Did you make sure the caliper pins are sliding freely?

 

UPDATE: Now suddenly I'm getting a loud chirping noise from the wheels when coasting or under subtle acceleration. This is in ADDITION to the horrible brake squeal. I'm at my wits' end with this issue.

 

XJ8JR,
So how did it work out? Don't leave us hanging, we got an investment here.

 

Still no joy. I tried BG Stop Squeal, and it disappeared for a few days, but now its back. I really thought I had it. I'm all out of ideas, besides wasting money on different types of pads.

EDIT: I did at least get rid of the constant chirping upon slow acceleration. It seems one of the anti-rattle clips had come loose. So now I'm back to just having the horrible squeal when braking.

 

Let's look at the reason brakes squeal. High frequency oscillations between the pad and the caliper piston is by far over 90% of all brake noise. How does this happen? The pads have to have some movement laterally, so that they don't bind in the holder, as heating and cooling causes metal to expand and contract. The pad under pressure by the piston grabs the disk and moves in one direction and releases by the force of the rotor movement and the inability of the to pad to stay stuck because it is held by the caliper holder. It happens on a very small scale in very high frequency. This is why manufacturers use material between the pad and the caliper piston to dampen this movement. It's why your efforts provide relief for a brief time.

The caliper itself play a vital role in the retraction of the piston to remove the pressure against the pad pressing against the disk. After years of service, the square cut seal inside the caliper becomes so stretched at the molecular level by heat and pressure that it stretches the square cut seal so that it no longer has the ability to pull the piston rearwards back into the caliper, and the pads stay in constant pressure against the rotor, creating more heat, and doing more damage. Brake squeal then not only happens when applied, but constantly because the brakes are always applied, even if you foot is off the pedal. It can cause premature brake pad wear, warped rotors, and brake squeal.

All of that was said to say this, rebuild your calipers. Seal kits are less than $10. I paid $7 each at RockAuto. Start there.

 

Box, thanks very much for your insight. I did replace the calipers with a younger pair, but still used nonetheless. I still have my original pair, so I guess I could try rebuilding them and see if that has any effect.

You mention the brakes squealing constantly due to constant pressure. I mentioned in my last post above that I had eliminated the constant squeal, so I don't think I'm getting constant pressure. I'm back to only getting the squeal when braking.

But I will try the caliper rebuild and report back. Thanks again.

 

Just ordered the rebuild kits from Rock Auto. $11.31 shipped. I love cheap repair options.

 

Another thought...could this somehow be indicative of a larger problem with the brake system, or is it most likely confined to the just caliper area?

Or could the wheel bearings somehow be connected?

 

Depending on pad, speed and the condition of the rotor, you may not always heal squeal when driving, however the residual pressure of the piston not being retracted is enough to create enough heat, that you get what I was talking about before.

I know that I've said this before, but the pad should have a coated shim between the metal backing plate and the piston as well as the outside pad against the caliper stops. I don't know if the pads you are using do, but if not, that will certainly be a source of noise as well.

X350's use Type III bearings on the front, and the hub itself is the outer race. You can check the bearing by raising the vehicle and checking for lateral movement or noise when spinning.

 

I got the caliper rebuild kit, so I'll be doing that tonight, along with a fluid flush. I'm not getting my hopes up. If this doesn't work, what's my next step?

BTW, my current pads do indeed have the shims, plus a coating of CRC disc brake quiet.

 

Please keep us posted...

 

Will do.

This is almost as bad as my epic battle against a clunking front suspension 2 years ago. It took A LOT of trial and error before I figured that one out.

 

XJ8JR , good luck with the calipers , there not leaking , there not sticking on and they only squeal when you brake .

I don't think so Box .

Cheers ,

 

Box may be on to something. If the following have been eliminated- pads,calipers,rotors, the bearings may be moving and cause the vibration/movement. Just a thought.
I remember on older Range Rovers, the only pad that did not squeal like a pig were the genuine pads and rotors from Land Rover. But that was not for sure, as there were 2 supliers to Land Rover, Mintex and Ferodo. Only the Ferodo pads worked, the Mintex squealed like a pig being beaten with a stick. It used to drive me crazy!

 

Hello Mark , your right about MINTEX pads , they still squeal today .

Mark , the squeal was there with the original calipers
the squeal was there with the second set of calipers
the squeal will be there after the o/haul of the calipers

A loose or worn wheel bearing won't cause a squeal when the brakes are applied , rather they may squeal with the foot off the brake or when cornering .

Same with Box's theory , if the caliper piston is not releasing fully , the squeal will be heard with your foot off the brakes , not on .

XJ8JR has greased , cleaned , and lubricated those calipers more than he needed to .

cheers ,

 

Your right, STOP with the calipers. At this point it has become hard to track what XJ8JR has done with replacement, and with which manufacturers. Too many posts. A simple list of repairs in order would help, with the brand. It would be much easier to disguard the the non issues. I think its time to stop throwing parts at the car, and diagnose it for good. Poor XJ8JR has been at this way too long and spent way too much $ for a simple brake issue. This should be a quick fix with all of us looking at the repair history. Only a dealer would throw parts at it like this, and we'er better than that!
"Simple deduction Watson, simple deduction"

 

Thanks for the support, guys. I did complete the caliper rebuild last night, however I have not had a chance to test it because one of the lug stud bolts on my right rear tire decided to snap off after the bleeding procedure. I'm not a happy man right now.

Here is a list of things done in order:
- scuffed up old front pads and rotors...quiet for a few minutes
- applied CRC disc brake quiet to all pads on all wheels...quiet for a few minutes
- installed new front rotors and pads...quiet for a few days
- cleaned and lubed all front caliper components...quiet for a few minutes
- applied extra rubberized shims to backs of new front pads...quiet for a few minutes
- installed used set of front calipers...quiet for a few minutes
- coated front pads with BG Stop Squeal...quiet for 2 days
- rebuilt front calipers and did a complete flush of fluid...the jury is still out on this one.

I don't think I mentioned that during all this time, I've also been getting heavy "creep groan" when coming to a stop.

 

Did you ever try the Jaguar brake caliper grease that is specifically for this issue? I had the problem on my car, bought the grease and applied per the TSB, has been gone for almost a year now. Grease goes on the back of pads, and where the pads slide (any metal-metal contact point).

 

I didn't there was a specific TSB for creep groan. I've applied many types of grease and solutions to the backs of the pads, to no avail. Is the Jaguar grease something different, I wonder?

Anyways, I just returned from a trip to Oreillys to get new wheel stud. During the trip, I noticed two interesting things:

Immediately, there was still a light squealing from the passenger side wheel. Nothing from the driver's side. It took a good 20 minutes for the driver's side to start squealing.

I also noticed something new...if I move forward very slowly with the brakes lightly applied, I hear a single cyclical squeak with each turn of the tire. Not sure if the passenger side does that too.

As I suspected, the caliper rebuild and fluid flush did nothing. At the very least, we know the calipers are 100% not the cause.

What's next?

 

" applied extra rubberized shims to backs of new front pads "

If that's the only shim you have it's in the wrong place and will never work as intended .

" I don't think I mentioned that during all this time, I've also been getting heavy "creep groan" when coming to a stop. "

no you didn't , may be just as well , who knows what you would have been told to do .

XJ8JR , get rid of what ever crappy brake pads you have fitted , most pads that are noisy don't have the proper steel shims supplied , I would suggest you buy AKEBONO pads , they cost a bit more but do have the steel shims fitted .

If your pads haven't glazed the disc rotors they'll be OK , if not have them skimmed or deglaze the best you can .

BTW , that rubberized shim is designed fit in between the disc pad and the steel shim .

Good luck with that .

Sid