Hi all,

Wanted to see if folks had any thoughts as to what this noise could be:
This is a longer video but my hope was that it could be valuable not just in determining what the issue is but also for the future if people are trying to chase down various noises (a troubleshooting sound library??). I took the wheel off today to do the check for bad bearings but didn't get any play; the noises seems to be getting worse over time so have been limiting my drives. It doesn't become audible until after I have been driving for a bit.

I currently have a coolant leak, source unknown. Adding some pictures that might help as well as some additional "footage". Primary issue is I don't have the full space to put the car up but was able to get under it today and poke around. It appears to be coming down around the passenger side of the engine, and potentially leaking where it enters radiator. The noise makes me wonder if the leak is on the top of the engine somewhere and this sound is wet belts; I do get a burnt smell and only once did I actually find any liquid that managed to drip off of the vehicle.


I have a quote for the following services too that I will probably be getting done in next couple of months, not sure if anybody has stamped out this sound with any of the following repairs:
Replace rotors/pads
Replace Rear sway bar links and bushings
Replace rear main seal, exhaust studs/nuts/washer
Replace Front Shocks, Isolators, Upper Shock Mounts
Replace Rear Shocks & Isolators

I have had most major engine maintenance completed however am having a hard time with my shop (Top Line in VA) pulling up the invoice for work completed from my file. If they can't get it together (main reason because they have 12k warranty on all their work), I'll probably end up taking this elsewhere for a diagnosis, but I have to imagine this is something they have already worked on. The sound is wretched enough that I wanted to get a sense of if it should be towed to a shop or if this was a familiar sound with a familiar resolution.


Thanks in advance for any input.

 

You might remove the tire to the back of the car and see if the sound moves with it.

 

Isn't that where the coolant pump for the heater is located? it might be related to both the leak & the noise.

 

When I had the tire off to get a better look underneath, I did notice that the rotor had a slight scraping noise to it once every full rotation. It was very slight but I guess it could escalate to the level in the video since it's a sound that seems correlated to rotating motion.

 

I have been reading about the intercooler pump - do you think/know if that would fluctuate with speed or be evident when not accelerating? I don't get any sound at idle.

Another thought is could this be a subframe mount (oil-filled) - I might have coolant and mount issues.

 

Hi Mr_Dude,

I couldn't get the video with the sound to play, but a very common cause of a scraping sound as you describe in the above post is a slightly bent brake rotor splash shield. The shields are just stamped sheetmetal, so it's very easy to accidentally bend the edge of one while, for example, replacing the brake pads. Since rotors often become slightly out-of-round or out-of-plane, one spot may contact the splash shield on each wheel rotation, making a sound that increases in frequency with vehicle speed. You can usually easily see if the splash shield is too close to the rotor in one area by removing the wheel and viewing the gap between the rotor and shield from several angles, including lying on the ground to view the lower edges.

Cheers,

Don

 

I'd have to go with Don's theory. I had a van with a intermittent scraping sound. I think what happened was that the heat from the brakes and such from driving caused the splash shield to warp and move just enough to make contact with the rotor. Thus, the sound came and went. Incredibly annoying because I had to commute and hour down and back each day. I got under there and bent the splash shield back with prejudice.

 

I remember the first time I heard such a scraping sound from the Porshe. I was alarmed, thinking
I might have ruined a rotor. It turned out that the brake pads had a piece of sacrificial metal that
is meant to alert the driver when it is time to change the pads. When the pad wears down to a
certain point the metal scrapes the pad as an alert. No damage was done.

 

Thanks, Don. Going to pop the wheel off and revisit. I had gotten so used to the quiet cruising that the new sound is quite jarring; have rotors/pads on my to-do list eventually so this gives me an opportunity to investigate the area further.

 

This is absolutely driven by annoyance. When I'm lower speeds with windows down, I could be driving through a Red Hot Chili Pepper's concert and I would probably still only hear the squeal. It's entirely unbecoming of this car; high speeds I think I can hear it but it's not a "LOOK AT THIS OLD CAR" type of scenario like it is in low speed situations.

 

So...spinning the wheel with it jacked up gives you no indication of where it's coming from?

 

I get the sense it is in the brake but nothing really stood out, the sound is pretty uniform:


Added some photos too, it looks like the bottom part of the shield could be pushed in but it looks like that is by design. Next thought is to pull apart brake - I really didn't think low brake pads made noise all the time which is why I'm a bit stumped on this but it's been a while since I have had an older car.

 

Today I tried to push out the bottom portion of the rotor shield to try and give it some clearance. Will get it on the road and see if that makes any impact.

 

Is it possible that a brake wear indicator/squealer would make noise constantly? I've never worn brakes low on any cars I've owned so I don't have any direct experience hearing the indicators.

 

When a pad wear indicator begins to come into contact with the rotor, it produces a strident squeal, squeak, scrape or whistle sound.

But the X308 uses electrical pad wear sensors, so the brake pads do not have the bent-metal pad wear indicators. So unless you have some unusual aftermarket pads, I don't think this is your problem.

One other possibility is that a caliper guide pin is corroded or caked with brake dust and is not allowing the caliper to release properly, causing a brake pad to contact the rotor intermittently.

Cheers,

Don

 

Going to give it a quick wash in brake cleaner and then work from there.

 

That is unlikely to make any difference.

If the problem is a corroded or dust-caked caliiper guide pin, the only real solution is to remove the guide pins, thoroughly clean them (I use a motorized wire wheel), clean the mounting bracket bores where the guide pins fit (I use the largest drill bit that will fit and a wire-bristle bottle brush). Clean the caliper mounting bracket rails on which the brake pads ride and the ears of the brake pads (I use a small steel-bristle brush). Then, flush all the parts with brake cleaner and allow them to dry or dry them with compressed air.

Apply a light coat of high temperature disc brake caliper grease to the ears of the pads where they contact the mounting bracket rails. If you haven't already compressed the caliper piston, do that now, slowly. I then apply a light coat of copper-based anti-seize compound to the face of the caliper piston and the contact surfaces of the caliper "fingers" that contact the back of the outer brake pad. The copper dust in the anti-seize compound helps reduce brake squeal and is long-lasting. Then apply a light coat of the caliper grease to the guide pins and reinstall them.

You'll get a lot of differing opinions on these procedures and products, but the above method works for me to help brakes work quietly without pad drag.

One other thought: if your rotors are well-worn and have a deep ridge around their perimeters, the ridge can sometimes rub on the brake pad in a way that produces noise.

Cheers,

Don

 

Update - need a new radiator. Liquid is getting on belts which is making the noise. Didn't really explore this route as I had a shop "replace" my radiator back in April 2022. Apparently not...now the fun begins.

 

Hmmmm.....

 

Must be a pretty bad leak for it to spray on the belts. My hope is that you have found the issue,
and that a new radiator fixes it.