Hello!

I bought a 1985 XJ6 from a Dealer who told me it needed front calipers, but the booster was fine.

It was very hard to stop car, then eventually the pedal would go to nearly the floor, I could hear "air" inside car, and the car barely wanted to stop.

So I found the master cylinder was leaking, the front calipers and rotors were rusted.

I replaced the master cylinder, calipers and pads/rotors.

I cleaned out lines and the job was clean, and I bled the air out.

Same problem!

Barely wants to stop, using a very strong leg, I hear air, and I just can't tell if the booster assist is working, tbough the engine idle does not change when engaging booster.

My question is one....

Should the car stop easily with just the fronts working in perfect order (plan on doing backs)

And two....

How do I know if booster is working?

I have plugged vacuum line and the effort to stop car does not change.

Sorry for long post, but it is getting frustrating......

Any help would be appreciated, thank you!

 

1/ The booster is not working. hard pedal.

2. the rear calipers may not be working..

Get a person to help you

jack up the rear weels. See if e rear wheels turn freely. run the engine, applyu the brake pedal. hard. do the wheels stop?

disconnect the vacum lie from the booster. does pedal effort change. is there vacum in the hose to the booster?

Carl

 

That was the first thing I did was jack up wheels and see if they stopped moving when applying brakes, but did it manually without starting car.

They all stopped, but I assumed my arms holding the tires was not quite what the wheels would do going down the road.

Yes, plenting of vacuum to booster.

It only "hisses" inside car when pushing hard on pedal.

​​​​​​​Thanx!

 

A reasonable 'quick' test of the booster is to start the car whilst your foot is on the brake pedal. As soon as the engine starts the brake pedal should go down more as the booster pressure builds up. Works for me, anyway !

 

The hard pedal and lack of easy braking makes diagnosis easy
It is very simple. Your booster is not working. I have experienced this in S2 and S3 XJ6 cars as well as other model Jags.
Time for a booster overhaul
Cheers

 

Yes, I pumped brake pedal which stops about half way, and while holding it down, started engine, then pedal went down, almost to floor.

Thanx!

 

​​​​​​

The car had no braking at all.
I would pump it and drop it in low, and after about 100 feet, it would finally stop, very slowly.

It seems to me that the difference on most cars between a working and not working booster is night and day, but a car would stop manually, a little difficult, but stop.

How obvious is the assist with the booster?

No effort, a little effort or just gives the foot a little relief?

Because I bought car like this, I don't know what "normal" should feel like.

And boosters are a bit pricey, which I don't mind, if it is money allocated out of necessity.

This had a leaky master cylinder, which I replaced. And bled all the air out.

Wouldn't the car at least stop with the fronts working fine, if the backs need work, but do not leak?

Thanx for eveyones time and help!!

 

IMO, that alone condemns the booster.

Cheers
DD

 

I agree with all the above diagnoses.
Your booster has bit the dust, doubtless well before you got the car.
Been there, done that, down a hill in the Bay Area with wall-to-wall cross traffic at the bottom, a RED light, and suddenly, "brakes" as you have described; Non-Existent with much hissing!

I like a bit of adrenaline rush but that was NOT pleasant!
(';')

 

Just to test it between manual and assisted

I reconnected vacuum line to booster.

 

On mosst cars, there is amrked difference between a boosted pedal and one with little or no boost.

A car will stop sans booster. but, you gotta push real hard.



Here,. we seem to agree. booster is a dudl.

If budget is an issue, try David boger at everyday xj for a good used unit.

So not mess with less than optimum brakes.

Way back when, my cars had lousy brakes. managable then, today, no way!!!

Carl

 

IF it isn't the booster, then check the mechanism that distributes the balance between front and rear brakes. I found mine super clogged and not working because the brake fluid went bad and everything became sticky. Don't know if this applies to the Series III you have. I have a Series II. But I thought I would throw it out there anyway.

Bill

 

I cut up a 2x4 to match my leg, and was able to bleed backs with the wheels on, and my kid at work! Lol

A lot of air came out, and it brought the pedal to the top.

Car stops better, but not easy.

I actually took off the brake lines, distribution block, cleaned inside, outside and painted them and polished the brass block.

New master cylinder and calipers on front.

Fluid is clean.

The inner fender wall was rusted from brake fluid leaking, so I pulled everything out, got rid of the rust, primed and painted it, and put everything back buffed and or painted depending on how it was originally.

It came out very nice, actually, and after a week of work.

The dealer I bought car from, for my son, said booster was fine.

So, I stripped it, primed and painted it, and now, I guess I need a new one.

I also polished the aluminum pedal housing.

Any HELP on where to find a new Booster?

So far, I have had no luck.....

Thanx!

 

A new booster ? Not likely. A remanufactured one. far more likely. check the adds here. Try rock auto.

 

As Carl suggested, or Amazon had mine. Cardone 53-5950 Reman Power Brake Booster.

Dave

 

I cut up a 2x4 to match my leg, and was able to bleed backs with the wheels on, and my kid at work! Lol

So I said to my wife with the wooden leg "Peg!....

 

The dealer I bought car from, for my son, said booster was fine.
When you start to believe a dealer's word ( in Australia we call them second hand car salesmen in training to be real estate salesmen) then you should also believe in the Easter bunny, the tooth fairy and Father Christmas.
Cheers

 

Yeah, circa 1960, I wanted a second car, cheap. I found a nice 55 Olds 98 hard top coupe. Nice carll but the lifters rattled. Salesman told me all that was needed was an adjustment. I knew better. But, I thought I knew how to fix that. So, after some negotiation, a deal was amde.

Once home, I pulled the intakle and found exactly what I expected. Tons of sludge. got it clean, Pulled the valve covers. Nore sludge. cleaned that up. Pulled the tovkers. And managed to wiggle out the lifters. Fiddly, but cleaned all 26!!!

Primed them in a can of clean oil Put it all back together., Changed oil and filter. more of a mess. Well, I should have dropped the pan. Nope, pooped. SOg, it fired, ran great ands was reasonably quiet. Teh ohnly thing that car missed was AC. not a good thing., it was PHX, AZ.

Drove it a while ansd then swapped it. and bought a company car trade in. Very cheap. Not as extic as the 98, but with coooool AC.