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Pigsy

Rx Rear Brake Caliper .. Please Help!

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Hey guys,

I have the most annoying issue with the rear calipers on my RX.

I'l cut to the chase rather than going down the long story route :)

The half of the rear brake caliper that is floating, and is connected to the sliding pins rattles about like hell when going over rough surfaces, which is pretty much 90% of the roads where I live ;)

I can physically grab the inside part of the caliper, and feel it clicking it up and down, albeit just a couple of millimeters.

I have replaced the slide pins for brand new ones thinking they were worn, but it made no difference.

I even replaced the damn caliper brackets which contain the slide holes that the pins actually slide into - nope, made no difference.

New pins, and new caliper bracket, and I have the same issue!

It's 100% the pins because when I grease them up liberally, the rattling goes away.

However, a few days later after the grease has "settled" or squeezed out, the noise starts to come back, and just gets ever louder until I take the pins out and regrease them up again ..

What the hell is going on?

I totally appreciate that if left alone for 18 months so they start to seize up again, the noise will probably go away, but this can't be normal, as they don;t do this when new right?

Anyone that can solve this for me, will be given a virtual pint! as I'm going mad trying to solve it .

Pigsy ..

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I know on some models the pins have a rubber type o ring, guide ring , on them to make them a tighter fit, grease up and then slide in taking up any slack, not sure what RX is like but may be these are missing from the pins ? Hopefully someone will be along. I will try and find a drawing and have a look.

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Looks like one of the pins has a rubber o ring/bush on it. So one pin nice a tight with the other floating. Hopefully drawing attached, looks like part number 47879R (attachment=11274:image.jpg]

post-24999-0-63894500-1418460281_thumb.j

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you really shouldn't use a lot of grease, it is counter productive. The slide pin with the bushing should stop the rattling. Some people remove bushing because an old one can be difficult to reinsert, or they purchase new slide pins but get two of the bottom ones.

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Thanks guys, but, I'm aware of the bottom pin having an O-Ring, and this has been fitted to both sides, again, new O-Ring to go with the new pins :)

It does make a difference, as without the rubber bush on there it rattles around even more, but still with it, it's rattling way too much

It's almost as if there should be some kind of anti rattle spring to stop the floating caliper just rattling around when not under braking pressure, but I've never seen one on any diagrams?

My confusion is this. I totally get why most RXs won't rattle, because after they start to seize up, the rattling will probably stop. But I have brand new pins, with new O-Rings and new grease sliding directly into brand new carriers, and it's rattling around like a bag of nuts and bolts so why the hell are they silent when driving them new off the forecourt?

Arrrrghh this is one of these things that's going to haunt me, I can tell!

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They don't rattle off the forecourt because the amount of play is very minimum and only a small amount of grease together with the bushing and seals stops any noise.

Have you replaced the rubber seals? Maybe that are worn and allow too much play at the point of entry. Normally this type of rattling is movement in the pads by not having all the clips in place but it does seem to be the calliper on your case as the noise goes when you re-grease the pins.

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Hey Colin,

I've replaced the rubber bellows seals as well. So the seals, the rubber bushes on the pins, even the carriers that contain the holes the pins slide into. So I see the current setup it as being "as new" as it's all been changed for new, not refurbished parts.

See where I'm coming from? this setup should be whisper quiet, but yet, I can grab the inner caliper on both sides and substantially click it up and down with my hands very easily, it's literally just hanging there clicking up and down as the car goes along any uneven surface, and this translates into a rather heavy cast iron clunking noise inside the cabin, as the calipers are quite a heavy cast item of course.

Regrease the pins liberally, and the noise goes away for about 7-10 days, and then slowly starts to return, until 15 days and then it sounds as though I've got serious suspension issues!

I like the idea of using two bottom pins, and may well try that, but the thing that's bugging me is that none of this should be required in the first place, as I've replaced everything .. Grrr :megaangry:

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Are you using the correct grease, Never ever use copper grease. Use silicon high temperature grease or if you can find it specific brake grease. I use silicon grease which has a very high temperature range and doesn't become fluid at temperature.

Hopefully that should help although this does sound like an unusual problem do you have all the parts from the above exploded view because there are a couple of clips that act as springs which should stop the rattle?

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Yep, I'm using the correct silicone grease, it actually came with the new caliper carriers, and it's 100% the right stuff, as I checked ;)

Now, I know that there are stainless steel spring clips that hold the pads in place, well, the pads just slide into them and then just sit there, and that's fine, but .. is there some other clip that you're referring to that I'm missing?

If there actually is a clip that should be in there designed to stop the floating caliper from rattling, please tell me about it! ;)

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surely if you have replaced everything it must be the other part or the caliper that is worn

suggest you take off the carrier have it drilled out and have copper bushes fitted to interferance fit

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Yeah but that's just the thing Joseph, I already have replaced the caliper bracket which is the very part that the pins slide into!

The reason I replaced them for brand new ones, was I came to the conclusion that somehow they had become worn, because if it's not that, what's left?

So, new pins, new bushes, new "holes" for the pins, the correct type, and amount of grease, and the damn things still rattle around like a bag of spanners ..

I really am lost with this ..

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This may be a daft post but are you sure that its the calliper?

The reason I ask is that having followed this thread from pretty much the beginning. You seem to have folowed a logical process trying to fix it. A couple of mills movement seems to me to not be very much to hear given the sound insulation on the RX.

Have you checked the rubbers on the rear hubs?

I ask because I had a similar noise on my RX and thats what it turned out to be The local dealer replaced the hub, bushes and all. I had no further noise.

Just asking.

Bri

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Hey Brian, as I said in the first post "It's 100% the pins because when I grease them up liberally, the rattling goes away." as in, immediately

and then eventually comes back after about two weeks ..

Yes, it's the pins, or rather, the movement that the caliper has floating about back there.

Imagine a whole caliper, which isn't exactly a light weight item, banging up and down 2-3mm over every single bump in the road, you hear it coming through the whole chassis, trust me ;)

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2 or 3 mm? There is something very wrong then. Incorrect sized pins or the wrong carrier. I could move mine but only about 1 mm.

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Can you hear your calipers rattling Colin?

I've not actually measured it to be honest, it just feels like a real good solid click up and down though .. maybe 2-3 was exaggerating slightly ;)

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Only when my callipers seized. I freed them up, reinstalling the old pin minus the bushing for a couple of days until I got new pins and bush.

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I think that either the rubber bushes I've got are somehow defective, as in too small, or more likely that the new caliper brackets are somehow too big for the pins.

That would explain it, although I'm making up the cause to fit the symptoms!

I wish I'd just left the damn things partially seized now :(

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can you tell if most of the movement comes from the top or bottom? I wonder it you could use slide pins with the bush top and bottom.

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That's one of the things I was thinking about Colin, using a bushed pin on top and bottom .. I do seem to recall seeing something somewhere that really warned against this, although not sure why as the last time I checked both pins seemed to be the same length ... I think it was some Lexus TSB about calipers, that had a huge WARNING about getting the pins the wrong way around :o

The play seems to be equal if I'm honest, lying under the Diff, and clicking both sides, I can't say that the top or bottom pins seem to have any more play than each other ..

I know there isn't but it's almost as if there should be like an anti rattle spring that attaches to the floating caliper, and just holds it there .. that would be ideal in this case!

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Friction from the floating calliper on the back of the pads should stop most movement, along with slide pin bush and dust seals, unless the pad clips aren't in place / tight and pads and calliper all move together.

The RX TSB regarding the rear slide pins states that the top pin, without the bush, has a slightly larger diameter shank but I'm guessing the bottom one is as wide or slightly more with the bush in place. The TSB just clarifies the correct procedure - I guess dealers were either installing the pins the wrong way, using too much grease or using the wrong grease.

I believe using the bush pins top and bottom can cause too much drag which means the pads won't properly release - leading to excessive heat and wear. Still if you have too much play anyway it could be worth a go, just check the temperature of the rear wheels after some journeys.

Putting too much grease can also cause excessive wear as you get air sealed behind the pin when you push it in, compressing the air which will try and push the pin out again. That pressure keeps the pads against the disc.

Using the correct grease is also important as certain grease will make the bush swell, leading to seizing.

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Thanks for that Colin, I'm hearing that Prius drivers are complaining about a similar issue .. investigation that now, and when I discover anything new I'll come back to update ;)

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2 or 3 mm? There is something very wrong then. Incorrect sized pins or the wrong carrier. I could move mine but only about 1 mm.

I agree replaced mine last year .... there was no movement around the pins ... have you got the right carriers fitted ?

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Hey Dennie, do you recall how tight the pins were going into the carrier?

I've got the right carriers as far as I know, I mean they fit, and line up and everything, no reason to suspect otherwise apart from the slight play that the pins have.

I mean it's not like you look at it, and think Whoa! that can;t be right or anything .. it's just enough play to rattle around, and boy do they rattle around when driving.

Passengers in the car look at me as if the rear axle is about to fall off!

It does seem as though Prius drivers are complaining about the exact same thing, but that doesn't really help me to explain why I've got the only RX to have this issue!!

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