grinding noise when coasting at freeway speeds
 

A couple weekends ago I changed (well actually my wife did, with my direction) the brake pads and rotors on all four corners of her '98 s70, which thankfully eliminated a horrible vibration on braking due to warped rotors. But now we're hearing a grinding sound when we let off the gas at speeds above 40 or so. Neither of us remember hearing this before doing the brakes.

It sounds to me exactly like the brakes sound if they're down to metal on metal. The sound sometimes goes away when I step on the brake, other times it will remain but get quieter. It's hard to tell but it sounds like it's coming from the passenger front.

It does not do it when coasting at lower speeds.

I haven't had a chance yet to pull the wheels off and look at everything, but I'm looking for anyone that might have ideas what to look for other than the obvious loose items.

I thought I remember seeing a post about the hubs causing a similar issue when I was going through posts before replacing my driver's side hub last summer, but now I can't find it.

The driver's hub was a pain to get off so I'm hoping to not have to replace the passenger side hub if I don't have to, but I will if that's what turns out to be wrong.

Hubs or wheel bearings usually have a rhythmic sound to them when bad. Did you guys bleed the brakes after replacing the pads, etc?

I highly recommend taking the wheels off and having a look.

I would look at the rear parking brake. The age causes the brake pad to separate from the shoe. I've experienced it myself.

The other thing to look at is the alignment of the pads on the rotors. Did you put the rotor alignment pin back in? Make sure the rotor pins are tight in the front and the caliper is sitting centered on the rotor. In the rear, the pins are a tight collar fit into the caliper. You have to align and tap those in place. If you didn;t do that and its lose the pat could be crooked. There is also a light croos looking spring that holds the pins and pads in alignment. Make sure spring is in place.

Bleed the brakes enough to get clear fluid, as rspi said.

Thanks guys, gives me a few things to look at. It's definitely not a rhythmic sound, it's solid. We didn't bleed the brakes afterwards, I was going to do a full brake fluid flush but haven't had time yet. Some personal stuff got in the way. I'll plan on doing a full flush and bleed while I'm looking at things.

do you all have a recommendation on type of brake fluid?

I'm a firm beleiver in brake fluid replacmeent - even if its only opening the bleeder when you push the pads back.

I think any good DOT 3 will work. I think I used Castrol last time.