could dirty brake fluid cause vibration under mild braking but not heavy braking??
03-16-2009, 01:53 AM
#1
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could dirty brake fluid cause vibration under mild braking but not heavy braking??
my brakes are brand spankin' new and i don't use my brakes hard...(i don't go 100mph and stomp on them)so i doubt they're warped...
and also 75% of the time my clutch won't come all the way back up after it's completely engaged. it flicks back up to where it should be after my foot is off it. i wait for it to tap the bottom of my foot.
and also 75% of the time my clutch won't come all the way back up after it's completely engaged. it flicks back up to where it should be after my foot is off it. i wait for it to tap the bottom of my foot.
03-16-2009, 03:10 AM
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When you say the brakes are brand new...
Did you clean the guide pins and lubricate everything really well when you did them? Or did the shop that did the work do it? Are your wheels torqued properly? (have you checked recently?)
As for the clutch... sounds to me like the spring inside the clutch MC is going. When I did my clutch in January, it was because something suddenly changed and when I released the pedal, the clutch would engage at the very top of the stroke. Clutch and release bearing showed signs they needed to be repaced (they were original parts, date-stamped 1987!), but they definitely had some life left in them. That didn't solve the problem... so I swapped the clutch MC. With the old one on the bench, i pulled it apart... the internal spring had broken into 4 or 5 pieces, and was no longer pushing the piston all the way back up. It had the same symptom as yours.. sticking part-way up and needing to be tapped to make it come the rest of the way.
As for the clutch... sounds to me like the spring inside the clutch MC is going. When I did my clutch in January, it was because something suddenly changed and when I released the pedal, the clutch would engage at the very top of the stroke. Clutch and release bearing showed signs they needed to be repaced (they were original parts, date-stamped 1987!), but they definitely had some life left in them. That didn't solve the problem... so I swapped the clutch MC. With the old one on the bench, i pulled it apart... the internal spring had broken into 4 or 5 pieces, and was no longer pushing the piston all the way back up. It had the same symptom as yours.. sticking part-way up and needing to be tapped to make it come the rest of the way.
03-16-2009, 04:39 AM
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it's so amazing to me how audi designs their parts to wear in a certain way...
giving you clues as to how much life is left in the part...
just awesome.
my clutch engages really high and i don't like it. i want it to engage lower..
looks like i still have a lot of work to do on her.
just awesome.
my clutch engages really high and i don't like it. i want it to engage lower..
looks like i still have a lot of work to do on her.
03-16-2009, 05:08 AM
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like I said... excessively high engagement could be the clutch MC...
the spring inside breaks apart, which changes the return force, and the MC dynamics. I haven't figured out why (because I still had 'full stroke'), but a spring broken in 5 places meant my clutch engaged VERY high and felt like it was going to slip.
03-16-2009, 05:20 AM
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be careful with anti-sieze on the bolts...
I've had atleast one caliper-carrier bolt that was anti-siezed completely back out and fall off. Made for an interesting drive, tap the brakes, whole carrier would rotate and the caliper would hit the inside of the rim.
Ended up jacking the car up, swapping the remaining bolt from the top to the bottom, and driving home (200km)... with the bolt on the bottom, the caliper would rotate inwards (fall in), and the rotor would rub on the edge of the caliper/carrier.
That was also when I discovered I was missing one subframe bolt, and the others were loose... and that you weren't supposed to reuse subframe bolts. hehe.
In general, you need to be careful with anti-sieze compounds whenever you use them... they change the torque-tightening characteristics of nuts and bolts, they change the friction-force characteristics that some components rely on (like your wheels)... If you use anti-sieze on your rims/hubs, only use a very small amount on the inside ring, and none on the bolts. The bolts won't hold their torque properly, and the friction generated between wheel face and hub face is critical in transferring forces (acceleration and braking)... your lug bolts are only there to hold things together and create a friction surface, not to transfer forces in shear-load to the bolts. (another reason why it's important to use wheels with the proper hub ID to match the hub on our cars).
Ended up jacking the car up, swapping the remaining bolt from the top to the bottom, and driving home (200km)... with the bolt on the bottom, the caliper would rotate inwards (fall in), and the rotor would rub on the edge of the caliper/carrier.
That was also when I discovered I was missing one subframe bolt, and the others were loose... and that you weren't supposed to reuse subframe bolts. hehe.
In general, you need to be careful with anti-sieze compounds whenever you use them... they change the torque-tightening characteristics of nuts and bolts, they change the friction-force characteristics that some components rely on (like your wheels)... If you use anti-sieze on your rims/hubs, only use a very small amount on the inside ring, and none on the bolts. The bolts won't hold their torque properly, and the friction generated between wheel face and hub face is critical in transferring forces (acceleration and braking)... your lug bolts are only there to hold things together and create a friction surface, not to transfer forces in shear-load to the bolts. (another reason why it's important to use wheels with the proper hub ID to match the hub on our cars).
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03-16-2009, 06:41 AM
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ya... need to be careful with it...
technically, when using a lubricant on threads, the torque value goes down (ie, you torque to a lower value)... if you lubricate your lug bolts and tighten to 90ft-lbs, you may end up stretching the bolts or damaging the threads in the hub. Ever had a wheel that just always seems to need tightening after you take it off, until some rust builds up on the threads?
When I got my 90q DD, after a winter/spring of driving it, the front end developed a weird tendancy to 'shift' when entering a corner. Turn the wheel, wait for the subframe to slide under the car, then the car starts to turn. Became quite scary within a couple days of it starting. Someone before me had obviously had the subframe off, reused the bolts, and put anti-sieze on them. Firstly... those bolts are stretch-bolts (tighten to torque spec, then 1/4 turn IIRC), and if you've got anti-sieze on there, the bolts won't hold a torque properly, and you will be over-stretching them.
Better off to replace the bolts, and when it's all back together, spray some grease up into the frame to coat the tops of the threads to protect from corrosion.
When I got my 90q DD, after a winter/spring of driving it, the front end developed a weird tendancy to 'shift' when entering a corner. Turn the wheel, wait for the subframe to slide under the car, then the car starts to turn. Became quite scary within a couple days of it starting. Someone before me had obviously had the subframe off, reused the bolts, and put anti-sieze on them. Firstly... those bolts are stretch-bolts (tighten to torque spec, then 1/4 turn IIRC), and if you've got anti-sieze on there, the bolts won't hold a torque properly, and you will be over-stretching them.
Better off to replace the bolts, and when it's all back together, spray some grease up into the frame to coat the tops of the threads to protect from corrosion.
03-16-2009, 09:25 AM
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Yes
Just enough (minimal) is the rule of thumb. I always go back and check them after a very short test ride too.
With graded bolts over torquing is less of an issue. With a grade 8 (min) lug bolts the max torque value with wax lubrication is in the area of 130+ lb/ft to 75% of the shear spec. So even if you torque to the area of 90 lb/ft you should be fine.
With graded bolts over torquing is less of an issue. With a grade 8 (min) lug bolts the max torque value with wax lubrication is in the area of 130+ lb/ft to 75% of the shear spec. So even if you torque to the area of 90 lb/ft you should be fine.