Sticking caliper on one side only

[Ricardo]

On my 1966 230SL the right front caliper started sticking after the car was sitting many months. First I thought I could free it by driving it, which did help somewhat: it becomes un-seized and stops dragging after I get going, but then when I apply the brakes it gets stuck on again, then after some more driving it gets un-seized until I next apply the brakes. It seems the pistons are not moving freely in the caliper.

These are 2-piston calipers, not Girling.

So, aside from taking off the caliper and checking/rebuilding/changing it, does anyone know any possible shortcut to try first to stop it sticking. I have tried applying the brakes with various pressures going backwards and forwards, but it still  gets stuck on again thereafter, if not the first time I apply the brakes then the 2nd or 3rd. Any methodology I can try, before going to the expense of taking off the calipers and servicing/changing them?

I know its the right front because I jacked up the front and it rotated when I had brought the car to a stop gently with the handbrake. but when I stopped normally with the footbrake it did not rotate. The left front caliper is normal.

And also if I do change the right caliper, all the advice is to change the left one also to avoid having two different vintage of calipers and therefore the risk of unequal braking. So that doubles the cost, even thought the left one seems fine.

[mdsalemi]

Ricardo,

Be careful of "throwing good money after bad"; in other words, wasting time, money or both on some possible, temporary fix, that will only continue to be a problem until you do the fix properly.

Here in the USA, a professional rebuild of a brake caliper is not that costly. If both front calipers L + R are of the same vintage, then what afflicted one may very well be on the way to afflicting the other and you just do not know it yet. Many auto parts stores, particularly those that cater to non-USA cars, can send these out and have them back in a week. Not that big a deal in time or money. Everyone has a different way of analyzing things, and doing things, but if this happened to me, all the calipers would come off, and all would be rebuilt. I did this when my car was restored and now it's 20 years later, so that's a good life out of a brake caliper. I don't know if I need to do this but if I did, I would not be annoyed...

Depending on the caliper you may be able to find rebuild kits to do it yourself, if you have the time and the ability.

Brake fluid is "hygroscopic" in that it absorbs moisture from the atmosphere, and this moisture is then what will begin to corrode the cylinders and pistons of brake calipers. If severe enough, a simple rebuild will not be possible and they may have to insert a sleeve in the caliper or simply replace the entire unit.

How often do you change your brake fluid? It should be done regularly.

[Cees Klumper]

How old are the brake hoses that connect the calipers to the rigid brake lines? More likely than not those are your issue. They swell up on the inside and the brake pedal force lets the fluid through one way, but it can't 'retreat' through the hose as easily and, with no pressure being applied 'in reverse', the pads stay sticky. In my case, so sticky that in the end I had a red-hot brake disc from the drag. Try replacing your hoses (and brake fluid etc) and chances are your issue will be solved. Hoses tend to also be inexpensive, compared to calipers.

Of course, while you are at it, you can also rebuild the calipers with new seals etc. I did that for my '71 Volkswagen recently, took little time or effort. For that, it helps to have compressed air to force the pistons out of their bores but be careful, they will pop out with some force.

[WRe]

Hi,
I had the same problem and refurbished the calliper with new pistons and rubbers for 20€ each (see https://www.daparto.de/Teilenummernsuche/FRENKIT/257926?categoryId=1541&kbaTypeId=931). I've just done it last summer, no rocket science.
...WRe

[Tyler S]

I second Cees’ hypothesis about the brake hoses. I had a sticking rear caliper that was hot enough to blister the paint on the rim. Replacing the brake hoses solved the issue.
When they get old they rust from the inside out and swell. Effectively creating a check valve that won’t release the brake fluid back towards the master cylinder when you release your foot. Hoses would be the cheapest way to start the parts cannon and should be done anyway.

[Nicolas Aristodemou]

I had a similar experience lately and the problem was the brake flexible hoses. Replacing those sorted my issue.

[stickandrudderman]

The simple way to diagnose if it's the hoses that are causing the sticking is to back off the bleed nipple of the caliper that has the sticking issue (whilst the problem can be witnessed by turning the wheel by hand) . If the wheel then becomes free it's the hose; if it remains stuck then it's the caliper.

[Nicolas Aristodemou]

The simple way to diagnose if it's the hoses that are causing the sticking is to back off the bleed nippple of the caliper that has the sticking issue (whilst the problem can be witnessed by turning the wheel by hand) . If the wheel then becomes free it's the hose; if it remains stuck then it's the caliper.

Really clever trick Stick, I hadn’t thought of that

[Benz Dr.]

The simple way to diagnose if it's the hoses that are causing the sticking is to back off the bleed nipple of the caliper that has the sticking issue (whilst the problem can be witnessed by turning the wheel by hand) . If the wheel then becomes free it's the hose; if it remains stuck then it's the caliper.

Yup, brake diagnostics 101 - you can't go wrong with that.  ( I read that in better braking magazine  )

[Shvegel]

Besides what Stick and BenzDr have said the Ate and Girling calipers are known for sticking brake pads.  You may just need a good clean up and re lubricate of your brake pads to end the problem.

[Ricardo]

Thank everyone for their excellent help!: I am going to try the least invasive (and least expensive) procedure first: Stic's suggestion of simply backing off the bleeder (after bringing the car to a stop normally with the footbrake), and seeing if that relieves the stuck caliper.

I will do this if not this weekend, next weekend and then report back.

[Ricardo]

Referring to my post above, indeed loosening the bleeder on the sticking caliper indicated that the problem was fluid-flow-related. Thereupon changed the rubber hose (and also the other 3), bleeding and re-bleeding the brake fluid appears to have cured it and also gives better brake pedal feel. Thanks for all the comments!