Stuck caliper or low on brake fluid?

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?

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Originally Posted by 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?

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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.

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.

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

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Originally Posted by 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.

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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.

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Originally Posted by Moneypenny

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.

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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.

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.

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Originally Posted by RichG

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.

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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.

Attachment 41522

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.

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.

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!

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Originally Posted by jmettee

It *could* also be that your parking brake did not fully release despite you disengaging the lever.
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If you find 1 stuck piston it will probably mean you need to rebuild the entire brake system.

Unfortunately, working on a stuck piston/caliper is above my ability level. I'll get a tow to a local shop and see if they can unstick my calipers/pistons. Thanks, everyone.

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Originally Posted by RichG

Unfortunately, working on a stuck piston/caliper is above my ability level. I'll get a tow to a local shop and see if they can unstick my calipers/pistons. Thanks, everyone.

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A lot of shops want to replace the entire caliper as an assembly so be sure to let them know that exact fit replacements are not available. Parts you'd find at autozone, rock auto, etc. are incorrect. If I'm remembering the crossover PNs are for Jaguar calipers which have a smaller piston diameter. These calipers will physically bolt up but due to the piston sizes being smaller it will change the ratio of braking force front to rear.

Be overly specific that you're wanting the existing calipers inspected for sticking and rebuilt, not replaced. If they're going through the trouble of pulling calipers off and removing pistons it would be a good idea to replace the inner rubber seals. These should be available from Napa and a few other online sources, or you can have them order parts directly from DMC Houston.

As long as you find a good shop willing to do the work and not just throw parts at it you shouldn't have any major issues. Rebuilding brakes isn't as common anymore but there are still places out there that can do it.

I found one auto shop in my local area who has stellar reviews on both yelp and yellowpages.com for being honest. I gave the shop a call and spoke with the owner. He was concerned he wouldn't know where to get replacement parts and referred me to a foreign car shop nearby (who didn't get stellar reviews). So, my plan of action is:

Step 1: I'll jack up the car and figure out which brake is stuck.
Step 2: order caliper rebuild kit(s) and piston(s) accordingly.
Step 3: beg the local honest mechanic to rebuild my caliper(s) with parts provided.

I guess I should be glad I discovered this problem this past weekend instead of finding out 200 miles from home on my way to the spring social. Bummer that the car drove and stopped just fine last week. Weird timing for my brake(s) to stick.

This will probably make a few heads explode:

I've resurrected old calipers by filling them with PB, then bleeding the system where the flex line attaches rather than at the bleeder screw (leave the PB in the caliper). Put a new pair of pads in the caliper so the piston is pushed all the way back into the PB.

Bill Robertson
#5939

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Originally Posted by content22207_2

This will probably make a few heads explode:

I've resurrected old calipers by filling them with PB, then bleeding the system where the flex line attaches rather than at the bleeder screw (leave the PB in the caliper). Put a new pair of pads in the caliper so the piston is pushed all the way back into the PB.

Bill Robertson
#5939

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If a piston is stuck it is because it has corroded from bad brake fluid. While this procedure may get things moving it cannot repair the damage from corrosion and the corrosion will not permit a good seal so the caliper will leak. There is no getting around the necessity of rebuilding the calipers. If one is leaking or stuck they must ALL be rebuilt including the master cylinder. Otherwise you will just be doing them all but 1 at a time as they fail.

I took the car out for a spin again today and could not reproduce the braking issue.

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Originally Posted by David T

this procedure

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Like I said: a few heads will probably explode.

Bill Robertson
#5939

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Originally Posted by RichG

I took the car out for a spin again today and could not reproduce the braking issue.

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It could be part of a break-in thing. When I rebuilt my calipers, I recall them being a bit "sticky" the first few drives. This stiffness in the system probably relieved itself with a few good cycles of the brake system as the pistons slid through the main seals a number of times.

I'd say try a few more short drives & purposely exercise the brakes. Obviously you want to be careful with this to work up the confidence in the system, but giving the system some good exercise will be good since the problem is apparently not a constant issue.

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Originally Posted by jmettee

I'd say try a few more short drives & purposely exercise the brakes. Obviously you want to be careful with this to work up the confidence in the system, but giving the system some good exercise will be good since the problem is apparently not a constant issue.

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Exactly my thoughts as well. Fingers crossed!

I have experienced 3 out of 4 clogged front brake hoses on both of my DeLoreans in recent years. It is also possible that the fluid passage between the two pistons clogged up. This was the case on both of 5052's front calipers; however, 5052 had been sitting for 20+ years.

I excercised the car over the past few days and wasn't able to reproduce the problem. I brought the car to a local shop to inspect the brakes, but they didn't have a low profile jack. So, they couldn't conduct the inspection. I checked my brake fluid reservoir and it looked like it was at max, so that's good.

This gave me the confidence to make the 350 mile trip to NJ for the spring social. I'm typing this from the Fairfield Inn & Suites. Hope to see you all tomorrow!