Outboard rear brake calipers

[almcl]

So this morning I discovered one of my outboard rear brake caliper pistons is seized.

I found a new replacement pair of rear calipers on the shelf, still in their genuine Jaguar boxes BUT a part number check suggests that they are for later XJSs than mine.

I can't see any difference at the moment (caliper is still connected to the car and the caliper mounting plate is awaiting the arrival of a 15 mm socket) but it looks as though the new parts would fit. The illustrations on the classic parts website are identical.

For reference, the part no I think is needed is JLM 12422 (VIN 188105 - TO VIN 198334)
the one I have is JLM 12427 (VIN 198335 onwards)

Needless to say the correct part, 12422, is out of stock (and at an eye watering £360, as well)

So, is there a difference, or are they actually the same part with different numbers - wouldn't be the first time, would it?

Strangely, the left hand one (which I would also replace) is in stock and £100 cheaper, but I wonder why, given the tendency to replace in pairs ?

[davidr]

Hi Al - the only change to the brakes I can think of is when the Teves system was dropped in favour of the conventional vacuum-assisted system from the X300 but this happened with the Celebration models from VIN 221855 which is well past the cut-off point you mentioned.
If the newer caliper looks physically identical is it perhaps the connections that are different?

[ptjs1]

Al,

The rear discs moved to vented from solid at 198335. Therefore, the caliper will be different to accommodate the thicker disc.

Good luck

Paul

[almcl]

Thanks both!

I hadn't spotted that vented disc change, but now you mention it, it's obvious on the side-by-side parts page.

Since posting I have come across a replacement piston kit. As I replaced the front caliper pistons with stainless a little while back it may be worth trying to refurbish the present rear ones.

[ptjs1]

Sorry Al, I meant "changed from solid to vented"

Paul