My boyfriend is doing a tune up and fixing somne minor things on our friends 1998 astro van. The van has been totally neglected and not kept up in general and minor maintaince. So before doing anything he pressure washed the engine. Aafter doing so it started squealing. He applied belt dressing on the belts and that seems not to be it. Any suggestions on what this may be.
Thanks, applevalgal:

what kind of shape is the serpantine belt in? i know you say its not the belt...but if the pulleys are still damp...it will sqeal. if the belt is ok...then the pulleys are just wet...let it idle for awhile and the noise should go away. odds are if the van has been neglected it needs a belt anyways....also check the belt tensioner...ive had them rattle thereselves off on some "higher mile..neglected trucks" you can get both parts at any auto parts store for fairly cheap...worth changing anyways because it sucks breaking down with a faulty old belt in the middle of nowhere. hope this helps

another quick thought that happened to me....make sure its not the ac compresor...if it is disconect the electrical connector on the back of it a.s.a.p. the compressor will kick on when the defroster is on to help defrost the windows...so dont let the cold weather (depending on your location) make you think different. if it is the compressor...it needs oil and hopefully you caught it early enough....unlike me. my astro is like a greenhouse in the summer now. ill probably get a junkyard one this spring and hope for the best. just an idea...good luck

the only other thing I've had squeal is the ac compressor. this time of year I wouldn't imagine you've been running the ac. But one possibility is that the clutch on the compressor locked up after the pressure washing.

There are additives that can be put into the freon to lubricate the compressor internally as well. Having this done saved the compressor on my Jeep. Alas, the compressor on my astro began to squeal and I didn't get it done soon enough. My compressor ate itself and trashed my whole ac system. The additive for the jeep ran $35. The rebuilt ac system for my beloved astro was...(choke) $1700.
blkmonday is right, don't run the defrost or ac till you get this fixed. Keep some paper towels handy till you can get it in the shop.