Stuck caliper or low on brake fluid?

[RichG]

I took my DeLorean out for a wash today in preparation for Friday's spring social in NJ. I noticed my brakes were engaged (not the parking brake). So, I limped home at 5mph. Does this mean I have a stuck caliper? Or is it possible that I'm low on brake fluid? The calipers were replaced on the car about 5 years ago. Brake fluid likely hasn't been checked since. The car has only been driven 1000 miles in the last 5 years. Looks like I'm going to miss the spring social, which would be a bummer.

Thoughts?

[David T]

I took my DeLorean out for a wash today in preparation for Friday's spring social in NJ. I noticed my brakes were engaged (not the parking brake). So, I limped home at 5mph. Does this mean I have a stuck caliper? Or is it possible that I'm low on brake fluid? The calipers were replaced on the car about 5 years ago. Brake fluid likely hasn't been checked since. The car has only been driven 1000 miles in the last 5 years. Looks like I'm going to miss the spring social, which would be a bummer.

Thoughts?

Possibilities include:
One or more stuck pistons in one or more calipers
A bad brake hose
A problem with the master cylinder

Low brake fluid is NOT a possibility although you may be low.

Since you say you haven't touched the brakes in 5 years we can assume the fluid wasn't changed either. Jack up each wheel and see if only one is stuck. See if the reservoir is still filled with fluid or if there are any leaks.

[jmettee]

I agree with Dave's advice, jack the car up & find the wheel(s) that are stuck. This is most likely the problem...then you know how extensive the problem is.

It *could* also be that your parking brake did not fully release despite you disengaging the lever.

Another word of advice is to drive the car more. 1000 miles in 5 years means the car is just sitting, which isn't good for a car. Things like frozen calipers can happen from lack of use.

[sdg3205]

The wheel with the frozen piston will likely have a hot rim and stink like hot brake pads.

[Moneypenny]

I agree with Dave's advice, jack the car up & find the wheel(s) that are stuck. This is most likely the problem...then you know how extensive the problem is.

It *could* also be that your parking brake did not fully release despite you disengaging the lever.

Another word of advice is to drive the car more. 1000 miles in 5 years means the car is just sitting, which isn't good for a car. Things like frozen calipers can happen from lack of use.

I am not necessarily recommending you do this, but I had a sticky parking brake for a while on my old beater Audi. I eventually had to replace the caliper, but as a stopgap measure, whanging on the caliper with a hammer would un-stick it.

[jmettee]

I am not necessarily recommending you do this, but I had a sticky parking brake for a while on my old beater Audi. I eventually had to replace the caliper, but as a stopgap measure, whanging on the caliper with a hammer would un-stick it.

The DMC has an odd parking brake setup, but it's easily inspectable if you pull the wheel off. Obviously the first place to start in diagnosing the problem. Since the parking brake & the normal service brakes are completely separate systems, the problem could be either system. Hopefully Rich come back here with some initial findings so we can get him going again.

[RichG]

I replaced the brake lines with stainless steel about 5 years ago (same time as the brakes were redone).

The problem seemed intermittent. Sometimes when I engaged the brakes, they wouldn't disengage. Other times, they did disengage. That tells me the problem is likely related to the braking system and not the parking brake. Mostly, the brakes stayed engaged.

I'll jack up the car at each tire and give them a spin to see which one is stuck. Q: When I find the stuck caliper/piston, any advice? What would cause them to get stuck? Surface rust?

Also, good advice about driving the car more. I want to and that's one of the reasons I was looking forward to the Spring Social this Saturday. Once I get past this brake issue and an unrelated electrical issue, I'll enjoy the car on weekends during good weather. Thanks, all.

[Jonathan]

I replaced the brake lines with stainless steel about 5 years ago (same time as the brakes were redone). So, I don't suspect the brake lines.

The problem seemed intermittent. Sometimes when I engaged the brakes, they wouldn't disengage. Other times, they did disengage. That tells me the problem is likely related to the braking system and not the parking brake.

I'll jack up the car at each tire and give them a spin to see which one is stuck. Q: When I find the stuck caliper/piston, any advice? What would cause them to get stuck? Surface rust?

Also, good advice about driving the car more. I want to and that's one of the reasons I was looking forward to the Spring Social this coming Friday. Once I get past this brake issue and an unrelated electrical issue, I'll enjoy the car on weekends during good weather. Thanks, all.

This sounds like a sticky caliper piston to me too.

If/when you find the stuck caliper/piston, you probably should take it off and inspect it. The cause for them to stick can definitely be rust related, but not the same sort of surface rust you normally see on suspension components. The pistons are a little more internal to that, but they too will rust and get pitted. The piston moves inside the caliper in a spot with very small tolerances, so any imperfections or rust or whatever can cause it to seize up. The braking fluid pressure will be enough to push it down into the backside of the pad for slowing down the car, but it won't be free enough to move to ease back to where it was. And now it is grabbing the rotors via the pads and this is what you see with a wheel that won't spin freely.

Rebuilding calipers isn't terribly difficult, but it isn't something I would want to start with as my first job on the car. Not knowing your level of mechanical expertise of course, just saying it is more intermediate than beginner level work.

The brake issue and electrical issue are indeed likely unrelated... physically speaking. But they both might be related to not driving the car. Easier said than done to actually get out and drive the cars though. Post back on the brakes issue and the electrical issue when you need more help.

Front caliper rebuild 1.jpg

This photo isn't as clear as I would have hoped. You can see the calipers opened up, the old pistons, and the new pistons and seals kit there too.

Rich_NYS posted some good photos in his rebuild thread of the pistons on his car as they were pitted as well.

[Mark D]

I've got a bunch of photos from when I rebuilt my brakes here that might be helpful:

http://dmctalk.org/album.php?albumid=97

I sand blasted and re-plated the calipers but if you've just got a stuck piston or two you wouldn't have to go to that extreme.

I cleaned up and reused the pistons...you can see in some of those photos there was a pretty good film of crud on the sealing surface. I was able to clean that away with a white scotch brite pad and brake cleaner. Don't use anything too abrasive that will scratch the surface of the pistons.

If you find you've got rust and pitting you'd be looking at replacement pistons which you can get in stainless steel for a reasonable price.

The calipers are DeLorean specific so if you're going to a shop to have any work done don't let them take your old calipers as cores. Whatever crossover parts they might try and sell you are not the same. Hopefully when you say you had them replaced 5 years ago it was with a DeLorean vendor who got you the correct parts.

[dn010]

I know you said 'could', but I'd love to see the day when a parking brake was engaged so forcefully on a stock D that it would actually keep you from going above 5MPH with that much stopping power. I really wish it was a better design!

It *could* also be that your parking brake did not fully release despite you disengaging the lever.
.