Section : Engine

Oil pressure 

Posted By : Ian Thomas, 16-Jun-2004, 09:48pm

• Oil pressure 

  Posted By : Ben Ferguson, 17-Jun-2004, 12:00pm

  Hi Ian,
  
  The book quotes 40-60psi once warm at 2000rpm as far as I can remember. Tickover giving 20psi sounds fine to me- I get 75 psi at 2000rpm when cold, which drops to less than 10 psi when hot at tickover....hmmm methinks an oil change is in order! This is after I changed the crank and bearings too, and the oil pump was way within the tolerances. Worn out bearings proved the problem then, and I think these new repro ones are shot after just a few thousand miles as I have a nasty bottom end rattle now at certain revs.
  
  What mileage has you engine done?
  
  Ben

  • Oil pressure 

    Posted By : Tim Everitt, 17-Jun-2004, 12:14pm

    Sounds about right to me.

  • Oil pressure 

    Posted By : William Davies, 17-Jun-2004, 01:31pm

    Hi Ben,
    Did you have the crank re-ground, or did you just put in new bearings? If the former, then I would suspect the quality of either the re-grind or the bearings. If you didn't get the crank ground, what's happening is exactly what I'd expect. Bearing changes are specified at certain service points, but this is preventative maintenance. If there is any noticeable noise from the bearings then the damage to the crank is already done - you can change bearings repaeatedly and no matter what quality you use, they won't last more than a few thousand miles.
    Cheers,
    Bill.
    

  • Oil pressure 

    Posted By : Ian Thomas, 17-Jun-2004, 03:33pm

    mileage 65,000 from new..thanks Ben

    • Oil pressure 

      Posted By : Graham Cowan, 18-Jun-2004, 09:58am

      Continuing the oil pressure theme........My 1200 doesnt have a rev counter but at 55 mph I always got 75 psi. But since putting miles on the car over the last few weekends I noticed this dropped to approx 70. I checked the oil level which needed a slight top-up (nothing serious about less than half-pint) and now the oil pressure is back to 75. Should the oil pressure vary along with oil level??? Or am I just being paranoid?
      Cheers,
      Graham.

      • Oil pressure 

        Posted By : Ben Ferguson, 18-Jun-2004, 07:31pm

        I cant think why It would really Graham, as aslong as the pump has something to "suck up" as it were it can build up pressure. The only explanation that I could give would be the changing viscosity of the oil over the miles. If the mixture of your carb is overly rich it will thin the oil out slightly, but only slightly. The top up may have restored the overall thickness of the oil I suppose, but with such a small amount its a bit of a long shot. My oil pressure varies with driving style. Took it easy this morning and overall it must have been 10 psi up on normal because I kept the revs and the power and so heat down.
        So I think a fluctuation in pressure by 5 psi can just be related to the heatwave thats just gone!
        Get worried when yours drops to 4psi at tickover!... like mine sometimes!
        
        Ben

        • Oil pressure 

          Posted By : Graham Cowan, 21-Jun-2004, 10:00am

          Thanks for the advice Ben, but what heatwave?? Remember I'm nearer the arctic circle than you are! I'm gradually building up confidence in the fettling and running of my first classic. Perhaps I should just chill out a bit more....easy to do in a Herald......the coolest cars around.
          Cheers,
          Graham.
          

          • Oil pressure 

            Posted By : Andy Vowell, 22-Jun-2004, 08:39am

            I believe oil pressure can vary with level even between the max/min dipstick marks, 2 reasons:-
            
            The more oil you have in the pan the more it can cool before being pumped back round the engine again, cooler oil is more dense so gives a higher pressure.
            
            As the oil returns to the sump after doing its job, it has been worked and possibly aeriated, therefore less dense. This used oil sits in a layer on top of the sump oil until it consolidates and settles back down. With less oil in the sump then the oil pickup is nearer this top layer of "just used oil" which being less dense a pressure loss is seen. With a full sump the pickup is well under this top layer in so in the more dense oil.
            
            Cheers
            Andy