Let me say at the start that I just purchased this 1994 XJS 4.0L convertible about a week ago. The car ran/functioned great until today.

Drove the car 15-20 miles doing between 60-70mph. Everything worked great. Parked the car for about 15 minutes, started it and found the brake pedal went to the floor. I very cautiously headed home, keeping a substantial distance between me and any other car. I would occasionally hit the brake and the pedal continued to go to the floor. After about 2 miles I applied the brake, got a little pedal but the car pulled left. Drove a little further, applied the brake, got more pedal and the car pulled left but no where near as great as the first time. After driving about another mile or two, the brakes function Ed as normal with no left pulling. After arriving home, I checked u der the hood and all 4 wheels. Nothing obvious. Took the car out in the neighborhood with no problems with the brakes.

i searched this forum and found a couple of interesting threads. On one, the problem with symptoms like mine, had one of the brake lines near the exhaust. Problem was solved after the line was wrapped with insulation. (I checked my lines and nothing even close to the exhaust). The other threads talked about the speed sensors needing cleaned or the ABS unit needing cleaned.

Has anyone experienced anything like this and, if you have, how was the problem solved.

Any help/ideas will be greatly appreciated.

 

As a start, since the car is new to you it could be that the brake fluid is old, has absorbed water and boiled on you. I'd start by flushing the fluid with fresh, noting that the bleed procedure for these Teves ABS equipped cars is very different from a conventional vacuum booster car.

 

Any help/ideas will be greatly appreciated.[/QUOTE]
It’s a master cylinder fail I think. I’ve been told that all brake fluids aren’t the same and the wrong type can destroy the master cylinder rubbers on older cars. Maybe it’s a bad repair or a bad service that caused the problem.

 

+1 on that and change the flexible hoses for new ones; they are known to collapse internally.

 

I'm not sure what model of the teves brake system you have, but if it's still the teves 3 then it could be your accumulator ball or a stuck valve in the block. I know when my caliper locked on my 93 and was dragging, I'm guessing it boiled my fluid, and along with my accumulator ball being shot, I had no brakes at all, then after it cooled a little I had some again. Just a possibility

 

rwolak,

You dont have a master cylinder per se on your car. The complex Teves ABS system uses an actuator unit and a small chamber at the front of thst unit acts as a master cylinder. In my experience, the actuator unit almost never fails. Faults in the system are always somewhere else in the system.

Good luck

Paul

 

Hi rwolac

As Paul (ptjs) says, you have the Newer and much more reliable Brake System on your Car with a 'Brake Booster' on one side and the ABS on the other side of the Engine Bay, where the ABS Part looks like a Cylinder, as opposed to the Older Type that has a 'Black Ball' Accumulator

You may have a Stuck Caliper or Stuck Brake Pad, which could cause the Brake Fluid to Boil (especially Old Brake Fluid with a high Water Content) If the Brake Fluid Boils you can lose all the Brakes 'I know as that happened to me'

So as has been already said, Change the Brake Fluid and Re-Bleed the Brakes and Check for Stuck Brake Pads and Calipers

 

new fluid

 

Thanx for all the comments. I haven’t had time to look into the problem but will get to it this weekend. I do know that the car sat for quite a while before I bought it so something “sticking” wouldn’t be uncommon.

 

I had exactly the same problem on my 94 - turned out to be a seized front brake caliper. This caused the brake fluid to boil resulting in the symptoms you describe, pretty scary,
I removed the and rebuilt the caliper with new seals. There was corrosion between the piston and caliper body leading to the stuck piston.

 

If there was a seized caliper would the car roll in neutral? Would you smell 'heat'? Would driver feel a dragging caliper and pad if it was dragging enough to create enough friction/heat to boil the brake fluid?

In my machine,,, a 1990 (and I have more to learn about this so bear with me) there are separations (I think) in the reservoir. Is the reservoir topped up? Have you noticed a puddle of brake fluid anywhere? An open or failed bleeder valve somewhere? A place where air can/is enter the system?

The intermittent braking and peddle to the floor is curious to me. In a sealed system full of fluid, old or otherwise (fluid doesn't compress), I wouldn't expect a peddle to just go to the floor unless there was air in the system or fluid was just escaping, or both. That, or a set of piston seals, rings or (I don't know this brake cylinder system at all) someplace where the braking fluid is moving around what creates pressure - rather than staying on the correct side of said pressure creation mechanism.

Staying tuned! I wanna learn about what's happening here

 

The seized/dragging caliper held the brake pad against the disk (rotor) just enough so the friction heated everything up and boiled the fluid. The car would still roll in neutral and there was no other change when driving the car apart from the pedal going to the floor.

I had no leak of brake fluid from the reservoir or anywhere else.in the system.

The only other symptom when I checked around the car was obvious heat from the bad wheel and a smell of friction material.

 

I see what you're saying... Thanks for the explanation...

 

I may have found the problem and it's exactly what you say. I jacked up the front end and tried to rotate the each of the wheels. Both would rotate but will a good amount of drag. The guy I bought the car from gave me new rotors/caliphers. Guess it's time to change them.

 

That's great news! Good for you.
Thanks to you all I learned something here...

Help me understand... When the brake fluid boils or get excessively hot it,,, what, expands and it's properties change? Any moisture creates air bubbles? It creates air/a gas at boil or extreme temps? What is it?

Thanks and a humble bow...

 

New dry brake fluid boils at 230C, If the brake fluid is old and contains a few percent of moisture will reduce the boiling point to ~ 150C,

Once if boils you get compressible vapor on the calipers and lines and the pedal goes to the floor.

When you change the calipers make sure you flush out all the old fluid.
The bleeding procedure for a '94 is described in the manual. a few things to note

1) For the front brakes make sure you pump the pedal (with the ignition off) until the pedal goes hard before attempting to bleed the brakes. This empties the accumulator vacuum reservoir, normally takes ~ 20 pedal pushes. If you don't do this you cannot bleed the front brakes.

2) Rear ones, Discharge the accumulator as described above. Open the bleed nipple and depress the brake pedal, with the pedal depressed turn on the ignition. This activates the pump. When you seen clean new bubble free fluid close the nipple and turn off the ignition and raise the pedal

I have never been able to get any of the vacuum or pressure bleeders to work with the Teves system.

 

I'm curious, Timeisrelative, I had a caliper hanging up, so I replaced both on the front. The other day, my ABS fault light came on and isn't going away. Any thoughts on why that might be happening?

 

rwolak,

I suggest that you might want to do some reading up on the Teves system. There are different schools of thought as to how the brakes should be bled. The Jaguar manual described a process whereby the ignition was turned OFF to bleed the front brakes, similar to the process described by Stuart above.

But, many Jaguar specialists believe that is not the right way to do it and use the process that was defined by Teves themselves. This involves ensuring that system pressure and accumulator is always in place and running to bleed both the rear and front brakes. It's the way that I've always done it. Here's the process:

Bleeding Teves brakes

Two people required

Start at rear left, then rear right, then front left, front right

One person in the car, ensure brake fluid level is fully topped up.

Turn on ignition and wait until both abs and low-pressure lights have extinguished and also the motor pump has cut out.

Then, open rear left bleed nipple and hold brake pedal down, with ignition on for 15 seconds – no more tighten bleed nipple, turn off ignition, release brake pedal.

Wait one minute and repeat from restoring system pressure as above for other nipple.

Then wait one minute at least before moving to front brakes – this prevents the motor pump from overheating.

At the front, ensure system pressure is created and then bleed calipers conventionally with ignition on, using slow strokes and go the full travel but do not force.

Once the left side has been done, again wait one minute and then restore system pressure before doing the right side.

Ensure brake fluid level is checked and topped up after each caliper is bled.


Good luck with whatever you decide

Paul

 

Paul,

Jaguar noted in their procedure for the fronts to start with the caliper furthest from the master cylinder, so your procedure is correct for a RHD car, reverse the order of doing the right and left sides for a LHD car.

 

Paul, I’ve been reading the various threads re: brake repairs, but have been unable to find any advice on how to replace the front brake hoses.

I am going to replace the 2 front calipers which appear to have seized pistons and thought that I would replace the hoses while I am at it.

Is there anyway to stop brake fluid from draining out uncontrollably when I disconnect the hose from the metal fitting protruding out of the wheel well?


The fitting in question

Since I need to change the brake fluid anyway, should I just let it all drain out? If so, do I just refill with new fluid and bleed the front brakes per usual?

Note that I am trying to avoid doing anything with the rear brakes at this time because getting under the car while it is on jack stands scares the bejeesus out of me.

I am also hoping (against hope) that I didn’t screw up the master cyclinder when I was fiddling around with the brake caliper cylinders without first having opened the bleed valve. (I read your posts too late!).

I have no idea if the car has ABS (the joys of buying a vehicle with no documents) and if so what version of the TEVES system it has. So I have attached photos of the black ball “thingy” below and the car is an ‘89 convertible with VIN 157803.



The black ball “thingy” on passenger side of LHD vehicle



Any advice would be greatly appreciated!!!