S60 D5 163 '03 - Revs rise when brake applied, limp mode

Ndavis · Jun 15th, 2019, 11:43

Hi there,

The car has 155k on it and suddenly, without warning, threw up the 'engine service required' message and went into limp mode whilst doing 70mph on a motorway

First of all, cycling the ignition didnt clear the code and then I noticed that whilst braking to make turns at junctions, the revs would rise from 750 to 900 rpm, increasing as the pressure is applied to the pedal.* The car drives in limp mode (i.e no turbo) and I managed to get home with it.

On inspection, pumping the brake pedal with the engine off firms it up, and upon cycling the ignition to 'II,' I cannot hear the (electric?) vacuum pump cut in.

When I start the engine, the brake pedal can be depressed again and the revs rise as stated to 900rpm, dropping back down when pressure is taken off the pedal.

I have looked at the vacuum pump underneath the cross brace and checked the elbow join there, and it appears ok.* There is vacuum making it to the valve mounted on the airbox...

The fuse for the vacuum pump (bay 3) was empty and putting a 15a in here as shown makes no difference.* I dont have a mityvac pressure gauge to check the output from the vac nipple on the side of the block...

Is there another, electric vacuum pump that I have missed?* Can this 'burn out?'* If so, where is it?

Failing that, has anyone seen this before and have any ideas?* The other large diameter pipe heading from the vac pump to the dash appears good, and has some sort of one way valve in it - not sure if this is prone to failure?* Any input greatly appreciated...

Thanks,
Nick

davebb · Jun 15th, 2019, 12:48

Hi The D5 does NOT have a electric vacuum pump,
the vacuum pump is on the left side of the engine,
you need to connect up a vacuum gauge to see what is going on,
it does sound like you have a leak at the brake booster, but you need to test with a gauge ,
Dave

Ndavis · Jun 16th, 2019, 18:52

Thanks Dave.* I have ordered one, but for now in the absence of a vacuum gauge, my extremely unscientific method was to disconnect the servo vacuum pipe and put my thumb over the pump servo nipple.* It sucks hard - enough to pinch my finger - and I cant feel any difference to the vacuum at the t piece for the mounts with it connected or disconnected and my thumb over it to simulate no vac loss at the servo.

If the servo was dodgy, I would expect a difference at the t piece with my thumb over the servo vac outlet?

Beyond that, it throws the message up as soon as the ignition is on before i start the engine.* Could the break pedal sensor be the culprit?

Thanks,
Nick

choosy54 · Jun 17th, 2019, 21:28

Watching this with interest. Mine is doing the same. Diagnostics says that the boost control sensor is faulty.

Ndavis · Jun 17th, 2019, 21:53

Interesting, thanks for this.

If you mean the thing under the big black pipe on the front of the engine, have you tried having it off and cleaning it up?

Ndavis · Jun 18th, 2019, 10:00

Tried cleaning the turbo governor under the egr pipe, which was cruddy and... no change.

Can these fail electronically? Wonder if its worth putting a multimeter on if people know what it should read?

Thanks

Jun 15th, 2019, 11:43	#1
Ndavis New Member Last Online: Jun 18th, 2019 10:00 Join Date: Sep 2015 Location: Canterbury	S60 D5 163 '03 - Revs rise when brake applied, limp mode Hi there, The car has 155k on it and suddenly, without warning, threw up the 'engine service required' message and went into limp mode whilst doing 70mph on a motorway First of all, cycling the ignition didnt clear the code and then I noticed that whilst braking to make turns at junctions, the revs would rise from 750 to 900 rpm, increasing as the pressure is applied to the pedal.* The car drives in limp mode (i.e no turbo) and I managed to get home with it. On inspection, pumping the brake pedal with the engine off firms it up, and upon cycling the ignition to 'II,' I cannot hear the (electric?) vacuum pump cut in. When I start the engine, the brake pedal can be depressed again and the revs rise as stated to 900rpm, dropping back down when pressure is taken off the pedal. I have looked at the vacuum pump underneath the cross brace and checked the elbow join there, and it appears ok.* There is vacuum making it to the valve mounted on the airbox... The fuse for the vacuum pump (bay 3) was empty and putting a 15a in here as shown makes no difference.* I dont have a mityvac pressure gauge to check the output from the vac nipple on the side of the block... Is there another, electric vacuum pump that I have missed?* Can this 'burn out?'* If so, where is it? Failing that, has anyone seen this before and have any ideas?* The other large diameter pipe heading from the vac pump to the dash appears good, and has some sort of one way valve in it - not sure if this is prone to failure?* Any input greatly appreciated... Thanks, Nick

Jun 17th, 2019, 21:28	#4
choosy54 Dangerous Dave. Last Online: Feb 16th, 2024 21:06 Join Date: Aug 2013 Location: tiverton, Mid Devon	Watching this with interest. Mine is doing the same. Diagnostics says that the boost control sensor is faulty. __________________ X reg 1.8 GDI estate. 221,000 miles so far and still going strong. Selling for £250 if you can use it. 2002 V70 D5 Estate. Brilliant car that drives like its new. 2008 C70 D5 Hard Top Convertible with small niggles. YES MRS JUST GIVE ME TIME ! ! !

Jun 15th, 2019, 12:48	#2
davebb Premier Member Last Online: Apr 17th, 2024 19:02 Join Date: Aug 2013 Location: Emsworth,hants	Hi The D5 does NOT have a electric vacuum pump, the vacuum pump is on the left side of the engine, you need to connect up a vacuum gauge to see what is going on, it does sound like you have a leak at the brake booster, but you need to test with a gauge , Dave

Jun 16th, 2019, 18:52	#3
Ndavis New Member Last Online: Jun 18th, 2019 10:00 Join Date: Sep 2015 Location: Canterbury	Thanks Dave.* I have ordered one, but for now in the absence of a vacuum gauge, my extremely unscientific method was to disconnect the servo vacuum pipe and put my thumb over the pump servo nipple.* It sucks hard - enough to pinch my finger - and I cant feel any difference to the vacuum at the t piece for the mounts with it connected or disconnected and my thumb over it to simulate no vac loss at the servo. If the servo was dodgy, I would expect a difference at the t piece with my thumb over the servo vac outlet? Beyond that, it throws the message up as soon as the ignition is on before i start the engine.* Could the break pedal sensor be the culprit? Thanks, Nick

Jun 17th, 2019, 21:53	#5
Ndavis New Member Last Online: Jun 18th, 2019 10:00 Join Date: Sep 2015 Location: Canterbury	Interesting, thanks for this. If you mean the thing under the big black pipe on the front of the engine, have you tried having it off and cleaning it up?

Jun 18th, 2019, 10:00	#6
Ndavis New Member Last Online: Jun 18th, 2019 10:00 Join Date: Sep 2015 Location: Canterbury	Tried cleaning the turbo governor under the egr pipe, which was cruddy and... no change. Can these fail electronically? Wonder if its worth putting a multimeter on if people know what it should read? Thanks

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