Honking Howling Brakes

[Ricky7774]

My low mileage (57K) 2006 X Type estate (2.5 petrol) makes a very loud noise at low speed and light brake pressure. Seems to be on the left and probably the rear. It is not the squeeling you get when the pads are down to the metal and there's plenty still on the pads. The discs look fine too with no scoring. The sound it makes is a really loud honking or howling and almost sounds musical. Brake operation seems unaffected. Car pulls up straight. No vibration either with or without braking. Given the sound is a bit like a trumpet I've theorised that given the rear discs are ventilated, if there is a crack it might be causing the honking sound thru vibration magnified by the vents and coming out as a loud honking! Under light braking this might allow vibration of the disc enough to generate the sound whereas harder braking does not allow the vibration. I haven't taken off the alloy wheel yet to put a dial gauge on the disc to see if there is any run out or warping as I thought I'd see if there is anyone out there who's experience a similar problem (and resolved it). A mechanic in a Jaguar specialist said I needed a new servo, (which frankly seemed complete BS particularly at the £600 Jaguar price for a new one and the fact that the brakes were operating normally apart from the noise). It also does not appear on start up when cold but only comes on once the brakes have warmed up.

Any ideas??

[cosmicma]

couple of things to look at

make sure the slide pins are not seized

put a little smear of copper grease on the back of the pads 

check the pistons for corrosion that can cause brake binding 

 

 

[Ricky7774]

Thanks for the tip. I've ordered a new set of slider pins/grease for the rear calipers so when we get a few days of dry weather again, I'll have some new ones to install if that is the problem. I'll update you after I've had a proper look.

[Ricky7774]

When I removed the rear left road wheel, which is where I suspected the noise was coming from, I checked the slider pins for sticking and the caliper piston to make sure it wasn't seized. They were okay. However, once I cleaned off the disc with meths it became clear that there were a number of very fine cracks running from the centre to the outside of the disc. You could not feel them even when running a finger nail across them. You can see some of the cracks in the photo but what you cannot see is that between the two cracks that run parallel, the surface of the disc is a slightly different colour to the rest of the disc - a faint yellowy gold - which may suggest the metal put in the cast was contaminated. There were probably about 10 cracks in all but only a couple were obvious on the other side of the disc.  Anyway I replaced both rear discs and pads. There were a couple of cracks on the right rear disc as well, but not as many as on the left. The howling has now stopped, so job done. Not sure if this sort of disc cracking is something other owners have had?

[Steve xf owner]

Ricky7774 you have just saved me a lot of time searching for answers to my problem. I have a 2.2d xf premium 55000 on the clock and the breaks have just started to make a noise like you have described. I have booked in with my local garage to have all the breaks done and will be having bremo dics and pads fitted. Glade I found your post and thanks for the info.

Steve xf 

[Ricky7774]

To be honest, I'm still a bit surprised that changing the discs/pads seems to have sorted the problem as the cracks were so fine I still do not see how they caused the honking. It may be that I did something else when refitting the new discs that cured the noise, although I did not find anything obviously wrong and everything was put back the same as it was originally. Of course, given that the problem only manifested itself once the car had been driven 15 minutes or more, it may be that once heated up the fractures became more pronounced and that's what caused the noise.

Bear in mind that your car is a different model entirely and even though you believe it is making the same sound as I have described, it could be down to a different cause.

In any event I'd like to hear if new discs/pads cure your fault too.

[Steve xf owner]

Will keep you posted about this. Should put a post up Wednesday and hope it's good news.

 

[Ricky7774]

Sorry but its just occurred to me that the backs of the old pads showed no sign of having had any copperslip/copper grease on them when removed and the new ones were installed with a smear of copper grease on the backs of the pads (obviously NOT the friction surface), so it is always possible that it was the absence of copperslip on the old pads that caused the noise and I didn't need to buy pads and discs! However, I lose patience having to do a job over and again so as the rear pads/discs were c£80, I went for the replacement option.

[cosmicma]

either way if the disks had fractures they would have to replaced anyway and that usually means new pads to go with the new disks 

 

[Steve xf owner]

Hi all, well got the new discs and pads done yesterday and my god what a difference. Stops spot on and no howling or squeaking thank god. Looked at the old discs and found to have the same issues as yours. Fine cracks in them and also no copper grease anywhere. Pads were in good condition but changed them any way. Was supposed to have this done tomoz but garage got me in yesterday so all good. Have changed to a full set of bremo discs and pads so happy with the car now. I also had a 4 wheel alignment done as well and that has made a difference to the way the car drives as well. Next job re map but that's a few months of yet.

Steve xf