CRC Unit (Clutch Re-engagement Control) - Strip Down and Overhaul

This post has been updated to correct an error. See a related post HERE. 

It was time to rebuild the CRC.......

All Rebuilt

So what's it for? Translated from a technical note issued by Citroen:

Clutch Re-engagement Control

Placed between the hydraulic block and the clutch cylinder, the clutch re-engagement control gives a progressive engagement and a fast disengagement.

Disengagement - the fluid under pressure arriving at the clutch cylinder is not slowed. Fast disengagement.

Engagement/Re-engagement - a lever controlled by the accelerator pedal determines the speed of engagement and re-engagement by the obstruction of the fluid flow (ball more or less seated).

The re-engagement will be faster since the driver will desire acceleration or a higher gear: accelerator pedal pushed.

When there is no action on the accelerator pedal, liquid under pressure contained in the clutch cylinder passes by the ball of obstruction (via indents made on the ball's seat).

So there you have it!

As with several other components, I'd done a basic tidy up job on the CRC that came off my car back in 2015. Other than ordering a new gasket so that I could split it before re-painting, I'd not actually cleaned it out.........

First effort - July 2015

I picked up another CRC over at Citromobile earlier this year and decided to rebuild that one. It had a load of silicone sealant spread all over it - suggesting a leak. I was hoping that was just because the 'O' rings were worn or the gasket had been disturbed (or maybe both) and not because the unit was cracked.

Spare CRC - But Possibly Unusable

Documentation on stripping the CRC is thin on the ground - probably because Citroen say you can't repair or service them. I couldn't find anything in manuals 518 or 814, but basic information can be found in Operation Dh.314-3 in volume 3 of French language Manual 583.  Here's a translation of what it says:

DISASSEMBLY

NOTE: any intervention on the corrector causes it to be unregulated. It is however possible to unblock the calibrated return holes. Simply deposit the ball (1)

1. Remove the rewind corrector.

2. Deposit:

- the spring (2)

- the ball (1).

MOUNTING

3. Mount:

- the ball (1)

- The spring (2) orients as shown in the drawing, the small diameter resting on the ball.

Wedge the bent end of the spring into the hole (c)

4. Fit and wedge the re-clutch

So if tinkered with, a serious danger of 'unregulation'. Looked like I'd be flying blind on this one........

Disassembly

The CRC body has two main ‘barrels’ with end caps held in place by ‘C’ spring clips. In this regard, it’s similar in construction  to the pressure regulator and so I used the same Citroen-recommended technique for further dismantling of the end caps.

Rotating the gap of the relevant spring clip to my chosen point, I drilled a 2mm hole 4mm in from the edge of the barrel. I then rotated the clip so it’s edge was just over the hole just drilled.

Drilling A Hole To Remove the Spring Clip

With the aid of a spacer, gently compressing the cap in a vice just enough to loosen its  grip (on the clip), I used a twist drill to compress the edge of the clip – which enabled me to winkle it out.

Pushing Out The Spring Clip Using A Twist Drill

I used the same technique to remove the circlip of the bottom barrel end cap. BE WARNED that if you dismantle this barrel to clean the slide valve and replace the spring and seal, then it is very fiddly to reassemble the pushrod mechanism in terms of aligning it with the bore. Not impossible – just fiddly…..

Although I was able to remove both spring clips, only the the cap from the top barrel came out willingly. Gentle tapping the unit on a hard surface gradually shook the cap off. 

Removing an End Cap

The cap itself has a sealing ‘O’ ring around it’s circumference.

'O' Ring On The End Cap

Removing the cap revealed a spring-loaded push rod which acts on the end of the cam in the CRC to limit it’s movement. 

Push Rod and Spring from the 'Top Barrel'

The other cap stay slightly pressed into the barrel and didn't want to move.

One End Cap Remained Pressed In

I undid the four Pozidriv screws to split the unit – though the two halves remained joined by an umbilical cord of sorts - in the form of the adjuster spring.

Using a flat headed screwdriver, turning the adjuster knob anti-clockwise released the ‘key’ holding the adjuster spring. 'Key' is a poor description as it doesn't rotate - just moves up and down two guide grooves. 

With the key released from it’s shaft, the adjuster spring was unhooked from the (pivot?), and the unit separated into its two main parts. There was a paper gasket between the two.

Adjuster 'Key' and Tensioning Spring

With the unit split I was able to work on that stubborn end cap: I removed the slide valve from the ‘inside’ end and used a piece of soft dowel down the bore (it is precision engineered and should not be scratched) to tap the cap off. This revealed another spring mechanism, which was removed. NOTE THE ORIENTATION OF THE PUSHROD ON THE SPRING

Most of the Components of the CRC

The ball bearing ‘restrictor’ was removed by unhooking the end of the retaining spring from the adjacent hole.

The end of the spring was hooked out of it's hole

The ball bearing was then removed from the hole.

Restrictor Ball and Retaining Spring

Preparation for Reassembly

I removed one of the studs for the hydraulic pipe union but left the other in place as a handle for when I painted the unit. CAUTION: the holes for these studs are tapped into the channel that guides the key that alters the spring tension - and the threads need to be re-sealed on re-assembly.

The return pipe union and copper washer were removed from the end piece

The rebuild kit I bought contained six 'O' rings - but I could only find homes for five..... I hate having bits left over!

Annoyingly Surplus 'O' Ring........

There is a cam, pressed against a ‘see-saw’ lever in the end piece. The spindles for these are fixed into the end piece and covered with a yellow glue. I’m not sure if this is to seal against LHM leaks, or some kind of a threadlock to prevent movement after they have been set in place. I decided to leave well alone and did not take the spindles apart.

(UPDATE: See my later post of 29 June 2019 HERE to find out where that pesky seal should go.....)

Both halves and the end caps were stripped of paint on the wire wheel. Together with other small parts, they were cleaned in an ultra-sonic cleaner. Small, delicate, pieces were hung on cotton to stop them rattling around. Everything was then rinsed and dried with compressed air before being brushed with LHM to prevent any flash rusting. The outer surface of the iron body was degreased then brushed with phosphoric acid. I was careful not to get acid inside and on the bores.

Suitably masked, the body pieces and the end caps were sprayed.

Painted and Ready for Reassembly

The Setting Position

Before re-assembly, I took a moment to familiarise myself with the concept of the ‘setting pin’ position. The setting pin holds the cam inside the end piece of the CRC in the right orientation relative to the ‘idling’ position of the carburettor (in other words it determines the correct rotational position for the shaft for fixing the ‘flextor’ wheel in place).

It is possible to fully rotate the shaft that operates the cam – and then insert the setting pin. Basically, the pin will have lodged in the curve of the cam, not the locating hole. This would give the wrong position for the shaft and so the flextor wheel.  

To find the correct position, I fully rotated the shaft clockwise and then moved it back just a fraction. I then introduced a setting pin (a 2mm drill or short length of coat hanger is ideal) into the hole and applied gentle pressure. I continued to rotate the shaft slowly anti-clockwise and the setting pin then dropped into a hole. This was the correct setting position.

Reassembly of the body

I reassembled the two barrels.

The top barrel was straightforward, using a new spring, ‘O’ ring and LHM to lubricate the moving parts.

A new ‘O’ ring was fitted to the cap and the cap pressed home. 

Refitting the End Cap with it's new 'O' Ring

The circlip was then fitted.

Circlip back in place

First time around (September 2018), I struggled with the second barrel - because I was trying to put the spring assembly together wrongly! I was inserting the push rod through the spring, like this: 

Don't Do This........

T-Mo - who is a member of the 'io' DS/ ID group and rebuilding his own CRC - contacted me in December 2019 to query this. I pulled another CRC apart and this is what I found:

As at December 2019, I'm going to have to pull and correct the build on my CRC, but the rest of this blog still holds good.......

With the second end cap and it’s spring clip fitted, I gave the cap ends and main body another couple of coats of paint.

When they were removed, I noted that the studs for the hydraulic pipe union were tapped right into one of the two grooves of the adjuster bore and seemed to have some kind of pitch sealing cap on them.

Studs are Tapped All The Way Into the Adjuster Groove

I didn’t want to reassemble the unit, then fit the studs and find they either leaked, or blocked the adjuster key, so I needed to fit and seal them before final reassembly. I wanted a sealant that was fluid but which would set hard – so that I could be sure it didn’t flow into the adjuster bore when in use.  I mixed up a tiny amount of Araldite and put it on the tip of the stud end. I put threadlock around the threads. I refitted each stud making sure the Araldite and threadlock did not seep into the adjuster channel. I left the bodypiece standing stud end down so that the Araldite settled on and over the end of the stud prior to setting hard. Hopefully that will have been enough to create a seal.

Araldite sealing cap on the end of the stud

Studs Refitted

A new ‘O’ ring was fitted to the adjuster – which was lubricated and pushed into place.

Refitting The Adjuster

I refitted the roll pin ‘stop’ and the collar on the adjuster. The collar is only really there to help limit the rotation of the adjuster, though I guess it could be positioned against the roll pin to limit further unwanted rotation. Well – in one direction anyway.

The slide valve was fitted inside the open end of the lower barrel – with the dished end for the operating pin sticking out.

End Piece Reassembly

I didn’t change the main big spring within the end piece as this is very hard to engage on the ‘see-saw lever hidden deep inside.

Bottom: 'see-saw' pivot with push-rod groove. Top: Cam

I did fit a new adjuster spring to the lever though. To the other end of this I then fitted the adjuster ‘key’.

Return nozzle with setting pin plug

With a new gasket first slipped onto the end piece, the two halves were brought together and the push rod pin that operates the ‘seesaw’ lever was slipped into place in the cups on the slide valve and the see-saw lever.

The adjuster key of the end piece was introduced into the grooves of the adjuster bore in the main body. Holding all this together, I used a slotted screwdriver to tighten the adjuster. With a bit of wiggling and jiggling the adjuster key finally (finally) bit on the end of the adjuster and began to allow the two halves to be closed together. It’s important to confirm that the key thread has engaged on the adjuster before closing the unit up.

I fitted a new restrictor ball and retain spring.

Locating the Restrictor Spring

The return pipe nozzle was fitted with a new copper ‘O’ ring. My kit came supplied with a new plug for the setting pin hole but, bizarrely, this was too small to slip over the return nozzle. I didn’t like the look of this anyway, as it was different to the one I had removed. Fortunately when I had first cleaned up the CRC back in Spring 2015, I had bought a couple of ‘proper’ replacement plugs when I bought a new gasket.

Top: original, middle: from the rebuild kit, bottom: from 2015

Adjuster and Lock-ring

  Job done for the moment. Hope it works!

Weber 28/36 DDE Carburettor (Part 2) - Carburettor Set Up

The correct carburettor set up is important on any car but particularly so on a bvh DS where there are two idling speeds and so much of the hydraulic wizardry is dependent on a hap[py carb.

Most settings should be done when the engine is hot – so running. At this stage of my rebuild that isn’t possible for my car, so I just needed to do an initial set up before bolting the carb to the car. I turned my attention to the primary butterfly throttle stop screw: the screw that was originally factory set by Weber.

Citroen Operation DX.142-3 of manual 518 (applicable to my DDE carburettor) offers no set-up instructions. It tells the reader not to tinker with the primary butterfly stop screw:

"IMPORTANT NOTE: Under no circumstances must anything be done to the stop screw for the first (small) butterfly, individual adjustment of this screw having been carried out by Messrs. WEBER on each carburettor"

Indeed, on my 28/ 36 DDE carb, it is a screw with an additional lock nut – whereas the screw for the secondary butterfly is a screw and spring.

The primary stop screw is on the right - with the lock nut

I have no more than a basic understanding of how I think the carb is working. Here we go:

The reason that this setting of the primary butterfly is critical is that it determines the degree and source of the fuel/ air mix when at idle, and ensures the optimum and smoothest acceleration as the throttle is opened up - which is achieved through a series of ‘progression holes’ in the side of the primary throat/ shaft: the successive exposure of the progression holes allows the initial and gradual introduction of additional fuel into the low/ mid revs driving range.

The cluster of three offset progression holes can be seen

With the engine running, and throttle closed, a vacuum is created below the butterfly. The principle is that, in it's 'stop' (idling) position, the edge of the butterfly should just block the 'first progression' port so that, in idling mode, fuel flow and mix is achieved only via the vacuums' draw of fuel through the idle jet.

As the throttle is opened, the primary butterfly flap moves such that one, then more, “progression holes” are gradually exposed and are also subject to the vacuum: additional fuel is pulled into the manifold as more air is introduced - thus the appropriate fuel/ air mix is maintained. If the primary butterfly is not set correctly then either the car will have ‘lumpy’ and/ or delayed acceleration (dead spots), or will not idle correctly because the idling mix is already partly via the progression holes.

I THINK that's the idea......

It is generally accepted is that it is very likely that the butterfly settings will have been tampered with in the past and so there needs to an understanding of how to reset these. Other than use of a CO2 meter, I’m aware of three approaches:

Operation D.142-00 in the later manual 814 offers general advice on adjustment of later variants of the Weber carburettor:

"With the butterfly closed, the edge of the (throttle stop) screw in contact, turn the screw 1/3 of a turn. At this moment, a feeler gauge of 5/100 (0.05mm) must pass between the butterfly edge and the bore"

This is only applicable to Weber 28/36 carbs where the stop screw doesn't have a lock nut - and so not my 'DDE' variant. I didn’t like the sound of this one anyway: my feeler gauges are flat. How could I possibly get an accurate and reliable reading pressing it against the curved bore of a carb throat? The fingers of different gauges might be wider and so sit in the curve in a different way?

Rotate the primary butterfly stop until it hardly touches the lever. After that rotate the screw by a further 1 1/4 turns inward. 

This sounds a bit arbitrary and assumes the stop lug hasn't been bent. It assumes standardisation across all carbs. If this was the case, then why would each carb have had a unique factory-determined setting in the first place? I've also seen similar instruction - but which instruct you to turn the screw in 1 1/2 turns......

3.   Adjust the locking screw for the primary butterfly so that, with the throttle in the idle position, the first progression hole is ‘just covered’ with the throttle in the idle position.

I liked this. Since the setting was all about fuel mix and acceleration, this was the approach seemed the most logical one and would be geared to the individual carb. But how to judge ‘just covered’? The advice I have read was to use a magnifying glass….

I came up with a different approach….. Likening the flow of fuel/ air to access for light (yes, I know how wrong that is!!!) I did the following: I removed the brass plug in the side of the carb that covers the progression holes. This tucked around the back of the carburettor.

The brass screw plug covers the progression hole passage

Removing the plug revealed the progression holes.

Progression holes revealed.......

Shining a torch in the bottom of the primary barrel, I looked through the small hole where the brass screw had been and adjusted the stop screw so that it ‘just’ cut out the light.

Adjusting the primary butterfly to cover the progression holes using a torch

I found the optimum point, beyond which any further minor tightening of the adjuster screw immediately began to allow light to show. I tightened the lock nut and blipped the throttle a couple of time to check that light was still cut out and that any miniscule movement of the throttle began to expose light. That was it. I'll have to see if that works......

Choke and Secondary Butterfly
Pulling on the choke lever turns the spindle of the choke flap/ strangler - but then further also starts to pull on a linkage mechanism that opens the primary butterfly. With the choke fully engaged, the primary butterfly is meant to open by no more than 0.9mm

I found that, if the choke lever/ was fully engaged, after the choke flap had closed........

Choke flap fully closed.

......the linkage still had scope to open the butterfly by a good couple of millimetres.It’s meant to be just 0.9mm.

Any further pulling will operate the linking mechanism

I reasoned that, when the engine was dropped in the car, by adjusting how I trapped the choke cable outer in the clasp on the carb, I could limit the length of pull on the choke cable so that it fully closed the choke flap – but only opened the secondary butterfly by just under 1mm. 

I aim to adjust the choke cable fitting to limit the  travel of the linkage

I just hope I’ll remember this when the time comes!

Refitting the Accelerated Idling Device
Following a re-zinc, the long studs were refitted to the carburettor body.

The spring-loaded valve was refitted......

.....and secured in place with its brass collar.

Plunger and collar refitted

I had cleaned and repainted the main body several years ago. I coated the slide valve inside with LHM and made sure it could move freely before bolting the body to the carburettor. 

There is no gasket between the accelerated idling device and the carb, so I'm not sure whether I should expect any LHM to leak past the slide valve?

UPDATE: I noticed a groove in the body of the idling device and a similar recess in the carb. Since there is no seal on this thing, I have a theory that any fluid that gets past the slide valve goes down a drain in the carb into the inlet manifold, and then drains away through the long hose on the bottom - just as excess fuel does. Just a theory....