airhead oil rad leaks, high oil pressure?

Discussion in 'Airheads' started by Professor Fate, Apr 22, 2013.

  1. Professor Fate

    Professor Fate Hand crafted

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    I put an aftermarket oil radiator on my 1983 R65 a few years ago and used the parts reguired at the oil filter for retrofitting for a cooler like a 1989 GS and have had two aluminum radiators pop and leak. The last one was tested from the factory at 150 #. I'm putting a rad from a cruiser BMW and it looks a bit more robust. I put an oil pressure guage on it and will go above 100# at high idle easily. That is with 20-50 castrol at about 60 degrees F. on the highway at 4500 rpm and oil temp at 160 the pressure is still 100# The oil pressure relief valve is supposed to be the cam chain tensioner and is supposed to open at 75#. The parts fiche shows the tensioner piston pushes on the tensioner and the spring goes in the opposite end and into the cylinder in the timing case. Is there a chance this diagram is backward? Seems to me the relief piston head should face the block and the oil pressure pushing it out until it pushes the piston out far enough to uncover oil relief holes and drop the pressure. Any Ideas?
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  2. Airhead Wrangler

    Airhead Wrangler Long timer

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    Actually the pressure relief is a tiny spring loaded ball inside your oil filter cannister which then dumps oil out into the timing chain. Try pushing on the ball with a long pointy implement to see if it'll still move. See the last couple photos on Anton's oil filter page:

    http://largiader.com/tech/filters/
    #2
  3. disston

    disston ShadeTreeExpert

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    [​IMG]

    Oil pressure relief is # 10, 11 & 12 on the front crank bearing journal. This is not the timing chain tensioner. There is also a by-pass valve in the oil filter canister.

    Airheads seldom need oil cooling. Why are you running an oil cooler?
    #3
  4. Plaka

    Plaka Brevis illi vita est

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    Mmmmm..,.no.That's one's just an oil filter (and cooler) bypass. You're thinking of the main relief up above the timing chain.
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  5. disston

    disston ShadeTreeExpert

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    Which is exactly the information posted directly above you with photo. Plaka, do you have me on your ignore list?
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  6. pommie john

    pommie john Long timer

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    I burst an oil cooler once when I let someone else dtart the bike on a cold ( 5 Celcius) morning.

    They gave it too much throttle and revved the engine and the oil cooler popped. It was an expensive Mocal brand that are tested to 200 psi.

    The oil pressure figures I get are with 15-50 oil on a warm ( say 20 degrees C ) day are :

    Initial start up I run it round 2000 rpm and the needle is hard up against the stop ( the gauge reads to 100 psi). After a couple of minutes the needle is bouncing off the stop and takes a couple more minutes to drop to 80.

    During racing when the engine is fully hot I see 60- 80 on the gauge depending on the ambient temp.


    If you're getting over 100 psi at full operating temp, there does seem to be something wrong with the oil pressure relief, or maybe somewhere else. There's not much to go wrong with the relief valve, it's just a spring loaded plunger. maybe debris could jam it or maybe a broken spring could stick the plunger.

    Look for other things like a kinked oil pipe returning from the cooler, or some blockage on the return side.
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  7. Plaka

    Plaka Brevis illi vita est

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    No, But you do it to me so often I though I'd try it myself and see if I'm on yours. :D
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  8. Plaka

    Plaka Brevis illi vita est

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    100 PSI fully warmed up indicates something wrong with the oil!. Figure 10psi/1000 rpm. IF it's making too much pressure then it's making too much pressure, fix that rather than trying to work around it with the reliefs. I don't know the setting for the oil filter bypass but if you run high enough pressures it's going to be open so no oil filtering.
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  9. Professor Fate

    Professor Fate Hand crafted

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    That valve is for if the filter is clogged and it bypasses the filter. That article talks about that and the pressure relief valve also. Has anyone hooked a guage where the pressure switch is? That's where I put the guage.
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  10. Plaka

    Plaka Brevis illi vita est

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    That's where mine is but I don't have any numbers yet. The reason I set it up is so I can evaluate different weight oils and find the one that gives the best flow at the least pressure.
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  11. disston

    disston ShadeTreeExpert

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    Darn. Caught again. :freaky
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  12. pommie john

    pommie john Long timer

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    The OP said that it was 20-50 and 160 degrees oil temp. ( Fahrenheit I presume) so I don't see what could be wrong with the oil, unless something really thick has been put in by mistake.
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  13. bmwrench

    bmwrench Long timer

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    R65s often run very high oil pressure. I've never investigated it.

    The R1200 coolers may not handle much pressure; the "Oilheads" have a secondary low pressure pump to circulate the oil through their coolers and heads.

    If you're going to use a cooler on a street bike, you really need to use a thermostat. I had a cooler failure long ago which dumped all the oil over my rear tire. Very exciting for a moment.
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  14. Professor Fate

    Professor Fate Hand crafted

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    If you've popped one with an even higher pressure rating then maybe it's normal pressure. Maybe those old GS coolers where heavy duty. I'm going to put a cover over the cooler so I can get the temp up higher and see if the pressure comes down more.
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  15. pommie john

    pommie john Long timer

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    160 is a reasonable oil temp. I can't see that normal oil pressure should burst any oil cooler.

    When mine burst it was dead cold and revved almost to the red line. ( I never let anyone else start the bike any more)
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  16. mikerox

    mikerox n00b

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    I have a 1984 R80RT, and installed an oil press gauge. It is showing high oil pressure. About 100psi at start (pegged hi at 100). Then after oil warms up a bit, comes down to about 80 to 90 psi at idle. It reads pegged hi with any rpm above idle. The gauge is tapped off the same location the bike's orig. oil press. switch was installed. Have I got a stuck oil pressure relief valve (the one at the front main bearing housing)??
    The oil pump may be capable of very high pressure output, beyond what I am seeing, so my relief valve may be working partially. But still, too high a pressure. It is supposed to open and maintain 75psi, per other info elsewhere. Any other ideas??
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  17. Rob Farmer

    Rob Farmer Long timer

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    Did you use a second hand GS oil cooler cover? The Later design had a larger hole in the cover to relieve oil pressure in the cooler. I think you need to open the earlier covers hole out to 4mm

    Anton has an article on it on his excellent pages http://www.largiader.com/tech/filters/
    #17
  18. ME 109

    ME 109 Long timer

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    There is no setting.
    It's controlled by differential pressure.
    #18