460 New Front Disks binding
I had the brakes all round worked on - including new front disks. After a few days the front disk pads are binding quite badly on the new disks. I recall the mechanic saying it was a tight queeze to get the brake calipers open enough to get the new pads in, and I suspect that the calipers are seizing. I was hoping the pads would wear a bit to ease it, but it could be getting worse!
Any suggestions? I am just going to have to get the garage to pop them off and see. The calipers are not new, just the original ones.
Fuel consumption is worse than ever ;)
sounds like the calipers, you could take them off and wind them back and forward a few times to try and ease them off but it might be better to replace them, they don't last forever.
Hi JD
do not mess with old calipers by the time you have paid to strip the pistons out and found the chambers in the casting corroded ( from water in the brake fluid) get exchange ones from Brakes Intenational for under GBP 100 per side less the discount for returning your old ones ..need to tell them if they are single or two pipe inlets... part number is 34801 or 34800 phone them on 01706 666999 or 01204 385888 (Mike) located in Bolton and Rochdale *** next day delivery
Hello jdring,
“I recall the mechanic saying it was a tight queeze to get the brake calipers open enough to the new pads in,”
My initial suggestion would be is to find yourself a new mechanic! He had admitted that it was a tight squeeze. That in its self should have alerted any descent mechanic to investigate and solve a seizing(ed) caliper before proceeding any further.
Establish if, infact, it is the caliper that is seizing or, if, it is the rubber hoses causing a seizing affect. Sometimes the internal lining of the rubber hose collapses. Apply the brakes and maintain the pressure by an assistant, inspect the rubber hose for any bulging; this would indicate weakness in the lining.
Relieve the brake pressure and check to see if the caliper piston FREELY returns back, if not, release a caliper bleed screw and recheck if the caliper piston freely returns. If the piston returns easily, then you would have confirmed that the rubber hose is defective. If the caliper piston is still seized, then remove the piston boot and check the piston surface, if rusty, then you have confirmed for a seized caliper.
Cheers,
Hmmm - its kind of tricky. Once stood for a while and cooled down, the binding goes away. If I am sparing on the brakes, it remains OK (to me this indicates that its not just the normal friction heating of the disks bringing it on).
If I brake gently, there is good response and a little brake pedal travel. If the G starts to run sluggish, I know its binding and when I brake then to shift it, I notice that the brakes are keen with almost no pedal travel.
If I pull over and reverse a bit, jab the brakes, try to release the binding - it 'sometimes' works.
Always after leaving to stand for 15 minutes, the binding is cleared.
Now I am not sure I even know if it is the front or the rear that is the problem - pretty fundamental!
I don't know the details of how brake hydraulics are controlled, but it almost seems like there is excess hydraulic pressure in the system after braking hard and that when left for a while it disapates - is that possible?
Hi JD
all the symptoms of hydraulic components corroded by the natural ingress of moisture hydraulic oil absorbs from the atmosphere 24 / 7 ...the pistons do not move freely and as a result the discs heat up and expand ....unable to move the siezed pistons the heat increases.. the expansion of the discs becomes greater and the binding more intense.. when they cool the binding is reduced ...if you have not FLUSHED the hydraulic systems ( including difflocks) every 3 years as recommended by MB for all there vehicles internal corrosion will result and increase until you experience the problems you are having...along with the calipers and cylinders the load related pressure regulator ..the inline equaliser valve.. master cylinders and the difflock rams may all be corroded.we recently recovered a 50.000 miles SWB 463 from a dry barn where it stood for ten years unattended GBP 2300 later the hydraulic systems were considered fit for purpose....
The thickness of the new discs should not present any problems. Had new brake pads been fitted with the new discs?
I would be inclined to ask if the caliper surface, the pad makes contact with, is thoroughly cleaned out for the pad to freely slide and further more, suitably greased.
The pads could be faulty, in so far as, the friction material has not properly been bonded onto the pad metal lining. Check to see if the pads have a square profile, put a straight edge across it to see if it is flat. Check carefully, in between the friction lining and metal backing to see if the bonding is secure, if the friction lining has a small gap, this could cause the binding, progressively worsening as you drive, and contracting as it cools down, whilst you are stationary.
Great. I put my G into local garage to fit the shiney re-furbed Calipers - I mean, how difficult could it be? The original mechanic was tied up til Monday. I was even contemplating having a go myself, but lack of hydraulic fluid and basic tools stopped me!
Well - the old calipers look pretty shagged, so definitely needed.
The Caliper bolt threads were a little suspect and worn, but OK by using slightly longer ones.
When it came to bleeding the brakes, they couldn't get it to drain. Turns out the master cylinder piston got pushed all the way to the floor and I suspect the piston is stuck in a part of the barrel its never been in in normal operation - probably rough and corroded internally and now the piston is
stuck on pull travel, preventing the fluid draining and any pumping of the brake peddle.
Now, I am no mechanic, but this seems like a pretty obvious likely fault on any older vehicle, and pressing the brake peddle to the floor seems like the wrong thing to do? The piston is going to travel into unknown parts of the barrel!
They are going to try to perform a vacuum bleed to suck fluid down to fill the calipers, then hope that pressing the pedal leaves enough travel to deliver some pressure and push the master piston back up to the operational part of the barrel.
A new master cylinder is about £175 and I feel it didn't need it if they had been more cautious on the brake pedal?
Comments?
Given the symptoms you described earlier and the fact that it was not just one calliper that was sticking I would suspect that you had a problem with the master cylinder anyway.
If the master cylinder piston was jamming due to corrosion that would explain the solid pedal and the brakes staying on. I think it would be a good investment to change the master cylinder and that should hopefully solve your brake issues.
Thanks. That's a very good point, and quite rightly could suggest a cause for what seemed to be retained hydraulic pressure in the master cylinder, causing both calipers to bind.
The rear nearside drum was also a little hot one time when checked, which is another indicator.
However, I still think the master cylinder was operating fine, there was smooth brake operation initially, but when the calipers/pads move tightly onto the disk and do not ease off, the next brake application is going to have less movement/compression and thus feel sharper.
I will continue with the garage trying to 'recover' the piston to the smooth part of the cylinder but its looking like a new one will be worth it.
may as well do the slave cylinder at the same time
Just an update.
The second garage used an airline (I think) to pressure the system and force the master cylinder piston back up its cylinder, then was able to bleed the brakes a bit more cautiously. I'm not happy about it, but these things happen with old cars I guess. At least the calipers and new disks are smooth and effective, although the brake pedal feels pretty spongey to me - feels like either not all the air was removed or the piston got damaged.
I'll schedule a new Master Cylinder next time I have something done. Slave cylinders (I assume you mean the rear drum brake shoe cylinders) were replaced. At the moment I need the G on the road.
Ok this is going to start getting boring.
After quite a bit of expense and 2 garages, new disks calipers and pads, the brakes were fixed and freewheeling smoothly again. All fine with me for a couple of weeks. Then I let the missus drive it for 3 days on on return when I jump in I can tell something is not right. Sure enough the front disks were binding again. The first clue was the sluggish pickup, the second was that the brake pedal has almost no travel and feels 'pumped' up. The third is when the disks heat up so much you can hardly move!
After cooling the calipers and waiting 15-20mins the front wheels get freed and I can drive it home (mainly using the handbrake).
What can be causing this? New fluid, calipers, disks etc. Could it be that the pads are catching on the guide rail pin things (I don't know the name), but they must move on something. (EDIT: I checked a maintenance manual - the pads are just slotted into the fixed caliper either side of the disk and retained there with a spingplate and pin - so no sliders to worry about)
Could the fluid pressure be getting trapped and forcing the pistons to the disks? How? Could the new calipers be poorly reconditioned???
Its driving me potty.
OK, another update post the site crash.
Garage that made a bit of a meal of the caliper swap and got the master cylinder jammed took a look and concluded it will in fact need a new master cylinder. So one is arriving today (not cheap, new at £180 (std Lucas Girling thing).
I am bowing to their better judgement, and a new master cylinder is not a bad thing to have, but still not sure how the symptoms point to a duff master cylinder?
For a start, they said that perhaps the piston was working on a previously unsmooth part of the barrel now that new disks, pads and calipers had been fitted. To me, this sounds wrong - surely the operational part of the master cylinder is the same regardless of that - all that changes is there is a litle less fuid in the system (because caliper pistons fully retracted now).
But since they jammed the master cylinder when bleeding the brakes, I thinks its possibly damaged the piston seal (when forced down into corroded part of the barrel), and not it is making it difficult for the piston to return smoothly based on hydraulic pressure only. Can only conclude that it takes time for the pressure to ease the piston back and that coincides with thinking that it is related to time needed for the calipers/disk to cool.
I think in hindsight the error was to use the old school method of bleeding the system in place of vacuum bleeding, but probably the barrel was well corroded. Will see tomorrow when it is removed and will attach a photo!
Hi JD see my PM
OK, another update.
Master Brake Cyclinder replaced. All free-wheeling again (but so it was for a while when the new calipers were fitted).
I got the old Master Cylinder - took it apart (could only remove the first piston and it looked absolutely fine - the cylinder bore was fine too and the seals perfectly good (not shredded or worn as suspected) - no pics of that yet. Couldn't see how to get the lower piston out though...
Old and New cylinder pics shown here - but they look almost the same.
I suspect the main issue was simply that crap from the old cylinder was flushed into the pipework when the calipers were replaced, and didn't make it out or past the t-pieces/valves. Then a bit of crap got stuck the wrong side of one of these junctions and wouldn't release the hydraulic fluid pressure from both front calipers. I asked them to flush a couple of DOT4 bottles through, so am hopeful its sorted and I have all new brakes bar the valves/junction pieces.
Rakesh/Peter, thanks for the inputs.
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Thanks Peter, Rakesh,
No answer from the Brake people so far.
My mechanic had freed what was previously a suspect seizure and given the caliper cylinders a good going over, but I think the combination of the new (thicker) disks means that it is operating on old and rougher/less worn surfaces now and prone to seize more easily. I think its time to replace. The rubber brake pipes look in good order - no sign on bulging.
Speaking to the brake folk now... none in stock but will try to source. James at G-Wagen is looking for decent spares too which will get me going at least.