AU11 suspension knock?

[robp]

Had this car fron new . When vehicle is well warmed up and going slow in traffic (up to 30KM per hour) there is a horrid more or less continual knock from the rear. I have checked and renewed brake pads and visually the suspension seems fine. This has gone on for years, but as it does not happen all the time I just put up with it. Can someone please tell me what the likely cause is please?

[hagarone]

It sounds like your exhaust pipe is hitting some where.Grab the end of the pipe and give it a shake.

[robp]

Definitely not the exhaust pipe.

[hagarone]

IRS upper shock mounts.

[hagarone]

Bounce the back of the car up and down, if it's soft it's a good chance it's your IRS upper shock mount.

[robp]

The rear end is a solid as a rock.
No indication it is the shocks

[BHDOGS]

wheel bearings?

[robp]

surely wheel bearings would not knock? and it has gone on for years

[mik]

how many k`s have you done?
"visually it looks fine"
does that mean you`ve had it up on a hoist or stands and done some pushing and pulling to check bushes, ball joints, tie rod ends, wheel bearings, universal joints,sway bar,etc,etc ?

[robp]

Done 80000ks. Have done pushing and pulling etc many times - and as well we have to get a Warrant Of Fitness every 6 months in NZ where they check virtually all of those things very thoroughly.
It is a real mystery, and will only happen after driving for half an hour or so and at low speed. Have had FORD check it out, but of course would not do it when they test drived.

[peterljohnson55]

Have you checked to see if your spare and jack are secure?

[Evgeni]

Sounds like handbrake knock. Just pull up very gently on the handbrake when it happens and see if this gets rid of it. If it is, you just need to adjust the handbrake shoes. Whilst your there, it doesn't hurt to put some grease or anti seize on the ends of the brake pads where it meets the caliper to stop the dreaded low speed brake squeal that often occurs after a handbrake adjustment.

[peterljohnson55]

If you have a loose baffle in your muffler, then it may well rattle until it gets really hot and/or until a strong flow of exhaust is pushed through it.

[robp]

It is really good that so many people have offered suggestions.
The entire exhaust system was replaced last year (and it is a knock, not a rattle)
It is definitely not the spare or jack.
I have not tried the handbrake and will do so (although I replaced the brake pads about 3 years ago as I hoped that might solve the problem(not!)

[peterljohnson55]

Is it possible to disable the handbrake without causing any mechanical grief or safety problems? Then give it a rip and see.

[rag top]

Check your rear caliper sliders. Was the source of my hard to find rear of vehicle knock. took 4 different workshops to find it.

[rowan194]

Originally Posted by robp

I have not tried the handbrake and will do so (although I replaced the brake pads about 3 years ago as I hoped that might solve the problem(not!)

Doesn't the AU use a separate shoe for the handbrake?

Do you get shuddering when braking hard? Could it be warped rotors?

[robbyj]

wheel bearings can knock. I had a knock in my front left.

Wheels are on properly?

[mik]

80,000 k`s is very low k`s for an au, the suspension very robust on these things, wheel bearings in my experience don`t even start to get noisey untill after 100,000 k`s, did my tailshaft uni`s at about 160,000/180,000 iirc for the very slightest of movement, do you have any mods RobP??

[robp]

The Fairmont was purchased in 2011 - I am an older guy, now retired hence the low kms.
No mods to vehicle and no shudders under hard braking. The difficulty about this problem is the intermittent nature. I can drive around town for weeks and it will not happen. However go/return on a long trip and slow down to crawling pace in heavy traffic back in the city and away it goes.I will check caliper slidings and handbrake.

[mik]

that`s rather tricky RobP, the only think i can think of is something has been missed, your gonna want to slap me , but all i can suggest is to double check over all of your work/mechanics work, ..........mechanics are not infallible and can miss things, let us know how you go, good luck.