Tired pumps

Xaccers · Unread post by **Xaccers** » 10 Jan 2010, 22:44

Not wanting to hijack lftgtr's thread, I thought I'd start my own.

Juliet often suffers from heavy steering when just ticking over.
Also, on start up, her rear stays up giving a hard ride at the back.
If I sit with the brake floored for a while, then release, the back will often drop down to normal and give a lovely soft ride. I've also found if I hold the revs at 3000 the back will drop to normal too.
It's as though not enough pressure can be gained to open a valve at the back.
I need to bleed the brakes as I've not managed to do that yet since replacing the LHM with hydroflush.
Would it be worth/possible to swap the pump over from my old LX TD as that seemed to be in tip top condition as the ride quality/steering was great?

Unread post by **CitroJim** » 11 Jan 2010, 08:23

Have you done a hydraflush and filter clean Xac?

The heavy steering and hard rear are unrelated as far as the pump in concerned as the PAS and suspension are supplied by two different halves of the pump.

You're right that the rear stays hard because of insufficient system pressure at the rear failing to open the anti-sink valve or failing to shuttle the hydractive electrovalve right over into soft mode. The MK2 differs from the MK1 here as the operating presure for the electrovalves are indirectly derived.

How long does it take for the STOP light to go out? Bear in mind that anything up to 40 seconds or so is normal on an Activa.

If the LHM is good and the filters are spotless then the pump has to be suspect on the PAS side. As to wether or not a 1.9TD pump will do is a moot point. If the mountings and the pulley size are identical it should be OK but somehow I don't think they are...

Xaccers · Unread post by **Xaccers** » 11 Jan 2010, 13:09

Still got hydroflush in there from just before when we found her heat shield was fouling the roll corrector, not done that many miles since.
Gave the filters a good scrub with a soft toothbrush when I did the change.
All sphere's on the back were replaced as I'm sure you remember, some were unbelievably low!.

Actually, what did we use for the rear Activa sphere? Was it just a normal A/S or Acc?

Takes about 40seconds to a minute for the light to go out, and then maybe another minute for it to reach height and settle, unless I rev her between 2-3000.

I was wondering if the pump was tired on the steering side, it may be tired on the suspension/brakes side.

Otherwise, could air in the rear brakes be affecting things?
Danielle and I had planned to bleed them and then get ready for new LHM, but the snow has put that on hold.

Unread post by **CitroJim** » 11 Jan 2010, 17:11

Sorry Xac. My memory was playing tricks. I remember letting you have a jar of petrol to clean the filters now

Yes, indeed if there is a lot of air in the rear brakes, that will indeed make a difference. A good bleed and new LHM may do the world of good.

Let me have a feel of the steering next time I see you and compare it with mine.

I reckon it will come down to being tired on the steering side. Best then to let Martin rebuild it for you... Has the steering always been heavy like that? Maybe some fresh LHM will help. How long has the Hydraflush been in now?

Spheres, I cannot recall now

I think we selected a more or less right accumulator using the sphere tester.

Timings for light going out and reaching normal height are OK. I've just fired mine up after standing for what seems week covered in snow. She started on the button

Xaccers · Unread post by **Xaccers** » 11 Jan 2010, 17:24

With the spheres as low as they were (I think one was down to 5 or 10) then that's going to be a lot of gas escaping into the LHM, so my gut feeling has been gas in the brakes, and actually thinking about it, they do seem a bit soft compared with Cassy.
Time for a bleed as soon as the snow clears.
It's been a few months or so with hydroflush, but she's be sat idle for most of that, I've probably done the 1000 miles though.
Will phone GSF tomorrow and order some LHM.

Steering's always had moments of heaviness, when idling so I notice it mostly when parking.

XantiaMan · Unread post by **XantiaMan** » 11 Jan 2010, 18:02

Steering going heavy has long been an Activa weak point, it was mentioned in numerous road tests. I've found its always at low revs, and worse after a cold start and you go round a mini roundabout for example.

Is there any sphere in the system which if low, would cause the pump to work harder?

Unread post by **xantia_v6** » 11 Jan 2010, 18:08

CitroJim wrote:The MK2 differs from the MK1 here as the operating presure for the electrovalves are indirectly derived.

Can you translate that into plain english?

Unread post by **CitroJim** » 11 Jan 2010, 18:37

xantia_v6 wrote:
CitroJim wrote:The MK2 differs from the MK1 here as the operating presure for the electrovalves are indirectly derived.
Can you translate that into plain english?

Sorry Mike

That was rather a vague statement

The eseential difference is this. On the MK1 Hydractive sphere block, there are two feeds into it: one from the height corrector/anti-sink valve and one from the security valve (i.e. a full system pressure feed). The purpose of this latter feed is simply to provide a high pressure under the Hydractive electrovalve to ensure it shuttles cleanly and rapidly toward its soft mode position. it's "helper" in essence. This feed also operates the shuttle that cuts the Hydractive centre sphere in and out of circuit.

In the MK2 sphere block, these duties are all performed by just the one feed from the height corrector and anti-sink valve.

Therefore, in times of high pressure demand, there is not necessarily the full system pressure available, especially if the anti-sink valve is closed, to cleanly operate the electrovalve and centre sphere shuttle across to the soft mode. hence why it seems a MK2 can suffer a hard rear for a while at first start-up whereas in the MK1 this is a rare occurrence.

That's my take on it and I'm not saying it's gospel. All I do know is that MK1 and MK2 sphere blocks are not interchangeable.

Quite why Citroen did this change so late in the day remains moot. Cost saving I expect as the block is simpler and there is less pipework. The MK2 block has a bleed nipple whereas the MK1 block hasn't. Not sure exactly the purpose of the bleed nipple just yet, It is either to depressurise the block to make sphere removal easier or maybe the new design can suffer air locks...

Gareth, no, there's no sphere for the PAS but I do wonder if at peak demand (i.e. when the Activa bits are pressurising) if these is insufficient feed capacity to the pump for both functions...

Xaccers · Unread post by **Xaccers** » 11 Jan 2010, 18:49

funny you should mention sufficient feed Jim, at times it can be like cassy was when i fitted the garden hose feed and it was slightly pinched.
with it clearing under revs it would suggest that the pump isn't quite up to the task wouldn't it?
smaller pulley is needed perhaps?

Unread post by **CitroJim** » 11 Jan 2010, 18:59

Yep, I reckon that's it Xac. Marginal and just up to the job.

It's telling that the V6, with it's big front struts and heftier PAS does have a higher output pump. Sadly they're not interchangeable..

XantiaMan · Unread post by **XantiaMan** » 11 Jan 2010, 19:06

CitroJim wrote:
Gareth, no, there's no sphere for the PAS but I do wonder if at peak demand (i.e. when the Activa bits are pressurising) if these is insufficient feed capacity to the pump for both functions...

My thinking is that if the Activa sphere is weak for example, that the pump will have to work harder in some circumstances, at higher revs, less of a problem as the output of the pump may be higher. I've never noticed it with the revs high. The pump may get weak with age but if the overall pressure is correct then there may be a weak point in the system which will show up as another problem, such as the heavy steering at low revs and for the first 5 minutes of a drive (hope that makes sense?)

XantiaMan · Unread post by **XantiaMan** » 11 Jan 2010, 19:08

CitroJim wrote:Yep, I reckon that's it Xac. Marginal and just up to the job.

It's telling that the V6, with it's big front struts and heftier PAS does have a higher output pump. Sadly they're not interchangeable..

Could a hybrid not be made, i.e could an expert look at modifying a pump to V6 output but correct Activa pressure?

Unread post by **CitroJim** » 11 Jan 2010, 19:17

Quite possibly Gareth... Except V6 pumps are as rare as the old proverbial and spare ones tend to be locked away in safe deposit boxes....

never try to use one on anything other than a V6 or you'll have the spectacle of an exploding steering ram to contend with; one major difference is the pressure control is in the rack on a V6, not in the pump itself as is the case with all other pumps.

You could fit a V6 pump and rack maybe....

KP · Unread post by KP » 11 Jan 2010, 19:25

Just my thoughts gareth

I wouldn't even mind fitting a tiny pulley and different aux belt to make it spin more? Ie one about an inch across should do nicely

Along gareths notes though could plaides possibly have some comment on increasing output from the pumps, i guess we would want to push more volume out of them rather than just go for pressure or am i way off the mark??

Unread post by **CitroJim** » 11 Jan 2010, 19:29

No, I think that's exactly right Will, more volume is what is needed.

In which case, upping the speed won't be fully effective. It needs bigger pumping elements...

I believe this is what the V6 pump has. Look at Lexi's picture hereabouts and to me the V6 piston looks bigger...