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Car Forum / Driving, Maintenance, Tuning / Maintenance and Repair / March 200650 + PSI on oil Gauge
Hi all, I hoped in my 90 Suburban after work and hit the highway. Looked down and the temp gauge was reading 100 and the oil gauge was reading over 50. Actually it was between the 45 and 60 so that would make it about 52.5 As the truck warmed up the PSI started to go down. I did notice this morning at idle it was a little over 30 PSI. I don't remember it ever doing that before. Should I be concerned? Thanks > Hi all, > [quoted text clipped - 10 lines] > > Thanks apariently your not very observent as this is normal. KB  SignatureThunderSnake #9 Warn once, shoot twice 460 in the pkup, 460 on the stand for another pkup and one in the shed for a fun project to yet be decided on > Hi all, > [quoted text clipped - 9 lines] > > Thanks They say ginko biloba is helpful. I wouldn't be concerned as long as you can remember the way home. Yeah. Thanks. What no kick to the gonads? LMAO > > Hi all, > > [quoted text clipped - 12 lines] > They say ginko biloba is helpful. I wouldn't be concerned as long as > you can remember the way home. Ok. I check it out again today and this time it topped out at just over 45 PSI. That's what I'm used to seeing. I think mid 50's is kinda high. 7 more PSI and the needle is buried. > Yeah. Thanks. > [quoted text clipped - 22 lines] > > They say ginko biloba is helpful. I wouldn't be concerned as long as > > you can remember the way home. > Ok. I check it out again today and this time it topped out at just > over 45 PSI. That's what I'm used to seeing. > > I think mid 50's is kinda high. 7 more PSI and the needle is buried. Hmmm.......maybe how the oiling system works isn't clear. The oiling system works by 'floating' the rods, and crank on a layer of pressurized oil. (Technically, a hydrodynamic bearing). I would be more concerned about lower pressure as opposed to higher. If the pressure between the bearing shell and the crank is not high enough to withstand the forces exerted, then contact is made between the two, with major bad consequenses in short order. The only time I would be concerned with high oil pressure is if it was WAY high, (say more than 150 PSI), indicating that something major is blocking oil flow. My truck runs 80-90 PSI cold, 50-60 hot both @ 2000 RPM. Manufacturer calls for at least 20 PSI @ 2000 RPM. SignatureAnthony You can't 'idiot proof' anything....every time you try, they just make better idiots. Remove sp to reply via email Cool Thx Anthony. That makes sense. I did not know what the range was. Hitting close to 60 seamed kinda high singe the gauge on read till 60. Not like the temperature gauge then :) Thanks again > > Ok. I check it out again today and this time it topped out at just > > over 45 PSI. That's what I'm used to seeing. [quoted text clipped - 13 lines] > My truck runs 80-90 PSI cold, 50-60 hot both @ 2000 RPM. Manufacturer > calls for at least 20 PSI @ 2000 RPM. >> Ok. I check it out again today and this time it topped out at just >> over 45 PSI. That's what I'm used to seeing. [quoted text clipped - 7 lines] >bearing shell and the crank is not high enough to withstand the forces >exerted, then contact is made between the two, That's a misleading description of how it work as any mechanical engineer could tell you. The oil pressure is merely a means of providing oil to the bearings and other surfaces. A rod bearing has maybe two square inches of surface on the upper bearings so that is a 100lb force maximum seperating them as far as oil pressure is concerned. What prevents metal-to-metal contact is a wedge of oil produced by the movement between the two surfaces. THAT is what is able to withstand PSI forces in the thousands. The oil pressure is irrelevant as long as adequate oil is provided to replace what is thrown off. Think of the camshaft lobe/lifter interface. Typically the only lubrication is provided by splash or drip yet this interface surfaces very high unit pressure. Don www.donsautomotive.com >with major bad consequenses in short order. >The only time I would be concerned with high oil pressure is if it was >WAY high, (say more than 150 PSI), indicating that something major is >blocking oil flow. >My truck runs 80-90 PSI cold, 50-60 hot both @ 2000 RPM. Manufacturer >calls for at least 20 PSI @ 2000 RPM. > Ok. I check it out again today and this time it topped out at just over 45 > PSI. That's what I'm used to seeing. > > I think mid 50's is kinda high. 7 more PSI and the needle is buried. Depends on the engine. If my '69 440 Magnum didn't kick up over 85 PSI cold and 65 PSI hot at highway speed, or 25 psi hot at idle, I'd be worried. Chevies are plumbed differently, though- lubricating the rocker arms through the pushrods bleeds off a lot of oil pressure because oil gets wasted at the lifter and the rocker arm tips of the pushrods. Lower oil pressures are normal in Chevies and Fords (and in the 'Magnum' Mopars that use pushrod oiling, for that matter). >> Ok. I check it out again today and this time it topped out at just over >> 45 [quoted text clipped - 9 lines] > oil pressures are normal in Chevies and Fords (and in the 'Magnum' Mopars > that use pushrod oiling, for that matter). I'm curious. How does the lifter bleed off pressure? Is it to lubricate itself in its bore? I was under the impression that the oil pressure was mainly redirected to the rocker arm where it was bled off there. -Bruce >>>Ok. I check it out again today and this time it topped out at just over >>>45 [quoted text clipped - 15 lines] > > -Bruce When you oil the rockers through the pushrods, oil is lost at each end of each of the 16 pushrods because there isn't a perfect sea. That's 32 extra little oil leaks that an engine that oils through the rocker SHAFT (ala Mopar, Buick, Oldsmobile, and Cadillac) does not have. >When you oil the rockers through the pushrods, oil is lost at each end >of each of the 16 pushrods because there isn't a perfect sea. That's 32 >extra little oil leaks that an engine that oils through the rocker SHAFT >(ala Mopar, Buick, Oldsmobile, and Cadillac) does not have. Well yes, but it's only the controlled amount of oil pumped by the lifters. I'm sure the total oil volume requirement of those engines is factored-in when designing the pump. Regards, Al. Oil can also leak around the lifter bores when the engine gets worn, this is a known problem on old Studebakers at least (very similar to early Caddy engine) which can cause low oil pressure as well. FWIW these engines do *not* oil through the pushrods, they oil through the shafts. I've heard of people completely blocking oil flow to the lifters (they are solid lifter engines) and letting oil draining down from the heads provide the lubrication for the lifters, without any ill effects. (Note: this is only a good idea for solid lifter engines, hydraulic engines need a constant feed of pressurized oil to the lifters, and consequently a higher volume oil pump. The real problem with a Stude is oil filling up the heads at high RPMs so most oiling system mods are aimed at reducing the volume of oil sent to the top end and/or improving drainback.) But to get back on topic, the behavior of the OP's oil pressure gauge sounds reasonable, engines can run with far higher pressures than that without any ill effects. If this is higher than usual, possibly this is due to colder weather (thicker oil) or a recent oil change? In any case I wouldn't worry, I regularly see 5+ bar (70+ PSI) on my Porsche (120K miles) and 80-90 PSI on my Stude (24K miles) on a cold start with no apparent problems. I've actually thought about switching to a 10W40 oil in the Porsche (I'm currently running Mobil 1 15W50) as over the 10K miles or so I've owned the car oil pressure has actually gone up slightly - not sure why that is, possibly the OPRV was sticking and a couple changes of Mobil 1 have freed it up? nate |
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