Oil leak!

[BlueSky]

My Aprilia has just developed a fair oil leak coming out the top of the distributor drive. Now having never been inside my engine or touched the oil pump does anyone have any ideas why this could be happening? I know the distributor drive shaft gets oil via a cup that is drip fed from the timing chain housing, but does it drain out somewhere? Is the a chance of some sort of pressure build up?
Running for 5 mins in garage no leak, but after a 50 km run oil everywhere!
Noel

[simonandjuliet]

1) any evidence of cr.ankcase pressurisation ? I had very tired rings on YRV , but that blew oil out of the filler cap
2) Have you tried removing and clearing the oil pressure relief valve ? Again on YRV I had problems with that. If it is stuck, it can be a pain to get out, especially if it has been replaced with a ball bearing !

Good luck

[ben]

Hi Noel
           Sounds like an interesting problem!
           I have three blocks that I can peer into and the little cast-in cup that picks up oil and feeds it into the space around the distributor drive shaft is different on all of them! The later engines have holes in the bottom of the cup which will greatly reduce the amount of oil that is fed across into the shaft space which suggests this may have been a known problem in the early days and hence a mod was introduced. However I have not come across the problem myself.
          Another difference between engines is that the later ones have the drilling for the fuel pump actuating rod carried right through into the crankcase whereas the early engines don't so surplus oil cannot escape so easily.There is just a very small bleed hole on the earlier engine which could easily get blocked.
          I do not think the oil is likely to be forced up the shaft by crank case pressurisation (eg due to worn rings) as this would be evidenced by heavy breathing from the vented oil filler cap 'tho I guess it is not impossible.
          The other mechanism that might pressurise the space (where the cup feeds the oil to) is the action of the cam and the rod that actuates the fuel pump. If you still have the mechanical pump you could try taking it off, together with the rod, and covering the hole with a blanking plate--assuming you have fitted an electric pump as well.
          Whether this makes any difference or not does not alter the fact that something must have changed to cause the leak to start.  Perhaps pressure could build up to cause the leak if the delivery hole from the feed cup had become blocked with debris of some sort. If you take off the cover on the front of the timing chain cavity --you might have to take off the radiator for access--and you will then be able to see the little cup without taking the head off.
          To inspect or open up the small bleed hole mentioned in paragraph 2 requires you to take the sump off.
          Another easier option would be to apply an air line to the hole where the fuel pump rod goes. This might blow out any obstruction.
                 I look foreward to another chapter in your bumper fun book. Plenty of time before the next Castlemaine!

[BlueSky]

The oil pressure hasn’t changed either way and is still excellent. There is no evidence of excess breathing from the filler cap, so don’t think the issue is there.
Checked the oil pressure regulator and that seems fine. Interestingly it had 3 copper washers under the cap, 5mm in total, which would have the effect of lowering the spring pressure, assuming it has the correct spring, and releasing the pressure earlier. It has been like that ever since I got the car so won’t be the problem.
Overnight the oil level in the distributor drive shaft dropped but not as far as the fuel pump, so I suspect that Ben is correct with the bleed hole becoming blocked. No electric fuel pump fitted yet. I don’t have an air compressor so this sound like the ideal time to get one.(How does one survive without one I hear you say!)
Just in case I get carried away and want to take the sump off is there anything involved in doing that that I should be aware of?
Thanks for all the advise, will let you know how I go.
Noel

p.s. Did anyone notice my sexy undershields?? I can see why they don’t last given the build up of oil and muck they collect, throw in a bit of leaking fuel from the carby and it could be exciting! They do make the car a little quieter and less fumes in the cabin though.

[lancialulu]

i have a pair of these "sexy" undersheilds in excellent condition if anyone wants to make me an offer??!!

Tim

[williamcorke]

i have a pair of these "sexy" undersheilds in excellent condition if anyone wants to make me an offer??!!

Tim

Yes please. Let's discuss when I pick the other parts up next week.

[simonandjuliet]

Did you sort out the oil leak ? No nasties when the sump came off ?

[BlueSky]

Haven’t pulled the sump off yet! Blew compressed air through the fuel pump rod hole and put an O ring on the distributor base. So far seems to be working fine, although due to a recalcitrant brake fluid reservoir leak we haven’t gone on a long journey yet, time will tell.