QuestionQUESTION: Hi sorry to bother you again. My dad had recently replaced the brake booster in a 1992 Cadillac deville. We put it back together. We found out that the brake booster got installed upside down. We tested it and the brakes still don't stop as good. I am going to bleed the brakes on it. They haven't been bleed in a while. I was wondering if it mattered if the booster got installed upside down or not. Thanks for any help.
ANSWER: Hello,
Is this question from the person that wrote me months ago with the hydro boost in which the car had been sitting, and the power steering was dry and we were trying to determine what you had, if hydro boost or vacuum?
If this is the same person, you have hydro boost.
Bleeding of the brakes has no effect on the ease that the vehicle stops. Bleeding controls pedal height and firmness. The booster serves only as a brake assist. Two separate entities.
With hydro boost, the hydro boost must be bleed (not the same as bleeding the brakes) to get all the air out of the system.
I wish I was at the vehicle to assist you. Over the Internet poses many challenges.
If you put this unit in upside down, there is the possibility you did damage to it by attempting to reverse the flow of the fluid, with high pressure feeding into the low pressure return line.
I do not know if this happened, but the potential is there.
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QUESTION: No I wasn't that person. I installed the brake booster upside down. This booster conects to the master cylinder. You have to take the bolts off the master cylinder. Then you have to go under the dash and remove the four bolts then you can pull it out. The booster is on the left driver side mounted on the back wall. Thanks.
ANSWER: Hi,
OK, I get it. Why was the booster replaced?. The booster only assists so the brake pedal is not hard to push down.
When is the last time you adjusted or checked the rear? Has car been exposed to lots of city driving causing the brake pads and shoes to glaze?
The only propose for bleeding is if for some reason air got into the lines, from a leaking line, calipers or wheel cylinders. Bleeding is not a maintenance issue.
If rotors are glazed up, you can go into a parking lot, pick up a little speed and slam the breaks on. Repeat about three or four times and it should takeaway brake fade, or if that doesn't work, you need to pull the calipers and sand the pads so they are not shiny an the same with the rear brake shoes.
City driving is bad for brakes keeping them hot, or if the person is a two footed driver.
Bleeding however is not a correction to make the car stop better.
As far as putting the booster on backwards, noting was harmed, however you need to make sure you have sufficient vacuum there. The car is20 years old an I would recommend changing the vacuum line.
If a booster is no good, you will no it, because the pedal will be hard and will be darn near impossible to stop, like when that piece of crap hydro boost failed today in my truck when my power steering failed. Lots of fun having no styeering and no brakes at the same time! I wish I had the same booster you have.
Caddillac played games with these and used either or and that is why I asked.
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---------- FOLLOW-UP ----------
QUESTION: The booster was replaced like you said it was impossible to stop the car and the pedal was hard. When you say has the rear been adjusted or checked what do you mean. This car doesn't do a lot of city driving. It only has 135000 miles on it. Most of it is long driving. I almost have to replace the booster every 2-3 years. Advanced auto told me that I need to bleed the brakes because they think there is air in the lines and also they haven't been bleed in years. Thanks.
AnswerHi,
Too many people listen to guys that sell parts and do not know what they are talking about when it comes to repairs. After all, they are selling cars aren't they? Not repairing them.
Mileage and brake wear don't correlate with each other and all depends on the driver.
You should never have to change a vacuum booster and the main reason I have seen them fail is from a leaking master cylinder with brake fluid swelling the diaphragm. Look, it does no goo for me to argue with a third party, but how exactly does air get in the lines? Not unless the ways I described or, if the calipers are out far enough from the pads being worn, that the reservoir empties and starts sucking air from the master.
Air doesn't just appear in a sealed system, or it wouldn't be a sealed hydraulic system.
When is the last time the brake pads and shoes were checked. The wheels ripped off and the drums pulled in the rear?
Although the self adjusters are supposed to work when reversing, many times they don't operate properly. When I would service them (sanding the shoes) I would crank the star wheels where the drum would fit tight on the pads. This will also give a higher pedal and stop better.
On the discs, there is no adjustment, but the lower the pad, the lower the pedal an the more effort to stop.
It is not normal to replace the booster every 2 or 3 years. Something is causing that event.
Kind of scary, today I was thinking about just how old I am, and I have been working on cars for 48 years. 11 of those years were with GM dealerships.
The very sad thing is to say I don't know the reason you are changing these boosters as often as you are. I have never heard of this.
I have run into bad check valves though. That is that little valve that on one end plugs into the booster and the other into the vacuum line.
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