Brake rumble

[ParaYeti]

My brakes have started to rumble and a slight undulating feel through the pedal. Both are worse at high speed. I took a quick look at the discs and saw a strange finish on the rear discs. Fronts are as expected for a car of 20 months/14,000 miles.
It looks like a material defect in the casting to me. It is the same on both rear discs. The strange finish is the same size on both discs too.

Any ideas other than casting fault?

Looks like a trip to the dealers

Rear disc

 

 

Front disc

Edited 7 July, 2013 by ParaYeti

[Llanigraham]

Pic links don't.

[Yety]

Nothing to do with a casting fault.

 

It's probably the old odd case of sticking pads in the caliper sliders, coupled with a load of road grit/debris caught against the pad material. Normally a good old fashioned freeing the pads off and lubing with some anti-seize compound, and using the brakes a bit more

 

The rear brakes take less use than the front ones - in your case the fronts look lovely and well wiped as they are probably compensating for the poor rear performance.

 

Nothing to really worry about that a bit of TLC won't cure. The discs will probably rub up well.

 

Modern car service intervals mean this sort of thing often appears, probably not an issue in the older generation type of service where a pair of hands runs over all these sorts of things to make sure they are working properly - and that takes time. Modern servicing is little more than the odd oil/filter change until something falls off/wears out :wonder:

Time is money.

[ParaYeti]

Does this clickable link work?

 

If you can see in the central part of the face there are small pimples, or high spots. Why would corrosion cause this.

The callipers and pads seem relatively clean and in good condition. The pads are contacting across all the face of the disc.

The hub is not corroded and the outer edge isn't bad either. Both rear discs have the same batch date. 

 

I've looked at pictures on Google of corroded discs and they show corrosion elsewhere too. Why would only the face of the disc corrode?

 

http://i1274.photobucket.com/albums/y421/photodave5/null_zps90443968.jpg

[trundlenut]

The rear discs on my old octavia looked like that when the metal shims between the pads and callipers got all gunked up, so that when the piston pushed the pad on to the disc it didn't move evenly.

[Yety]

The rear discs on my old octavia looked like that when the metal shims between the pads and callipers got all gunked up, so that when the piston pushed the pad on to the disc it didn't move evenly.

 

That's what I said above

[ParaYeti]

That's what I said above

 

Every answer helps even if they give the same advice. Ta.

 

Hmm. I'll take the wheel off and maybe the pads out tomorrow evening and have a closer look.

[trundlenut]

That's what I said above

Posting whilst watching TV, so I didn't actually read all the replies.

[ParaYeti]

Posting whilst watching TV, so I didn't actually read all the replies.

Are my posts that boring? :zzz:

[ParaYeti]

Hmm...

Dealer quoted £330 for new rear discs and pads, fitted.

Or £80 to do it myself.

No brainer!

The old disc was shot on the inside face

[The Plumber]

Have the same issue.

 

Problem is the rear calliper sliders, which can get glued up with the white grease used by the factory; can start turning solid with age and heat. Stripped mine down and re greased with LM & Copper Slip as a tempory measure.

 

Too late though for mine, as the discs were already beyond salvation but I'm trying to keep them going to the 40k mark, then I will fit new discs/pads.

 

 

TP

[rockhopper]

I guess this is the price we don't pay having sliding callipers rather than opposing pistons. Can of course upgrade the callipers......

Maybe I should check mine. The car is now at 40k.

[The Plumber]

Well looks like I'm going to have to replace the rear discs/pads sooner than I hoped. Nearside disc surface is starting to flake off in clumps. Took the callipers apart again to find the sliders/pads are seized once more and both disc inner faces has the equivalent of the old ridge and furrow field system.

 

Also found the rubber sleeve that fits over the lower slider has swelled on both sides and therefore no longer fits back in the carrier tube; had a job trying to get the pin out due to the expansion of this rubber sleeve. Also one of the boots has split; possible the regular taking them apart has not helped; rubbish quality product from Mr Bosch.

 

 

TP

[steve20bore]

Nothing changes.

 

My old Passat and Mk.4 Golf both suffered from the same problem

 

The rear brakes do not have to work hard enough.

 

 

 

Steve.

[ejstubbs]

Problem is the rear calliper sliders, which can get glued up with the white grease used by the factory; can start turning solid with age and heat. Stripped mine down and re greased with copper slip.

 

Could you possibly post some guidelines for doing this?  My rear discs look very similar to the OP's, and I've started to notice a "swishing" noise between about 35-45mph on the overrun in fourth/fifth (ie when the engine isn't working and so is fairly quiet) which I think could be brake-related.

 

(I managed to finish making my own example of 33q's mesh lower grille cover yesterday, so I've suddenly become all enthusiastic about doing DIY on my Yeti.  OTOH I might ask the garage to do it at the next service, which is only 2,100 miles away...)

[The Plumber]

Could you possibly post some guidelines for doing this?  My rear discs look very similar to the OP's, and I've started to notice a "swishing" noise between about 35-45mph on the overrun in fourth/fifth (ie when the engine isn't working and so is fairly quiet) which I think could be brake-related.

 

 

Yes no problem, hoping to do the work this weekend if the new kit arrives in time; orderd from Rainworth as there cheaper than the local dealers and no charge for posting. Pads I already have after picking up some original VW/Skoda one's from ebay.

 

 

TP

[Billcbf1000]

Is there a guide on how to change rear pads on a yeti -I've never changed the pads on a car with rear disc brakes that has the handbrake on them!

[ejstubbs]

Yes no problem, hoping to do the work this weekend if the new kit arrives in time; orderd from Rainworth as there cheaper than the local dealers and no charge for posting

 

That would be great, thanks!

[175GDY]

You may find some useful guides at youtube. Search for "rear brakes Golf mk5". I removed all original lubrication from the guide pins and lubricated with this: Permatex® CeramicExtreme Brake PartsLubricant. Also carefully lubricated the contact surfaces between brakepads and yoke and back of brakepads.

[ParaYeti]

@ejstubbs....

 

Check the bolts holding the bracket that carries the calliper. On my 2011 model they were cap head bolts with a 12 point spline. They are size M14 spline tool. I had a set already but it only went up to M12 so had to buy one (easily available)

 

 

Also the piston in the calliper has to be screwed in as well as pushed in because of the handbrake mechanism. It can be done with a bit of bodging with a G-clamp but it's easier with the correct brake calliper tool. 

 

 

:sun:

[ejstubbs]

Thanks for that advice ParaYeti.  I followed 175GDY's helpful suggestion to look on YouTube and the first hit was a very clear guide to replacing the pads and discs.  It didn't look particularly scary or difficult but the specialised tools put me off a bit.  However, it looks like both the spline tool and the piston tool can be had off eBay for reasonable money so maybe it's not out of the question after all.  I don't fancy coughing up more than £300 for something I could do myself in a couple of hours or less for just the cost of the materials and about £20 in tools.

 

I'd still appreciate guidance from TP on the details of the strip down and clean.  Torque numbers would be useful to know as well.

[ejstubbs]

Another question (in a new post because for some reason the forum s/w isn't allowing me to edit my previous post): that YouTube video seems to suggest that you should use new a disc retaining screw and new caliper carrier bolts.  Are these actually necessary?

 

The part numbers for the pads & discs would be handy, too...oh hang on, I think I've found those here:

Pads: 5K0698451 for a set of four

Disc: 1K0615601AA for two

Disc retaining screw: N10648301 - one for each side

Carrier bolt: hmm, still not sure of part number or quantity...

 

This is for the 272mm x 10mm discs, which I believe is correct for my Yeti (2010 Elegance 4x4 140 TDCi).  I'll check with Rainworth Skoda before ordering.

Edited 20 August, 2013 by ejstubbs

[ejstubbs]

That was quick.  Rainworth Skoda have confirmed the part numbers, and advised that the disc retaining screws and caliper carrier bolts do not normally need replacing unless damaged (fairly obviously).

 

I still need to know how many torques to dial in to my wrench when the time comes.  Anyone?

[ParaYeti]

I'll stick my neck out here and say don't worry too much about torque settings. In my experience** it's to prevent people overtightening bolts. I googled torque settings and found this.

 

 

 

It's not usually dependant on application but on size and grade of bolt.

The bolts securing the calliper are M8 thread and probably Grade 8.8, you should get a set of new ones with your pads. These will have pre applied thread lock.

 

The disc bolt....use the same one and tighten hand tight. The wheel bolts secure the disc in place.

 

The carrier bolts, which have the spline cap head, are M12 thread and a probably Grade 10.9 maybe 12.9...again, use the same ones. Usually you use new ones when the bolts will have been stretched (e.g. cylinder head bolts) or under heavy load.

 

If you are not used to jobs like this the splined carrier bolts will seem impossible to undo. They will undo, but go with a crack. Do NOT use a hammer as you will round the bolt off. I managed it with my torque wrench which is about 18" long. Otherwise use a length of pipe on your socket wrench. You will not manage it with a standard length socket wrench.

 

The bit in the video made me laugh where it says only use VW tools on the callipers as others may cause damage. Then he gets out his home made job.

 

In my opinion it's not worth buying Skoda dealer discs and pads. Buy from a reputable motor parts dealer and they'll be half the price. They will probably be made in the same factory.

 

YouTube clip of disc manufacture

 

http://www.youtube.com/watch?v=-J4RlAmBuEo

 

 

**my experience mentioned above is being a CNC machinist.

[ejstubbs]

Thanks for that advice, ParaYeti.

 

If you are not used to jobs like this the splined carrier bolts will seem impossible to undo. They will undo, but go with a crack.

 

Is that due to thread lock - and if so, should thread lock be used when re-installing them?  (It would seem to make sense that you want brake calipers to stay attached to the vehicle...or is that just me?)

 

The parts cost you mentioned is about 75% Rainworth Skoda's eBay prices.  I've looked at Euro Car Parts (ie the lazy online option) and they don't seem to be significantly cheaper for non-VAG parts - certainly not half the price.  There's a balance to be reached between time spent looking for a better deal vs the actual cash that might be saved.  I'd be saving ~£200 doing it myself anyway, so it could be a case of diminishing returns.

 

Come to think, though, should I even be contemplating DIY just now?  The car will be due another service before the warranty expires so if I mention it then, would it be a warranty job, or would they class it as "normal wear and tear"?  (And if I do it within the warranty period, could that affect the warranty - or even an after-market warranty should I opt for one?)