 | Home > Technical > Clunking and cooking half shafts 130 - Just back from LR |
 
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| blackwolf Member Since: 03 Nov 2009 Location: South West England Posts: 17520   
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Could be tight wheelbearings or dragging brakes making them hot. It's hard to see a reason why simply changing to the final design would make that much difference so it does suggest that something is amiss.
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24th Jun 2016 5:31pm |
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| familymad Member Since: 13 Dec 2011 Location: Bucks Posts: 3481  
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Brakes haven't been touched, in fact they reported the rear pads are low so I bought some ready to do.
Sounds worrying. I have 2500 miles to do in it back end of July 1951 80" S1 2.0 1995 110 300TDI 1995 90 300TDI |
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24th Jun 2016 5:56pm |
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| familymad Member Since: 13 Dec 2011 Location: Bucks Posts: 3481
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Done a few miles in her this weekend and tried not to touch the brakes. Rear flanges get really hot. Local Inde used laser heat gun and flanges getting to 68deg after 7miles!
He agrees with over tightened wheel bearings blackwolf. 1951 80" S1 2.0 1995 110 300TDI 1995 90 300TDI |
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27th Jun 2016 8:07am |
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| blackwolf Member Since: 03 Nov 2009 Location: South West England Posts: 17520
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Seems distinctly possible, it is amazing how quickly a tight wheelbearing will generate heat. It is something that the dealer may not have spotted whilst working on driveline slop, but equally wouldn't be halfshaft related. Do you know if they got hot like this before you had the new halfshafts fitted? If not, then the dealer has messed something up severely.
If you do think that it is caused by tight wheelbearings, you need to sort it asap. Running that hot they are likely to fail completely (the lubrication will break down, and the hardened running surface of the outer race will start to 'Brinell' off the base metal) and that is not good. Are you sure that the rear calipers are not sticking - you do say that the rear pads are well worn? This again will raise the hub temperature quite dramatically and quickly, and will also compromise performance and fuel consumption. Both faults are easy enough to diagnose. |
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27th Jun 2016 8:22am |
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| familymad Member Since: 13 Dec 2011 Location: Bucks Posts: 3481
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It's a good point well made. I am not sure they were hot before.
I assumed no heat in the discs (by driving it around with minimal to no braking) would mean no brake issues. What rough diagnosis would you use for proving sticky brakes and or wheelbearings? I haven't ever. Hanged. Half shaft to assume they don't touch the bearings and this wouldn't be their fault?! 1951 80" S1 2.0 1995 110 300TDI 1995 90 300TDI |
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27th Jun 2016 8:32am |
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| pannawonica Member Since: 21 Nov 2010 Location: Clackline Western Australia Posts: 568 
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I don't think that it takes too much extra preload on bearings to generate heat. The effect of course is culmative with load speed and distance as we know. My new twin axle trailer had one hot bearing, all it took too fix was a reduction of one flat on the castle nut!
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27th Jun 2016 9:05am |
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| blackwolf Member Since: 03 Nov 2009 Location: South West England Posts: 17520
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Whilst replacing the halfshafts they won't have touched or even looked at wheelbearing or brakes, and may not even have jacked the wheels off the ground.
To check for sticking brakes, remove a roadwheel and see if the pads can be pushed away from the disk using a thin flat lever between the pad and the disk, or with a lever between the backplade of the two pads. It should take firm pressure, but they should move smoothly and easily. If they are stuck, it will be difficult or impossible to move them. (If the piston is sticking in the caliper, the fluid pressure produce by your hoof on the pedal will normally be enough to push the pads out, but they won't ever release the pressure. When you press the brake they will apply, and they will then stay in contact with the disk. If the front brakes are OK, since they provide 60%+ of the brake force, it will feel as if everything is working and the brakes are releaskng, but the rear will drag wearing out the pads and heating up the disks). IF YOU DO PUSH THE PADS AWAY FROM ThE DISK MAKE SURE YOU PUMP THE BRAKE PEDAL SEVERAL TIMES UNTIL IT FIRMS UP BEFORE DRIVING! (Sorry, don't intend to shout with this last comment but failure to do this will lead to a 'laundry moment' if you don't do it)! To check for tight wheelbearings: The best way is to jack one side of the back axle only, and jack it reasonably high. Unbolt the drive flange/halfshaft from the hub, and withdraw it (you'll get some oil and gloop coming out, but if you've jacked the axle high enough not much). Now spin the roadwheel and see how freely it rotates. It should spin very freely with virtually no resistance to movement, but beware that the brakes aren't dragging (it is best of all if you push the pads off the disk as outlined above. If the wheel feels stiff, check the brakes, if not the brakes, the wheelbearings are too tight. Whilst the wheel is jacked up, rock it top/bottom and side to side, there should be no perceptible movement (movememnt indicates loose wheelbearings). If you spin the wheel, it should keep going for a while by itself. Note that you can do this test with the halfshaft in, but in this case it is best to jack both side up remember that you're turning a lot more of the transmission, so everything will be stiffer to turn. Both these tests are simple enough to do, but especially the latter requires a little experience and judgement to know what is OK and what is not. |
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27th Jun 2016 1:06pm |
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