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Celine 10/7/2019

1999 Lexus LS400 Base 8 Cyl 4.00L


Booster AND Master Cylinder?

Brakes are not working right, they feel funny, unable to press all the way down, or when I get them to go down, I cannot count on the timing to get the car to completely stop, but not making the sounds I normally hear when you need to replace them. Mechanic says it needs a booster. I'm okay with that, but the mechanic is saying that when the booster is replaced, the master cylinder probably needs replacing, too. I asked him, how will we know if it does? He said when we take take apart the car to put in the booster, we will be able to tell. But, it cost a lot less to do it then since we already have the car taken apart and you won't have to pay for labor twice. Okay, all this sounds fishy to me. I don't like it when someone says you "probably" need this and then gives me a quote. Please help.

1 Answer


Jimm 10/7/2019

It is easy to test the power brake booster (large vacuum diaphragm behind the master cylinder) - with the engine off, place your foot on the brake pedal.

Start the engine and you should feel the brake pedal slightly move downward - then get firm.

If the pedal does not move, or does not get firm when the pedal travels forwards the floor - then the issue is a leaking / faulty brake booster.

This part (brake vacuum booster) can be replaced without replacing the master cylinder itself - if the master cylinder is operational and does not have any internal or external fluid leaks, then it does not need to be replaced.

If there is any question on your part, as to why the master cylinder should be replaced then find another repair shop - and be sure to obtain 2-3 written estimates for the same work.

Try these various on-line parts resources; www.autopartswarehouse.com; www.partsgeek.com; www.rockauto.com - to list only a few.

In fact, they (RockAuto) list the vacuum booster from around $120.00 and the master cylinder from around $87.00 for your vehicle.

Power brake vacuum booster = SKP part #SKBB007 or Cardone part #532769 - or their equivalent.
Brake master cylinder = BECK/ARNLEY part #0729767 - or it's equivalent


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