So... Mary's car sat overnight to see if it sets a different code when it cold vs warm. She gets in to back up and has what feels like no brakes. Pulls forward still nothing. Not happy. The fluid was up to the max mark.

I tried it and the brakes felt like the pads had pulled back from the rotors, not the pedal to the floor bad master feeling. Using the brakes a few times brought back some of the performance but i did not have time to get out and drive it to see how it acts. Ideas before I have to test drive it tomorrow ?

Thanks

Greg

Take that car out of service until you find out whats wrong.

It's time to examine the brake pads, flush the brake fluid, check calipers, etc.
and if the rotors look bad replace with ATE (German Rotors) NOT the junk from China. (I think ATE is OEM.)

Check the flex brake lines, they may need replacing....
rubber goes to U-Know-Where with old age.

Bill

No being excited to drive a car without brakes I did look it over and bleed the brakes. There was no sign of anything wrong. Once the brakes pumped up again they work well enough to trigger the ABS on a hard stop.

Mary refuses to drive it until I find a conclusive cause. I'm at a loss for a good guess.

Greg

It is possible that the brake booster check valve died or the vacuum line to the check valve has a crack. Check the line from the intake to the booster. If the line is bad, get a couple of new clamps and some heater hose to replace it.

https://www.matthewsvolvosite.com/forums/viewtopic.php?t=47142
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Keeping it running is better than buying new

If your booster vacuum hose is bad then your pedal would get firm as you mentioned. Common place the hose can go bad is where it is routed under the air filter box. Mine was fine until after driving a few miles then it became warm and would colapse since it was softer. Pedal became very firm since vacuum was lost.

If the pedal is soft after you have properly bled the system it could be one of the seals in the master cylinder. Fluid has to go somewhere. With the engine off does the pedal continue to drop as you apply foot pressure?



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It takes a great deal of intelligence to recognize ones own ignorance

No, only with the engine running. My 240 pedal stays at the same level engine running or not.

Greg

I'd have a close look at the brake booster check valve and its hose.

Have a look at this:

https://www.yourmechanic.com/article/symptoms-of-a-bad-or-failing-vacuum-brake-booster-check-valve

I'll have a look at the vacuum line and check valve but I don't believe the check valve keeps air from getting into the brake lines. For example, my 120 has manual disk brakes. They work just fine.

The pedal on the V70 was soft, just like the pads had been pushed back from the rotors. A bad booster or check valve seems like it would lead to a rock hard pedal.

Greg

Vacuum booster works as expected. One thing that I did notice is that the pedal continues to sink towards the floor with the engine running but is stable ( and hard ) with the engine off. Compared to my 240 the pedal only goes so far with the engine running or not.

Bad master cylinder ? It is a Volvo part and only a few years old.

Greg

It has to be either a MC seal or a brake line that is ballooning to about 3 inches in diameter! Rock hard without vacuum is normal. Sinking after initial pressure is a bad seal.
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Keeping it running is better than buying new