Hi folks.

OK so it's christmas eve and you've all probably got lots more important stuff to do, but I need some help.

Today my XF has started making a thumping noise at low speed.
Comes from the rear of the car and is speed (wheel / tranny speed - not engine speed) dependant. I cannot hear it above 30 mph but that may because the tyre noise starts to drown it out, and you can still feel it a little up to about 40 mph.

Have checked the tyre pressures and all are at 29psi which I'm told is fine. There have been no bumps or bashes (unless the wife has had one which she hasn't mentioned, but there are no visibles).

I did get out of shape the other night on a tight bend but this was at less than 30mph and it only slid a little at the rear.

Anyone got any idea. I go on holiday on Wed 28th (400mile drive) so would appreciate any advice before then.

Happy Christmas to you all.
Steven

 

I had the same noise on mine and they tightened up something in the suspension tho they never told me exactly what they fixed and the noise disappeared.

However on your psi. My car i have 32 front and 33 in the rears and it just perfect. try that and see.

 

Depending on the noise, could actually be your gas tank imploding as some others have experienced. Not to scare you, But do a search on the site... Seems to have happened to a few people... at low speed a low thumping noise for a short period of time, then goes away. Worth a look...

 

I had a loose sway bar on mine. Fixed it while I was waiting.....I LOVE MY CAR...
MERRY XMAS AND I HOPE IT IS SOMETHING SIMPLE...

 

Scottish FX:
Low speed knock is generally caused by worn universal joints. A worn pinion shaft bore will also cause a low speed knock but your car is too new for the latter. Check for a faulty or damaged U joint.
Merry Xmas

 

Put the car on a lift with the transmission in neutral and turn the driveshaft by hand. If it's a bad universal joint, you should be able to feel which one it is.

 

Thanks all. I'll be taking it into the shop at some point before Wednesday. I'll let you know what they say.

Steven

 

Just had the word back from the garage. Seems the Anti-Roll bar at the back nearside was loose. They've torqued it up and everything is fine now (according to them - I've not picked it up yet, will let you know if it's not).


Thanks to all of you who posted ideas.
B/r
Steve

 

Thanks for posting back... I'll try and remember that when I bring mine in for its first service. I'll ask them to check the sway bars.

Cheers!

 

Guess what?

Half a mile from the garage, the noise is back but by the time I turn around and go back to them, they've all gone home!!

Car going back in Tuesday 11th. Will reserve my reply until I'VE done the road test this time!!

 

Scottish XF,

Ring Chrysler Assistance (CA) 0800 777146. I have nothing but praise for them after our dealer in Farnham forgot to put back on O-Ring on our PT Cruisers cooling system.

CA sent a mechanic to the house at 07:00 and he identified the problem as an air-lock and he bled and pressurised the system. Since this didn't cure the problem I called CA again a couple of days later. CA took my details and within an hour our car was collect from my work place and I had a similar-sized hire car delivered. Chrysler Weybridge found the fault, fixed it and delivered the car back over the weekend. They had cleaned it inside and out.

 

Thanks for the above! I'll give the dealer the chance of repairing it tomorrow as I've already planned for that. If it's not fixed I'll definitely be taking your advice.

 

Quick update:

The day I was taking the car to the dealer, the noise stopped!!! Can you belive that?! Hasn't happened since either - which I am graetful for, but I would have liked to know what was causing it in case it is something that is going to fail later on.

I'll draw a line under this for now, but let you know if anything else happens.

Again, thanks for all your input

Steve

 

I just noticed a noise similar to this a couple of days ago...and I wasn't sure if it had something to do with my rims. But after reading this I guess I'll see if I can take her in and have her looked it soon.

 

As mentioned in an earlier post I made, (This may sound weird) but look at the gas tank. or do a search on this site for "gas tank implosion"... I think it was on this site or one of the MB SLK sites...

I vaguely recall an issue with the gas tank being sucked in by negative pressure because the vent was clogged or not attached properly. The sounf you are describing is exactly what I read...

The only way you can prove this to yourself is to run the car down to very low fuel level and then fill it. If the amount of gas it takes to fill your car is much less than the rated fuel capacity in the tank, you can assume the tank has been sucked-in and kinda crushed by negative pressure, much like sucking the air out of a plastic water bottle and then refilling it...

Worth a check, unless the dealer is willing to pull the under-cover of the tank and do a visual inspection.

 

I am very interested in the tank imploding also. What ever happened with the member who had the post about it? The last I heard is that it was fixed but not what caused it. Although I can't see how this would make a thumping noise, as the tank is behind the rear end.

 

Do a search on this forum "LOUD BANG" and I think you'll come-up with more info...

Not to say your problem has anything to do with the gas tank, but it could...

 

HDDP:
I did look at "LOUD BANG" prior to the reply however it says that they changed the tank and "cat converter" but it doesn't say what caused it. Sure would like to know!

 

My situation was really weird...I would hear a "popping" noise occasionally from the rear area, but couldn't develop a pattern. Sometimes it would "pop" while sitting absolutely still. I kept looking and one day discovered that the interior trim in the hatch area looked loose around one edge. Upon investigation, the "plugs" that pop into the metal holding the trim had come loose. As I tried to "pop" them back in place, a few more came loose! The dealer confirmed that the parts had failed and ordered more from Germany. They were able to pop the trim back in place somewhat, but I'm still waiting on the parts to arrive. It's no big deal...just weird.

Fritz

 

The noise on my car was a definite "thump" as oppossed to a pop or bang, and was wheel rotation related (certainly sounded it).

HDDP: I checked what you suggested the first time you posted - sorry, forgot to update on that. Fuel tank capacity is normal though. Thanks for your advice though.

Car is still running fine under all driving styles and even on super smooth roads, the noise is no longer there. Weird!

B/r
Steven