area of the alternator pulley. When swapping these older style 2G trucks, we are only using 30% or so of the surface area. I had this problem for nearly a decade before I accidentally fixed it. If you can get away with bypassing the air pump, you can run a 90.5" belt and run right from the alternator to the crank pulley. This uses far more surface area of the alternator pulley and eliminates the squeal entirely. I have a 130A 3G alt on my '89 and haven't dealt with squealing since doing this.

 

My 89 F250 had belt squeal, after checking/replacing belt, idlers ect. I found the crank pully was glazed and caused the noise. A few hand fulls of sand feed into the pully with engine running fixed that noise. 10 years later and never had a squeak yet even with a 3G upgrade a few years ago.

 

Thanks Festus. Good advice about trying to fix the bracket. The pulleys are all lined up, maybe we do need to **** the bracket slightly to give a tad more tension.

Thanks for the suggestion Sandy. Looks like I got some reading to do.

GNR - this makes sense, except we are using the 3G factory bracket so the belt is wrapped around the alternator pulley a fair bit.

Ok Eddie we'll have to check out the pulleys for glazing. Did you sprinkle the sand on with the belt on?

 

I should also add, guys. The issue is EXTREMELY inconsistent. We might have one trip where it'll squeal the whole time, sometimes it'll quit while we drive. It will always squeal on startup. Now before the 3G swap it was whisper quiet, and the intermittency is making me wonder if it isn't something to do with the alternator. Not sure why though, the pulley was brushed clean and the alternator tests good. It's an original Motorcraft and I'd rather not replace it if its still working fine.

 

Is the tensioner out of it's effective range?

 

I'm not sure. I don't think so, it seems to be in the upper 1/3rd of its travel when the belt is tight.

Took a look at it today. I believe I know what's going on. On startup it squeals, when the alternator is working to charge the battery that's just been depleted from starting the vehicle. Let it idle for about 10 min and the squealing stopped entirely. Brother reports that it may start squealing again out on the road randomly at times. Spinning the alternator by hand revealed the slightest wobble in the pulley. Not sure if that's relevant or not, but wanted to provide all the information so we can make an informed decision to fix the issue.