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  1. #1
    Join Date
    Mar 2005
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    Northampton
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    Oil change puzzle

    I've just changed the oil in my 4.6 RV8.

    I was a little surprised, that despite the engine being warm and up to the "minimum" level on the dipstick that I only got 2 litres out of it. We even jacked the car up to tip the car towards the outlet and turned the car over on the starter for 10 seconds, but that was it. We didn't remove the oil filter, but did remove the dipstick. Having spoken to the engine builder he doesn't recall it being a shallow sump, nor is it baffled. 3 litres filled it to the maximum mark.

    The sump capacity of a RV8 is 5-6 litres. 2 litres got it back to the minimum mark, another litre took the level to the maximum mark.

    Having used a piece of wire to assess the depth of the sump from the top of the dipstick tube, it would appear that the end of the dipstick is about 11cm above the base of the sump, so logic would indicate that there's 11cm of oil under the dipstick. The oil coming out on the dipstick is blacker than I would have thought after running the engine for ten minutes.

    Can anyone hazard a guess why I couldn't get an estimated 3 litres of the old oil out, and what to do about it ?
    David (AKA Firestarter29)

    Lead, follow, or get out of the way.

  2. #2
    Join Date
    Sep 2010
    Location
    Nova Scotia
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    734
    The unlikely combination of having both an incorrect dipstick and an oil cooler could yield the results you are describing.

    As far as the pan goes, do you know anyone with the same engine where you could measure the pan depth for comparison?
    John

    my world... my universe... my garage.

  3. #3
    Join Date
    Aug 2016
    Location
    WELLINGBOROUGH
    Posts
    86
    If you have an oil cooler then the volume of oil in the filter, the cooler and the hoses adds up to about 2.75 ltrs.
    Add the oil left in the engine - rockers, hydraulic lifters etc and the total could be over 3 ltrs.
    Put in 2 ltrs of fresh oil to the low mark plus another litre to the full mark and you have a total of about 6 ltrs.

    If you drain the sump the oil pick up is uncovered so cranking the engine will not shift any oil.
    I you add 3 ltrs of new oil to 3 ltrs of old oil and mix it by running the engine the whole thing will quickly turn darker if not black.

    Hope that makes sense.

    sceptic

  4. #4
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    Northampton
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    Cheers Sceptic, I’m not running an oil cooler so whilst everything you say makes sense I’m still puzzled....
    David (AKA Firestarter29)

    Lead, follow, or get out of the way.

  5. #5
    Join Date
    Mar 2006
    Location
    Oxfordshire
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    David,

    Echoing John's comment, the most likely explanation is that your dipstick is incorrectly calibrated. If the specified oil capacity is 5 to 6 litres, I suggest you drain the oil again, put in 5 litres and etch a new minimum mark on the dipstick, then add another litre and etch a new maximum mark. Remember to check if the specified capacities are with or without a filter change. It's good practice to change the oil fitler at every oil change, so I suggest you put a new filter on, and use the "with filter change" capacities.
    Alan

    CRC Thames Valley Regional Rep
    UK Rep for European Cobra Club (eurocobra.boards.net)
    Dax 427 DeDion - Huddart SBC 383

  6. #6
    Join Date
    Mar 2005
    Location
    Northampton
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    Thanks Alan, I’m quite prepared to believe that the dipstick is incorrectly calibrated, however as we drained the sump, and then put 3 litres of oil in which then made it 2-3 inches up a dipstick that was too short anyway (as it’s 4 inches shorter than the depth of the sump) I’m concerned that draining it again and adding in 5l of oil may overfill it quite substantially with the attendant problems that will cause.

    I’m toying with the idea of measuring the sump pan to calculate its capacity, and I’ve also bought an endoscope so might drain the oil, and have a look thru the drain hole...
    David (AKA Firestarter29)

    Lead, follow, or get out of the way.

  7. #7
    Join Date
    Oct 2006
    Location
    Toton, Nottinghamshire
    Age
    45
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    821
    Quote Originally Posted by Firestarter29 View Post
    Thanks Alan, I’m quite prepared to believe that the dipstick is incorrectly calibrated, however as we drained the sump, and then put 3 litres of oil in which then made it 2-3 inches up a dipstick that was too short anyway (as it’s 4 inches shorter than the depth of the sump) I’m concerned that draining it again and adding in 5l of oil may overfill it quite substantially with the attendant problems that will cause.

    I’m toying with the idea of measuring the sump pan to calculate its capacity, and I’ve also bought an endoscope so might drain the oil, and have a look thru the drain hole...
    David,

    Could it be you dipstick that is too long? Although mine is an SD1 3.5L Rover engine, it is 22inches /56cms from the min mark to the top of the tube cap. May help, may be a red herring?

    Russ.
    Joint Area Rep - East Midlands Region
    1984 DAX Cobra
    Rover 3.5 V8 with Holley carburetor.

  8. #8
    Join Date
    Jul 2012
    Location
    NW England
    Posts
    376
    I remember a similar thread on here some time ago and, IIRC, it turned out the guy had an odd sump pan with reduced volume.

    If you have 11cm under the dipstick and that represents the 2L you got out that would mean the sump dimensions equate to about 5" square (or a rectangle making up similar proportions ) that seems very small.
    Bearing in mind the end of your stick will not be the minimum mark that would indicate an even smaller size. Or you didn't measure right with your wire.

    An oil cooler, filter or other device which holds oil won't make any difference as it's obvious that any oil held in these remained in place during emptying. Or you would have got more out originally. So will not take any oil during fill up.

    WhAt does your sump look like underneath?

  9. #9
    Join Date
    Mar 2006
    Location
    Oxfordshire
    Age
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    Another (probably unlikely!) possibility is that you have a racing oil pan fitted with hinged baffles that are preventing the oil from draining out fully. Something like this:

    https://www.tickperformance.com/holl...e-with-302-20/

    However, these normally fit around the oil pickup, leaving the rest of the oil pan contents free to drain off - unless it also happens to enclose the oil drain plug, that is! If so, that would represent an area very similar to GDCobra's calculation above!
    Alan

    CRC Thames Valley Regional Rep
    UK Rep for European Cobra Club (eurocobra.boards.net)
    Dax 427 DeDion - Huddart SBC 383

  10. #10
    Join Date
    Jul 2012
    Location
    NW England
    Posts
    376
    Can't find the previous thread at the moment (maybe not even this site!) I'm not good a looking for things! However going from memory the deep part of my sump was around 8" square (maybe a bit longer than wide. For a depth of 11cm that would give 4.4L. OK maybe a bit less as it's not a square tank with vertical sides and 90° corners but then you also have to allow for a bit of volume up to the min or max lines to consistent with the circa 5L I generally put in for an oil change.

    What does the sump look like underneath? Can you get a photo?
    Maybe a good idea to get it off and check where the dipstick marks are relative to the sump mount face to check if you have the right stick. Also good to have a good look inside the sump and a great opportunity to put a decent sump gasket on.

    BTW. I would not recommend tuning the engine while the sump is empty, if you draw air into the oil pump it may need priming again. Out with the Vaseline!

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