While on a trip this weekend all seemed fine until I pulled away from a toll booth with the window down. Whoa, there was a very piercing noise from the engine that changed with the engine rpms.

My wife would describe the sound as draging a stick against a picket fence at a high rate of speed. It sounds to me it's a bit like a belt squealing. At idle there is no noticible problem, but as the engine speed picks up so does the noise it changes pitch with the engine speed. I spent some time in the dark with a flashlight trying to see what was up. Looks like the fan isn't hitting anything and there is no obvious problem with the belt.

Last work I did was to change three of six glow plugs, change oil and check fluid levels.

BTW, the engine shut-off (diesel) is taking longer than it used to since I worked on the plugs.

Thanks for any opinions that you may have.

Check this sooooon! It could be simple like an alternator on the way out, but it may be more involved. Be sure that the vacuum pump does not come apart. It has ruined many of these engines.

Will do, Benzmac. Any easy tests for vacuum pump failure? Meanwhile I'll do a search. Thanks,