Trailer brakes lock-up!

[seastrength]

Thanks Getout
I replaced the caliper assembly yesterday. The piston in the old one was completely frozen. The Trojan manufacturer will not warrant the new assembly if it is submersed in salt water. Do you spray the WD40 before or after submersion or both? Just wanting to extend the life of the new assembly as much as possible. The trailer guy reckons 12 months is good going for any trailer brake system!!

[scottar]

My Tinka has Meher brand calipers. These have a solid stainless piston with cast iron calipers. I have had the pistons seize in the housings on a couple of wheels now and while there was some corrosion on the caliper and a bit of road grime courtesy of the lanolin, this wasn't the issue. The actual housing had "grown". I ended up stripping each caliper, lightly flap wheeling and then polishing the inside of the cylinder in the caliper until the piston could be rotated 360 degrees without catching, polishing the pistons and reassembling. No further issues to date. It's not the first time I have encountered this sort of situation - I have seen a similar issue in cast alloy autopilot pump housings that used a stainless piston. I don't know whether the cause is contaminants attaching themselves to either the piston or the housing or whether there is some sort of galvanic reaction going on???? Any of the brains trust here shed any light??

[seastrength]

Thanks Scottar for the explanation of the problem. It seems to be a common scenario with disc brakes on submersible trailers. Stripping and polishing the inside of the brake cylinder is beyond my mechanical ability so I went with replacement of the caliper assembly as per the advice from the trailer guy. I am just wanting to know if I should spray the caliper with Lanox before submersion each time and wash down with fresh water afterwards to extend the life of the new brakes beyond the previous 2 years. The trailer guy recommended waiting until the brakes cool and also turning off the brake controller before submersion. Would you guys agree with this advice in order to minimise corrosion? I realise there is a risk of losing traction on a slippery ramp, but I normally launch from MBTBC ramp which is well maintained and has good grip for my BT50 4x4.

[scottar]

Thanks Scottar for the explanation of the problem. It seems to be a common scenario with disc brakes on submersible trailers. Stripping and polishing the inside of the brake cylinder is beyond my mechanical ability so I went with replacement of the caliper assembly as per the advice from the trailer guy. I am just wanting to know if I should spray the caliper with Lanox before submersion each time and wash down with fresh water afterwards to extend the life of the new brakes beyond the previous 2 years. The trailer guy recommended waiting until the brakes cool and also turning off the brake controller before submersion. Would you guys agree with this advice in order to minimise corrosion? I realise there is a risk of losing traction on a slippery ramp, but I normally launch from MBTBC ramp which is well maintained and has good grip for my BT50 4x4.

I don't bother now - Good wash with soap via the Karcher to break down the salt, a lap round the block while activating the trailer brakes to get them warm and just a spray once they are dry with a bit of WD. Went away from the Lanolin for the brakes as it remained sticky and attracted the road grime. I have always disconnected my trailer cable prior to backing down the ramp. I also changed to stainless backed brake pads when I did the service. Nothing to stripping a caliper if you have a compressor and Google.