Oil layer on top of the antifreeze liquid
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  1. #1
    Member Rob Caris's Avatar
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    Default Oil layer on top of the antifreeze liquid

    Hi, some advice from the R10 / R12 experts please.
    I am undertaking some clean up a spray painting work in the engine bay of my R10.
    Have pulled out all the under trays and the radiator cowling panel to have them all chromed and the entire boot area is being re painted.
    When I extracted the anti freeze over flow glass bottle, I notice a reasonable amount of oil residue floating on top of the green glycol. The engine had a head gasket replaced approx 6 months ago after being cooked. Since the gasket replacement the engine has only done limited klms from what I was advised by the previous owner. The head has also not had a retention since the gasket was done. From what I can remember when I owned Renaults in the 70's that when a head gasket was replaced - it was mandatory to have head tension rechecked after 1,000 miles or sooner?

    There could also be a more serious problem underlying the presence of oil in the glycol... At this I don,t even want to think about that.....
    The head was shaved when the gasket was replaced - only slightly though - no problems noticed around corrosion of the oil/ water galleys as advised by the mechanic.

    I am going to tackle this problem by firstly cleaning out the expansion bottle and removing all oil traces. Recheck the tension on the head bolts and if needed, retention them to somewhere between 40 to 50 foot/ lbs. refresh the coolant in the expansion bottle and watch to see if anymore oil appears.
    I have checked the oil under the oil cap and there is no coolant in the oil - no white sludge at all.
    This oil could just be the residue from the original head gasket failure as the mechanical advised that the cooling system my not have been fully cleaned at the time.
    Is it still recommended to use the original Renault endorsed BP coolant/ antifreeze? Green and I think was called 30/70. And is the mix ratio 30% coolant 70% water? It' been 40 years since I worked on these engines...
    Any other suggestions would be greatly appreciated. I just hope the bloody head does not need to come off. I won't a happy camper..
    Many thanks
    Rob C....

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  2. #2
    Contented Peugeot Driver addo's Avatar
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    Hi Rob, as oil pressures generally are much greater than coolant pressures (you have a coolant system with 14PSI or less maximum pressure vs an oiling system that might reach 60PSI revved hard) it is "natural" for the oil to force its way into coolant passages rather than the other way around.

    Drain the coolant, flush thoroughly twice with Nulon system flush or similar, then refill. You'll be safe with the old school type glycol based coolants; Supercheap's one is perfectly OK and the concentrated version will allow several refills at 1/3 strength. Oil left in your coolant will quickly rot rubber hoses from the inside out.

    If it's not too difficult, whipping off the rocker cover and checking for adequate oiling up top, might be a good idea.

  3. #3
    1000+ Posts renault8&10's Avatar
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    I would retension, clean out the expansion bottle and monitor based on the cap not having any "mayo"
    I run, and a number of people I respect recommend Nulon Coolant the green concentrate.

    I tried running Penrite SIN (supposedly suitable for motorsports as being glycol free) but I had a water pump gasket failure shortly afterwards - may or may not have been connected.
    Internet research (always a dangerous thing) showed Rolls Royce not recommending it (or other red coloured coolants) for wet sleeve motors.
    KB


  4. #4
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    As already suggested, it may be oil residue in the motor and radiator coming to the surface. Check the compressions, re-tension the head, and get the radiator checked to make sure it is clean and not partially choked by oil and sludge. Also if the heater was in circuit when the head gasket went, it could also be partially blocked, or the oil in the system is gradually being flushed though into the glass jar.
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  5. #5
    Member Rob Caris's Avatar
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    Thanks KB and Simon
    Will do as you have both suggested ~ fingers crossed its a simple problem and is self correcting.

    Cheers gents

  6. #6
    Member Rob Caris's Avatar
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    Thanks addo all good tech knowledge - I did know that the oil was at a higher pressure than the coolant not sure of the numbers now I know. It will be best to drain the whole system and be certain I have at least cleaned out the crap. So head re tension, pressure test and coolant flush and system bleed is on the menu for the week end...
    Cheers mate

  7. #7
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    Hi. Sorry to be contrary, but what is the concern with a little oil floating on top of the coolant in the overflow bottle? Providing that it hasn't emulsified with the water, and the rubber hoses aren't softened by the mineral? oil, then what is the issue?

    If it was me, I would just drain and clean the overflow bottle, top up and monitor. If the oil returns, then then sure proceed with the suggestions above. If not, you have saved a lot of work for yourself.

  8. #8
    Too many posts! JohnW's Avatar
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    Quote Originally Posted by renault8&10 View Post
    I would retension, clean out the expansion bottle and monitor based on the cap not having any "mayo"
    I run, and a number of people I respect recommend Nulon Coolant the green concentrate.

    I tried running Penrite SIN (supposedly suitable for motorsports as being glycol free) but I had a water pump gasket failure shortly afterwards - may or may not have been connected.
    Internet research (always a dangerous thing) showed Rolls Royce not recommending it (or other red coloured coolants) for wet sleeve motors.
    I agree completely with retensioning and clearing out, then monitoring. We know the oil feed is a weak point in the R12, albeit rarely a mega-issue. And your internet research shows again that we are are still some way off having a clear understanding of coolant matters - I have heard so many contradictory accounts of what to use and why and what not to use and why that my head is reeling.
    JohnW

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    1000+ Posts jo proffi's Avatar
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    Hello Rob.

    A few month ago I finally gave up my efforts to epoxy the hole in the radiator and used a bottle of bars leak.

    Within a short time the coolant reservoir had an oily film.
    I decanted the oily substance and it never returned.

    Jo

  10. #10
    Member Rob Caris's Avatar
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    Thanks Guys - appreciate all your feedback. Hi Whippet your point is noted, but mate just bought this car and spending quiet a few bucks sorting everything body paint wiring and chrome parts of the engine bay - but aware of the heat with chrome.... With the 8 different model Renault cars I owned when younger R10,1 2GL,15TS,16TL and TS, 17TL and 2 fuegos)- I never had oil in the coolant bottle - it's usually a sign that something is a miss.
    Basically because this head has not had a re-tension since the new head gasket by the prior owner 6 months ago there could be a pressure imbalance between the Oil and Water Pressure. Or it could just be the slops left after the gasket was done.
    So I just want to make sure and if it's the gasket again - then the head is off - and we move to a wilder cam and side drafts - stuff the expense... i suppose...

  11. #11
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    Hi Rob Caris.

    As they say, "it's your money Ralph". You earned it, you spend it as you please.

    I doubt if the re-tensioning of the cylinder head bolts will have any affect on the presumed oil leak path. I strongly suspect that the source of the oil scum in the overflow bottle is from the foreign matter in the coolant system. Anyway, that's my prediction.

    If I were to re-tension the cylinder head bolts, it would be to ensure appropriate clamping of the head gasket in regards to the combustion chambers / cylinders. However, I will defer to others as I have no specific experience with this engine.

    All the best with your project. Remember the engine is just like a chain, there is no point having one link stronger than any other. You need to strive to ensure that all the modifications are matched and balanced, unless you need some latent reserve for future performance upgrades that can then be taken advantage of.

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