I probably wouldn't be writing this if my ABS Brake Pump hadn't gone wrong or if a New ABS Brake Pump was available at a sensible price

But unfortunately it has and while I could probably have my ABS Brake Pump sent off for repair, given the choice I would rather fit a Brake Booster

Which were fitted OEM on XJS's from inception up to around 1987 where my decision will be based on whether I can find one and whether my Insurance Company are OK with that

Because it gives me no pleasure to say that my 20 year old Mercedes with the Brake Booster System, gives me a far more positive feel when Braking, than any of my other XJS's all apart from one and that is 'Misty' my 1987 Arctic Blue XJS

Which also has a Brake Booster and when you hit the Pedal you just know this Car will Stop, as you can feel exactly what is happening

The same with 'Fern' my Metallic Green XJS which gave a really good 'driver feel' when Braking

Its a much more Simple System, with not much to go wrong and if it does is easier to sort out, where New Vacuum units are available

Which seems to beg the question, what Braking System do you prefer and why?

Brake Booster or ABS?

 

For me: ABS

Reason: safety

Yes, ABS extends your emergency braking distance compared to a pro-driver in a non-ABS car BUT 99% of all drivers - like myself - are just drivers. And keeping a car steerable under emergency conditions (example: emergency braking in a curve) counterbalances the slightly longer braking distance. Modern ABS systems are a lot better.

For me, I wanted an ABS car. ~300 hp, 1.7t mass and a nose heavy car required the needs of something like that. Sure, the used TEVES system could be a little more reliable, but even as is, I prefer it.

My XJ8 had the typical cracked solder spots on the high pressure pump. Braking with that not working would quickly lead to some flat spots on the wheels/tires.

 

I have to agree.

And even 'pro' drivers struggle. Turn on your TV and watch any form of car racing. It's not unusual to see a driver become a mere passenger. All four wheels locked up, no steering..... and the car skidding right into a barricade!

In the real world many drivers, given time to think, can properly modulate their brakes in a hard stop. But, hard stops and panic-stops are two different things. In a true *panic-stop* situation, with no time to think, they'll typically mash that brake pedal as hard as they can, lock the brakes....and lose steering control.

Sometimes you'll hear someone claim that, because of their skill and experience, they can out-think and out-modulate an ABS system. I don't buy it for a minute.

Cheers
DD

 

I haven't come across the term 'brake booster' before; isn't that just a servo?
Surely boosting the brakes and the activation of an ABS system are completely different things?

 

Yes, the 'booster' as OB calls it is a servo. Vacume assistance of the master brake cylinder.

The ABS system fitted to the XJ-S from ~88 onwards doesn't have aservo. It uses pressure produced by the high pressure pump to assist with braking effort. So the ABS as defined by the TEVES ABS is technically always activated. You can't compare it to modern ABS systems with a servo and pump. There is no vacume connection in the TEVES setup. It is all high pressurr brake fluid.

 

Slight correction... from 88 to early 95.

In late 1995 and 1996 Jag used the same ABS as the XJ6 which had a traditional Booster and separate ATE add-on ABS system with the ABS controller directly mounted to the pump.

Ingenious system...very precise, modern, simple and fast acting. Co-incidentally mine failed this week on my Red coupe. I simply unbolted the controller (2 screws) and installed a new one. I never had to open a fluid line. It works again.

 

I like my non-ABS system personally. Simplicity is it's own reward. Reliability too.

I've had to brake HARD and Frequently driving in this town. This car sits low. Todays drivers apparently expect an SUV or nothing. I am almost invisible at the bottom of their mirrors if they were to ever look in those.

I have never lost control nor even felt concerned as to my ability to control the car with all four locked down. And there is one feature this system offers that the ABS does not.

Both hands on the wheel, and braking hard I can still signal the other driver that I am unhappy with their choices. Most younger drivers have never even heard a car lock it's brakes up. I can see this is so from their reaction when it happens. A few may have had to return home for new trousers.

BWAAAAAAAAAAAAAAAARRRRRRRRR! Yes, yes, you screwed up.

 

Hi JigJag

I'm with you on that one, my hard top Coupe 'Misty' has the Vacuum Servo and at the time of writing it has never gone wrong and has a proven track record since Jaguar first fitted it in the XJS

While the ABS is not some sort of a 'magic pill' that prevents a driver from having an Accident, where in my own experience when the ABS has gone wrong

It very nearly spun me off the road, as after about 20 years of continuous heat, the wires inside the Valve Block can go Crispy and so fragile, that one jolt when driving, could be enough to have one of them break

Where with the Vacuum Servo you don't have that kind of problem cropping up, which makes me feel a lot Safer and the pedal seems much more responsive to the lightest touch

So providing my Insurance Company are quite happy to go along with that mod, then a Brake Servo is what I would like to install

 

Hi icsamerica

Thanks for posting that, as it looks quite ingenious as you say

 

Hi Steve

Yes it is a Brake Servo, though I have heard it called a Brake Booster which is the word I used

 

Cheers for the correction. Yeah, that was also fitted to the X300 and even my X308 has the same ABS hydraulic unit.

I wrote from 88 on, as before, even though a car had a higher VIN than Jaguar states on the Jaguar Classic Parts site, which would determin his car to have a servo-ABS, he had the 'normal' TEVES.

 

Doug, 100 % with you here. A friend claim he can outbrake amhis ABS system. Just lumping onto the brake pedal and lockig the wheels up won't make you stop quicker.

People who claim they can get a vehicle to standstill in an emergency quicker than a person in an ABS car can has either:

1. A very fine feeling in their foot with lots of race driving experience
2. Is a professional driver with lots of driving experience
3. Someone talking a load of poop

I like driving. I like accelerated driving. I like cornering hard and fast. And I have no problem whacking the brakes on. BUT I know I would lock up non ABS brakes. I wouldn't consider pumping them.

 

You can't possibly pump as fast as an ABS system, it's physically impossible.
The best that you can manage is cadence braking.
My ABS has only kicked in once when I ran in to a herd of deer.
Stomped on the brake pedal and felt it vibrate like mad whilst I swerved around the first deer.
Unfortunately didn't have time to react to the second one and twatted it.

 

That's my point. You can't react as fast as the ABS system, simply due to the delays in processing what is going on around.

 

Sorry Guys, while I do agree that for the "average" unskilled driver. Abs is quite excellent. As it takes the guess work/feel, out of the equation. To someone that has logged Millions of miles, in Semi Trucks, hot rodded, and raced anything with wheels. I have found several times during a near panic stop. When you first slam the pedal down, and the abs starts to kick in, and your trying to modulate the pressure as you normally would. It's like you confuse the system, and it sort of lets loose, all of the sudden it feels as if the brakes let go completely, and you push the pedal down in reaction, and then it activates the abs, and it pulses as it should. The sad part is it's very hard for someone that does know how to modulate the brakes, to realize you need to simply apply the damn brakes, and let the ABS do it for you. I don't like having things done for me! It's damn unnerving when it happens! I guess if I didn't know how to "Drive" it wouldn't bother me. But I do, and it does! So I'd go for the standard style with the booster. Just my thoughts.

Jack

 

ABS Master Cyl, anyone price one or try getting a rebuild kit yet ? Safety ! This Forum is loaded with threads about speeds far exceeding 100mph. Safety shouldn't even be a thought traveling a 100 and beyond.

 

Why shouldn't safety be a thought when travelling at higher speeds than 100 mph? Brakes are the thing you need at higher speeds. So ABS is a must have. Here on the Autobahn, ABS is a daily requirement.

 

Exactly. Let the ABS do its job !

I know how to modulate brakes but the ABS does it better. And in a ** true panic stop ** it can think and react faster than I can.



Takes a bit of getting used to and a bit of time to develop the confidence that it'll do the job.

Cheers
DD

 

There is no Autobahn in the US. We have roads in the states with long remote roads that 100+ MPH is possible and done regularly. I personally don't know of any legal speed limit over 75 or 80 in the US. Regardless, I'm not getting into an email/Forum debate about the speed legality or safety of a street driven equipped XJS with ABS brake's at 100 +MPH or 45 MPH for that matter.
My other point is my XJS is 27 years old, at some point those ABS parts, especially the master cyl, pump, etc. will need replaced or rebuilt. Nobody I know makes or sells those replacement parts except a dealer or even rebuilt parts. So if you need to rebuild your ABS today what's the price comparison to a vacuum boost system change over. Last check the dealer's price for a ABS master cyl was $3000 USD.

 

You can get rebuilt units and rebuild kits. You just need to search deep enough and get the part references right. The only XJ-S specific part of the ABS system is the ECU. The rest is off the shelf ATE. As most ABS units are...

Here nearly all late 80ies/early 90ies ABS cars had the same or a slight alteration of the ABS system. TEVES is like Bosch... Used under different numbers in different cars but technically the same.

I'm trying to get hold of a catalog from ATE from 1989 with all parts to crossreference them.