Restoring a 1983 GS. Engine runs strong but there is a noise like a bearing or belt which produces a high screech start at 4k rpm upward. I have tightened the Alternator belt and A/C Belt. Is there a bearing in the A/C or Alternator which could be bad? Really sounds like a bearing issue at high rpm. Any ideas? Also - anyone going to Caffeine and Octane in ATL this Sunday?

 

The alt does have a bearing. You can test by removing the belt and rev above 4k.

 

Could be locked up fan clutch causing belt squeal? Also this scenario long term can cause damage to drive end bearing in alternator from heat. While belt is off,spin alt pulley and feel for roughness/noise.

 

As stated, strategically remove belts to find source of noise. Could be alternator, ac compressor, wp or air pump.

I went with 2 other rx7s to last C&O. Very fun trip. Its a long drive for me, so not something I'll be doing again for awhile.

 

I should also note that the water pump can make a squealing noise even if it's good at the 4k mark if it does not have good tension. Most notably seen (heard) after removing the air pump.

 

I was just going to bring up the water pump as well. How new is the belt? I had a new one squeal on me pretty good for a while and it eventually sorted itself out. Make sure to not over-tighten the belt either.

 

Thanks all for the suggestions and the help. The problem ended up being that the water pump belt was too loose. It felt snug when at rest but when the engine rev'd up, the belt would loosen. Ended up tightening the belt and all good. Now, how tight is too tight?

 

1/2"-13mm deflection of belt in longest run of belt is about right

 

Agreed with above! I run my belts about 10mm of deflection knowing they will stretch a shade into that acceptable margin.

If the belt was loose, it may be time to start looking for a replacement. If the belt is stretched and worn you will notice that it will loosen again, causing noise. I would advise replacing the belt if its not a newer belt. Just preventative maintenance.

 

I was afraid of over-tightening my water pump belt after removing the air pump so I got a pulley to double up the belts for the water pump. Solved my high Rpm squealing....but now my power steering pump is making noise. Solve one thing, and another pops up.