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Sticking Caliper, Brake lights on without touching the brake pedal


Seaway

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1985 720, 5 Speed manual

 

Truck was sitting for about a week and when I drove it it felt as though the left front caliper was sticking.  When I brake the truck pulls left and it does not roll freely in neutral.  Brake fluid is dark so it is definitely time to swap out the caliper and flush the brakes, no big deal.  While I haven't done it on this truck I assume it is as straight forward as it is on all the other vehicles I have done this job on.

 

When I got home from work yesterday (in a different vehicle) I looked over and noticed that the brake lights on the truck were lit up.  Nothing I did would get them to turn off so I finally removed the negative cable on the battery.  I assume that this going to be some sort of short or relay causing the issue and it is probably just coincidental to the sticking brake caliper?  

 

The truck has been running really well recently so I guess I should have expected something new and exciting to pop up!

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The caliper is likely the 'floating' type, in that it self centers itself on the rotor. For this, the caliper must be free to slide side to side usually on pins that have a special coating or certainly grease. Naturally water dirt and corrosion can lock the caliper in one place. It may just need cleaning and some brake 'grease'.

 

Brake warning light can be a foreign object like a tree branch jammed in the E brake cable or the switch not adjustewd right. Some vehicles have a low brake fluid switch in the master reservoirs. Last is the pressure differential switch that warns of loss of hydraulic brake pressure in either the front or rear system caused by a leak or just low fluid level..

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I will pull the wheel and check the caliper.  My guess is that it needs some grease or something simple as I was able to brake hard and get it to free up for a bit.  The filthy brake fluid can't be helping things either.

 

I should have been more clear, the actual brake lamps on the tailgate are lit up!  There is no brake warming lamp lit on the dash.

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I had a similar issue with my 720 a couple years ago. After a 900 mile trip, I noticed the brake lights were stuck on. I found what looked like pieces of broken green crayon on the drivers side floormat, peeked behind the dash at the pedal assembly and realized that the crumbled pieces were part of the stop light switch "cap", if that makes sense, it's the piece from the pedal return action that contacts the switch plunger and turns the stop lamps off. Hard to explain without pictures, but was easy to fix with a small nut/bolt combo until I got the right parts to fix it.

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These pins have a special coating or plating so scowering them clean of any rust is not advised. I've done it though (temporarily) and lubed them with white lithium grease. It's dry and won't melt and run when heated. Not suggesting you do this. 

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I found the green "crayon" pieces on the floor board, so it looks like I know what is causing the brake light problems. I must have broken it when I stomped in the brake pedal to free up the caliper. Now to figure out how to fix it....

 

When I get a chance over the weekend I will look into the caliper. The whole assembly is cheap if I need to replace it, which is a welcome change after working on Volvos.

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In addition to the broken green crayon issue, I also had an issue recently with the drivers side caliper sticking. I noticed when I pulled into the garage, I could smell a faint burning smell. The rotor was way hot, so I disassembled the caliper and sure enough the piston was stuck. Oddly, the pins were in great shape, well-lubed and slid freely. Popped out the piston, cleaned a little scale/rust, put in new seals and put it all back together (and these calipers are only 20k miles old, genuine Nissan NOS) and bled. All was well for a week or so, and it started to pull left full time. The real problem was an internally collapsed brake hose (the rubber line to the caliper). It wasn't allowing for a full return of the fluid after the pedal's release, causing the piston to "stick". The hose looked fine on the outside, you can't always see a collapsed hose.

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 The real problem was an internally collapsed brake hose (the rubber line to the caliper). It wasn't allowing for a full return of the fluid after the pedal's release, causing the piston to "stick". The hose looked fine on the outside, you can't always see a collapsed hose.

That's good.

 

I always forget about the collapsed hose issue.

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