Replacing pistons in front calliper

[piman]

Hello Brian,

I'm guessing here a bit but I seem to remember from somewhere that the stock screwed rod is in the order of 4 or so whereas mid range high tensile bolts are 8.8. Also I have found that standard screwed rod seems to have little ductility and snaps quite easily if you try and bend it, I know that being threaded does give a stress riser, but even so. It is very soft and being used under tension the threads pull quite easily.

I am happy with the rod I used although it has only dismantled one pair of springs but shows no sign of any distress. Car manufacturers use standard 8.8 for all safety critical applications and they are ductile and tough.

Alec

[Martec]

Thanks Alec, I'll think this one through again.

I finished assembling the MkII this morning and this afternoon filled up with gas and then went for a blast. It all worked perfectly except I could hear one of the indicators wasn't. Back home and a bulb change and all was fine until I checked the brake lights, requires a heavy shuve again. So when it all cools down and stops burning me I'll fit the new pressure switch I got last time. If I'm quick enough I may not have to bleed the brakes.

Brian

Edit, New switch fitted and soldered on spade fittings, all working fine.

[RichT]

Hi guys

On the subject of the ball joints there are the original types on top with grease points and sealed for life on bottom, both sides are fairy stiff but near side def has a rough spot near full lock I suspect that previous lack of use and grease has taken its toll, so I am going to replace the whole lot as I am sick at looking at the front suspension and don't want to be back here anytime soon

This is now becoming an expensive exercise

Still can't take it with you

Cheers

Richard

[Martec]

Its a 50 year old car Richard, so you can expect to do repairs, most modern cars of 20 years are now scrap! Besides they are lovely to drive.

I fitted the greaseless ball joints 14/15 years ago and have not had a problem since, every time I've had to change springs these ball joints have still been good and tight, so you will be down to 8 grease nipples now.

Best wishes

Brian

PS count the shims and photograph the top ball joint.

[RichT]

Hi guys

Brian Of course you are right its old and I should know better, I don't own any new cars youngest being 1994, my wife has a new merc and I think it will be dead in ten years as it is made of tin foil and cling film, personally I am always delighted when I find anything working on old cars and I am amazed at how good the condition is of the other suspension components is on this car the other stuff has just worn out. main problem is the risk that a few hundred quid multiplies by 2 when potential hand bag and shoe compensation kicks in with the better half (only joking here) actually main problem is that I am tight as the proverbial ducks rear end!

I have replaced all the ball joints and the steering is now very smooth, the old ones looked fine on car and had no play but were all shot when removed, the only prob I encountered was the lemforder ball joints from sng barrett were a tight fit with the original shims I measured the old and new upper ball joints and the new ones were very slightly thicker meaning( couple of thou at most) the last shim had to be lightly tapped home, they were uniformly tight at both inboard and outboard ends of the offending shim so I don't think the arms were distorted I was assured that they were a straight swop by sng barret so I hope I am not stressing anything here other than myself. (I noted the shim postions and number to preserve geometry before removing and cleaned all the shims from surface corrosion) apparently lemforder are oe for jaguar and BMW and they look like a quality part. new bearings and stub axles in tomorrow.

Just waiting for shiny new coopercraft brakes which is the bulk of the cost with equally shiny good ridge hoses front and back, when they are on happy days again as long as rear callipers are not shot if they are if anyone has some decent xj callipers I would be willing to give those a go

I am convinced that most of the problems with this car is because the previous owners just did not drive it certainly this and the lack of brake fluid changes have not helped, even though I change all fluids when I first got the car. The more I drive it the better it gets and the more I love it

I think I will make brake fluid changes an annual event

When I rebuilt my mg I replaced the whole braking system and used silicone fluid and have never looked back but I wouldn't like to try this without replacing every single rubber seal in the system.

Cheers

Richard

[oldtimer]

Richard,
You may be tight but I bet not as tight as Martech

[oldtimer]

Hi Rich/Brian,
Just had read through this thread, makes good reading. Can't argue with what Brian has to say.
BUT I've just had a look in my old S type Jag manual for a reminder. As I thought, when you jack up on the cross member and lift the front wheels off the ground, the suspension drops and the top wishbone has rubber down stops which make contact with a contact point on the cross member tower, so the road spring is still under tension. So please ensure you have a good quality spring compressor to hand. Would hate you to seriously injure yourself. There I feel better for that.

Oldtimer

PS What seems about a hundred years ago, I obtained a pair of XJS 4 POT calipers and fitted them to my '72 XJ 12, displacing the 3 POT calipers which are boxed up on the shelf. In view of what you have said I think I shall hold on to them. By the way it was a pig of a job. Another story for another day. Fortunately in those days I got my parts at cost plus 5% - not bad ay

[RichT]

Hi old timer

I agree if you jacked on the crossmember and released the ball joints the spring would spring out rearranging your face

I think i didn't explain how I jacked this up very well. I jacked this up on the front crossmember then dropped the crossmember onto two large blocks of wood either end so the bottom of the upright is only a few inches off the floor, then I jacked up the side I was working on with a low entry jack with a wide jacking plate just enough so the weight of the car holds the spring in compression making sure that it can't shift this is only a couple of cm to compress the spring. It is so low that you have to watch the opposite side does not touch the floor.That way the whole thing is close to the floor and unlikely to shift, if it did drop the car would fall a couple of centimetres onto the timber and there is also not enough room to allow the spring to unwind, you have to make sure you jack from the front of the pan otherwise you can't drop the upright and once you have undone the nuts you cannot play with the jack otherwise It would be very dangerous. Also you need a large low entry jack that can't topple and not forget that until you have connected both top and bottom joints you have a lethal spring under compression. Obviously this way you do one side at a time. Additionallyl I also tie the spring to the suspension tower with climbing rope, this would not stop it unwinding but should limit travel

I agree using a spring compresser is the only totally safe way to do this but involves more dis assembly and having to jack the front end up quite high which carriers it's own risks.

This method is in the original blue service manual however that doesn't mean that it is up to current best practice and I wouldn't recommend it to someone that isn't experienced with jacking vehicles.

Cheers

Richard

[Martec]

Oldtimer, hi old friend nice to see you back on here.

The outrage, me tight!!! just because I like good secondhand prices.........., in practice new stuff for these old cars is often expensive and not up to the quality for longevity. Also some of the people I've met doing the reconditioning work are of questionable ability, so I prefer to work and repair to my own standards, not cost (that should get the emails flying!!).

Richard you sound to be getting on well and I believe going down the right road, I would suggest you take a couple of points into consideration.

Brake fluid DOT4 effectively for safety has a life of 2 years, as nodoubt you know it is hydroscopic (absorbs moisture, which is then able to corrode throughout the system, in practise it is usually at the calipers). I initially used silicone fluid but found the brakes holding on for 5 seconds before releasing (interesting getting out of busy junctions). It appears the silicone is fine with girling rubbers, but not Lockheed (servo) which swell and jam.

Also although the front crossmember LOOK substantial, it is 50 years old and can bend if jacked up in the centre, hence creating more positive camber and understeer.

I have made a wooden beam 6" by 4" that can sit between the two angled wishbones and is scolluped out to accept the big trolley jack plate and axlestands. I lift the car with a small trolley jack under the front chassis rail enough to get this wooden beam and big jack into position. I feel this is safer for me and doesn't damage the car.

These cars are so low and so tightly packaged it almost becomes an artform to work on them

Brian

[RichT]

Hi all

Thanks for all your posts and help

Just to finish the post it is all back together and working (for now )

It's been an interesting process, changing stub axles bearings and ball joints and then the front callipers for the cooper craft product and refurbing the back pistons. I managed all of this using various sockets as drifts to remove and reinsert the bearings and even learnt to lockwire (the person who inspected this car for me and even my mot inspector should never have passed these as they were done with stripped out electrical cable on the calliper bolts)

I have to say all my brake problems are from previous owners ( plural) having neglected fluid changes judging from the rust coloured snot accumulated in the old pistons -also the pads were clearly the wrong size when compared to the correct ones(back) supplied from coopercraft and were binding in the calliper body. The old ones were installed judging from receipts by jag specialists although I cannot comment on the thriftiness of past owners influencing these decisions. The moral here is when you buy a classic car strip the brakes! I should know this and only have myself to blame I am surprised that this lot passed the mot

All in all it proves that in the first couple of years you own a car you always have to overcome its shortcomings as you get to know it and to be very wary of cars that see little use

Cheers until the next "project"