How common is is for the brake fluid reservoir to rupture during a brake flush?

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I just took my car to the dealership to have a routine brake flush. I got a call saying unfortunately while bleeding the system under pressure, the reservoir ruptured. Is the dealership at fault?
Do you
have the same problem?
Tuesday, December 27th, 2011 AT 7:23 PM

1 Reply

Bleeder balls have pressure-limiting valves that keep the fluid under 15 pounds of pressure max. Over that, air above the fluid, (both in the bleeder ball's tank and in the reservoir), can be pushed into the fluid. The air bubbles will expand once the pressure is removed and you'll have that air in the hydraulic system. That causes a spongy or mushy pedal.

Given that 15 pound maximum pressure, it's highly doubtful the mechanic did anything wrong. Even if they were able to circumvent the safety valve, the reservoir would not have ruptured unless it already had a weak spot. Since most are made of plastic now to save weight and make manufacturing easier, it's not really suspicious to find a problem with one.

Given that, replacement reservoirs for most cars are very inexpensive. Volkswagen is a different story though. They are very proud of their parts and charge accordingly. A reputable repair shop would replace the reservoir at no charge to you if they felt they caused the problem, and they would typically donate the labor but ask you to pay for the part if they felt you already had a weak or defective part on the car. Some shops, GM dealers for example, are very short-sighted and are more concerned with squeezing every possible dollar out of you right now vs. Building customer goodwill in hopes you'll become a regular / repeat customer.

In my state we have the right to have old parts returned to us unless there's a core charge. If the shop pays for a new reservoir, that may not hold true, but if you end up paying for it, take the old one to a different shop for an opinion on what caused the problem. Don't mention the name of the first shop as that can bias the opinion favorably or against them. At least it might put your mind at rest that the mechanic wasn't at fault. Also look for a seam where two parts of the reservoir were glued together. If it is split there, suspect it just had a weak spot.

Having a brake fluid flush is something everyone recommends but very few people do. Even now with brake jobs or with maintenance flushes, very few shops use pressurized bleeder balls because they have to own so many different adapters to fit the wide variety of master cylinder reservoirs. Many years ago two adapters covered all cars. The brake fluid can also be sucked out by each wheel rather than forcing fluid in under pressure. That would have prevented this problem but it is slower and takes a lot longer.
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Tuesday, December 27th, 2011 AT 7:51 PM

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