Little help for brake unusual behaviour
 

Hello guys
i've got a Miata of a customer wich is making me scratching my head. It's a 1992 1.6 115hp.
No race prepped, everyday or so use.
The car brakes perfectly (for a street use 250mm FR rotors), BUT if the customer press slightly the brakes, a single, big "CLUNCK" comes from one of the two right calipers.
If the driver press hard and fast, no noise. The car except this noise, brakes perfectly.
Once noise happening, it takes like 10 other brakes istance to happen again.


​​​​​​Customer also complain that the noise is more frequent during low speed low braking.

Really, help us please. Both the problem and the customer itself (he is like a male Karen if you follow the internet trends) are diving us crazy.

My best guess would be a rusty/sticky slide pin on the calipers or a likewise brake piston. I have a similar issue every once in a blue moon if my car sits but never bothered diagnosing it.

I agree with guide pin as the probable culprit but do check and confirm that a caliper bolt isn’t loose. I had an odd sound from the back right area and tried to diagnose it while driving slowly. The caliper tilted up on the second bolt after the first one dropped out. Broken caliper, broken rotor, bent hub and destroyed wheel was the result moving about 25 or 30 mph.


https://cimg6.ibsrv.net/gimg/www.mia...30e6fe75e5.png

We already check correct bolt torque, good pads fitment, the condition of caliper pins... And with no solution. We could try to change the sliding pins, however.... But god help us if it is not the definitive solution. The customer is such a pain in the back that i would not be surprised if he pretend an allowance for leaving the car and return with the same problem again.

I had a MSM with a strange intermittent clunk in the rear.
Found one of the control arm eccentrics with a not fully tightened bolt.
It was tighter than finger tight but allowed movement under certain low speed bumps.