<VV> Re:infrared thermometer readings

[djtcz at comcast.net]

-------------- Original message -------------- 

> From: "D. Monasterio" 
> Subject: Fan & idler pulley bearing temps. 
> 
> Today, while preparing/checking "El Andariego" (the 67 cpe.) for a 1,300 
> miles round trip, I heard some bearing noise. By touching with a finger, felt 
> some vibration on the idler pulley bearing while the fan bearing was silent. 
> This remind me about these same bearings on the GB (new ones, unknown brand, 
> probably Chinese) which seemed hot to touching under normal operation. 
> So, took out an infrared thermometer for checkings and comparisions. On the 
> car, temps. were 100° F on the fan bearing and 131° F on idler bearing. On the 
> GB, they were 98°F both. These tests confirmed that car's idler bearing needs 
> replacement and the new bearings on the GB are fine. Both tests were made with 
> warmed engines and hood open. Thermometer was at about 1" and pointing to the 
> shaft. 
> Have somebody tested these and other bearings operation by temperature 
> measurement ? If so, which temps. were found on good working bearings. 
> 
> Thanks 
> 
> 

Infrared thermometers are mighty convenient, but work on the emissivity of the surface being measured, so some surfaces need to be modified to read true. 
If a ball bearing with rough or failing innards is well lubricated it is >>possible<< for it to run cool. A bearing with too much grease runs hot even if the balls and races are perfect.  Excessive temps by themselves can kill a ball bearing if it causes the internal clearance to get used up. 
http://64.233.169.104/search?q=cache:OeODyHNX1icJ:www.food-management.com/article/7359+infrared+thermometer+tricks&hl=en&ct=clnk&cd=4&gl=us

--
Dan Timberlake