If you've read my 29 September 2018 post about rebuilding a CRC unit, you will know that my repair kit seem to have an extra 'spare' seal in it. Surely that wasn't right?
I'd done a pretty comprehensive strip of my CRC, but had ducked-out of pressing out the shaft with the cam on. I couldn't really see how it came out or went back together, so thought it best not to disturb it.
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| Strip Down |
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| Where did the mystery seal go? |
Was it a mistake in the kit? I checked a few other kits and they too seemed to have one seal more than I could account-for. In fact the kits varied greatly: some included the hook ended springs, others didn't. The CRC on an IE car doesn't have the flow restrictor ball bearing - though at least one of the kits I found included a bearing. It was all a bit of a lottery.
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| Seal kit bingo....... |
Having accounted for everything else, I was pretty sure that the seal was something to do with the rotating shaft, though I couldn't think why an IE car would have the seal but a carb car wouldn't. The shaft seemed to be the kind of thing that should be sealed, but I would have perhaps expected it to have two seals - one either end? However of all the kits I looked at, I could only find one 'O' ring without an obvious home......
I made some enquiries about the differences in the kits and had some interesting ideas in response. One person I spoke-to thought the extra one went onto the end of the pipe that the return hose is connected to. Another thought it was an 'anti-rattle' fitting that went between the CRC and the inlet manifold. Another just thought it was included as a handy spare (for what?).
Unconvinced by these ideas, I left the last, spare 'O' ring off. I got the CRC all back together again but that extra 'spare' 'O' ring niggled me.
It must go somewhere? I carefully put it away in a box. I was keen to get to the bottom of this and shortly after my rebuild I got a response to the thread I had started over at 'Aussiefrogs'. Firstly 'Myourd' posted that he'd knocked the shaft out of a CRC and had found a seal. A day or so later Michael ('Michaelr') posted a photo. It solved the riddle of that last seal!
Here's the photo. You can see that the single, black seal fits into a groove on the rotating shaft.
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| Location of the mystery seal revealed! |
So - how to get at that seal? There is a bush on the end of the shaft that does not connect to the carburettor - so the other end. It looks as though the bush (on the right hand side of the picture above) has been pulled off the shaft with mole grips or similar. It looks quite chewed up. More recently I have seen photos of work done on the CRC by 'Timo'. It looks as though he welded a length of threaded rod to the end of the bush and then, by rigging up a nut and spacer around the bush with a piece of tube......
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| Using a nut to wind off the seal bush (photo by Timo) |
.......slowly wound the bush out. Very much like pulling the cork out of a bottle of wine. You can see the bush and welded rod at the bottom of the photo below.
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| Bush with welded threaded length (photo by Timo) |
With a bit of cleaning up, I reckon that bush could be re-used for the rebuild after replacing the seal.
Going back to Michaelr's photo, you can also see that the 'O' ring seal ion the removed shaft looks quite worn and flat. Maybe it leaks....
The spare CRC I'd bought at Citromobile was covered in silicon sealant and it was very likely that was because it leaked in some way. Maybe because it lacked the gasket between the two halves, but maybe that difficult-to-get-at last seal was the culprit?
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| Smeared-on silicon sealent points to a problem of some kind.... |
The photo from 'Michaelr' was also helpful in another way. Now when people say they need another CRC, they often say the reason why is that the rotating shaft has become stiff or 'knotty'. If you turn them by hand, they do get a bit knotty and 'lock' - reluctant to return. Here's a link to a video of someone demonstrating this:
Anyway, when the CRC is fitted to the car (on a carburettor car at least), the return springs of the throttle pedal help with that 'return' action. However, it wouldn't hurt to make sure there are no flat spots on the cam.
From my own rebuild, I noticed that the cam was slightly worn and wondered whether it had developed a flat spot and whether it would perhaps benefit from a polish. However as I wasn't confident about getting the cam off, I had to leave that thought there. Seeing Michaelr's photo now, helped to demystify this part of the puzzle for me: I could see that the cam fits to splines on the shaft.Not so sure about that chewed-up part on the right side of the photo though.
As I've got a spare CRC, perhaps I'll buy another rebuild kit and go the whole hog this time - replacing that 'spare' seal and polishing the cam.
