C5 rear supension not going down
Moderator: RichardW
C5 rear supension not going down
i bought a 2002 c5 on friday it went well all weekend but when i went out to go to my work this morning the rear suspension is fully up and wont go down. the front suspension is working perfectly is there a quick way to get this down
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cachaciero
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Re: C5 rear supension not going down
In a word no.barassie wrote:i bought a 2002 c5 on friday it went well all weekend but when i went out to go to my work this morning the rear suspension is fully up and wont go down. the front suspension is working perfectly is there a quick way to get this down
As a get you home measure assuming that the distance is not long you could pull the fuses for the pump, natural leakage should cause the back to drop after a few miles maybe a little or a lot depending. This also applies to the front so you need to watch that the front doesn't get to low and YOU WILL drive slowly.
It rather sounds as though the height sensor for the rear suspension has failed. This is actually not a particularly expensive or difficult thing to fix but it does mean working underneath the car ideally on a ramp because you will need to re-calibrate the ride height after fitting the new sensor which needs all four wheels on a level service.
cachaciero
2006 Toyota Prius T Spirit
2001 2.2 C5 Exclusive SE
1996 XM 2.1 TD Auto VSX
1995 XM 2.1 TD Auto SX died @ 140K
1987 CX 2.5 Gti Turbo II dead
1984 Ford Scorpio
1981 CX 2.4 Pallas Auto
Renault 21
1220 GS Club
Rover P6 2000TC
2001 2.2 C5 Exclusive SE
1996 XM 2.1 TD Auto VSX
1995 XM 2.1 TD Auto SX died @ 140K
1987 CX 2.5 Gti Turbo II dead
1984 Ford Scorpio
1981 CX 2.4 Pallas Auto
Renault 21
1220 GS Club
Rover P6 2000TC
Hi,
Replacing the height sensor is very straightforward.
Support the rear of the car so that it cannot drop, although this is unlikely as long as the power is off to the pump.
The sensor is a potentiometer, about £35 from dealer. There is a similar one at the front.
It fits in a braket on the rear suspension cross member and is held in place by a small bolt and has a removable plug for its electrical connection.
Connection to the antiroll bar is by a link between a ball joint on the pot wiper arm and one on a bracket on the AR bar. As long as you do not move the bracket on the AR bar by loosening its clamp or ensure that if you do you mark the location and return the bracket to the same point, then the "normal" suspension height will remain the same.
The height control works by: - There is a set point in the suspension ECU that corresponds to the pot reading at its centre point. The car moves up or down, AR bar is rotated and this moves the pot centre wiper which generates a error signal, the suspension ECU moves the suspension to move the AR bar, to move the pot to cancell out the error signal.
If you want to change or reset the "normal" height of the car you either move the bracket on the AR bar and the ECU alters the height to obtain the same pot reading as before but this now corresponds to a different height or I thnk you can change the set point in the ECU via a Lexia.
A common fault/cause of failure is wear around the centre or "null" point on the pot where the wiper spends most of its time and slowly wears away the wiper contact track.
Once you have the car safely up in the air say it is 10 min job to channge the pot.
Regards
John
Replacing the height sensor is very straightforward.
Support the rear of the car so that it cannot drop, although this is unlikely as long as the power is off to the pump.
The sensor is a potentiometer, about £35 from dealer. There is a similar one at the front.
It fits in a braket on the rear suspension cross member and is held in place by a small bolt and has a removable plug for its electrical connection.
Connection to the antiroll bar is by a link between a ball joint on the pot wiper arm and one on a bracket on the AR bar. As long as you do not move the bracket on the AR bar by loosening its clamp or ensure that if you do you mark the location and return the bracket to the same point, then the "normal" suspension height will remain the same.
The height control works by: - There is a set point in the suspension ECU that corresponds to the pot reading at its centre point. The car moves up or down, AR bar is rotated and this moves the pot centre wiper which generates a error signal, the suspension ECU moves the suspension to move the AR bar, to move the pot to cancell out the error signal.
If you want to change or reset the "normal" height of the car you either move the bracket on the AR bar and the ECU alters the height to obtain the same pot reading as before but this now corresponds to a different height or I thnk you can change the set point in the ECU via a Lexia.
A common fault/cause of failure is wear around the centre or "null" point on the pot where the wiper spends most of its time and slowly wears away the wiper contact track.
Once you have the car safely up in the air say it is 10 min job to channge the pot.
Regards
John
Hi,
Yes it does commonly cause "hunting" and this was the reason I changed my rear sensor.
Mine came to light after replacing the rear radius arm bearings when the car immediately bgan hunting.
I assume the stiffness of the failed/failing bearings con trained the suspension movement and may have accelerated wear at the centre of the pot travel. The stiffness would also have provided additional damping to suspension movement and supressed the hunting. Once the bearings wee replaced the additional damping was removed and the suspension hunted.
It was most noticable when the car was stationary and quite amusing seeing the xenon lights correcting in antiphase to the suspension!
The hunting also continued with a period o a couple of seconds or so when the car as parked with the engine off, until I wa able to replace the sensor I had to leave it with the suspension in the lowest or highest position to stop movement.
Regards
John
Yes it does commonly cause "hunting" and this was the reason I changed my rear sensor.
Mine came to light after replacing the rear radius arm bearings when the car immediately bgan hunting.
I assume the stiffness of the failed/failing bearings con trained the suspension movement and may have accelerated wear at the centre of the pot travel. The stiffness would also have provided additional damping to suspension movement and supressed the hunting. Once the bearings wee replaced the additional damping was removed and the suspension hunted.
It was most noticable when the car was stationary and quite amusing seeing the xenon lights correcting in antiphase to the suspension!
The hunting also continued with a period o a couple of seconds or so when the car as parked with the engine off, until I wa able to replace the sensor I had to leave it with the suspension in the lowest or highest position to stop movement.
Regards
John