how good are you at diagnosing a problem??

[Kryton]

ok, this isnt a "I need help....whats the problem" type thread, the problem has been found and solved.
this is a thread to see what you believe the problem to be, to see if you can solve a problem with the given info, to see if you would have had to pay someone to fix your car or if you would have wound up dead.
the answer will be given at some point in this thread.

the Car:
03 BA Fairmont.
150000
serviced, running smooth.
new front tyres last week.
brake pads need doing in around 10000km according to Ford.
small amount of BA brake shudder.
no other faults........till 2 days ago.

the Facts:

2 days ago: knocking sound occasionally occuring very faintly taking a left hand bend.
cant replicate, cant distinguish front or rear of car.

Yesterday: knocking sound becoming more evident more often. also getting louder. seems to be coming from the rear of the car, yet occasionally seems like the front. cant feel it in the steering wheel.
knocking sound is a "knock....knock.....knock...knock...." not a swoosh sound.

today: on the highway to work, 30km @ 100kmh. ok, now its really bad. definately from the rear of the car. sounds to me like its from the drivers rear. this is bad, it does it in a straight line (most times), it does it on a left hand bend, it sometimes (but not often) does it on a right hand bend. if i slightly swerve the car so the weight is on the right side it is really bad and really loud.
it also does it when i am braking. if i accelerate, the knocking stops. this is the case at any speed. as soon as i get off the accelerator, the knocking is back and its bad.
this isnt the greatest thing to hear doing 100kmh either. i have visions of my wheels falling off and crashing.

ok, these are the ideas i have had today:
a CVD: possible, dont really know what they sound like when they are stuffed.
warped rotor and very little pad left allowing the CALIPER to be hit by the rotor.
possible but it would have to be really warped. i was expecting to have boiled brake fluid and a car fire at work. car didnt catch fire. warped rotor and very worn pads arent really making 100% sense to me. still possible though.
a blown shock/shock rubber. maybe, but not likely. the roads are bad, but they arent that bad enough to be that rough. hit a few potholes to eliminate this and ive eliminated the shocks.

other than that, it had me stuffed. i knew it wasnt the diff, it didnt do it all the time but its did get worse and more consistant over a 2 day period.
this is a sound, that if you hear in your car, you know its serious, you know you better get straight on to it, you know this could end up killing you.
the best way i can describe this sound would be to go get something made of heavy solid steel and hit it with a hammer.....thats the kind of sound it sounded like in the car.

what i have described is what I heard, what i believed, what i tested while i were driving. there is a very good reason i havent just got up and said what the problem was, everyone should know exactly what the problem is if they hear it in their car. it WILL save your life, ignore it and you will find yourself wishing you had have had a shot at diagnosing this thread.

take the time, have a good think about it and see what you come up with.

[Yellow_Festiva]

Loose wheel nuts causing play between the wheel and the rotor?

[gtfpv]

engine/or transmission mount.

[Interceptor]

i'm with yellow festiva

[peterban]

Uni joint would be my guess or something to do with aux drive shafts that connect from diff to wheel

[King Nothing]

Given you mention new front tyres, id take a guess it was a problem with the rear tyres. Tread came loose on the inside edge and was hitting against inside of wheel arch/suspension? Accellerating *maybe* pulled it back into line?

The other thing it might be is the rear sway bar came loose. Mine did this a few months back in the BA. Was a faint knocking sound, was worse when turning but I had a look under and saw the nut was just hanging onto the thread and the bar was dancing along the bolt. Maybe the nut had come off on yours, and the sway bar was bouncing on the road and hitting the bottom of the car?

[GK351]

uni joints would be what i would look at first.

[beepbeep]

im with peterban there, commodore done that and it made a racket inside the car. but still guessing that it would be the uni joint as it doesnt have thesame load pre rolling as under acceleration.

[Powdered Toast Man]

I'm also with yellow festiva, I'm going loose or missing wheel nuts and the wheel moving/wobbling causing the knocking sound.

[King Nothing]

cmon davway, give us a hint? I have to go to bed soon and if I crash tomorrow due to not knowing what some crazy knocking sound is im going to blame you! :

[Kryton]

Originally Posted by King Nothing

cmon davway, give us a hint? I have to go to bed soon and if I crash tomorrow due to not knowing what some crazy knocking sound is im going to blame you! :

hahahahaha nice one.
ive explained what i heard.
the knocking sound sounded like a 'clunk' instead of the 'ting' sound you might find if you hit a hammer against something steel.
that isnt a hint either, thats just better explaining the sound from inside the car.

some pretty impressive answers so far. got some things up i would never have even considered or thought about, yet they are all very plausible.
keep em commin.

[jed67]

your cat is stuck in your wheel????????

[dave351cid]

i haven`t really studied how the independant rear suspension works but i guess it would need to have ball joints.

i would be checking these out first, after checking the wheel nuts of course.

maybe a loose brake caliper too.

[AUIII]

I am really interested in what this noise is, my AU has a knocking noise that comes from the front and disappears when you accelerate, mine only comes on after a long drive then disappears the next morning , I have had it to my mechanics a couple of times to try fix the problem but he has never been able to locate it.

[The Robot Devil]

You ran over Neil Crompton yet he's still banging on about the Watt's linkage?

Uni joint? I had one of these drop out (from the front) in a pos Escort once, wasn't pleasant & certainly made a lot of noise...

[Racecraft]

diff craddle bush or CV for sure

[Kryton]

Originally Posted by The Robot Devil

You ran over Neil Crompton yet he's still banging on about the Watt's linkage?

now THAT is funny!

[superpursuit83]

Centre hanger bearing on driveshaft (If a sedan has one?)

[OJ_Pursuit]

Sounds like a loose or damaged wheel bearing, or maybe a worn ball joint or bush in one of the suspenion arms close to the wheel.
Its really hard to guess though, id be under there having a look instead of driving it at speed.

[t2te50]

Au's and Ba's actually wear out lower front end ball joints relatively quickly AU111 with the noise being more prominent first thing in the morning when car is cold.
The noise your talking about DAVAWAY I think is coming from those retarded bushes that bolt the main rear control arms to the stub assembles. Ba's are renowned for it, god I love later model Fords.

[t2te50]

Actually they're more like a rose joint, which is is like a ball joint.

[1970galaxie]

You had your CD player jammed on the beginning of "Hells Bells"!

[joolz]

Some of the answers like UJ's, hanger bearing (Centre Bearing) would cause a driveline vibration and if clunking at lower speeds the vibration over 60km/h would be quite loud. Does it have the original SP Sports tyres on it which are common to bubble on side wall? Possible bubble hitting something!

[V3RSAC3]

im with the boys, i'd say uni joint OR, it may SOUND like it's comming from your rear, but seeing as you just had your front tyres replaced, I'D check your ball joints!!

[PaulMac]

Wheel/Tyre out of round.
Paul

[Kryton]

ok, ill give you all the rest of the day and post up the answer tonight.
Joolz, it doesnt have the original SP tyres on either.

[superpursuit83]

Originally Posted by davway

ok, ill give you all the rest of the day and post up the answer tonight.
Joolz, it doesnt have the original SP tyres on either.

Noooooo!

[cuz]

My guess might be that one of the mounting bolts for the rear shocks has come loose or the rubber on them is worn out. That would cause it to hit the mounts and be a metal on metal sound.

[MotherNatureVer2]

Im going to go out on a limb and say your break pad has halved itself(or gone into pieces)......... Your breaks were foopared ........

[Wally]

Had an acquaintance with a similar problem with another brand and ended up being the tail shaft trying to seperate.