Dennis
What exactly is leaking air ,oil , antifreeze.
My guess would be an oil leak from the lower cover on the compressor.
If this is the case it should be as simple as replacing the gasket.
The first thing your going to need as Bill stated is the manufacturer model number of the existing compressor. ( Usually located on a small tin tag on the compressor) the compressor was likely sourced from Bendix or Midland.
There are many new and rebuild suppliers out there the compressor on the engine would have been selected for the truck application depending on the number of axles and accessories which would require air volume for this reason it is important to get the numbers from your old one as even to identical engines could have different compressors installed.
Once you have the tag numbers any good ruck parts store should have no problem finding you a gasket set or a complete compressor.
On line a place like find it parts or Michigan truck spring should have no problem locating one .
Prices vary from $500. To over $1000. Depending on make and model.
If all else fails you could buy one through your local CAT dealer but the price will reflect the gold colour of the paint. Lol
Most mechanics will opt to replace the complete compressed with a rebuilt or new as it limits their liability and warranty obligations to those of the rebuilder and with labour factored in its sometimes more cost effective to replace rather than repair
Hope this helps
Eric
