Dry Unlubricated (DU) bearings versus greased for A/C Compressor pulley

[tracktor]

I have a '93 Audi where the A/C compressor pulley bearing recently started to make a grinding noise. I realized it was the bearing and opted for replacing it, since I've done some pulley bearings on my newer Toyota.

I got the bearing out (not easily) and it's the original Japanese NSK bearing and I've had a hard time finding the right bearing to replace it. The bearing part number ends in DU which I've read means that bearing is Dry, Unlubricated. I have found a replacement bearing that is not DU. It has lubrication in it.

Do you think there will be any issues with using a standard, lubricated bearing? The original DU was probably used for a reason. Maybe due to heat?

 

[Jdeere562]

Personally, I would never run a dry bearing with no lube. Maybe I am missing something?

 

[Chris142]

Apparently that means it's a bushing. If you can find a bearing I'd put it in. Millions of cars are running around with bearings instead of a bushing.

 

[Chris142]

Personally, I would never run a dry bearing with no lube. Maybe I am missing something?

I had not heard of it till I googled it. It's a bushing. Bronze maybe?

 

[Jdeere562]

Apparently that means it's a bushing. If you can find a bearing I'd put it in. Millions of cars are running around with bearings instead of a bushing.

OK, bushing is different than a bearing. Why would they use a bushing in a spot like that? Makes no sense to me.

 

[Chris142]

OK, bushing is different than a bearing. Why would they use a bushing in a spot like that? Makes no sense to me.

Engineers being silly

 

[Jdeere562]

Engineers being silly

Spins too fast and too long for a bushing. Bushings are for starters, carb shafts, shift levers and such!

 

[tracktor]

Yeah, I'm not 100% sure how they work. I read there is a teflon coating in them in one google result. Might have to crack it open to see how it works. I've attached a picture of the original bearing.

 

[Jdeere562]

Yeah, I'm not 100% sure how they work. I read there is a teflon coating in them in one google result. Might have to crack it open to see how it works. I've attached a picture of the original bearing.

That's a bearing, not a bushing.

 

[tracktor]

Thanks. Starting to think it's just outdated nomenclature on the original and it is a greased bearing. I'll crack it open later to confirm.

 

[ripcord]

You can easily pull that plastic cover off the side with a pick and check.

 

[Dave9]

I suspect DU means "contact rubber seal on one side only", and it should be a (factory pre-) greased bearing. However, the original is now 30 years old, wouldn't surprise me if the original grease has dried up and mucked up as it wore out, so it looks more like graphite sludge.

See this PDF, page 4: https://www.nskamericas.com/content/dam/nskcmsr/downloads/americas_bearing/TI - Bearing Dimensions & Designations - Rev 2.pdf

 

[ripcord]

I suspect DU means "contact rubber seal on one side only", and it should be a (factory pre-) greased bearing. However, the original is now 30 years old, wouldn't surprise me if the original grease has dried up and mucked up as it wore out, so it looks more like graphite sludge.

See this PDF, page 4: https://www.nskamericas.com/content/dam/nskcmsr/downloads/americas_bearing/TI - Bearing Dimensions & Designations - Rev 2.pdf

That seems to be exactly what it means according to that document. Page 4, table BEARING DIMENSIONS AND DESIGNATIONS.

 

[oil pan 4]

Depleted Uranium

 

[KrisZ]

There is no way a ball bearing would be dry. I would forget trying to match the part numbers exactly. As long as the size is the same and it has dust seals, it will work.