Oil pressure drops when hot

Discussion in 'Touring Models' started by Goatie, Jul 13, 2015.

  1. Goatie

    Goatie New Member

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    My 2009 Electro Glide Ultra Classic had been in the shop for 6 mo. from an accident I had in Oct. 2014. I picked it up at the shop an was told that they had changed the oil out to Amsoil 20w50. Cranked it up cold and the oil pressure was around 34psi. The bike rode good. About 30 miles later I let up off the throttle and noticed that the oil pressure looked like it dropped to zero. It was a warm day and the heat from the motor was real high. I was afraid that I had a leak and lost oil. I checked the oil and it was still full. At 70 mph the oil pressure went up to about 15 psi. The idle pressure was about 6 psi. I took it back to the shop and they checked the pressure gauge and the new gauge checked the same as the old one. Another sending unit was put on and by this time the bike had cooled quite a bit, so when it was cranked the pressure read 32 psi at 2000 rpm and about 15psi at idle. 30 miles later the pressure dropped down to 15 at 70 mph and about 6 @ idle.
    Took bike to Harley shop to put mechanical gauge on. They had to wait for bike to cool some before they could hook up the gauge. Reading was 32 psi at 2000 psi. Paid to put a new sending unit on and when I left every thing was reading good. 30 miles later the psi dropped to 15 psi at 70 mph and about 6 psi @ idle. Every thing was still the same when bike got hot.:(
    I replaced the pressure relief spring with another and now the cold crank is about 55 psi, about 10 miles later the 2000rpm pressure is about 32 psi and the idle is about 15 psi. about 10 miles further the 2000 rpm pressure is about 16 psi and the 70 mph is about 24psi. New spring increased pressure by about 10 psi. Idle hot is still about 6 psi. Are these pressures safe to run? What can be opening up enough when the engine is hot to allow the pressure to drop?
     
  2. brownfoxx1

    brownfoxx1 Active Member

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    when/if you install a S&S gear cam which will remove the cam shoes . have them install a beisley oil spring which will rise the oil pressure a bit, or a a fueling spring which will raise the oil pressure to 55 psi above idle . i've had the fueling
    installed in my '09 t/g at 11k. shoues showed some sign of wear. now 32k. no problems. S&S says they want the higher instant oil pressure because the gear cam used a sqiul cage bearings; & the immediate oil pressure to prolong the bearings life.

    how many miles on the bike? you are getting close to have the cam shoes inspected with normal riding.i highly recomend the S&S gear cam . it really wakes the motor up. i've had one installed for 20k. miles with no problems.
     
    Last edited by a moderator: Jul 15, 2015
  3. Jeff Klarich

    Jeff Klarich Well-Known Member Contributor

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    I believe the number you should be looking for is more around 32 psi at cruising speeds. You may have a oil pump going south on you or possibly an oil passage blocking up.

    At idle and not showing pressure did the oil light come on or flicker?
     
  4. TQuentin1

    TQuentin1 Well-Known Member Staff Member Moderator

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    Remember, the new HD oiling system is about volume not pressure. Additionally, the piston skirt sprayer has a ball check valve in it that stops the flow of oil to the underside of the pistons when the oil pressure gets to about 12psi or so. That is supposed to happen when the bike is idling.

    Having said all that, it does seem like the pressure was a bit low initially, but the numbers after the new spring installation seem high.

    Just make sure that the port that the plunger moves in (oil pressure relief system) is clean and allows the plunger to move/slide in it freely.

    Cheers,

    TQ
     
  5. dolt

    dolt Senior Member Contributor

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    The OP definitely has a problem that should be addressed and the new relief spring is a bandaid that addresses the symptom but not the problem. Was the new spring stock or aftermarket?

    Oil pressure dropping when hot usually points to two sources:

    1. Relief valve sticking open on cold start and never closing to regulate pressure. Remove the valve and polish it up with #1500 grit paper. The valve should drop in the bore and move freely.

    2. Worn or cracked gerotors in the oil pump. Too much clearance between the gerotors on the feed side of the pump or too much clearance between the face of the cam plate and feed gerotor will cause erratic oil pressure as described by the OP.

    A partial blockage in the feed line to the cam case could also cause the erratic oil pressure but two sources listed above are the usual suspects.

    Oil pressure should read 40-50psi on start up but drop to 8-12 when warmed up and rise to about 32-34psi at cruise and stay there. Anything else indicates a fault in the system which could be a faulty gauge or sending unit but the OP has addressed those already.
     
  6. Goatie

    Goatie New Member

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    70 mph is cruising speed on most roads in Texas. The psi is about 28 at that speed after about 30 min on the road. The manual says that the pressure is supposed to be 32 psi with oil temp @ 230 deg. f. @2000 rpm (55 mph). I don't know what the temp. of the oil is, but there is a time when the pressures will meet those specifications, which is about 20 min. on the road starting from cold. I'm thinking the oil is getting a lot hotter than 230 degrees f. After about 30 min. on the road the psi is about 16 psi @ 2000 rpm. This scenario repeats its self every time. Maybe an oil cooler would be a cheaper fix?
     
  7. TQuentin1

    TQuentin1 Well-Known Member Staff Member Moderator

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    Dolt has you covered above. As suggested, polish the plunger and clean the bore so that it (the plunger) slides easily in the port with no binding.

    While you are in there, pull the plate and check out the pump. Make sure to use new orings when reassembling and ensure the pump is aligned. Check out that part of my pictorial for the process:

    Harley Davidson Forums

    Cheers,

    TQ
     
  8. dolt

    dolt Senior Member Contributor

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    I live/ride in south Texas. One of my bikes is a 2002 FLHT, all bore 107" built motor (124TQ/110HP). I run a Jagg low mount 10 row oil cooler and even now, in the mid 90s, oil temp rarely sees 220*. Your oil temps may see 230* or even 250* but that would not change your oil pressure which is not a function of the oil temperature.

    Of course, I think an oil cooler would be a good idea but doubt seriously that it would solve your problem which I believe lies elsewhere. At the end of the day, it's your call but I think you are inviting trouble by not digging in and finding out why your oil temp drops as you have described. JMHO.:s
     
  9. Bodeen

    Bodeen Well-Known Member Staff Member Moderator Contributor

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    I think he meant pressure in the last sentence....:s
     
  10. dolt

    dolt Senior Member Contributor

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    And you are correct sir!:s