1990 xj40 stiff brake pedal and vcm code " PAD fail "

Hi everyone! I am new to the forum and I hope everyone is safe and ok. My xj40 suddenly the brake pedal got stiff and I can’t barely push it down , so no brake power. The vcm says pad fail and the brake indication light on the dash board remains on solid. Please any advice will be much appreciated.
Best regards to all!

Welcome to the forum Alberto. It sounds like you have two problems.
The pad fail could be a false indication or some of your brake pads are due for replacement, they have a wear sensor on some of the pads.
Its a long time since I had my ‘40, can you hear the teeves pump working when you first turn on the ignition?

Thanks for your reply, I’d replaced all of the pads even though all of them still have about a quarter of an inch to wear out. I notice when pushing one of the calipers piston in ( the rear one left) it felt like it was stuck but it release after keep on pushing with the tool. About the pump, I can feel a light touch on the brake pedal and the pedal remain stiff, but this morning, I was trying to move the car forward just a few feet, the pedal was stiff but suddenly the pedal start shaking and went down smoothly if it was OK. That lasted 5 minutes and the pedal got stiff again.

Did you push the fluid out of the caliper or open the bleed nipple and evacuate the dirty brake fluid?
The danger with pushing fluid back into the system is that the fluid has to go through the ABS block and that can foul the solenoids.
You haven’t answered whether you hear the pump in the engine bay working when you turn on the ignition?
Just because you changed the pads does not mean the sensors haven’t worn through causing the dash warning.

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I know this one personally , the stiff pedal is your brake accumulator pump , ball or switch have failed . Try a wrecking yard or maybe ebay , not going to be cheap unfortunately . Good luck

If you replaced the pad wear sensors when you renewed the brake pads and the ‘PADS’ light is illuminated it could be down to a bad connection where the sensor plug connects to the loom. The plugs can corrode and expand a little so the pins are not a tight fit. However if you reused the old sensors I would definitely recommend changing them.
I spoke to a mechanic at a Jaguar dealership a few years back and mentioned opening the bleed nipple when changing the pads, he said they never do that, his reasoning was that the brake fluid is recirculating in the system constantly so it won’t be any dirtier at the calipers than anywhere else in the system. He said they’ve changed hundreds if not thousands without doing this and never had a problem with the abs valves. I must admit even after hearing that I ALWAYS open the bleed nipples when I’m changing pads, if only to make pushing the piston in a lot easier.

I would disagree with your Jaguar technician. Here in the USA when these cars were new we had many warranty issues with the ABS valve body due to forcing potentially contaminated fluid backwards in the system. The valve bodies were (and are) a very expensive warranty claim. Once we required dealer technicians to open the bleed screws when doing pad replacements the issues with valve bodies dropped off greatly. Since I live in an area where the ABS does not operate for extended periods I sometimes take my 1990 XJ40 to a gravel road and jam on the brakes a few times to exercise the system as it is intended to do in slippery conditions.
(former Jaguar Cars North America warranty manager)

And I would add, periodic brake fluid changes are an important maintenance procedure.

He wasn’t ‘my Jaguar technician’ I just happened to be chatting to him in a workshop I was visiting to repair the rolling road brake tester. He was changing the pads on an XJS and I asked him if the procedure regarding opening the bleed nipples was the same on that car as an XJ40 and that was the reply he gave me. I agree regular brake fluid changes are an important part of the maintenance and it is sensible to give the abs a periodic workout as you described.

Wow! I I am very but very thankful for all your responses, for taking your time and help me out with this matter. I just receive today from ebay a whole set of accumulator, pump and switch and tomorrow will be a very interesting day, so I’ll be more than happy to share how it goes. Thank you very much to all for your tips and advice.
Best regards,
Alberto Vicent

Hi every one!!! I replaced the pump,switch and accumulator and now the brakes are working smoothly, the fail error is gone,now next step is the pad error so next weekend I’ll be working on that!!! Thank you very much to all for your big help!!!