Engine looses power when brake is pressed

You have a bad vacuum booster. The diaphragm in the booster is ruptured resulting in vacuum loss and no power assist to the brakes. Do not drive in this condition, loss of control (stopping) hazard exist.. Replace Power Brake Booster. Since replacement of the booster requires removal of the master cylinder, replace the master cylinder as well, It is old (2003) and time for replacement

If its only when you press the brakes, there may be a vacuum loss in the power brake system. Check the hoses from the manifold to the master cylinder booster or the connection on the booster itself. The hose may be split or the connection loose and leaking air. The booster itself may have a ruptured diaphragm. To check this, start the engine and run for a few minutes. Press the brake pedal and hold in. Turn off the engine. You should feel the brake pedal drop slightly. Remove your foot off the pedal and press the brake pedal a few times. Each time you press it , the pedal should keep dropping slightly and feel harder and harder to press. This will let you know that the booster is working properly.

Long shot: Bad master cylinder - Typically the brake pedal will slowly sink to the floor. On early 2000 vintage Chrysler products you need to check brake lines as they have been known to rust (and fail catastrophically)

u gut a master cylinder or booster issue--chec proper fluid level and condition--u cant see a leak in brakebooster where master attaches--u may have air inlines--bleed them if--a pro shud be considered

if you talking brakes not clutch. you can pump the brakes all day long and they don't build pressure and you not losing fluids the master is out. now if you pump them up and they are rock hard your hydrabooster is out.now if your mechanically incline you can order a master cylinder rebuild kit for like 20-30 bucks which is basically orings from local parts store and only tools you need are snapring pliers. or you can change the master ,bench bleed it first then bleed out the rr,lr,rf,lf in that order.hope i help.all under 100 bucks

Replace the brake master cylinder.
Check for any signs of brake fluid loss (leakage) on brake system.

that is your brake fluid reservior. if you have fluid and no brake noise you may have a faulty mastercylinder. the first thing i would check is to make sure the vaccum hose to the brake booster is connected to the brakebooster and to the rear of the engine (since you did not know where your brake fluid reservior was the master cylinder is the meatal part that holds the reservior and the brake booster is the big round bubble that the master cylinder is bolted to) hope this helps you out.

check the master cylinder fluid level under the hood, there is a line on that plastic reservoir that shows proper level, if that is ok u have some other problem like a loss of brake pressure.

sounds normal.... when the engine's running, there's power assisting you as you brake to move all that hydraulic fluid from the master cylinder to each of your wheels... when the car's off, there's no power assist as you press on the pedal causing it to feel hard as you have to use your own strength to push on the pedal. also with the car off, the fluid pressure just keeps in the line and is not returning to the master cylinder, causing that pedal to feel harder with every press

If the pedal has sunk further than usual or gradually sinks then usually a Master cylinder gone bad, but also can be a ruptured barke hose or line. It can also be leaking brake caliper or wheel cylinder (will show a fluid level loss in Master Cylinder)