I’m looking for technical help or recommendations on: Sticky front upper caliper slide pin
Sadly, my wife and I have not used our MX’s much over the last 2 years - too much to do helping daughter with new home and new (first) baby… it’s been brilliant becoming grandparents, but absolutely ZERO time to drive or maintain our MX’s. So the sun shone the other weekend and out came our PRHT - at first corner where serious braking needed to be done, the car lurched sideways horribly. Immediately suspected “sticky” caliper slide pin.
This is my first weekend with time and acceptable weather to investigate; O/S/F upper slide is more than sticky… I can only move it with 17mm socket on the end of a 2ft breaker bar - shame on me for allowing it to get so bad I guess… 2 years of little-use and zero home-maintenance
I’m going to persevere for a while, trying to get the pin out of the caliper bracket; but do those guys who know these cars well suggest I give up and buy new bracket and slide pin(s)???
Brackets seem thin on the ground though - nothing at MX5Parts, no stock at autolink, though I’ll contact Andrew to double-check, and probably PH Sportscars as well.
Same happened to me a couple of years ago.
I needed up replacing both calipers and slide pins as I found the caliper bores too scored and slightly oval from excess heat.
I would do the same as I reckon the other side will be going the same way…
Is this the bolt holding the slide pin in, you have a nut too on the other side of the caliper bracket? So 17mm spanner on the nut and a socket or spanner on the nut/bolt.
Surely they can’t be that seized?
The bolts (14mm?) that screw into the ends of the slide pins shifted very easily, and the caliper itself looks in pretty good nick; the visible part of the piston is pretty bright, so I’m happy no issues with the caliper itself.
It is the stand-alone upper slider pin that’s stuck “BFT” in the upper bore of the caliper bracket. The lower pin (with rubber sleeve on its end) was pretty tight, but came out OK with a bit of persuasion. I’ve resorted to a bit of plus-gas sprayed under the rubber boot, hoping it can find its way down the bore of the caliper bracket - will have a go tomorrow eve to see if it’s eased up a bit. Even if I can get slider pin out, I’m guessing the bore in the bracket will be so damaged that I’ll be best to fit new bracket/pins anyway.
A reasonably good video here for how the NC Mk3 caliper operates… 4min26 shows caliper removal and 5min21 shows how the slider pin operates in the bore(s) of the caliper bracket… not the caliper:-
The video shows slider pins popping out with a gentle pull… mine barely turn with a 2ft breaker bar!
A few years ago, I had the same happen to mine. I was going to buy a new bracket but, like you, I couldn’t find one.
Removed the bracket, put it in a vice and I heated up the housing around the pin with a blow lamp. Took about 3 minutes to get the temperature up high enough and then it just made a popping noise and suddenly went loose enough to just withdraw with pliers.
BTW One pin has a rubber sleeve towards the buried pin end and the other doesn’t. I can’t remember which was stuck fast on mine.
CAUTION: I’m sure you know that PLUS GAS is HIGHLY FLAMMABLE.
once you have removed the 14mm bolts that secure the pins, the 17mm is effectively the pin and that freely rotates. The top pin should slide out but the bottom if the seals have gone over the end stop it lodges itself between the pin endstop and the OD of the guide. To get it out rotate it with a 17mm socket and use something to grab it but allow it to rotate and apply a pulling motion at the same time you are rotating it.
You can get replacement pins but they are not OEM quality and these need to be serviced and checked regularly. to service them use copper grease on the 14mm bolts (so they wont cease) and silicon grease on the guiding pins (obviously after thoroughly cleaning the guide).
Thanks Japester - relieved I’m not the only one!
If plus-gas doesn’t work, then heat was going to be my next option - I’m hoping the slider-pin bores in the bracket will be OK to clean up, but I will search for new (or good replacement) bracket just in case. Thankfully the pin that’s stuck isn’t the one with rubber sleeve fitted… that would’ve been interesting with heat! I’d love to know WHY one pin has rubbber sleeve fitted and the other doesn’t.
Thanks for reminding me about fire risk… I’ll make sure to take precautions and work outside
Its obviously a design feature so that usually you have a partialy stuck calliper instead of a completely stuck one. Changing the bulbs is another feature I “love” about this car…
After a couple of days with plusgas, FINALLY managed to get upper slide pin shifted - thankfully no heat needed. Lots of rust evident.
Cleaned slide pin and caliper bore (slightly undersized drill wrapped in wet’n’dry), all lubed, refitted and road tested… much better but still not perfect, so I think the eventual solution will be new carrier, slide pins and pads (both sides to give best chance of long-term fix).
I went down the same route as you without touching the pads, which had plenty of wear. When I got someone to give it a proper look over up on ramps it turned out to be the cheapest thing.
The brake pad clips had seized up, probably due to lack of use in the six months before I bought it. Both cars I’ve bought off a forecourt recently have needed their brakes freeing up within weeks of buying them.
Cost me an hour’s labour.
