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| Clutch Oil Leak https://www.ausmini.com/forums/viewtopic.php?f=2&t=98702 |
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| Author: | stewartrjh [ Thu Jun 20, 2019 11:56 am ] |
| Post subject: | Clutch Oil Leak |
Hi, Some technical questions for the experienced Mini engineers out there. I have an oil leak on the clutch. The full story is that the engine has been running for about 8 months now. When I built the engine I used the same primary gear and bushes that were on it, shimmed for end float but as there was nothing in the manual I saw about bush clearance to the crank and it had been running and not leaking when I got the car I did not worry about it. Initially there was no oil leak, after about 3 months on the road a couple of drops of oil appeared under the car each time you drove it, coming from the wobble pin. About 4 months later the clutch slips. So I have taken it apart and the oil appears to be coming out of the end of the primary gear. The seal on the engine end looks fine and very little oil there, but quite a bit on the flywheel. See pics. I used assembly lube on the primary gear so possibly why it did not leak for a while and over time was washed away by the oil. The question is, given there is no seal on the primary gear to the crank it is never going to be a perfect seal, there are holes in the primary gear on the engine side of the seal to let oil onto the bushes so there will be oil in there. I read that the flywheel has oil drain holes in it to let this bit out and drain out the bottom. My engine has a steel flywheel C-AEG421 and it has no drain holes. Looking at pictures of all the aftermarket flywheels I can not see any, so it is not like mine were missed out. If I fit a new primary gear with new bushes will this still leak a bit and with no drain holes and eventually oil up my new clutch plate ? I can measure there is wear in the old bushes, but fitting a brand new gear to the crank I can still feel play between the primary gear and crank. It looks like a pain to drill oil holes in the flywheel, and a little scary to go modifying a flywheel. Am I worrying too much ? But better to ask now before I put it all back together. Thanks for reading. Stewart. |
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| Author: | simon k [ Thu Jun 20, 2019 4:28 pm ] |
| Post subject: | Re: Clutch Oil Leak |
I put new bushes in my primary gear and get a little bit of oil through it the same way, though my clutch doesn't slip. The oil does pool just inside the friction face as per your image, but I don't think I get as much oil as you I originally had a 'floating' inner bush but it was spinning between the bush and the primary gear instead of between the bush and the crank, so I pressed in an original type bush and had a machinist friend machine it to spec. I wonder if there isn't a little bit of wear on the crank tail that needs to be catered for |
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| Author: | lomin [ Thu Jun 20, 2019 11:05 pm ] |
| Post subject: | Re: Clutch Oil Leak |
Hi, I have fitted a lot of bushes, inner and outer over the years , and generally if the bushes are correct dimensions, and you have the correct end float, you will have very little problem with that specific leak. But, it is common from my experience to have the inner end of the 1275 crank undersize by a minimum of .001" , and the bush often has wear of 4 or 5 thou. That will leak for sure...need to machine bush to suit, although todays new bushes don't seem to have much meat to remove . I like the floating bushes , and I believe they are supposed to spin on both surfaces, but you do need a good size crank for these. Very thin oils and an engine that "breathes" too much don't help oil leaks either Cheers Lindsay |
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| Author: | stewartrjh [ Fri Jun 21, 2019 9:52 am ] |
| Post subject: | Re: Clutch Oil Leak |
Thanks for the replies. It is an 1100 engine so one bush is not available. So I just ordered a new gear with Bushes. Measuring the old to the new with good vernier calipers (not real good I know) the old one is about 4 thou bigger, so that is probably the majority of the issue. Thanks for the figure it leaks at, it is hard to tell how much you need to make a leak. There is a very small texture change on the crank between where the bushes run and don't run I can feel with my finger, so probably the 1 thou wear there as well. So the new gear and bushes should basically cure my problem. I am still confused about the drain holes in the flywheel, not having a factory flywheel to look at I assume they are there, can anyone confirm they are ? Next step I think is to get a micrometer for a proper measure, I would rather not pull this apart too often. |
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| Author: | drmini in aust [ Fri Jun 21, 2019 11:17 am ] |
| Post subject: | Re: Clutch Oil Leak |
Factory flywheel has drain holes, I guess for racing they felt no need. |
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| Author: | Hinesy1275 [ Fri Jun 21, 2019 11:29 am ] |
| Post subject: | Re: Clutch Oil Leak |
Agree with Lindsay - check crankcase pressure and whether the right 'orifices' are breathing |
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| Author: | 1071 S [ Fri Jun 21, 2019 4:59 pm ] |
| Post subject: | Re: Clutch Oil Leak |
".....I am still confused about the drain holes in the flywheel, not having a factory flywheel to look at I assume they are there, can anyone confirm they are ?...." I have an ultra light Minispares flywheel and it has holes.... Mine has a groove just like the one you show above - that seems to have oil spilling out at 6 o'clock... but mine has holes drilled from the outer circumference of the groove through to the back of the flywheel. Any oil that leaks past the bushes would be collected in the groove and would then be spun out, exciting at the back of the flywheel .... well away from the clutch plate/friction surface. Mind you, after umpteen years, there are no signs that oil has ever leaked past the primary gear bush onto the flywheel.... From memory.... I seem to remember that the primary gear has similar drillings behind the inner bush that would spin oil out behind the seal ????..The outer bush would seem to run pretty much dry. Cheers, Ian |
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| Author: | stewartrjh [ Fri Jun 21, 2019 11:45 pm ] |
| Post subject: | Re: Clutch Oil Leak |
Interesting that a Road/Rally flywheel has no drain holes, but maybe they figure you should put new bushes in and stop the problem. The engine has a tappet chest breather on it, the one with the can, which I cleaned all the sludge out of before the engine was built, I checked inside and it was not blocked. It did not have steel wool type stuff in it. I ran the engine initially with a just a breather filter on top, but to see if the oil leak could be stopped I connected it to the HS6 SU port via a Corolla PCV-013, but it made no difference. It did breathe quite heavily for the first 100 miles or so but has settled down quite well and now has about 1000 miles on it. I will clean it all up and do a proper measure of the crank and if that is ok measure up the new bushes and put it back together and see how it goes. Thanks for all the info, nice to have good confidence that you have not missed anything before you put it all back together. Stewart. |
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| Author: | gtogreen1969 [ Sat Jun 22, 2019 12:16 am ] |
| Post subject: | Re: Clutch Oil Leak |
stewartrjh wrote: Interesting that a Road/Rally flywheel has no drain holes, but maybe they figure you should put new bushes in and stop the problem. If using your using a PCV then the hose should be connected to the manifold. If your connecting the hose to the carby port then you dont use a PCV.
The engine has a tappet chest breather on it, the one with the can, which I cleaned all the sludge out of before the engine was built, I checked inside and it was not blocked. It did not have steel wool type stuff in it. I ran the engine initially with a just a breather filter on top, but to see if the oil leak could be stopped I connected it to the HS6 SU port via a Corolla PCV-013, but it made no difference. It did breathe quite heavily for the first 100 miles or so but has settled down quite well and now has about 1000 miles on it. I will clean it all up and do a proper measure of the crank and if that is ok measure up the new bushes and put it back together and see how it goes. Thanks for all the info, nice to have good confidence that you have not missed anything before you put it all back together. Stewart. |
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| Author: | stewartrjh [ Sat Jun 22, 2019 7:27 pm ] |
| Post subject: | Re: Clutch Oil Leak |
I was told running a PCV was not really needed with the Carby port but better if you had a backfire as the valve shuts. I am sure I have read that on this forum that other people run it for that reason. |
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| Author: | stewartrjh [ Sun Jul 07, 2019 9:31 pm ] |
| Post subject: | Re: Clutch Oil Leak |
Measured up all the bits with a Micrometer, .003" wear on the bush, .001" on the crank as a couple of you predicted. To make sure I got some oil drain holes put in the flywheel. Put it back together and so far not a drop of oil. Nice result actually as I put a new radiator in and the mist of coolant that was getting out has also also been cured. Happy to have it running again, and now you can wind it out in second gear and go into third without the clutch slipping it is far nicer to drive. I also changed to softer "genuine" engine mounts while it was all apart which has cut down the vibration and noise very nicely. Thanks for the replies and information everyone, much appreciated. Stewart. |
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