I'm having major break problems, but the pads and rotors are in good shape. The calipers are not locked up and there is fluid in the reservoir. I've come to the conclusion that it is either the power brake booster or the fact that there is no mineral oil in the power hydraulic system reservoir. It looks as though someone has tampered with the power hydraulic system in the past. I've ordered some castrol mineral oil and will top it off when it comes.

What I really would like to find is a diagram of the power hydraulic system in relation to the rear shocks and over all braking system, just to make sure everything is correct. The haynes manual I have does not show a diagram for this.

Even if someone could explain the way the metal hydraulic lines are ran to each component would be very helpful.

thanks

 

sportsterd,

Jag-lovers.org has an XJ40 e-book which covers a variety of maintenance for XJ40s. You have to register, but it's free. Hopefully, you will find the info useful.

Mike

 

Sportsterd,
Email me @ hrdknox88@aol.com and I'll email you the diagram of the power hydraulic system. I have an '88 Vanden Plas and have converted the rear suspension to conventional shocks and will soon convert the brake boost system. Many owners are converting from the original hydraulic system because of the problems associated with the mineral oil and leaks. You can find much information on the conversion in the jag-lovers forums.

 

After installing the mineral oil I did get my brakes back. Although, as I assumed, there is a leak in the hydraulic system. It took me a while to figure out what the unit that was leaking was called because my Haynes repair manual does not show or elaborate on the hydraulic system.

It seems to be the brake accumulator switch, which I also found out was a recall item:

Recall Date:
FEB 08, 1990

Model Affected:
1988 JAGUAR XJ6

Summary:
BRAKE ACCUMULATOR SWITCH WHICH CONTROLS HYDRAULIC FLUID FLOW TO AND FROM THE ENGINE DRIVEN PUMP, COULD LEAK, CAUSING LOSS OF FLUID IN THE POWER BRAKE ASSIST SYSTEM. THIS LEAK IS ALSO IN THE VICINITY OF ELECTRICAL WIRING.

Consequence:
THE LEAKING BRAKE ACCUMULATOR SWITCH COULD CAUSE ELECTRICAL POWER INTERRUPTION AND COULD CAUSE THE ASSIST FEATURE OF BRAKES NOT TO RECHARGE. ALSO, FLUID LOSS COULD LEAD TO SUDDEN LOSS OF POWER ASSISTANCE TOTHE BRAKING SYSTEM, WHICH COULD RESULT IN LOSS OF VEHICLE CONTROL AND AN ACCIDENT.

Remedy:
REPLACE BRAKE ACCUMULATOR SWITCHES WITH REVISED SEALS.

Potential Units Affected:
29000

Notes:
JAGUAR ROVER TRIUMPH INC.

How long does a recall period last? I guess too much time has passed since its been 19 years since the recall was issued. Another question, besides buying a new brake accumulator switch, which is going to run me around $277 is there a less expensive fix to repair this problem?

Another question. there seems to be two switches coming off the
brake accumulator are they both accumulator switches? only the one
is leaking.

 

The lower unit is the Brake Charging Switch, the upper one is the Low Pressure switch. They are attached to the accumulator sphere.

Make sure that you order the correct one and also, they are different part numbers for early serial numbers and later serial numbers.

SNG Barret has them listed for $228 (w/o shipping or taxes/VAT) for the Brake Charging Switch and $350+ for the Low Pressure switch for serial numbers from 575,000 and earlier.

The units for 575,000 and up are over $300 each.
There is no other fix than replacing them.

There are kits available to replace the rear shocks and springs with non hydro units and another kit that replaces the hydro boost brake unit with a standard vacuum booster, but from what I've heard, A) they are as would be expected, fairly expensive... $425 for the shock kit (although, $425 for springs and shocks isn't that bad) and nearly $500 for the brake kit and that does NOT include the actual vacuum booster, you need to source that yourself.
B) I have also heard that you can't really do one and not the other.. so... one could easily spend over $900 to correct the Power Hydro system or replace the brake charging switch when it goes. and
C) I have also heard that switching to the vacuum booster creates other issues. Not sure what, but was told that it was sort of a toss up. Replace and pay or don't replace and.. pay...

The one in my 88 just went and thats after 90K miles. I got mine from Motorcars Incorporated in Plainville CT, $270 total.

I asked around about getting a used one and all the Jag tech guys winced. Not a good idea.
Probably not what you wanted to hear, but, on the good side, they are very easy to remove and replace.

The way I look at it, if I need to replace the unit 3 times in the next 6-10 years..? did I save money or lose money? It took 90K miles for it to go, will this one last another 90K? At that point, there will probably be some more pressing issues to deal with.

Talk soon,

 

Lagged on this post

 

Good points, thanks for the help. Would you happen to know the torque specs on the accumulator switch and if there is a special socket (like with O2 sensors)? or would wrenching it a little tighter than snug do the trick?

By the way, it is the lower switch. So you're saying i should remove it and get the number off the switch before ordering the part?

 

Don't know the torque specs, I just tightened mine until.. well, tight.. LOL

The lower unit is called the Brake Charging Switch, the upper unit is the Low Pressure Switch. They are both attached to the Accumulator Sphere.
You can pull and get the number but the best way is to get the last 6 digits of your VIN, those are your vehicle serial number.

The part for my 88 XJ40, which is serial number 542,421 is JLM1562.
The part number for 40's with a serial build number higher than 575,000 is different.
Now, I don't know what the difference is between the high and low serial numbers, but its significant enough to create a nearly $100 difference in cost.

SNG Barret has them all listed: http://www.sngbarrattusa.com/

BTW, I am NOT a Jag tech. AAMOF, I'm fairly new to the world of Jags, but not to cars. I tend to dive in really deep when I get involved with a new make though and do lots of research.

There is almost as much tech support and parts availability out there as there is for Toyotas and Jeeps.

The Jag-lovers site has helped me tremendously as has this one.
Check out Christo's thread on the factory manuals... I dloaded them and have read through them, nearly page for page.. VERY helpful!

Talk soon,

 

Thanks Brill for your help.

 

Quite welcome,
Just doing my part as many others have done for me here.

Talk soon,

 

Like I said, there are aftermarket accumulator charge and low pressure switches available for less. Sounds like you didn't find them, I offered.

You can't positively identify the two switches by location, they can be swapped in the accumulator housing. Best to confirm which is which by the color code of the feed wire.

Updating the ride levelling struts to tube shocks and the appropriate springs is the only way to go. This has no relationship to the hydraulic brake booster, which rarely requires replacement. Once in a while they leak, or an internal fault yields a little free play at the top of the pedal travel. Accumulator vessel and charge switch faults are the main concerns, and I have never seen the booster conversion done. Or deemed it practical. If you're telling me that guys have done this conversion and created other side effects to deal with, my mind won't be changed anytime soon.

A 30MM open end wrench, and a big pair of channel locks to hold the accumulator body is all you need to replace a charge or low pressure switch. If you buy a Lucas/ Girling OEM style replacement switch, you need a terminal tool to replace the terminals in the green PM4 connector. Remember to pump the brake pedal 20-30 times with the engine off to exhaust the accumulator reserve pressure (in case it is still holding a charge, if it's still any good) before you open up the accumulator body for any reason.

With the ride levelling pressure control issues made moot by the installation of the tube shocks, there is almost no chance of a valve block solenoid fault affecting the brake assist.

 

Yes, I did think about that. What are the color codes? So I know which one is leaking and that I am purchacing the correct switch.


And, I'm assuming that you were talking to brill about an earlier post. Where can I find aftermarket accumulator charge and low pressure switches available for less?

The last 6 digits of the VIN fall below chassis number 594575 as stated earlier.

 

Greetings Sportsterd,

From memory, they each have a black/ pink. One is yellow/ red (low pressure) and the other is yellow/ black (charge). I'll look tomorrow to confirm, and you can tell me what color the wires are on the leaker you have.

 

Been busy, just got around to pulling the switch. It is the yellow/black, so I guess I'm looking for a charging switch. Cheapest I've seen was the one Brill pointed out at sngbarrettusa.com for $228.00 (JLM1562). although I dont know what (exc. VAT) and (inc. VAT) mean, when ordering.

If anyone knows where to get a cheaper on (new) let me know.

 

Ok, i read back a little. VAT = tax

 

I replaced the part, jagtechohio I didn't get your pm until after I ordered. Mineral oil is topped off and there are no more leaks. Now where do I bleed the system at? and how do I bleed it?