DS19 early water punp/hydraulic pump rebuild
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Thread: DS19 early water punp/hydraulic pump rebuild

  1. #1
    Fellow Frogger!
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    Default DS19 early water punp/hydraulic pump rebuild

    I penned this rebuild treatise some time ago but never got around to publishing it. As it it the silly season I thought that it may relieve the mind-numbing cerebral assault of Xmas and the New Year.
    You will never need to attend to one of these lovely little engineering pieces, but you may be interested in what is involved in bringing one back to life.

    From it's launch in 1955 until September 1960, the DS19 wasfitted with a ingenious combined water pump and low pressure hydraulic pump.

    The water pump was completely conventional and served todistribute coolant around the engine cooling circuit. However, co-axial withand in front of the water pump was a positive displacement hydraulic pump, bothpumps being driven at the same speed by a dual-belt drive.

    The hydraulic pump is of the gerotor design (derived from “generated rotor”). The gerotor moduleconsists of an inner and outer rotor. The inner rotor has 4 teeth, and theouter rotor has 5 teeth. The outer rotor is located off-center and both rotorsrotate. The geometry of the two rotors partitions the volume between them intodifferent dynamically-changing volumes. During the assembly's rotation cycle,each of these volumes changes continuously, so any given volume first increases,and then decreases. An increase creates a vacuum which creates suction, andthis part of the cycle is where the intake is located. As a volume decreasescompression occurs. During this period hydraulic fluid under low pressure isdelivered to the hydraulic bloc (or “brain”).

    Within the hydraulic bloc this pressure acts on a largediameter piston, and if the logic is correct, the high pressure in the clutchcircuit (holding the clutch dis-engaged) is dumped, and the clutch isprogressively engaged.

    So this is the function of the low pressure pump – to providea source of pressure to control the engagement of the clutch.

    After September 1960 the low pressure pump was replaced by acentrifugal regulator, which serves the same purpose. It's worthwhilespeculating why Citroen decided to dump the pump. With any engineering changethere are always a number of reasons driving the change, maybe with a primaryreason. The combined pump is a fairly complex assembly which relies on threeface seals and a couple of O-rings to keep the fluids in place. The old adageis that oil and water dont mix, and having the two fluids in such closeproximity may have driven the change toseparate them. As we dont have any data on warranty claims from the time Iguess we can only speculate.

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    To be continued.
    roger

  2. #2
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    The following details how I have gone about bringing one of these pumps back to life. It should be read in conjunction with both the factory workshop manual and the spares parts catalogue. I dont recommend someone undertake this overhaul without having access to a reasonable-size lathe and the skills to use it. Access to a milling machine would also be useful.

    When you pull the grotty pump off the engine it will look like this. It may however be severely corroded around the coolant stub and this may rule out the body being re-used.
    DS19 early water punp/hydraulic pump rebuild-ds19lopresspump_2.jpg
    DS19 early water punp/hydraulic pump rebuild-ds19lopresspumpdiag.jpg
    In the following text I will refer to parts with the above factory workshop manual numbers.

    Disassembly.
    This is where the fun starts.
    Bend back the tab washer (if fitted) and remove the nut and washer (2). Support the drive flange in one hand and hit the end of the shaft with a soft hammer to remove the flange. Don't lose the woodruff key (1). Unscrew the bearing retaining ring (5). This can be drifted if you're careful, but is much easier with a proper tool (refer to workshop manual).

    The next task is to remove the ball bearing (6). This is tricky, as Citroen made no provision to extract this bearing. The workshop manual shows a puller which inserts between the balls and pulls on the inner race. I machined up one of these from solid and it didn't work. Maybe it works for others. The alternative is to make up a simple puller, the base of which can be welded to the outer race, with a screw bearing on the end of the shaft. OK, it roots the bearing but you weren't going to re-use it anyway. I have had zero success rate in using MIG welding to weld the mild steel extractor to the hardened bearing race. Maybe others can have better results. I dunk the whole pump assembly in water up to the bearing height and nickel-bronze weld the bearing to the extractor.
    Once the bearing is removed the rest of the dismantling isstraight forward – just take your time and don't lose anything.

    Inspection
    All the components suffer from corrosion and/or wear.
    Items that should be replaced as a matter of course are the front bearing (6), the shaft (17), the water pump seal (22), the two O-rings (12 & 19), the two locking half-rings (8), and the paper gasket between the two halves of the body. Other replacements depend on the condition of the used bits.
    From what I've seen, the gerotor parts (14 &15) don't seem to wear much, and unless the mating faces are obviously badly worn or scratched, they can be re-used.
    Coolant leakage within the pump is controlled by the water pump face seal (22). The carbon face acts on a machined face in the aluminium housing and the housing face is subject to both wear and corrosion. Unless badly pitted and worn, a new face can be machined.
    Hydraulic fluid leakage from the pump is controlled by two spring loaded bronze face seals (13 & 20) acting on machined steel bushes in the housings. These seals are complemented by a pair of O-rings on the shaft. The bronze/steel faces do wear and their condition is crucial to the proper operation of the pump.

    DS19 early water punp/hydraulic pump rebuild-ds19hydfaceseal_1.jpg

    This is a new hydraulic face seal. The sealing face is the black portion. I'm not sure what the black surface treatment is, it's either a anti-corrosive treatment or a anti-scuff film. The height of a new seal face is only around 0.4mm, so if yours are down to zero, then they may be able to be recut in a lathe. Alternative is to try and find some new ones, or have replacements machined from phosphor-bronze stock.
    Leakage of hydraulic fluid along the shaft is prevented by 2 O-rings. These harden with age and the shaft corrodes. Only fix is a new shaft and new O-rings.
    Impellers – of the ones that I have seen, they seem to survive very well. They are quite soft, and I think they are either aluminium or a zinc-based alloy. The impeller should have the part number DS 231-7 visible on the face.
    Examination of the other bits and pieces is really only to determine whether corrosion has put them past their use-by date. If the springs (9 &21) have serious pitting I would look to find some replacements.
    Check that the 'drool tube' (25) and the breather hole in the main body are clear – run suitable twist drills through.

    To be continued.
    roger
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  3. #3
    BVH Roger Wilkinson's Avatar
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    Great stuff, thanks Roger.

  4. #4
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    There a number of special tools which are either essential to successful reconditioning of these pumps, or just make life easier.
    The first, which is really essential, is a support plate MR 3676-180. This enables the pump body to be held securely during work. It has a stub underneath which is held in a vise. The height of the spacer in the middle is 10.5mm to suit the impellers marked DS 231-7.
    DS19 early water punp/hydraulic pump rebuild-dslopresspumptool_1.jpg

    The next tool is essential. This is the front bearing extractor mentioned earlier. It's shown still welded to the bearing. Made from a machined plate at the bottom, a piece of tube with a 8mm flanged nut welded into the top.
    DS19 early water punp/hydraulic pump rebuild-dslopresspumpbrgpuller.jpg

    These are the mandrelsused to reface both the hydraulic seal faces (left) and the water pump sealface (right). Circular discs of varying grades of abrasive paper are supergluedto the mandrels and rotated against the relevant face.
    DS19 early water punp/hydraulic pump rebuild-dslopresspumptool_2.jpg


    There are a number of other special tools which are of useand details of these can be found in the workshop manual.

    OK, this is where it gets serious.
    First up is the shaft/impeller.
    Unless the shaft is in perfect un-corroded condition, it should be replaced with new. New shafts are available from Citrotech in Holland.

    Here is a comparison oftypical old with new.
    DS19 early water punp/hydraulic pump rebuild-shaftoldnew_1.jpg


    The shaft is a press fit into the impeller and a suitabletooling arrangement should be made in a hydraulic or arbor press to press theshaft out. When this is done you will probably find that the bore of theimpeller is scored and irregular. Unless you have some seriously accuratejigging to locate the new shaft when pressing it into the impeller, it wont runtrue.

    To be continued.
    roger
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  5. #5
    Real cars have hydraulics DoubleChevron's Avatar
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    Amazing, your going to have anyone and everyone with an early DS19 referencing this for the next 50years!

    seeya,
    Shane L.
    'Cit' homepage:
    Citroen Workshop
    Proper cars--
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    '72 DS21 ie 5spd pallas (last looked at ... about 15years ago)
    '78 GS1220 pallas
    '92 Range Rover Classic ... 5spd manual.

    Yay ... No Slugomatics


    Modern Junk:
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  6. #6
    BVH Roger Wilkinson's Avatar
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    We are a fairly small audience, but a very interested one.

    Roger
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  7. #7
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    Quote Originally Posted by Roger Wilkinson View Post
    We are a fairly small audience, but a very interested one. Roger
    Well said. Amazing contribution!
    JohnW

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    National Co-ordinator, Renault 4CV Register of Australia

  8. #8
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    The solution to getting the impeller and shaft to run true is to set the impeller into a holding jig in the lathe and machine the bore to around 17mm to accept a steel sleeve.

    DS19 early water punp/hydraulic pump rebuild-clockingds19impellor.jpg

    The impeller here is held onto a face plate in the lathe and is set up for concentricity with the seal mounting face prior to boring. (The rear face of the impeller was lightly skimmed true prior whilst still attached to the old shaft).

    DS19 early water punp/hydraulic pump rebuild-ds19boringimpellor.jpg

    A steel sleeve is machined to be a sliding fit within theimpeller bore and have a internal diameter which allows it to be bored to suitthe shaft (15mm dia). The sleeve is held into the impeller with Loctite 620which is designed for the bonding of cylindrical fitting parts and isparticularly suitable where temperature resistance up to 2000C isrequired. Once the Loctite has cured the sleeve is bored to be a sliding fit onthe shaft, and the shaft fitted into the sleeved impeller again with Loctite620. It is essential that the Loctite “Directions for Use” are followed, andthat the original axial relationship between the impeller and the shaft ismaintained – refer workshop manual.

    Here is the completed assembly, before the water pump seal ispressed on.

    DS19 early water punp/hydraulic pump rebuild-ds19pumpshaft.jpg


    The next step is to recondition the sealing faces within thepump bodies.
    The water pump body should be mounted in the lathe on asuitable face plate and a light skim taken on the seal face with a boring bar,just enough to remove any scoring or corrosion. A mandrel then needs to be madeto hold abrasive paper discs to improve the surface finish of this face. Istart with 240 grit wet and dry paper plus oil and finish with 800 grit, and rotate the mandrelwith the fingers. The face should end up with a matt finish free from anymarks. Now measure the depth of the face – measurement 'f' in the diagram posted earlier. A suitable shim should be made up and fitted to the shaft to restorethe pump seal end loading – refer the workshop manual.

    Fit the water pump seal to the shaft. This may prove to bedifficult to get the rubber to seat onto the shaft, and may require a suitablemandrel to get it to seat.


    Inspect the 2 steel hydraulic seal faces in the bodies. Theseshouldn't be badly worn – if they are, I'd be looking for another pump. Theworkshop manual details a procedure for lapping these faces with “a very fine polishing paste”. The problemwith this approach is that the main bronze bearing should be removed duringthis procedure to avoid contaminating the bearing with the abrasive. Finding areplacement sintered bronze bush of the right dimensions and getting it inplace concentrically is a challenging task. Rather the steel faces can berectified using a mandrel with abrasive discs as for the water pump seal face.The faces of the bronze seals can be reconditioned by rubbing on oil-wetted 800grit wet and dry paper on a surface plate.

    Once all the rectification is done we can start someassembly. Here are all the parts.

    DS19 early water punp/hydraulic pump rebuild-ds19lopresspump_1.jpg

    To be continued.
    roger
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  9. #9
    1000+ Posts gerrypro's Avatar
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    Roger you maintain amazingly high standards. This is another example of the class of work that we have come to expect from you!
    Cheers Gerry

  10. #10
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    REASSEMBLY

    First a stepped bush has to be machined – MR4251, referworkshop manual for dimensions. This is used in temporary assembly to check forleakage from the seals in the main body.

    This is the test setup. The breather hole is plugged and air at 14 psi is supplied to the body via the drool tube. This test rig is also used after final assembly to check leakage of the three seals where one port of the hydraulic pump is closed and the air is applied to the other port.

    DS19 early water punp/hydraulic pump rebuild-ds19lopresssealtest.jpg


    The assembly of the rest of the pump should follow theworkshop manual.


    A few points to note.
    It is essential to get the axial relationships between all ofthe components right otherwise you can run into clearance problems - this starts at the back of the pump wherethe distance between the back face of the pump and the end of the shaft must be10.5mm.
    The width of the gerotor parts exceeds the depth of the recess in the front housing by around0.08mm. Thus the paper gasket between the two bodies has to be of sufficientthickness to provide clearance for the pump elements. I use paper measuring0.18mm uncompressed.
    I have a dummy front bearing to use for checking all is OKaxially. If you press up the assembly with a new bearing and then findsomething is wrong you will not be pleased.
    Use a sealed front bearing – SKF 6302-2RSH. This means thatthe grease nipple is not required and the hole can be blocked off.
    There is a spacer (3) between the front pulley and the frontbearing, the thickness of which can be used to adjust the position of thepulley.
    The front shaft nut should be loctited in place.


    After all your hard work this is the end result of bringingback to life a component that Citroen would have never envisaged having a lifebeyond 20 years.

    DS19 early water punp/hydraulic pump rebuild-dslopresspumpassy_1.jpg
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