(Brake) Pedal to the metal

XJ-S
#1

Just took my recently acquired 94 XJS out for an oil change today (first time I have driven it since bringing home from sale) and the brakes failed close to the house! When I press the brake pedal, nothing there, but the ABS light comes on while pedal is pressed. Heat from front right rotor also, so am guessing piston is seized and may have blown seal, but i don’t see any leaking brake fluid. Sunday’s job will be to flush brake fluid and see if i have tree travel of caliper pistons, but i am wondering if there is anywhere else i should look while i have the front wheels off?

On the actual failure, when i pumped the brake pedal several times, the brakes did come back, but the next time a pressed the pedal (1/2 mile down the road) i again had no brakes and the pedal went all the way down with no resistance. When i went out to the car this morning and pressed the pedal without anything turned on (key out of ignition), i have regained pressure on the pedal.

#2

Sounds like a brake servo problem to me, having to pump it a few time would indicate loss of pressure or air bubbles in the fluid, hopefully its just air bubbles and you can bleed these but this happened to me and I had to change the servo which isn’t an expensive part. I’m sure others will be more detailed…

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#3

If you have a seized brake piston that is generating excessive heat then you will be boiling the brake fluid. Which may well cause the brake fade you experienced, without actually leaking fluid. Once cool, the brakes will become effective again. For sure you need to get that caliper attended to as a priority.

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#4

I seem to remember posting this answer yesterday on a different post and here we have another post with the same question?

#5

Robin, you did and thanks, but someone else requested that i split the two issues (wheel stud and brake issue) into separate posts, which is what i did. Sorry for any confusion.

#6

Yes I saw that after I posted here, understand now.

#7

My hope is that he does not have the problem I have on my 92 XJS with no brakes and no leaks. I think by 94 they may have fixed the problem with the Teves? system. My nightmare has no simple solution other than going for a retro-fit of a vacuum booster. Yes, the ball on the electric thing is fine…checked first and bought another one.

#8

I hope not also…but at least I now know someone named Ronald with a solution if this does indeed turn out to be the problem! Thanks for responding and hope I don’t need to get back in touch…if you know what I mean.

#9

I know exactly what you mean, and I had a Thunderbird that mimmicked the BMW 6 series, 89 I think, and it had that system. All that was wrong was the motor on the electric pump on that system that drove the hydraulics. I drilled a hole in the housing and oiled the bearings. Bingo! Breaks again. Just got lucky; that’s all.

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#10

Welcome to the joys of Teves III ABS!

#11

This is why I’m SO glad my 1988 has this old-fashioned Brake System.
Glad Paul got home safely!!!

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#12

Same problem on my 90. You can look at the archives. first problem 10 or 14 years ago. The short cut was to remove the fuse from the Main box under the steering wheel. Also, unplugged the blue switch on the back of the master cylinder. This will tell you if the problem is with the III. I drove mine for years with the fuse out…it worked great. Then one day the peddle went to the floor again. I removed the ball, and the complete brake and cylinder along with the brake fluid reservoir. Also the tube against the firewall and every other brake tube I could find. Washed the whole thing out with spray brake fluid. Lots of water was in the system. Also, disconnect at the calipers and flush also. I disassembled the master cylindar and cleaned the pistons. It was very difficult to remove the Blue master cylindar switch. Had to take it into the shop and put it on a big vice and use a 3 foot (1 meter ) in order to get it loose. All done with brake cleaner spray. I was particularly concerned about any rubber hoses or connectors but have not seen a problem. I think this spray is only for cleaning the outsides but since no one could tell me what to use to flush the system and NAPA, Autozone, Advance and others had no idea of what to use and nothing to lose I just flushed with the spray. Then ran brake fluid through the system a couple of times. Put it back together and it has worked perfectly ( knock on wood ) since. Time required for this, 1 complete day in the summer.
WARNING: Brake fluid will strip any paint instantly. If you can wash it off fast enough,it will just streak your paint and look really bad.

#13

De-natured alcohol (methylated spirits) is what you can use to flush brake systems safely.

#14

Thanks you, appreciate the history and potential fixes. Am looking forward to getting stuck into it this weekend.

#15

Or you can fix it right: remove the Teves III system lock, stock, and barrel, and fit the vacuum boosted power brake system from a pre-ABS XJ-S.

#16

De-natured Alcohol….great news, Robin. Thanks. And it wipes out covid 19.

We use Everclear 98 here at the office for hand sanitizer.

#17

Another difficult day. This is a left hand drive car, so I started by bleeding the front right (the one heating up) and was able to bleed it quite easily, following the Jag-workshop manual. It did smell of heat, but interestingly, the hub turned by hand. Fluid was a nasty dark brown, so definitely needed flushing. Then went to install new shock absorbers whilst wheel was off, only to find the bottom bushing was 2mm longer than the stock shock, so wouldn’t fit. Regardless, I moved to the front left and for some reason, it was harder to bleed this one (positioned right under the master cylinder) than the right, taking much more force on the pedal to pump. I would assume that this would mean the right side is braking more than the left, which is maybe why the right side is heating up and the left isn’t? Anyway, went through a lot of fluid, and the left side did get easier, so on with the rears tomorrow and then when I get the correct struts, will venture out round the block to see if the flush fixed the problem.

#18

Paul, You must drain and flush every line in the system…not just one or two but every tube, hose, pipe and master cylinder. Robin said to use de-natured alcohol. I used brake cleaner spray. Have you pulled the brake fluid reservoir? Everything has to come off at the same time. I would not worry a bout the shocks until you get the brakes worked out… .Harry

#19

Harry, interesting thing is that the Jag shop manual specifically states “do not use methylated spirits to clean brake system”. What I have done is basically follow the manual on how to flush the system with fresh fluid, without completely disassembling the system. Wouldn’t this be the first thing to try before a more evasive complete brake system tear down?

#20

Harry, when you had your issue with the ABS, was it a dramatic, permanent failure, or did it happen intermittently? I just finished flushing front and back brakes (was quite nasty) and went out for a (very local and slow) test drive. Brakes are working really well, no issues, pedal is very responsive, front right was not binding (no head in rotor after 15 minute drive) and no ABS light on dash. Does this mirror what you saw, or I wonder if our issue is different?