Anyone heard of this - "PAS self-protection"
Discussion
Looking at a 2008 CRV (yeah, I know...not very PH). Looks like a tidy car, except the steering 'rocks' rhythmically back and forth in your hand when under quite a bit of lock, e.g. going around a 2nd-gear roundabout or parking.
There's no other vibration from steering or brakes at any other time, so don't think it's disks, wheel balancing or tyres.
The dealer says it's a consequence of the "self-protection" built into the hydraulic PAS pump (i.e. "they all do that sir, go away"), but I think that's a whole pile of manure - never had it on any other PAS-equipped car, Honda or otherwise.
So...any suggestions what it can be?
(It's been suggested elsewhere that it's a tell-tale of the rear diff needing a fluid-flush / possible replacement...but not been given the mechanical explanation of why...although if you've a sticky rear diff it could be taking uneven amounts of power away from the fronts, I guess...)
Thanks,
Martin.
There's no other vibration from steering or brakes at any other time, so don't think it's disks, wheel balancing or tyres.
The dealer says it's a consequence of the "self-protection" built into the hydraulic PAS pump (i.e. "they all do that sir, go away"), but I think that's a whole pile of manure - never had it on any other PAS-equipped car, Honda or otherwise.
So...any suggestions what it can be?
(It's been suggested elsewhere that it's a tell-tale of the rear diff needing a fluid-flush / possible replacement...but not been given the mechanical explanation of why...although if you've a sticky rear diff it could be taking uneven amounts of power away from the fronts, I guess...)
Thanks,
Martin.
I vaguely remember a car of mine doing this - may have been a Rover SD1. I thought it was just the power-steering pump pressure relief valve doing its job - on full lock, pump comes up to maximum pressure, valve opens to relieve pressure then closes; rinse and repeat.
Could be wrong, though.
Could be wrong, though.
Walk away!
There are few cars, where during very very low speed maneouvering using lots of handwheel input, a noticable cyclic oscilation in the steering effort and rate can be noticed (early DB9's are the worst offenders). Here, the lateral stiffness of the steering system is of a similar magnitude to the tyres rotational stiffness. As such, this system is not critically damped and can easily oscilate.
However, once moving at any significant speed (say above approx 5mph) the rotational stiffness of the tyres ceases to be a driving force (because the tyre contact point can now "progress" across the road as it rolls, rather than be dragged across it when slow/stationary) Hence, there should be no noticable oscilatory behavoir in the steering system. if there is, it's because something is worn, jammed, or loose!!
There are few cars, where during very very low speed maneouvering using lots of handwheel input, a noticable cyclic oscilation in the steering effort and rate can be noticed (early DB9's are the worst offenders). Here, the lateral stiffness of the steering system is of a similar magnitude to the tyres rotational stiffness. As such, this system is not critically damped and can easily oscilate.
However, once moving at any significant speed (say above approx 5mph) the rotational stiffness of the tyres ceases to be a driving force (because the tyre contact point can now "progress" across the road as it rolls, rather than be dragged across it when slow/stationary) Hence, there should be no noticable oscilatory behavoir in the steering system. if there is, it's because something is worn, jammed, or loose!!
Done some more digging, seems to be a fairly common thing on Mk3 CRVs but no consensus on how to fix. Two contenders:-
- Likely one is PAS relief valve setting up a harmonic pulse in the fluid (407s have this, I'm told). Tricky one to sort though - some people have suggested PAS fluid change but can only see that ameliorating symptoms not fixing.
- Other known one is minor rear diff issue (ATB style), i.e. gunking-up through lack of use (CRV is part-time 4wd). Flush is usually supposed to help/cure, but the dealer allegedly did that before I drove it...I'm not 100% convinced they did though.
I'm reliably told the way to tell between the two is to check when stationary - if it does it then it can't be the diff, which makes sense.
So not sure 'walking away' is necessary here - the car seems in good nick aside from this, clearly better than the one we saw before at an unnamed car supermarket which had noticeable turbo whistle, pulled left quite badly, needed new front disks and pads, new tyres pretty soon and was advertised for a similar price. But would like to work out how to fix it...
- Likely one is PAS relief valve setting up a harmonic pulse in the fluid (407s have this, I'm told). Tricky one to sort though - some people have suggested PAS fluid change but can only see that ameliorating symptoms not fixing.
- Other known one is minor rear diff issue (ATB style), i.e. gunking-up through lack of use (CRV is part-time 4wd). Flush is usually supposed to help/cure, but the dealer allegedly did that before I drove it...I'm not 100% convinced they did though.
I'm reliably told the way to tell between the two is to check when stationary - if it does it then it can't be the diff, which makes sense.
So not sure 'walking away' is necessary here - the car seems in good nick aside from this, clearly better than the one we saw before at an unnamed car supermarket which had noticeable turbo whistle, pulled left quite badly, needed new front disks and pads, new tyres pretty soon and was advertised for a similar price. But would like to work out how to fix it...
havoc said:
Done some more digging, seems to be a fairly common thing on Mk3 CRVs but no consensus on how to fix. Two contenders:-
- Likely one is PAS relief valve setting up a harmonic pulse in the fluid (407s have this, I'm told). Tricky one to sort though - some people have suggested PAS fluid change but can only see that ameliorating symptoms not fixing.
- Other known one is minor rear diff issue (ATB style), i.e. gunking-up through lack of use (CRV is part-time 4wd). Flush is usually supposed to help/cure, but the dealer allegedly did that before I drove it...I'm not 100% convinced they did though.
I'm reliably told the way to tell between the two is to check when stationary - if it does it then it can't be the diff, which makes sense.
So not sure 'walking away' is necessary here - the car seems in good nick aside from this, clearly better than the one we saw before at an unnamed car supermarket which had noticeable turbo whistle, pulled left quite badly, needed new front disks and pads, new tyres pretty soon and was advertised for a similar price. But would like to work out how to fix it...
Having worked in a Honda dealership I can tell you what you are experiencing with 90% certainty is the diff issue. EXTREMELY common in the Mk3 CRVs. Flushing should cure it.- Likely one is PAS relief valve setting up a harmonic pulse in the fluid (407s have this, I'm told). Tricky one to sort though - some people have suggested PAS fluid change but can only see that ameliorating symptoms not fixing.
- Other known one is minor rear diff issue (ATB style), i.e. gunking-up through lack of use (CRV is part-time 4wd). Flush is usually supposed to help/cure, but the dealer allegedly did that before I drove it...I'm not 100% convinced they did though.
I'm reliably told the way to tell between the two is to check when stationary - if it does it then it can't be the diff, which makes sense.
So not sure 'walking away' is necessary here - the car seems in good nick aside from this, clearly better than the one we saw before at an unnamed car supermarket which had noticeable turbo whistle, pulled left quite badly, needed new front disks and pads, new tyres pretty soon and was advertised for a similar price. But would like to work out how to fix it...
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