Brakes: XC90 parking brake woes

[TruckbusUK]

Originally Posted by bobdabuilda

I have the same year model and my economy is around this mark. I envy those who get 33mpg!! A full tank does me 360miles at best, so you are getting 420plus?

Its maybe the weight of your right foot Bob.

My April 09 D5 Geartronic (12k miles) gets approx 19-27mpg (290-380miles) around town (depending on who is driving) but if its a longer journey (Just back to Glasgow from Disneyland Paris, 3 tanks of diesel round trip) and on the outward journey we did 487miles on the first tank, 507 miles on the second and 521 on the third. I drove all the time and the trip said average speed was 68 MPH, so I was not hanging about, aircon runs all the time on ours, and we use eco pressures.

Hope it helps...

[gillberry]

Ours is a 2009 d5 geartronic and we use eco pressures on ours and we have the climate control left on . Around town 22-23 mpg but on a recent round trip of 480 miles with a mix of country roads and fast cruising spped on motorways 31 mpg was returned . I'm pretty sure that if I switched the climate off and used light throttle everywhere I could increase the mpg particularly on a run but if I wanted economy I would have bought a tiny eurobox .

[RT Mechanics]

Originally Posted by msmith

I sometimes get over 500 on a tank. It is a manual and I do keep the tyres on the 39 psi eco setting which makes a big difference..

If your gettting much higher then normal mpg i would double check that the car is actually running in 4wd mode..

[msmith]

My understanding is that the car is AWD ie., 4WD only operates when necessary. In my case this is probably <2% of the time and so whether the 4WD system is working or not will make little difference to the MPG...Correct me if I am wrong...

[TruckbusUK]

Originally Posted by msmith

My understanding is that the car is AWD ie., 4WD only operates when necessary. In my case this is probably <2% of the time and so whether the 4WD system is working or not will make little difference to the MPG...Correct me if I am wrong...

Now this could run for a long time, and I'm no mechanical expert ... but my understanding of how the Volvo/Haldex installation works is that the XC90 is more or less a FWD car that utilises an automatic coupling (the Haldex unit) that directs drive to the rear when needed.

That said, because, as with any car in normal conditions the driven wheels (fronts in this case) always rotate slightly faster than the non driven (rears in this case) due to slip,in the Volvo XC90 installation only 97-98% of the drive is going to the front and 2-3% of the drive is directed to the rear due to the Haldex unit detecting this slip and directing some drive to the rear wheels. As conditions deteriorate then the distribution of power will continue until the maximum distribution (55/45 in this installation I believe) is achieved resulting in "full" all wheel drive while the conditions interpreted by the control unit require it.

The system constantly monitors the "slip" and adjusts the drive accordingly, so mud, snow, rain, ice, yaw detection etc will all influence the distribution of the drive, so you are likely to be running more "all wheel drive" than you realise for most of the year but never less than 2-3% due to the inherent slip.

Edit : - unless its not working see threads on 4WD loss

I'm happy for anyone to correct my non expert/user interpretation of how the system in the XC90 works.

Robin

[Clan]

with one addition , since 2007 volvo have had "Instant Traction" where the software was altered to give full 4 wheel drive when starting off until the car gets going , then the clutch lets go until the rear wheels are needed again ...

[RT Mechanics]

Originally Posted by msmith

My understanding is that the car is AWD ie., 4WD only operates when necessary. In my case this is probably <2% of the time and so whether the 4WD system is working or not will make little difference to the MPG...Correct me if I am wrong...

The best way to check your car when its next in for a service etc is to ask the technician to grab hold of the propshaft where it come's off the transfer box and see if it turns the front wheels.

The haldex unit will not be doing anything if it does not have any drive getting to it.

As i said quite a few of the XC90 etc we have in for servicing are running in 2 wd mode as the mpg read out usually shows..

[chunderground]

I think all these figures can be very misleading. A simple way to give like for like comparison is to to quote average speed along with average MPG.
My average MPH is 23mph average MPG is now 25.5MPG (based on computer readout which when tested was 2.5% optomistic)

When I have taken it on a run Mpg rises to 33 - 36

2009 d5 auto with DPF

Placid driving style - when the car was new I was only averaging 23mpg

[v70-xc90man]

Originally Posted by Clan

has the travel of the pedal changed since they had it ? if the travel is more than before they may have tried to bed in the shoes for better grip , because MOST xc90 users with autos very wrongly NEVER use the parking brake and the drum surface rusts , hence poor grip . i would think most dealer technicians know this and try to improve it whilst testing the vehicle ...

If the travel is still the same then they wouldnt have done anything to the actual parking brake on a service other than adjust the pedal travel if necessary .
You really need the rear disc/drums and shoes inspected again ... you say it doesnt hold when warm , it could be binding and heating up when on the move hence that problem ..

Hi please can you give me advice as i am away on holiday this week and my xc90 is vibrating badly at 60mph + and just came back from a day out back to our apartment and the rear passenger wheel is red hot to touch,but it does not vibrate below 60mph,do you think it is a wheel bearing due to the vibration? are they common to go on these? it has done 134000 on a 54 plate,also we are due to drive back 130 miles on sunday so don't know whether to take it to a garage or ring greenflag to take us home ?I can jack it up tommorrow on hol and check for any movement,and see if brake is binding as i could smell brake smell at the time i got out the car and felt the wheel was red hot, i might of answered my own question but if the brake was binding would it vibrate badly above 60mph?? Glad i bought my laptop on holiday!

[GJB]

Originally Posted by v70-xc90man

Hi please can you give me advice as i am away on holiday this week and my xc90 is vibrating badly at 60mph + and just came back from a day out back to our apartment and the rear passenger wheel is red hot to touch,but it does not vibrate below 60mph,do you think it is a wheel bearing due to the vibration? are they common to go on these? it has done 134000 on a 54 plate,also we are due to drive back 130 miles on sunday so don't know whether to take it to a garage or ring greenflag to take us home ?I can jack it up tommorrow on hol and check for any movement,and see if brake is binding as i could smell brake smell at the time i got out the car and felt the wheel was red hot, i might of answered my own question but if the brake was binding would it vibrate badly above 60mph?? Glad i bought my laptop on holiday!

If it is hotter than the other side would suspect wheel bearing.