Right rear under car clanging noise Topic is solved

[leapdragon]

Hi all,


2007 XC70, running great, in overall good mechanical condition. We seem to have developed a loudish clanging noise that's intermittent. Clanging noise factoids:

- Relatively loud
- Not "thuddish" but definite "clang" like hitting a wrench on a thin steel pipe
- Sometimes one or two clangs, sometimes rapid fire (4-5 per second for 10-12 seconds regularly at a steady beat)
- Not tied to rotation of wheels
- Not tied to rotation of engine
- Most likely to be heard at very, very low speeds (<5mph), esp. if making a wide left turn
- Never in evidence at high (>40mph) speeds
- More likely to be heard when car is cold
- Sound seems to be coming from somewhere under car, just at or behind back seat, slightly off to the right

I've been underneath and I'm damned if I can see anything out of place or get anything to make any noise by jiggle-poking around. Everything seems thight.

- Brake pads, calipers, and rotors are newish (<10k miles), have checked all and they're nice and tight
- Lugs are nice and tight
- Newish Meyle sway bar links front and back (<10k miles)
- Axles seem solid, CV joints intact
- Exhaust seems solid, hangers intact
- Rotor/wheel guard plates not bent
- Fuel filter tightly clamped into place

Based on the sound, I was sure at first something was hitting the rotor/wheel guard plates or the exhaust somewhere, it's not the sound you'd hear if a something was banging on a rotor or a suspension part, the clang sound has a lot of "ping" or "ring" to it. But I can't find any problems.

This has me flummoxed. Has anyone had a noise sort of like this before?

[BlackBart]

I think that’s gotta be exhaust. A clang sound, metal on metal, and you said it changes with temp.

[scot850]

Check if the muffler mount forward of the rear muffler has not broken. They rot and break off. Volvo sells a repair bracket for that.

Neil.

[leapdragon]

Thanks guys, I'll get under there again today and go over the exhaust system and mounts with a fine-toothed comb.

[motormikeyman]

Did you check the e-brake shoes?

[darylrobert]

I notice you fitted Meyle end links. when i fitted my Meyle end links i noticed the ball joint was really tight, the effect of this is noises. google "meyle hd end links clunking"

[chrism]

Your description kinda sounds to me like when the honeycomb inside our catalytic converter came loose. It made a rather “tinny” repetitive noise. I believe the exhaust pulsations caused the honeycomb to rattle back and forth inside the cat chamber.

[leapdragon]

Hi again all,


So I got under there and looked around. There was play in the exhaust and indeed one of the hangers had broken off at the weld, but no matter how far I pushed it in any direction I couldn't make it hit anything. So I got an exhaust fix bracket and bolted it on and took it for a drive.

Noise is def. coming from something else.

My working theory right now is prop shaft every now and then is pinging when a bearing gets hung up. There is some play in the prop shaft and more to the point when I rotate it that ~0.5cm in either direction I do get a little tiny bit of ping/clang, though very quiet (presumably when being turned at speed if it hangs up it will make a louder noise?) It does feel a bit... off.. when I play with it.

Does that sound reasonable or silly?

And more to the point, I can source one for not too much so there's a part of me that says may as well give it a go but I can't find any directions for what needs to come off to drop it. Bunch of YouTube videos on unbolting the ends, which is fine, can follow, but presumably the exhaust has to be dropped at the very least.

I know there's a bit of a flex pipe at the front, is it enough to undo all the hangers and just let the exhaust sag to the ground, or is there more to it than that?

Anyone have a write-up/images/video on replacing a prop shaft on a P2 XC70?

[leapdragon]

Just found this:

I'm pretty sure it's something in the drive shaft assembly now—my sound has more "ping" to it and is somewhat louder, but apart from that, the sound patterns (or sort-of-patterns) are very similar.

So now the questions above become relevant. Just drop the exhaust with the car slightly elevated and then remove the whole thing and install a replacement? Any gotchas?

[- Pete -]

Sounds like your zeroing in on it.

Where exactly are you detecting this play?

There is a hanger/carrier bearing about halfway between the ends of the driveshaft. It has rubber isolation surrounding it & it is normal to be able to move the driveshaft (some) up, down and side to side with the flex the rubber allows. When the carrier bearing goes it is very evident & easy to diagnose.

If you are near the AOC/Haldex/rear final drive you may have some rotational “give”, but with the ignition off (Haldex/AOC not powered) this “should” be coming from the bevel gear/transfer case. There is a normal amount of “slop” at this juncture as well. It should be very minimal, but is easy to feel with your hand rotating the output side of the bevel gear or turning the driveshaft by hand.

When you look at the rearmost end of the driveshaft, is there wetness or grease slung around?

While your back there, try to get as good a glimpse of the final drive/rear diff input (1) and outputs (2) so see if evidence of gear oil/dirt accumulation is present.

If the car is in the air, check the rear wheel bearings for any play as well. Usually it begins as an intermittent click that develops into a groaning sound.

Lastly, the CV axles can make pinging/clicking noises if the outboard bolt loosens some. Typically this is in the front vs the rear.
I’d take a close look at the rear CV’s as well. The inner joint is pretty much impossible to assess with any accuracy, but you can tell if the boot is torn & has allowed the grease to escape.