Groan from breaking after stop and other questions

[FireFox31]

Hello, my 2000 V70 makes a groan when I power off the car after driving. It sounds for two seconds, stops for two seconds, repeat. The groan stops when I press even slightly on the brake pedal, starts again when I release. The groan sounds like it is coming from the driver's side of the engine bay, thus likely the brake booster or brake fluid reservoir. What could be causing that sound?

Some other braking questions:
Must I replace brake dust shields which are slightly rusted through? They're expensive at $75 each.
Is there a trick to seeing the inside of a rotor (against the dust shield) without taking it apart?
How pristine must my rear caliper pins be? Mine have some rust pitting.
Can I reuse the caliper bolts even though Volvo says not to? Add thread lock red?

Edited: Brake fluid reservoir, not power steering fluid reservoir.

[scot850]

Lots of questions so let me try to answer them for you:

1) Do you use the parking brake when you stop? If you do the groan could be dust on the rear parking brake pads allowing the car to move slightly. It could be a vacuum leak somewhere, but I don't think ti would groan. Trying to think what else it could be other than a dry bushing in the front suspension. I had a groaning on my car but it was my wallet! It turned out to be the front sub-frame bushes but that only happened when moving not at rest. Power steering pump is on the RHS of the engine. Possible it could be the steering rack?
2) Dust shields - At the front you don't even need them. They are there to cause pain and expense. Unless the holes where they mount are bad then don't worry. On the rear you do as the parking brake attaches to it. Again if they are rust check where the parking brakes attach to and sit. If that is good then should be ok. If they are getting frilly, I would consider replacing the rears. If yo have an AWD then chances are you are hooped as I believe all the rear dust shields are NLA.
3) Seeing the rear of the front rotor - It is hard to get access to see. There is a little room either side of the brake caliper you might be able to see with a mirror on a stick and a flashlight. I would suggest jacking both front wheels off the ground and with the car on axle stands, you can rotate the rotors and check the rear of the rotors. It is easier with the wheels off. I found my front rotors were bad this way only on the back.
4) Rear caliper pins - If they are badly pitted they may prevent the pads moving correctly. Rub then down with sandpaper to try to make them more smooth but I'd recommend replacing them. Rear calipers I tend to find fail quicker than fronts as they work less hard and move less. Maybe the cause of them seizing more often.
5) These bolts are a personal choice. I have re-used them many times without issue. They are a torqued bolt but not a torque to yield one Make sure the threads are clean and use new thread locker. If they are pitted and badly rusted I would replace.

You may get some different opinions from others but this is what I have done for 20+ years on my P80's.

Neil.

[FireFox31]

Thanks for the reply, as always. I really want my braking system to work fully.
1) I'll have to dig deeper into this groan which stops when I lightly press the brake pedal. Sounds like it's not a simple common problem.

2) Thanks for this info. I will replace my rear dust shields when I rebuild the parking brake system since they're interconnected.

3) I was hoping there was a better way than looking at such a narrow slice. For the rears, I pull the pads and look at the inner rotor face where the pads were. It's a larger area to look through.

4) I sanded down my rear pins, then worried that I made them worse by doing so. I assumed there was some coating I was wearing off. I'll keep them sanded smooth and check them regularly.

5) Thanks, I'll reuse the bolts after cleaning them and applying thread locker red.