When my XJS V12 Was on the road, everything was fine until I changed the front brake pads. (which I've done on loads of cars before)

I have never bothered about clamping the brake hoses (of other cars) and so I didn't do this on the Jag (Big Mistake!)

I could drive around for miles without any problems but then without any warning, when I put the brakes on the car would violently pull to the right.

Not every time but sometimes.

I thought it might be the Calipers, so I changed them but the same thing seemed to happened at random times.

Could it possibly be that by not clamping the brake pipes, I have upset something in the master cylinder?

I know you can get a repair kit but I'd rather spend £100 and get the lot brand new if that is the problem?

Anyone had this happen before?

 

I doubt seriously this is your master cylinder. It sounds more like either a sticking caliper or brake pad slider. I would suggest you remove the pads and thoroughly wire brush and lube where the brake pads rest on the assembly, and clean and lube the caliper slider bolts. Then try it out to see if the problem continues.

 

I am a bit confused about which model the OP is discussing here. But, if it is a pre-facelift HE XJS, or pre facelift 6 cylinder, the front brakes are not floating calipers, but 4 piston, and do not have sliders.

Still and all, cleaning everything up is a good start, particularly check that the pads can move in and out their slots. In fact, I usually file the edges of the steel carriers a bit to ensure the pads are free enough to easily push in and out. A sudden violent pull on a non ABS car, would indicate that the other side is NOT braking.

I helped someone with an ABS pre facelift car that pulled, and when we looked at the pads, some ape had whacked them into the calipers with a hammer one side! Took 4 hours to get them out, replaced pads and filed the edges of the steel backing a bit and cleaned out the slot in the calipers and all 100%

If it is an ABS model, it could still be a pad refusing to grip the disc, but also some fault on that ABS circuit, but as you did the pads and the trouble started, take them out and check!

Greg

 

Adding to Greg above.

When you replaced the pads, you obviously pushed the pistons back inside the caliper to do the job.

I am going to assume???????, that you cracked the bleed nipple PRIOR to pushing the pistons back, NO?, then any crud, and there is always heaps, sitting behind the piston, and you got 4 on the front on each side, has now been pushed back into the system, not good.

Not sure which car you are discussing, but '89 onwards has ABS, down here anyway, and if any of that crud has found its way the short distance to the ABS hydraulic unit, you are NOT going to be happy.

 

Greg@Grant@JameyXJ6 Many Thanks Guys

She is a Pre-Facelift XJS V12 1990

It could be the ABS if she has abs? to tell the truth I'm not sure, as this is the car that has been off the road for a few years now.

Where is the ABS located? not even sure what to look for

 

If it is ABS equipped, and I am pretty sure it will be, the brake stuff will be on the UK passenger side under the bonnet and feature a black tennis ball shaped round thing sticking upwards from the brake actuating casting, just in front of the bulkhead, next to where the bonnet latches are.

If you look at the engine bay photo in this advert, the thing I mean is right at the bottom of the photo, with a yellow sticker on it, just to the right of the LHS engine bay bracing strut.

http://www.ebay.co.uk/itm/A-Beautifu...item19d834fb84

Greg

 

It's possible you aggravated the situation by not clamping the brake hoses, but it most likely would have happened anyway. The trouble is probably the Hydraulic Valve Block, mounted just below the reservoir and power cylinder. I've seen these be so bad, that stepping on the brake violently jerks the steering wheel right out of your hands. Dangerous, to say the least.

They made the valve block available separately so you didn't have to replace the entire power unit for even more $$$$.

Attached is the bulletin regarding the valve block.

Good luck!

 

Is there a wheel speed sensor on your car? (I have a 96)

When I changed out the ball joints on my car I disturbed one of these on my car. I was experiencing the same issues.

 

Xjrguy

You are my guardian angel! You've gone and hit the nail right on the head!

That is exactly what happens:

You can drive for miles without any problems (probably down to normal gentle braking)

Then one day you hit the brakes and the Car tries to tear the Wheel right out of your hand.

Very sudden, violent and totally unexpected, just the sort of thing you need to happen on a bend or bridge in the wet.

I've been very lucky, not to have spun the car into oncoming traffic.

But the fact it only happens on occasions, lulls you into a false sense of security.

I've never bothered to clamp the brake pipes on any other car and never had any problems in not doing so.

As such I never did it on the Jag, which with hindsight I can see is Absolutely Essential, so I will get myself a valve block repair kit.

A friend of mine with an XJS Coupe has got the very same problem and he couldn't figure it either.

So you've probably saved Two Lives instead of one!

What I would love to know is: What actually happens when fluid is pushed up into the valve block from the wrong direction.

It almost doesn't seem possible that this could make a difference, although it obviously does.

Thanks also to you other guys for all your suggestions but xjrguy does seem to have nailed it.

 

Does Anyone know where I can buy a Valve block repair kit JLM 11337 or how much they are?

I did come across one, which was a whopping £450! can they really be as much as that, it almost doesn't seem possible but as it is for a Jag then it probably is.

 

Yes! They are generally rather salty. Because of that, I have had a few folks show up with used ones from wrecks for me to install. I'd rather use a new one, but sometimes the cost is just too much for some.

In that block there are six valves that are open/closed/hold. They can stick and in some cases simply block fluid to a front wheel, as the system does normally when under ABS actuation. I understand pressing fluid backwards can POSSIBLY introduce matter that can cause one to hang. But no one has real proof that was the cause.

Good luck!

 

Orangeblossom, have you checked this yet?

Greg

 

Hi Greg

No I haven't tried that yet, so perhaps I better look into it before I splash the cash!

£450 seems an horrendous price and its hard to believe that fluid going the wrong way up the pipe can do so much damage.

In a way its seems inconceivable that the block cannot be cleaned out, how can such a tiny part be as expensive as that.

 

The same basic ABS system was used in a variety of vehicles and doesn't have the best reputation.

Jeep recalled many thousands....possibly hundreds of thousands, I can't remember....with assorted ABS ills. The recall procedure had a lengthy checklist/test procedure to determine what the repairs should be on a car-by-car basis. I recall that dirt and/or old fluid was considered a major part of the root cause.

I recall reading (maybe in Kirby's book?) that a sticking valve block can sometimes be brought back into operation with some agressive exercising: find a large, safe area with a low-traction surface and make numerous hard stops. The idea is to bring the ABS into operation repeatedly to free-off a sticking valve.

<shrug>

I'd be tempted to try it before spending big money on new parts. If it works, a thorough fluid flush would follow and be repeated every couple years. And...a once-a-month intentional operation of the ABS to keeps things exercised :-)

Additionally, I'd do a bit of Googling on "Teves ABS repair". I'm pretty sure there are some outfits that repair these old systems. I dunno, maybe you could send 'em your valve block and a check for $100 and it comes back like new? That sort of thing? Worth some research, perhaps?

Cheers
DD

 

Same thing is happening with my XJS, except it happens all the time- every time. I disconnected the LF line from the MC...no fluid. P.O. must have made a similar mistake.

 

Guys

I think we are being conned into shelling out £450 for a repair kit.

What can go wrong with the metal block in which you place the new 'O' rings?

IMO nothing!

Having googled the problem, there are plenty of 'O' ring kits in the States for about $20

But I've never seen any for sale in the UK unless of course you want to spend £450 for a metal block that you already have on your car.

That's my Conspiracy theory, what do you guys think?

As for me I think they've seen us coming!

 

My friend with a Coupe tried that trick and put all the tracking out, it didn't work and he almost did more damage.

I'm pretty convinced that all you need are a new set of 'O' rings after you have carefully cleaned the metal block, possibly by washing it in clean brake fluid.

I can't see you need a new valve block, I think we are being conned into buying something that you may not really need.

In fact to-day I was quoted TWO GRAND for a new master cylinder!

Absolutely crazy, you could buy a good car for that money and keep the rest for spares.

 

Which trick? The agressive exercising of the ABS as I mentioned?

If using the brakes agressively put the tracking out of kilter then obviously there was a problem in your pal's car that was just waiting to surface!





You could be right and it's certainly worth a try!






Typically all tech bulletins and revised repair procedures would go thru a vetting process. In this case, considering that brakes are involved, I strongly suspect that Jaguar's corporate legal eagles were concerned about liability issues and wanted a repair that had the highest chances of success and smallest chances of failure....thus replacing rather than cleaning the valve block

<shurg>

Just speculation on my part




It's what I call "stupid expensive". Of course a "master cylinder" on the old Teves system is essentially the entire ABS assembly.....usually called a "brake actuator" in Teves-speak....so I wouldn't expect it to be a inexpensive as a traditional master cylinder.

I'd be tempted to convert to convnetional brakes, personally. I'm usually a big advocate of ABS but these early systems weren't all that great, IMHO.

Cheers
DD

 

Hi Doug

Aggressive braking would be ok if the Car in question stopped in a straight line but with the car being thrown to the right (while trying to fix the problem) I can only see that as putting an abnormal strain on one side of the suspension.

While I can see the repair kit as erring on the side of caution and leaving nothing to chance, there should still be the option of just replacing the 'O' rings.

After all you are able to buy a Caliper repair kit for fairly sensible money aftermarket.

I am going to take my block apart just to see what's in there, give it a clean in brake fluid and then replace the 'O' rings and see if that fixes the problem.

I'm thinking of using Dot4 fluid, is that the right one to use?