98 S70 N/A: Vibration in brake pedal while at stop.

[theWIFES_S70]

Hey all, so, of course, you can't go a few weeks without something creeping upon these P80s.

Our brakes...

They seem like they have a little air in them. I have been meaning to bleed the fronts because I bled them with my dad and he's great at many things, but sometimes he gets confused with the brake pedal and with the clutch! I haven't gotten around to it, and will definitely get to it.

Today, as I was driving around my wife's car, I felt a "mechanized" vibration in the brake pedal while we were stopped at red lights. Car stops fine and the car rolls backwards and forwards when you let go of the brakes the way it's supposed to.

As we drove around, I paid attention to this sound, and it didn't always happen. But it did occur about 75% of the time.

Any ideas as to what this might point to? I'm hoping a brake bleed or a swap of the brake vacuum line takes care of this... Does the master cylinder or brake booster or brake booster check valve ever cause something like this? Thanks guys.

edit:
I replaced both front calipers in the winter. And both front brake lines last August. Master cylinder is not low.

[scot850]

I'm not sure what you are asking. Is it a noise or a vibration or both? Vibration is possibly unrelated to the brakes (car is at rest I am assuming?).

More likely one of the engine or torque mounts failing/failed. Check top torque mount, lower torque mount and also the main mount under the crank pulley. Carefully jack the engine with a piece of wood or rubber between the jack and the engine oil pan with the RHS front wheel off and the access panel peeled back so you can watch the mount under the crank pulley. They metal part of the mount and the rubber portion separate with age or any leaking oil in this area will accelerate the issue.

Neil.

[theWIFES_S70]

Thanks for the heads up, Neil. You think it could be caused by the upper torque mount? I replaced the rear, front and side engine mounts and the transmission mount. (Transmission mount is Proparts so I should check that out...) You know, the upper torque mount slips and slides up there. I had to purchase a replacement bracket and went with the Proparts version that came with a Proparts bushing. It was never in there tightly at all! I hope that's solves it.

[E Showell]

I agree with Neil. Sounds like an engine mount issue -- most vibrations at stop are.

[theWIFES_S70]

Thanks E. Just checked. Seems like my Proparts transmission mount has already ripped. Sigh...