Why does my AC compressor keep eating pulley bearings?

5VZ engine if it matters.

AC compressor pulley bearing has gone bad a few times now. My first replacement I pressed in a new bearing myself - didn't last 2 days. Ok, maybe I pressed it in just a little crooked I thought.

Next, I bought a brand new pulley and coil. Pulley already had the bearing pressed in, awesome. Within 24 hours the bearing had so much play that it caused the pulley to drag on the coil and seize up.

I'm on my second AC compressor and the low and high pressure readings are within spec. The compressor blows ice cold when I have a working pulley/bearing in there.

My idler pulley/bearing is brand new and works great, has no play or drag.

I'm thinking the only thing left is to buy a brand new OEM AC compressor. But my pressure readings are fine, telling me there is no issue inside the compressor. But an issue inside the compressor wouldn't affect the pulley bearing anyway, right?

What am I doing wrong?

 

When I put a new pulley/bearing on, there is no play. However within a few days the bearing will develop so much play that it starts to fail.

I do have a new goodyear belt. I have about 1/4" to 1/2" of deflection in all three belts.

 

Are things out of alignment that your putting a side load on the bearing that will cause it to fail .

Which seems to be what you describe happening .

Poor quality bearings might come into play .

Backing up when did these bearing failures start ??

Was the compressor bracket removed??

 

alignment and tension are the killer of bearings. There is the possibility of just plain ol crap bearings. I quit using bearings made in china for your exact reasons. A bearing made in the USA or Japan you are going to pay more for but it is because it is a better bearing. I do not use the deflection method for seprentine belt tension, I use the 90 degree twist method. If I can easily twist the belt past 90 degress it is too loose. Been using this method for decades with no issue.

 

Maybe the alignment part is what I'm missing. I've never removed the compressor bracket. How do I make sure the compressor pulley and idler pulley are in good alignment with the crank pulley?

 

Most times I can just look and see the belt not riding in the pulley correctly

 

there is one other strange possibility and that is the the number of ribs on the belt do not match the ribs on the AC compressor pulley. I have only seen this once where a JDM motor was put in and they did not transfer ALL of the original accessories to the new block. It would be pretty obvious but you never know... I know this is the alternator but this is easier to get this pitcher that the AC compressor.

 

Thanks Glamisman, these are the fine details that are easy to overlook! I went out and compared the ribs on the belt to the ribs on the pulley - everything matches up.

At this point I'm thinking that the bearings I've tried are crappy and that I'm probably over-tensioning the belt. But to only last a day or two? Can't help but feel that something else is off.

 

You didn't remove the bracket but you do have a new aftermarket compressor on there correct?

Sounds like an alignment issue.. not sure on the 5vz engine bay but in my 3rz bay I've got enough room to put a straight edge from the crank pulley (where the ac belt rides) and check to make sure the straight edge lines up with the edge of the AC pulley

 

I swapped in a factory Denso unit from a low mileage 4Runner. Never removed bracket. I'll take a closer look to make sure I'm lined up.