Where is the vacuum pump for the booster on the braking system of a volvo 240 dl 1988?

Booster diaphragm is bad .

IT is probably a vacuum leak in the brake booster. With the pedal going to the floor There is either no brake fluid or you will have to bleed the system. Replace the booster and bleed the brakes starting at the longest line first

NO. the vacuum is used to make the brake pedal easy to push, power brakes. the pedal would be hard without vacuum, that is why the pedal gets hard with the key off and engine not running. the problem you are having is more of a hydraulic problem.
Have the brakes checked asap. the brake system may have a leak causing the pedal to go low. check the fluid level and if it is low or empty then there is a problem, could be a rotted brake line leaking or a wheel cylinder leaking.

could be booster, could be air in system, could be master cylinder. Check reservoir. If it is out, you have leaks and air in lines. If no, listen for air leaks under dash as you push pedal. If air leak, replace booster.
If no air leak, check for vacuum at hose going into booster. If no vacuum, check hose connection to intake manifold.
If no leaks and booster is good, suspect master cylinder.

Let me know if you have questions.

Could be brake booster leaking. When engine is off the brake pedal should be firm and not go to the floor. If the pedal goes to the floor engine off, there may be a master cylinder problem also.

Check for fluid leaks and your brakes. If you see no leaks and your brakes are in good shape replace the brake master cylinder and bleed the system. The air you hear is because the pedal went to the floor. If the booster goes bad the pedal will get so hard you can hardly push it at all. I think you will find if this happened suddenly either you have a major leak or the master cylinder went bad.

you will have to bleed them again. air must have gotten in while (nipple) was still loose.

you did'nt say why you changed the rf brake hose, but i'm assuming it was leaking, check to make sure the new one is not leaking and there is no other leaks in the system, this includes the other 3 calipers and hoses, the rear hose in between the rear hard line on the frame to the rear hard line on the rear axle. if there is still air in the right side line then the left side would be doing all the work and may cause your abs to kick in on the left side if it is attempting to lock up. this may be the noises you are hearing. if you still have power brakes after you shut the engine off, (you should be able to pump the pedal 3 or 4 times with the engine off before the pedal becomes hard) then the booster is ok. if it has a swooshing sound inside the car, (hard to describe that sound on a keyboard), then you may have a leak in the seal on the brake pedal side of the booster. brake master cylinder sounds like it is bypassing. if it still goes to the floor after you rebleed then replace the master cylinder. if a brake pedal goes all the way to the floor, it is possible to ruin the cylinder and cause it to bypass, this is caused by rust or corrosion, the seals on the plunger are compromised letting brake fluid leak past. any other questions please let me know. thanks

HAS THE LARGE VACUUM LINE TO THE MASTER CYLINDER COLLAPSED, I.E. FLATTENED?