Hey all,

I've been having a concerning problem in my '86 XJS HE -- the front right brake will come on randomly, after something like 15 minutes of driving, sometimes without my depressing the brake pedal and sometimes after I apply the brakes. Sometimes it just smokes the pad, sometimes it's hard enough that it stalls out the car. When it happens, I have to wait about five minutes until it cools, upon which time I can drive the car again. I suspect it's either because the calipers need rebuilding/replacement or because the brake hose is getting heated up and doing weird stuff because it's old, but I'd like to try to figure out what's actually going on before I start throwing parts and time at it. Does anyone have any suggestions?

Also, I've got an issue on the rear where someone hammered the mushroomed head of the pad retaining pin into the caliper from the wrong side, and I can't get the retaining pin out. There's just the steel on the rear pads, so I would like to get this fixed ASAP -- I'm leaning towards cutting the pin, if I can get a saw or cut off wheel in there. I may also just take it to a mechanic and have them deal with it because the boots are shot and the rotors probably should be replaced, and I can't drop the rear end myself, but if there's a relatively easy solution I'd be all ears.

Oh, and the dash isn't getting power, but I should be able to track that down myself.

 

Probably brake hose perished / collapsed internally and steering inputs or suspension movement is triggering application, but if it is binding up too this could be the hose, could be the caliper. 15 minutes heats things up and the fun starts - hard enough to stall out the car on a single brake sounds serious - a V12 shouldn't be stalled out by one wheel and I doubt a hose degrading can apply the pressure it would take to resist the V12.

Honestly sounds like you're better off getting the rear subframe dropped, if you have been running any length of time with only steel against the discs for sure they're toast or I'd have suggested a good ol Dremel with a cutting disc, but which boots are you talking about - there are no CV boots on the rear ??.

When you say the dash getting power you mean just the gauge cluster ? - it probably is getting power but has a bad ground which isn't unknown on these. Redundant Ground

 

I'm pretty sure it's the front right because that's the only one that I've seen smoking, and it pulls hard to the right when it happens. I'll order a set of hoses and do all three at the same time because if one is gone, I'm sure the other two aren't far behind. I can usually keep it going if I'm able to downshift, but sometimes it'll happen sitting at a light or something and I'll have to stop, and I can't get started again. I also am trying to not abuse the clutch too much since I know exactly how much of a pain in the *** it is to replace it, having installed it, so I've been working hard to avoid slipping it too much.

I suspect nobody's done the rear brakes in quite a while because of the screwed up pin, and I'm more than happy to burn through rear brake pads at an accelerated rate until I can get the subframe down. I'll order a set of new pins and see if I can find a way to get a dremel in there, I might need the flex cable head thing that they make. The boots I'm talking about are the rubber ones around the brake pistons, they're completely nonexistant.

The gauge cluster isn't getting power, correct. The warning lights are, I've got an oil light that's intermittently on for reasons I can't fathom, I just changed the oil and I check it every time I go to drive the car, and the parking brake light is on even though that's disconnected right now. The turn signals dashboard lights and ticker also recently cut out. I'm going to pull the instrument cluster this weekend and give it a look to see what's going on, because it's only been doing this since I reinstalled the radio after the transmission swap.

 

If the boots on the caliper pistons are toast the calipers themselves aren't far behind them but perhaps getting the pads changed will at least buy you some time. You can replace caliper boots if you can get the pistons out some and may be able to get to those when the pads or what's left are out - fiddly but do-able.

Electrics are voodoo on these cars - all hail Lucas prince of darkness - corroded and loose connections can cause bedlam and it doesn't need to be those in the circuit with the problem, grounding is particularly sensitive and stuff that loses its own ground often finds another route - same issue you see when lights go dim at the rear or the indicators illuminate when you apply brakes - that's a ground issue. Good luck tracking anything behind the dash down - that ain't no fun, no sir, no fun at all ...

 

I've got a set of new brake hoses on the way from SNG Barratt, so hopefully that fixes it. I'll poke around at the electrics with my multimeter until then, cause I'd really love a working instrument cluster. The speedo will still be still dead cause I need to set up a GPS-based one, but a tach would be really, really helpful.

 

Hi Iceboatguy

When it comes to doing the Brakes its an 'All or Nothing Job' and removing the Rear IRS is really not that difficult, although it took a lot of persuading from Forum Legends 'Greg and Grant' before I dare give it a go, so don't waste your time in Cutting that Pin, as at the end of the day its easier to just drop the Rear End

Although you can expect a Bill of $2,500+ if you let a 'Shop' do it and that is without the Parts!

The Parts are not that expensive and I am on my Third one now and to date have never Spent anymore than Ł150 on Parts for each of those, although of course you need to be hands on and you are talking to someone who used to buy their Spanners from the 'Pound Shop' and so if I can do it so can you

Where in the unlikely event you get Stuck, someone on here is going to have the Answer or at least a Virtual Bottle of JD and a Shoulder to cry on, which I'm very sure you will not need, as once you get the IRS out, then you will start to see how easy it is

Good Luck on whatever you decide

Alex

 

There's not a lot to figure out. From a technology standpoint the brake system on your '86 is very ordinary.

My suggestion is to throw parts at it. Fully overhaul the brake system. Do it all, do it right, do it once. You can then forget about it for years. The ála carte method just prolongs the misery.

Cheers
DD

 

And, it must be said, driving a car in the condition IBG describes is extremely dangerous to road users.

 

Concur on the recommended fixes - I offered only temporary get out of a bind solution but did not intend that to be 'long term'

Binding discs - refurb calipers and hoses, replace disks and pads (check wheel bearings at same time), should plan to replace the hoses at 10 years anyhow, any metal to metal contact - replace disks and pads, perished rubbers - refurbish calipers and check hoses thoroughly, should be replacing fluid at most every 2 years - and that isn't topping up.

I pressure bleed all my systems, I also have the Fosseway kit but it is on the bench presently as the subframe is on the floor ... 16 bolts(think it was 16 including the propshaft), 1 hose, two exhausts, 1 cable ... biggest challenge is the height but I agree this is intimidating but not hard (if you disregard the potential for siezed bolts ;-) )

 

The main issue I have with dropping the rear end is that I don't have a shop -- I've been doing everything in a parking lot, and my landlord doesn't like me working on the car during the week.


I'm going to get it done before I drive the car again, because I don't want to have it fail and have an accident. Fortunately, I have a daily driver.

 

Well, I got the new brake lines in and bled the brakes -- it was pretty darn easy all things considered, but now the turn signals aren't working. I'm guessing it's the relay but I'm going to have to check it out before I can drive the car to check the brakes.