Oil pressure problems
Thread Starter
Le Mans Master
Joined: Mar 2003
Posts: 6,477
Likes: 1
From: Albuquerque NM
St. Jude Donor '08-'09-'10-'11
Oil pressure problems
About 8 months ago, I posted a question very similar to this one. After taking it to the mechanic, things seemed to be fixed. But I'm not so sure right now.
Anyways, here's the deal:
My oil pressure sucks. I just changed my oil to 10w30, and at idle, when the car is all warmed up, the pressure is around 10 or 11 psi. Once the car gets moving, this jumps to near normal levels (around 30 cruising).
Around 8 months ago, I got a new oil pump and it seemed to fix things. The oil pressure was hitting as low as 3 or 4 psi.
Should I be concerned that my engine is about to fail? Is it time to save up some money to get ready for a rebuild? Or would putting some thicker oil in there simply do the trick? :confused:
Anyways, here's the deal:
My oil pressure sucks. I just changed my oil to 10w30, and at idle, when the car is all warmed up, the pressure is around 10 or 11 psi. Once the car gets moving, this jumps to near normal levels (around 30 cruising).
Around 8 months ago, I got a new oil pump and it seemed to fix things. The oil pressure was hitting as low as 3 or 4 psi.
Should I be concerned that my engine is about to fail? Is it time to save up some money to get ready for a rebuild? Or would putting some thicker oil in there simply do the trick? :confused:
Team Owner
Joined: Sep 2001
Posts: 62,127
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From: Athens AL
C7 of the Year - Unmodified Finalist 2021
C4 of Year Finalist (performance mods) 2019
Re: Oil pressure problems (UA89Vette)
If the sender is fine, then either that pump is bad (unlikely with Mellings) or your bearings are about done.
Le Mans Master
Joined: Feb 2000
Posts: 9,715
Likes: 27
From: Kempner Texas
Re: Oil pressure problems (UA89Vette)
I'll bet that the pressure is fine until the oil temperature climbs above 200 degrees F, then it begins to fall below 20 psi at idle; the hotter it gets the lower the pressure at idle too.
Oil temperature, oil weight and bearing clearances are all playing a part in the low pressure readings at idle.
Without rebuilding the engine and/or installing a better oil cooler, the simple fix is to switch to Mobile 1 15W50, Valvoline VR1 20W50 racing oil, or Pennzoil GT 20W50.
Don't get locked in on the factory recommended oil weight. The correct oil weight for your specific engine depends on several variables; just choose the weight that works for YOU.
Jake
[Modified by JAKE, 12:51 PM 3/11/2004]
Oil temperature, oil weight and bearing clearances are all playing a part in the low pressure readings at idle.
Without rebuilding the engine and/or installing a better oil cooler, the simple fix is to switch to Mobile 1 15W50, Valvoline VR1 20W50 racing oil, or Pennzoil GT 20W50.
Don't get locked in on the factory recommended oil weight. The correct oil weight for your specific engine depends on several variables; just choose the weight that works for YOU.
Jake
[Modified by JAKE, 12:51 PM 3/11/2004]
Thread Starter
Le Mans Master
Joined: Mar 2003
Posts: 6,477
Likes: 1
From: Albuquerque NM
St. Jude Donor '08-'09-'10-'11
Re: Oil pressure problems (vader86)
If the sender is fine, then either that pump is bad (unlikely with Mellings) or your bearings are about done.
Thread Starter
Le Mans Master
Joined: Mar 2003
Posts: 6,477
Likes: 1
From: Albuquerque NM
St. Jude Donor '08-'09-'10-'11
Re: Oil pressure problems (JAKE)
I'll bet that the pressure is fine until the oil temperature climbs above 200 degrees F, then it begins to fall below 20 psi at idle; the hotter it gets the lower the pressure at idle too.
Oil temperature, oil weight and bearing clearances are all playing a part in the low pressure readings at idle.
Without rebuilding the engine and/or installing a better oil cooler, the simple fix is to switch to Mobile 1 15W50, Valvoline VR1 20W50 racing oil, or Pennzoil GT 20W50.
Don't get locked in on the factory recommended oil weight. The correct oil weight for your specific engine depends on several variables; just choose the weight that works for YOU.
Jake
Oil temperature, oil weight and bearing clearances are all playing a part in the low pressure readings at idle.
Without rebuilding the engine and/or installing a better oil cooler, the simple fix is to switch to Mobile 1 15W50, Valvoline VR1 20W50 racing oil, or Pennzoil GT 20W50.
Don't get locked in on the factory recommended oil weight. The correct oil weight for your specific engine depends on several variables; just choose the weight that works for YOU.
Jake
I'll change out the oil next time to one of the one's that you recommended. Hopefully it'll help.
Any other ideas of what I should do?
Thread Starter
Le Mans Master
Joined: Mar 2003
Posts: 6,477
Likes: 1
From: Albuquerque NM
St. Jude Donor '08-'09-'10-'11
Re: Oil pressure problems (frank j. moran)
72k miles on the engine total, on the oil pump, maybe 4k or so.
[Modified by UA89Vette, 12:33 PM 3/11/2004]
[Modified by UA89Vette, 12:33 PM 3/11/2004]
Racer
Joined: Dec 2003
Posts: 277
Likes: 3
Re: Oil pressure problems (UA89Vette)
your orig post indicated 3-4 lbs. which is not good, if you have 11 lbs after it is real hot, after a long drive then I would not be too concerned. Letting it idle up to temp is not a real good indicator unless you let it run a long time. pressure problems from bearing wear/clearence usually surface after a road drive and you come to a stop in gear (AT) the light or guage flicker or the pressure is real low on a gage. Pressure is derived from resistance to flow, the resistance is the bearing clearance usually around .0008-.0025in. Did you check any of your readings with a good mechanical gauge? engine idle speed correct, eng temp in limits?? correct sending unit?? , your mileage is good and bearing wear should not be evident unless it was abused or lack of oil changes etc. the higher viscosity oils will mask the problem but you need to continue your diagnosis...I had one with 11 lbs and it was fine. I know how you feel
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Burning Brakes
Joined: Nov 2003
Posts: 935
Likes: 2
From: Beverly, NJ
Re: Oil pressure problems (frank j. moran)
:iagree:
I would also hook up a oil pressure gauge kit directly to the motor after a good drive, and messure it with a diagnostics gauge. Verify that the sender is working and reading properly. You could always have a malfuntioning sender, regarless of how new it is. Once you verify the pressure really is at a dangerous low, then go from there. Do not sit on this though. do something as soon as possible to avoid any further damage. Just my .02.
:cheers:
I would also hook up a oil pressure gauge kit directly to the motor after a good drive, and messure it with a diagnostics gauge. Verify that the sender is working and reading properly. You could always have a malfuntioning sender, regarless of how new it is. Once you verify the pressure really is at a dangerous low, then go from there. Do not sit on this though. do something as soon as possible to avoid any further damage. Just my .02.
:cheers:
Melting Slicks
Joined: May 2000
Posts: 2,148
Likes: 1
From: Chandler AZ
Re: Oil pressure problems (darkman5001)
First check the senders, etc as suggested. Then consider:
10w30 is made from a 10w base; extremely light. Try 20w50 as that's a 20w base.
Or since you're in AZ, nothing wrong with straight 30w either.
10w30 is made from a 10w base; extremely light. Try 20w50 as that's a 20w base.
Or since you're in AZ, nothing wrong with straight 30w either.
Pro
Joined: Oct 2002
Posts: 586
Likes: 0
From: Schmuckville SA
Re: Oil pressure problems (frank j. moran)
I agree with Frank...
My 85 runs 12-15 psi at operating temp (540 rpms idle)
Jumps right up 40 when I hit the gas... 50's when cold.
You might want to listen to your motor under hard accelaration
and make sure you dont hear anything bearing related. If those
bearings are suspect, you'll hear them..definitely.. Barring that,
Just go with it.
My 85 runs 12-15 psi at operating temp (540 rpms idle)
Jumps right up 40 when I hit the gas... 50's when cold.
You might want to listen to your motor under hard accelaration
and make sure you dont hear anything bearing related. If those
bearings are suspect, you'll hear them..definitely.. Barring that,
Just go with it.
Le Mans Master
Joined: Feb 2000
Posts: 9,715
Likes: 27
From: Kempner Texas
Re: Oil pressure problems (Unriced)
The second of the two numbers, in your case the "30", is the cause of low readings at idle (if the gauge is fairly accurate).
It indicates the resistance to flow at 212 degrees F, which I believe is the temps call for by the SAE.
The first number, in your case "10" indicates the oil's resistance to flow at 32 degrees F.
Try this. Let the car sit overnight. Next day fire it up, place the trans in gear (auto) and note the oil pressure right away.
Now let the engine idle until the oil temp starts coming up. Again put the trans in gear and note the oil pressure at idle.
I'll bet it'll be lower and the hotter the oil gets, the lower the idle in gear reading will be.
Now drain the 10W30 and pour in 20W50 or 15W50 Mobil 1. Do the same test and you'll see the idle, in gear oil pressure will be higher than with the 10W30 gave under the same conditions.
The second number - 50 - will not thin as much as the oil temps climb, so the resistance to flow will be greater and the psi reading will be higher.
Ballpark, you'll want 20 psi idle in gear with oil at 200/210 F.
Jake
[Modified by JAKE, 5:30 PM 3/12/2004]
It indicates the resistance to flow at 212 degrees F, which I believe is the temps call for by the SAE.
The first number, in your case "10" indicates the oil's resistance to flow at 32 degrees F.
Try this. Let the car sit overnight. Next day fire it up, place the trans in gear (auto) and note the oil pressure right away.
Now let the engine idle until the oil temp starts coming up. Again put the trans in gear and note the oil pressure at idle.
I'll bet it'll be lower and the hotter the oil gets, the lower the idle in gear reading will be.
Now drain the 10W30 and pour in 20W50 or 15W50 Mobil 1. Do the same test and you'll see the idle, in gear oil pressure will be higher than with the 10W30 gave under the same conditions.
The second number - 50 - will not thin as much as the oil temps climb, so the resistance to flow will be greater and the psi reading will be higher.
Ballpark, you'll want 20 psi idle in gear with oil at 200/210 F.
Jake
[Modified by JAKE, 5:30 PM 3/12/2004]
Team Owner
Joined: May 2002
Posts: 24,337
Likes: 25
From: San Diego , CA Double Yellow DirtBags 1985..Z51..6-speed
Re: Oil pressure problems (JAKE)
Ballpark, you'll want 20 psi idle in gear with oil at 200/210 F.
I guess every motor is different, but 10psi is too low... i'd hook up a mechanical guage to it....
Also, pull out the fitting that feeds to your sending unit, and make sure it's not clogged.
Burning Brakes
Joined: May 1999
Posts: 1,179
Likes: 0
From: waller texas
Cruise-In I Veteran
Re: Oil pressure problems (CentralCoaster)
my 89 had low oil pressure about like you are seeing. The motor is about all torn apart now as I think I have spun bearing. Heads are off now and I can't believe how clean this engine is. I will be pulling the pan today and checking for a spun bearing. I really suggest you pull all the rod and mains before you have a blown engine like I have now.
Le Mans Master
Joined: Feb 2000
Posts: 9,715
Likes: 27
From: Kempner Texas
Re: Oil pressure problems (Motorworx)
:confused: My L98 makes about 55-60 psi at hot idle... hits 80 regularly. I'd be glad to give you some of my oil pressure...
Same here.
Same here.
You're either using heavy oil or have tight bearing clearances or a combination of both.
When you said ". . .hot idle. . ." what temp (F.) are we talking about?
Jake
Le Mans Master
Joined: May 2003
Posts: 5,203
Likes: 0
From: Las Vegas Nevada
Re: Oil pressure problems (Unriced)
I agree with Frank...
My 85 runs 12-15 psi at operating temp (540 rpms idle)
Jumps right up 40 when I hit the gas... 50's when cold.
You might want to listen to your motor under hard accelaration
and make sure you dont hear anything bearing related. If those
bearings are suspect, you'll hear them..definitely.. Barring that,
Just go with it.
My 85 runs 12-15 psi at operating temp (540 rpms idle)
Jumps right up 40 when I hit the gas... 50's when cold.
You might want to listen to your motor under hard accelaration
and make sure you dont hear anything bearing related. If those
bearings are suspect, you'll hear them..definitely.. Barring that,
Just go with it.
[Modified by Southern Comfort, 11:24 PM 3/13/2004]
