Very low oil pressure at warm idle, otherwise normal?
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From: Pequot Lakes, MN
Very low oil pressure at warm idle, otherwise normal?
I've noticed a couple times now that my '89 5.0 oil pressure guage will drop way down to barely above "L" when idling after the engine is warm. On startup pressure is normal and when warm anything off idle, even if I barely tap the gas the guage comes right back up to the middle of "NORMAL". Is this ok or is there likely a problem here? Should I not let it idle if the pressue really is low? Just changed oil for the first time since I bought the truck to fresh 10w30 for winter with a new FRAM *gasp* filter, could this be the cause? I've heard bad things about Fram causing oil pressure issues and usually always run Purolator in my old vehicle but I sent someone else to get my oil/filter and they got a fram so I threw it in...
Note: motor runs very strong, no smoke, no knocks w/ 170K if that means anything to ya... Thanks in advance for any help given
Note: motor runs very strong, no smoke, no knocks w/ 170K if that means anything to ya... Thanks in advance for any help given
Last edited by pickupfish; Dec 9, 2005 at 08:48 PM.
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From: Central NY
Also note that the stock oil pressure gauge, is not a real gauge. It functions like an idiot light, if there is some oil pressure the gauge will read somehwere in the range.
Hence quicklook's recommendation of putting a mechanical gauge on it to see if you have a real problem or not.
You can try cleaning the connector at the sensor on the block, this resolved my issue last winter.
Tim
Hence quicklook's recommendation of putting a mechanical gauge on it to see if you have a real problem or not.
You can try cleaning the connector at the sensor on the block, this resolved my issue last winter.
Tim
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From: New Jersey
The gauge is an idiot light as stated.
It will swing to the left "somewhere" when there is less than 7psi, and swing to the right "somewhere" if it's over 7spi. That's the pressure that the oil pressure switch closes. Where it swings to depends on the battery voltage, and the resistor soldered inside the cluster.
If you search for t-bird oil sender you'll find a thread where I offered advice in how to turn this into a "real" oil pressure gauge, but without any useful accuracy. You'll just have a ballpark as to oil pressure rather than "under 7psi, or over 7psi. Essentially it's a resistor, and a t-bird oil pressure sender. Requires soldering.
There are a lot of reasons why you can have low oil pressure at idle, assuming you do have this issue, bad bearings is definately one... valve stems sometimes can cause this if they are really shot, plugged oil filter while the bypass spring and plunger is "stuck" or "sticking", and so forth.
It will swing to the left "somewhere" when there is less than 7psi, and swing to the right "somewhere" if it's over 7spi. That's the pressure that the oil pressure switch closes. Where it swings to depends on the battery voltage, and the resistor soldered inside the cluster.
If you search for t-bird oil sender you'll find a thread where I offered advice in how to turn this into a "real" oil pressure gauge, but without any useful accuracy. You'll just have a ballpark as to oil pressure rather than "under 7psi, or over 7psi. Essentially it's a resistor, and a t-bird oil pressure sender. Requires soldering.
There are a lot of reasons why you can have low oil pressure at idle, assuming you do have this issue, bad bearings is definately one... valve stems sometimes can cause this if they are really shot, plugged oil filter while the bypass spring and plunger is "stuck" or "sticking", and so forth.
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From: Pequot Lakes, MN
Thanks guys. I will definatly look into getting a better reading on the pressure one way or another. frederic looks like I might have to try the t-bird sender. Solder I can do. I doughted the accuracy of the guage but didn't realize it was just a resistor. Ford should have just installed a stupid light instead of a guage...doesn't make sence to me. I guess I'll try everything I can for now short of pulling the pan and screwing with bearings, ect...looks like quite a job. I don't think I'll ever run Fram again but i still dought that its going to make any real big difference.
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From: Wetaskiwin, Alberta
In all probability the Fram filter is probably not to blame for your perceived "low" oil pressure. I would follow the above advice and get a mechanical guage on the line as soon as possible and verify the oil pressure before you start to fret about bearings. Yes, loose bearings will definitely cause low oil pressure - lets find out what your pressure (oil - or blood - or both if you feel the need!) is first though before we jump to the nightmare reels. You stated that you run 10W-30 for a "winter" oil - what do you normally run? Up here just a few hundred miles N of the 49th I run 5W-30 in the winter and I have 250,000KMs (150,000Miles) on my old girl. I have a mechanical oil pressure guage and with the 5W-30 the pressure will drop to around 15lbs at idle with a hot motor just coming off of a highway run. I don't consider this low at all and when I up the RPMs the pressure comes right up.
Let us know what you motor is putting out when you can get a guage on there. Keep an eye on your oil level and ear on the engine just in case it does start to knock or something. I would also suggest a different filter than a Fram when you next change out your oil.
Cheers!
Mike
Let us know what you motor is putting out when you can get a guage on there. Keep an eye on your oil level and ear on the engine just in case it does start to knock or something. I would also suggest a different filter than a Fram when you next change out your oil.
Cheers!
Mike
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Joined: Aug 2004
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From: Tennessee
seems like a good topic to post my question
I have mecanical gauges for the oil, and water temp, I hate the dead spot on the dash and want to hook up a "T" to install the sending unit for display and of course keep the mecanical gauge for true readings. Does this sound stupid and is it do-able. I realize the sending unit is tapered and may pose a problem but I had seeing the needle doing nothing.
Question two is I have a surpluse of oil (new from my big rig) and wondered if adding a half quart would hurt this engine. The stuff was expensive and I dont like having it set in the garage and dont want to add even a quart till I ask here and get some ideas. Is it too thick to flow through the filter? or even the pick up. The price of oil is cheap and I dont want to make a terrible mistake over $.3.00 a quart. The diesel oil has tremedous cleaning capabilities and that is whey I ask. To even run a QT. for a few days then change oil, is that out of the question? Foolish questions and if I am out of my mind just say so I can take it. Probally will just soak parts in them.
Question two is I have a surpluse of oil (new from my big rig) and wondered if adding a half quart would hurt this engine. The stuff was expensive and I dont like having it set in the garage and dont want to add even a quart till I ask here and get some ideas. Is it too thick to flow through the filter? or even the pick up. The price of oil is cheap and I dont want to make a terrible mistake over $.3.00 a quart. The diesel oil has tremedous cleaning capabilities and that is whey I ask. To even run a QT. for a few days then change oil, is that out of the question? Foolish questions and if I am out of my mind just say so I can take it. Probally will just soak parts in them.
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From: West Mansfield, Ohio
Originally Posted by pickupfish
Ford should have just installed a stupid light instead of a guage...doesn't make sence to me.
Lol Remember the trucks back in the late 70's? Some ford instrument clusters consited of a Fuel gauge, a Coolant temp gauge, and two lights (Oil pressure and battery.) The "luxury" models actually had the two gauges, although the oil pressure gauge was still an "idiot light."
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From: Pequot Lakes, MN
Originally Posted by MRL123
You stated that you run 10W-30 for a "winter" oil - what do you normally run? Up here just a few hundred miles N of the 49th I run 5W-30 in the winter and I have 250,000KMs (150,000Miles) on my old girl. I have a mechanical oil pressure guage and with the 5W-30 the pressure will drop to around 15lbs at idle with a hot motor just coming off of a highway run. I don't consider this low at all and when I up the RPMs the pressure comes right up.
I have no idea what was normally ran in the truck, I bought it a little over a week ago. I just kinda guessed with the 10W-30. I'm guessing my my old girl is just slightly more tired than yours and probably has similar oil pressure, but I will get a mech. guage on there as soon as I have a chance.
raysvan: I've heard of running 100% diesel oil in a gasoline engine with good results and considered doing it myself with my old Jeep . Engine was a tired Jeep 242 that probably had enough "play" in the internals to handle the heavy oil. I'm sure a google search would bring up some good stuff...
handyman: lol yeah I remember those trucks, instrumentation wasn't any better back then...
Post Fiend
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From: Topsfield, MA
Originally Posted by quicklook2
i had low oil pressure because oil pickup screen was clogged.
If you start the truck cold, and the pressure goes up to 40-60psi at idle, then warms up and drops really low - it's an indication of rebuild time.
When the engine heats up, the oil thins out, and the gaps/spaces in the worn bearings reduce the pressure. It'll get good oil pressure at other RPM but at idle it drops down, eventually to single digits and eventually the engine will let go on ya. When the oil pressure is in the single digits, it's time to rebuild as you wouldn't want the engine to grenade on ya as it'll be more difficult to rebuild.
If the oil pressure varies at different RPM, isn't consistant, and is low at higher RPM or low while cold, then I'd start looking into oil pump/pickup problems.
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Probably not
I had exactly the same symptoms after an oil change on my '94 F-150. I got the oil changed again and made sure they used a good brand name oil. The symptoms stopped. Hopefully that didn't happen to you, but I thought I would mention it.
Post Fiend
Joined: Nov 2001
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From: Topsfield, MA
Originally Posted by wildaardvark1954
I had exactly the same symptoms after an oil change on my '94 F-150. I got the oil changed again and made sure they used a good brand name oil. The symptoms stopped. Hopefully that didn't happen to you, but I thought I would mention it.
But generally, if you have low oil pressure at warm idle but the oil pressure is fine otherwise - it means you're engine is pretty tired and ready to be rebuilt with new bearings and such.
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From: Pequot Lakes, MN
Just bought a new mechanical oil pressure guage off ebay (hasn't arrived yet). It comes with line and fittings. Will I need an aftermarket sending unit to install? I plan on somehow hooking up both the idiot guage and the aftermarket one and was wondering if i needed 2 sending units?