i dont know what to do, ive replaced all the calipers because they were bad but still when i drive, its like the front brakes are on. A mechanic said it might be the master cylinder.

 

Welcome to the forum javsalvi,

A little more detail may result in some answers.

1. Model and Year
2. what was 'bad' with the original calipers
3. whether the replacements are new / used / rebuilt
4. what has already been done to attempt to rectify the issue

When you get a minute, please follow this link New Member Area - Intro a MUST - Jaguar Forums - Jaguar Enthusiasts Forum to the New Member Area - Intro a MUST section and post some information about yourself and your vehicle for all members to see. In return you'll get a proper welcome together with some useful advice on finding your way around the forum.

Graham

 

1. 2005 x-type 3.0 vdp
2. the pistons were stuck
3. they are brand-new
4. i thought replacing the calipers would fix the problems but it still happens.
it happens after driving it for a few minutes and it feels like its the front brakes.

 

If the original pistons were so stuck as to require new calipers, that would suggest that the brake fluid had not been changed every two years iaw with the service plan. Possibly never changed at all! Anyway, if the calipers had deteriorated that much, it would be a minor miracle for the master cylinder not to have followed suit! IMHO a new set of calipers deserves a new master cylinder. I hope you already changed the fluid that probably caused the trouble.

 

+1 to Master Cylinder and fluid change.

As you've replaced all the calipers, this leaves:

1. Parking Brake not releasing correctly (but would affect the rear and not the front)
2. Brake Booster fault
3. Hydraulic Control Unit fault

Are the new pads showing excessive wear on one or more calipers?

Graham

 

i just bought the car like a month ago and the previous owner didnt take much care of it but it has all new brake fluid, i also changed all the rotors and the front left rotor is showing a lot of wear already

 

Could be related to ABS - in a previous car (not a Jag), residue from master cylinder seals (or some other crud) caused havoc with the ABS (one wheel permanently locked solid).

I managed to resolve by removing the ABS valve block - soaking in an ultrasonic bath of brake fluid, re-fitting, bleeding the ABS unit (diagnostic computer needed). I had to repeat about 3 times to finally sort it out.

I suspect that one or more of the de-pressurise valves was blocked/stuck closed.

It's possible you have a similar issue. BTW, were the pistons actually stuck when you got the old calipers off ?

 

yes, the pistons were actually stuck and its both front wheels that lock after braking for awhile.

 

Have you checked the brake booster? Because I just replaced the front brakes and got the same result. The brakes are holding the car. And it's getting worse as you drive.
Check the rear wheels in the air. Are they spinning freely?

 

So a mechanic checked it out and pretty much, the previous owners of the car replaced the master cylinder but not with the exact one for the car, they got it from the junkyard so there's air going into the master cylinder cause the front brakes to lock.

 

On motorcycles, if the brakes work ok, but after a few miles they drag, and after another mile they lock, the problem is water in the brake lines and calipers. The water expands into a gas as the fluid heats up from use, and applies more pressure to the calipers, which drag on the disc, which adds more heat, etc.

If the brakes work ok, but after about 5 stops, they drag, and after another 5 they lock. But if you wait a minute they loosen up, then the return orifice in the master cylinder is blocked or partially blocked.

Considering your master cylinder has a questionable history and it seems that one wheel's brakes are wearing more than the others. Also, if the car has ABS, then this latter situation might be more prevalent, either in the master cylinder or in the ABS block. Also, you might have this problem in the proportioning valve, if your car is equipped with such.

 

Hi David, I have a sticky/locking brakes. It's the front left and rear right wheels. This started when I replaced my rear pads. Prior to replacing the pads, the brake system works fine. I ended up replacing both the rear calipers, both rear brake hoses, and installed new master cylinder. It did not resolve the issue up to now. I'm thinking of removing the valve block and clean juist like what you did. Can you please give some pointers ion opening the valve so it can be cleaned properly and without damaging it?

Thanks.

 

5+ yrs ago and low post count. Don't expect a reply...

 

Just to close off my sticky brakes issue, I retracted the master cylinder push rod by 2mm and it did the trick.

 

you just unbolted the two nuts to the booster and pushed in