'89 XJ6 (XJ40). Brake pedal is hard most of the time, sometimes it does give power brakes, but mostly not. The rear hydraulic shocks have been retro-fitted with std springs and shocks, so I think I want to just convert the brakes to vacuum booster as well. Here's a couple of questions I have:

With the hydraulic booster removed, I plan to also remove the other hydraulic components. What should I do with the pump, can it be removed easily? I don't want it to just run dry and seize up.

Can I get a vacuum booster from an earlier model (say '85 XJ6) ? From pictures, it looks like they both mount up the same on the "pedal side" though I'll need to fabricate a way to mount the master cyl so that it is aligned straight up. Is there a better booster to consider for this? I know there's a company selling the instructions and a few bits for this conversion, and that may be the simplest way, but I really don't want to spend almost $500 ! Any insight, I'd sure appreciate.

Thanks!
-Russ

 

Doesn't the hydraulic pump also power your steering? Seems like it would be better to repair what you have.

 

The power steering is a separate system on this model. The hydraulic system runs the brake booster, and also the rear "SLS" self leveling suspension. Since the suspension has already been converted to springs/shocks, I want to convert the brake booster to a vacuum system. My accumulator is shot, and spending the $$ for that again is just not my plan. This hydraulic system on older cars can be a repeatingly costly item.

I did get a vacuum booster from an '85, and am in the process of fabricating a mounting plate. Weather turned cold today, so I'm taking the evening off, plan to finish the project this weekend.

 

Got the vacuum booster in today. What a difference! Of course my accumulator was bad, so I've had real crappy brakes for some time- this works as it should.

 

Did the master cylinder bolt up directly??
Mount plate made from steel?? Pics??

The hydraulic pump can be removed from the front of the engine and you can install a blanking plate if you want but no fluids should leak from that area as there is a seal for the drive coupler. All the hydraulic lines/hoses/valves can be discarded as well.

I always remove all the extra parts when I convert a 1990 onward from SLS to standard spring rear suspension. I have not done the vacuum booster conversion so I might try it someday.

bob

 

Pics would definitely be helpful here. It sound like something I would try if.... if..if...

 

I used 1/4" aluminum for the adapter. I got the holes "almost" correct, but my master cylinder is not quite level, but it's not off far enough to cause problems.

I did remove the pump, and was wondering the need for a cover where it came off. In the end, I did make a thin shield to go over the pump drive hub, I guess just to keep dirt/debris from possibly damaging the seal.

 

So what vacuum booster did you get? (i.e. from what model)

Larry

 

I got a used one, came off a '85 XJ6. It works fine, however I was disappointed that two of the studs were slightly bent. Caused my holes to not line up exact. Also, the vacuum line fitting was broken. That was no problem, as I used a universal fitting that included a one-way check valve. The original Jag fitting, was just a fitting- no check valve. For a vacuum source, I ended up drilling a hole right into the intake. There were a couple of vacuum ports already there that were not used, but they were too small, and I wanted 3/8" vacuum supply line.

 

Drilling sounds like a smart move - I've heard of folks doing this conversion who had issues getting enough vacuum using existing ports.

Thanks for the info but a few pics wouldn't hurt either, mate!

cheers

Larry

 

Neb, I am in process of doing this conversion. I picked a 2000 brake servo. I can tell you this one is difficult to adapt. I am curious what you did with the radiator overflow tank? Now that the booster is in the tapered coolant tank of my 88 will not fit. Did you use the manifold port that is recessed and sealed by casting? It is closest to the servo and sits between the 5 & 6th cylinders. Is this the one you used? I picked the 2000 XJ6 (X100) servo because it was an 8" servo of the right length and looked like it would fit. The bolt pattern is not the same as the original but is close enough that I had to rotate the servo 90deg to mount it on an adapter plate. This resulted in further adapting. Did you short the minimum hydraulic pressure switch (jumper in connector) and the hydraulic fluid level switch? The master cylinder also has a close but no citar bolt pattern to the new servo. Another adapter plate was needed. I used 1/2" aluminum for the servo to pedal adapter, all I could get at a scrap dealer, and 1/8" steel for the master cylinder to servo adapter. Dont know if that is a problem yet since I don't have vacuum yet. The pedal sits a little lower in the car- not a problem for position but I did have to put a spacer on the brake light and cruise control shut off tab of the pedal. The hydraulics are all removed, which I will not miss. So the questions I have are where you drilled the vacuum hole, which switch connectors need to be shorted and did you have to move the coolant overflow tank? Thanks, glad to hear your is working. Ron.

 

Ron,
I'll post pictures as soon as I get a chance to in the daylight. I drilled a new hole in an intake runner, because I wanted a larger port than what was already there. It's nothing fancy at all, but it works.

I did have a little trouble getting the coolant tank to fit, in fact I had to grind a little bit off the top of a rib that's on the inner fender- not enough for a strength problem, but just enough to fit.

The master cylinder fit the '85 vacuum booster without an adapter, although the studs were too large to fit the cylinder so I had to drill them out a little.

As to the wiring, I have not yet done that part, so yes I get a "low brake pressure" warning. I had to adjust the brake light switch slightly to keep the brake lights from staying on all the time. That was real easy.

I will post pix soon, but you'll have to forgive a dirty engine compartment

 

Just FYI, I did this with the kit. When you see the "kit" you will shocked that you payed so much for what all fits in a envelope. I used a booster for a 87 XJ6. The coolant tank must move forward. And the manifold must be drill and tapped for the vacumm. It is a lot of fiddling around but none of it is really hard to do.

 

Just thought I would relate my adventures thus far. This post outlines the procedure I used to convert to a X100 vacuum brake servo.

I looked around quite a bit and could not find a series III brake servo for anything less than 400USD. That's about 550 CDN for me by the time I bring it in, without mounting kits. From pictures it seemed that an X100 servo would be about the right bolt pattern. How wrong I was. By the way this is an Ate servo from Germany. The part number is 03-7747-2501-4. You may be able to find a listing for an Ate servo that fits a Series III if you have more success and resources than I. On the X100 servo the mount pattern is about 1/2" wider and the master cyl bolt pattern about 1/4" wider. I have installed the servo and find now that it leaks. That is yet to be resolved with the ebay seller. The pictures are attached. This is not a conversion for the faint of heart. I was surprised by dbeck54's post re the conversion kit. The suppliers of these kits say that they will include the year and model of a readily available booster once you pay the (exorbitant) price. I don't know about you but I wouldn't say the 87 brake servo is readily available.

The process for using an X100 servo is as follows:
Remove the hydraulic pump and plastic drive plate, cover the recess with sheet metal cut for the hole. Use the same size metric bolts but about 13mm long. Remove the accumulator and hydraulic reservoir. Insert shorts in the plug for the reservoir level switch and low pressure warning from the accumulator. You can either cut the wires and use the connector or remove the plug and use 0.125"molex pins with a wire. The pins are available at Mouser.com. Remove the two hydraulic lines going to the hydraulic servo. Remove the servo, no need to disconnect the brake lines from the master cylinder. There is plenty of steel line to allow it to move to the side. I found it easier to remove the brake pedal tower and pedal to perform the mods. If you do this there are 5 nuts (13mm head) and 2 wires that must be disconnected. You will have to remove the dash panel and heater duct on the drivers side. My car is LHD so if yours is RHD some of the requirements of disassembly will be different.

After removal of the hydraulics and brake pedal tower the next steps will be modification of the tower and moving the radiator overflow tank. There also needs to be a hole drilled in the intake manifold. The tank repositioning is not required on a RHD car. You have other problems to deal with.

Tower mod: I used a 10mm aluminum plate, all I could get locally, and cut a 6" (approx 15cm) round disk. You will have to drill 4 holes for the tower mounting and 4 holes for the servo mounting as well as a large hole for the servo to insert into the tower. The tower mount holes are best countersunk. Use M8 bolts with a flat head (tapered/flush mount) that are 5/8-3/4" long. 1" may be too long you will have to check. The servo should be rotated 90deg to allow 2 of the bolts to miss the tower. Holes will be drilled in the tower for the other two. These will align on the vertical casting line. I filed the tower smooth on the top of the existing mounting portion of the tower. To remove the hydraulic servo you will need to remove the clip that holds the pin to link the actuator rod and the brake pedal. This is accessible through the two 1 1/4" hole plugs on the tower visible in the engine compartment. The input rod of the servo will need to be extended by the thickness of the plate you use minus approx 3mm. The X100 rod is approx 3mm longer than the hydraulic rod you are removing. Hydraulic input rod 92mm, X100 rod 95mm. It's up to you to check my measurements, I may have that backwards. Make sure the cruise control shut off and brake light switch actuate properly. You should hear the two clicks as you move the pedal. I cut the hydraulic u-bracket off the servo and cut the X100 u-bracket at the appropriate length to increase the rod length by 13mm (10mm plate thickness plus 3mm rod length difference) Again check the measurements. The servo should be rotated until the vacuum port is now as close to the intake manifold as possible.

The master cylinder also requires an adapter plate since the bolt pattern is slightly wider on the X100 servo. Turning the X100 servo 90deg allows the adapter plate to accept the master cylinder and the new servo bolt patterns with enough space to tighten the bolts. I used a 1/8" steel plate countersunk to accept the master cylinder bolts. I used 5/16" NF flat head bolts. M8 also works. I have yet to extend the servo output rod into the master cylinder by 1/8". There is a bit of play in the brake pedal before the master cylinder begins to move. I am thinking of drilling and tapping the rod-the hydraulic servo used this method or using a 5/16 or so stand off threaded onto the output rod.

Drilling the manifold: The last thing you want is metal filings in the manifold. After trying a few things that didn't work I finally removed the #5 cylinder input port. Pls see the pics. It is U shaped, black and held on by 8mm head size bolts. There are 4. The port is sealed with black silicone so it is very easy to reseal after removal. I would suggest to limit aluminum filings that you use liberal amounts of grease on the drill bits and metal tap when you thread the hole. There is a small area of the plenum that appears to have a port shoulder that was not drilled. I suspect this is for the 87 XJ40 vacuum servo. I used this port. I drilled a 1/4" hole followed by a 3/8" hole. The shoulder will have to be drilled to fit whatever brass fitting you are threading into place. I used a 1/4" barbed fitting with a 1/2" NF thread. Your results will vary. I found it helpful to remove the throttle and kickdown cable pivot on the plenum for access.

Using grease on the drills with light pressure and drilling small amounts allows you to ensure that a minimum of aluminum cuttings enter the plenum. With the port removed it is possible to remove all cuttings. I used several greased Q-tips to pick up all small pieces.

Moving the rad overflow tank: For LHD models only. This was probably my least successful effort in this process. I hope you have better success than I. Neb Russ states that he cut the bracket that holds the front shock enough for the tank but not enough to weaken it. This may be the better way to go. I tried removing and heating the tank to allow me to reshape it. This resulted in some cracks that I needed to seal. I moved the original mounting plate below the rad cap (pressure cap on the overflow tank) and mounted it farther back so the tank could clear the servo. I also moved the rear mounting tab on the tank closer to the firewall but it kept breaking off. I cut a strap to fit and bolted it down with this. The tank is a tight fit in the new position even with the increased clearance due to reshaping the tank. I did have to cut the shock bracket as well. Only about 3/8" cut and bent the top to provide a shoulder against the tank rather than a sharp edge. Definitely not weaker than before. I also used a piece of 3/32" neoprene sheet to provide some protection for the plastic tank against the metal of the shock mount. Doing it again I would probably just cut the shock mount as much as needed and reweld where possible.

Hope you find this helpful. Mine is not yet fully functional but the servo is failing all tests. Hopefully a replacement solves the hard pedal issue.

Pedal and tower with adapter plate. Pardon the butchered hole. In real life the tower was not obliterated by the tile.




X100 Servo




X100 mounted in tower. 4 nuts attach it to the tower. One is inside at the bottom. Two are on the sides and one sits between the plate and the tower above the original mounting plate.




open port to allow cleaning, loosened dipsticks and brass fitting for servo vacuum on plenum. I removed the throttle plate and kickdown cable for easier access.




Finished product except for the expansion tank. Tank not yet mounted.

 

dbeck: I was really considering the "kit", and in fact talked to the guy selling them. Nice guy and all, I just couldn't get past the price, especially when considering what these cars are worth these days. Figured I could fabricate something aftermarket, and did!

British Ride: You went to more trouble than I did, and ended up with a neater job. It looks really good!. I ended up finding a used vacuum booster from a wrecked '85 XJ-6 for $50 plus $10 shipping. Rk Auto has a "rebuilt" for less than $200, but I wouldn't have had a core, so there would be an add'l $40.

All in, I probably spent 4 hrs making this adapter, and doing this conversion. It really wasn't hard at all. I'd sure recommend it.

 

Some recently discovered detail and corrections to add.
First the corrections:
The plenum port is actually for cyl #6. It is located between 5&6 cylinders but runs up to the intake of #6. I forgot to add that the tower will need to be filed at the flange for the servo. This is located at the point the servo boot enters the tower. See picture above for visual. You have to also add notches for the new servo bolts and holes in the tower. Again see the picture above.

The leak in the servo I have is not the servo. The X100 uses a gasket between the master cylinder and servo. Aptly named the master cylinder brake servo seal. The master cylinder/servo adapter I made has a small gap at one point of the master cylinder. At the bottom in the most invisible place. I didn't even try to put it there. I have sealed it with gasket silicone for now. I will have to make a new mounting adapter out of 1/8" steel. I will also have to apologize to the ebay seller. I used some more 3/32" neoprene sheet to make a gasket for the servo side of the adapter. This allows me to remove the master cylinder without breaking the silicone seal.

I extended the servo shaft to the master cylinder with a 1/8" brass fitting. I drilled it to fit just over the larger portion of the shaft and enough to allow a tight fit for the stepped portion of the rod. I rounded off the hex (7/16" head) and to round the end to fit the master cyl. using my little drill press and a file.

So the job can be done.. with care.

 

Hello Group. My name is Wendell and I need help. I own a 1989 jaguar Vanden Plas. The brake accumulator is no longer working. Can anyone in the forum advise me where I can find a replacement and if I can not find a replacement, how can I solve the problem of hard brakes?!

 

Wendell, welcome to the forum. I have found it very helpful in keeping the costs down and the driving experience good. See all the above posts if you are interested in converting to a vacuum system. The hydraulic system was only used from 88-90 on the XJ40. I tried to keep my system going and thought I had it until the hydraulic pump failed. To this point I spent about $200 repairing the hydraulic system. I replaced one pressure regulator switch and spent `too many hours. For less than $80 I have converted it to a vacuum brake servo. I just tried it in the garage, no driving, it appears to be fixed. The pumps and the accumulator are too expensive in my opinion. There are several Jag X100 servos on ebay for $40 USD. Some have found series III brake servos for a reasonable price. There is a certain appeal to keeping it original. If a switch goes and then a pump goes I had no confidence it would keep going after this repair. Best of wishes whatever you decide. By the way I have seen XJ40 hydraulic parts on ebay, Jagbits and other suppliers. Some are much more expensive than others.

 

I drove the car today. The vacuum booster works great. Light pedal pressure with some feel. Very easy to control. If you are willing to put in the work I would recommend the X100 servo.