Mechanical smell from engine compartment

Today I got to changing out my ac pulley bearing, hoses, belts, a heater valve and new radiator. A mechanic had told me I needed a new compressor, because of the bearing so since A/C was running fine I decided to just change out the bearing. I got the belt off and spun the pulley and it's quiet, and turns smoothly so now I'm not sure I need to pull it off and change it. This all stems from a faint, but obvious mechanical smell I get from the front of truck, noticable when I exit truck and walk forward. It's not rotten eggs it's not electrical and it doesn't smell like oil, it smells....mechanical. Has anyone had this issue ? I'll be putting the new belts on this afternoon.

 

Sorry I have no idea what a mechanical scent smells like. Two things come to mind though. First in working on your vehicle, you may have smeared or splatered gunk on some areas (ex: exhaust) and what you're smelling are the gunk bits and pieces slowly burning off. That smell should go away in no time. The other one is the transmission oil cooler lines which are right under the radiator. You can check them and make sure that they're not leaking.

 

In process of changing belts right now, the trans lines were good. I did change a leaking heater valve, on the firewall, and it potentially could have been leaking on either the block or perhaps part of the exhaust. But that's not a mechanical, machine smell. Should be able to put rest of belts on after dinner, then drop new radiator in. I drained out a nice mix of red and green coolant out of old radiator, so I will flush and refill with red.

 

When my AC pulley froze up and burnt up...I got something like "a machine smell". But it did it all at once immediately...then I had no AC.

 

And that's exactly why Im in there - but the A/C pulley spins quietly and smooth, so I'm reluctant to change a bearing thats not bad.
My A/C makes no noise, blows cold, and the tensioner is good. I'll put it back together and see if it's still there...

 

Update- yesterday I finished installing new hoses, belts, radiator and heater valve. Everything went in well, after flushing system and refilling with red coolant I took for drive. No issues and I haven't detected "machine/mechanical" smell anymore. I'm thinking it may have been a belt too tight, or maybe the ac tensioner too loose. I will evaluate over next few days

 

Thanks for the followup. I am glad to hear all is well now.