1989 XJ6 Brake problems

[Tophatchef]

Right, so I just got 4 new tyres, replaced the rear brake pads, turned the rear rotors, and bled the brake system. My car says that I've got low brake pressure, an anti-lock failure, and the brakes are pumping hard. What can I do to fix this? Is their a way to bleed the master cylinder? If so, will it help?

 

[jessebogan]

Whew... Boy are you going to get an education in the first series XJ40 "trouble prone" areas. You need to find a copy of the "power hydraulics" book, publication number S 73, published in 1992. I see them on E bay from time to time.You will need a good DVOM, and a lot of patience. The ABS is another issue. It is most likely a bad wheel speed sensor, but at this age, anything is possible. It is a Bosch unit, but I have never found a good diagnostic manual for it. I would hunt down a copy of the 5 volume factory manual (ebay again), and just follow the diagnostics in there. I wish you the best, I did a lot of this stuff when the cars were under warranty.

 

[Tophatchef]

Right. Can you give me the exact title of the power hydraulics book, or a link where I can find one? Why do I need "a good DVOM, and a lot of patience"? Is this anything a mechanic would be able to fix for a reasonable price?

 

[Silverghost]

Please take this with the tongue-in-cheek it is intended - the words Jaguar and reasonably priced can't be used in the same sentence! :laugh: Of course service for a Jaguar could be said to be reasonably priced compared to a Rolls Royce!

 

[jessebogan]

The book is called "power hydraulic system", publication number was S 73, and it was published by Jaguar and given/sold to the dealership mechanics so that they could fix the 88 and 89 model year cars and their insane power hydraulic systems. As built, the car had ride levelling rear shocks that were powered by this system. The "power brake booster" is part of this system, and finally there is a pressure accumulator for the ABS that has a pressure switch and a charge switch of its own. So, there are 5 solonoids, that are somewhat electrically interlinked. There is a pump, and a accumulator ball, and the hydraulic booster. Plus there is the reservoir for the green mineral oil in the rt front of the engine bay They were notorious for leaking and are no longer available new. Your avarage mechanic is likely to rake you over the coals diagnosing this system, because they won't know any more about it than you do. You are going to need to find an independant shop that has technicians that lived through the XJ40 dark ages. They will still be familiar with the system, and can likely fix it without bankrupting you. Or, you can take the time and learn how to fix it your self. If I were you, I would take that approach. The S 73 book is great, and lays out testing procedures very clearly. I don't think you can buy this book new, but a lot of these Jag tecnician training books show up on ebay from time to time. If you like, I will ask around some of my old Jag buddies and see if anyone wants to get rid of one of theirs.

 

[Mike H]

Most likely you have two problems. First is the brake accumulator sphere that probably has gone bad. This would cause the low pressure warning and the hard pedal. Not an uncommon problem. This sphere is not the same as the '90 and later models. It may also cause the ABS (anti-lock) light, I'm not sure.

Second, the ABS light may also be the relay located in the boot on the left side. Try opening it up and resoldering the joints.

Mike

 

[Steve]

Hmmmmm, accumulator spheres, green mineral oil, brakes and self-levelling suspension on the same system. Sounds like something off a Citroen!

Is it based on that of the French cars? I'm intrigued.

 

[DrEntropy]

Look to Rolls Royce then, Steve. Green mineral oil, brakes and self-levelling suspension on the same system... with TWO pumps and TWO accumulators.

Real "sport" chasin' problems with these systems. They work beautifully when they're RIGHT, though...

 

[Tophatchef]

Can anyone tell me where the brake accumulator is located on my car?

 

[jessebogan]

On the bottom side of the engine compartment under the frame rail, more or less under the right headlamp. Access ids from underneath. It will be tight!! A strap or chain type oil filter wrench will usually work.

 

[Tophatchef]

I found a way to test to see if the problem with my car really is the brake accumulator, but I don't quite understand it, can anyone explain it to me?

It's halfway through this eBay ad.
https://cgi.ebay.com/ebaymotors/_Car-Truc...p4506.m20.l1116

 

[Tophatchef]

In addition to my previous post, what are the odds of me finding a functional brake accumulator on an xj6 89-90 at a junk yard. I just need it to work for a month or two.