Poor turbo response Cause (HDi) (FIXED)

[citroenxm]

Hi all.

On a delayed - by four days - response, I found a reason for my intemittent "Lazy" morning Turbo unit.

I didnt find out through investigation but more by chance. I broke a Vaccuum pump on a customer car, a C5 HDi - LONG STORY, I dont want to discuss further - so to get out of jail - as C5's have normal Servo brakes and NEED a vaccuum to work I decided to do a swap for my Xantia Vaccuum pump. Xantia having powered hydraulic brakes didnt need to Vaccumm - only for Turbo wastegate operation - so Id manage for a couple of days. Anyway, I was called back to the C5 and discovered the vaccuum had stopped, so swapped it for another working one. Customer happy.

So, had to source a third, which I had, fitted it to my car... and woo hooo what a HUGE difference!

The turbo works ALL the time now, and I have even noticed MORE get up and go like a scalded cat. I always thought she was a bit down on power. But now, theres a very noticable difference when on boost!

There must be a stronger vaccum on this pump which is opening or closing the wastegate better then before.

I did open the old pump, to have a look inside, and its a strange setup.. the pump relies on filling up with oil, then theres three "Scrapers" that when the engine is running come out under centralfugal force from the end of the cam. Then it must do something with the oil to create the vaccumm, the oil is drained out lower down into a return drilling in the head.

Ill have to open this spare pump up again and take some piccies to put on here...

[Stewart(oily)]

I had a similar problem with those vane type vac pumps on another vehicle, replacement pumps would work for a while then stop, stripping them revealed nothing, reassembled with a squirt of oil in them they would work again, for a while, the cause turned out to be a sliver of silicone gasket blocking the oil feed to the pump, they need a generous oil supply to work, there was enough oil around to stop the pump from getting damaged so no other symptoms.

[Lighty]

Our first tool in diagnosing HDI's is a Miti vac (after Lexia) it's a brilliant little device for testing and creating vacuum.

[isisalar]

Hi guys
Good to hear you now have a working turbo Paul. Mine has also always seemed a bit flat, which I'd put down to the ticking injector(s). The continued use of V power is steadily improving things and the ticking is getting far less evident and performance is improving. A damned good thrashing seems to help as well so last Sunday evening, taking advantage of the improved performance after a fair bit of Motorway driving the previous two weeks, I got it up to a previously unseen illegal speed for about 20 miles. The performance improvement since is nothing short of astonishing, and despite giving it continued treatment all week in an attempt to get the now faint ticking finally nailed, fuel consumption seems much improved too. Previously the turbo was obviously working and it made a quite high pitched screeching noise, this is now the quiet whistle I would expect and the turbo can be felt working A LOT more than ever previously. It would seem some cobwebs of some sort have been blown out, it's now like the turbo is working and it wasn't before.
Ideas anyone?
Did a service about 2000 miles ago, and I did use some engine flush, possibly something was sticking and now isn't?
Last two weeks, first the mystery suspension 'cure' and now I've suddenly got a sports car!!
Don't you just love Citroens.
Cheers
Paul

[Old-Guy]

I did open the old pump, to have a look inside, and its a strange setup.. the pump relies on filling up with oil, then there's three "Scrapers" that when the engine is running come out under centrifugal force from the end of the cam. Then it must do something with the oil to create the vacuum, the oil is drained out lower down into a return drilling in the head.

I've never seen one of these let alone opened up one, however - this type of pump is fairly common: the axis of the cylindrical rotor that drives the vanes is eccentric to the cylinder in the body, the two creating a crescent shaped 'chamber'. Animated explanation on YouTube.. I've worked on vacuum pumps of this type used in milking parlours with cylinder diameter and length both over a foot. I've also seen diddy little vane-type oil pumps in small engines - on the nose of the crankshaft is quite common. They don't work filled with oil, but may be designed so that oil tends to accumulate in them when the engine is stopped - vanes and cylinder will wear extremely rapidly without generous lubrication.

The normal wear mode that causes serious inefficiency is wear in the cylinder ends and vane ends. Centrifugal force (aided by a couple of small springs) keeps the vanes in firm contact with the cylinder bore but if the gas being pumped can simply escape past the ends of the vanes, then the displacement pump degenerates into a fairly crude blower.

IIRC, when buying replacement oil pumps for Austin 'A' series engines (and various other car engines of the 50s and 60s), if you were technically aware you had a choice of gear or vane type. Gear type were a bit more expensive, but generally worked much better and for longer. Bit like buying spheres -