Low Oil Pressure at Cold Idle

Messages
13
Location
OH
I have a 2005 Pontiac Grand Prix GXP with 128,000 miles. At cold idle, the oil pressure drops to 3.5-4 PSI and the engine has a tapping noise. After the engine has warmed to normal operating temperature, the oil pressure is 12 PSI at idle. At cruising speed, oil pressure is 50 PSI. GM recommends 5w-30 oil. Would I benefit switching to 0w-30 which would make the oil easier to pump when the engine is cold? I've also read of using a heavier weight oil to increase oil pressure, but understand while it may increase pressure it won't get oil to the necessary parts of the engine to stop the tapping.
 

OVERKILL

$100 Site Donor 2021
Messages
46,243
Location
Ontario, Canada
What you are observing is the exact opposite of what should be happening. Heavier (thicker) oil produces higher oil pressure, not lower. I'm thinking your oil pressure sensor is acting up. Either that or your pick-up is partially plugged... But based on the symptoms I'm not inclined to lean that way. The tapping noise may be piston slap, which goes away as the engine warms.
 

thumper75

Thread starter
Messages
13
Location
OH
The tapping noise only seems to present itself when oil pressure is low. If I increase the RPM's while the engine is cold, thus increasing the oil pressure, the tapping stops.
 
Messages
9,808
Location
New Jersey
sometimes if you have very heavy oil in your engine when cold it shows low... 5w30 is what should be used with a good oil filter such as a wix or most other brands.
 
Messages
3,858
Location
Cape Cod, MA
The GXP is a conventional pushrod motor, yes? Maybe you have a bad lifter or the oil gallery to the lifters is clogged. I had a 1980 Malibu with the 229 V6 that wore the lobes on the cam...it made ticking noises and had oil pressure issues, too.
 
Messages
16,014
Location
NE,Ohio
since oil is much much thicker cold the oil pressure should be much higher than when warm.. so your story does not make logical sense. Something is missing.
 

thumper75

Thread starter
Messages
13
Location
OH
I'm not sure what you think is missing or what part of the puzzle I'm not sharing. Holding back information doesn't benefit me when searching for an answer.
 

OVERKILL

$100 Site Donor 2021
Messages
46,243
Location
Ontario, Canada
Have the intake gaskets ever been done on it? Is it losing coolant? Not sure if this engine is prone to the LIM issue but I figured I'd ask, LOL!
 

thumper75

Thread starter
Messages
13
Location
OH
Gaskets have not been touched and no loss of coolant. I'm going to give the oil pressure sensor a shot as I found a source to get the OEM part for under $20. Through some further research I found that while the sensor is not a common failure on the LS4's, it is documented on several different forums. I expected the issue to present itself differently, but for the price it is worth a shot.
 
Messages
1,238
Location
upstate NY
Originally Posted By: Chris142
Could the pickup screen be restricted and not allowing cold thick oil to get through? Once it warms up and thins out it can get through OK?
Same thing crossed my mind. Is the car new to you? Do you know the maintenance history?
 
Last edited:

thumper75

Thread starter
Messages
13
Location
OH
I've owned the car since it was new. Oil has been changed every 3000-3500 miles. While I know there are varying opinions of additives to oil, I have tried Rislone engine oil treatment about 1000 miles ago without any change.
 
Messages
13,261
Location
North Carolina
I wonder if there is a problem with the oil filter, some kind of restriction.I might change the filter to another brand first. When did this start? suddenly or can you pinpoint it to an oil change? Do your change the oil or a quickie place?
 
Last edited:

thumper75

Thread starter
Messages
13
Location
OH
The oil filter was a thought I originally had too as most of its life, the oil has been changed by a local shop (not a quickie lube place). About 3 weeks ago I performed my own oil change with a different brand oil and different brand filter, but no change in the symptoms. The issue has been going on for several months now.
 
Messages
1,509
Location
gulf coast FL.U.S.
The year dosen't match the tsb but i'll bet they use the same parts. Here is a TSB concerning low oil pressure from 2007 to 2010 GM Vortec family engines. PIP4158C: Low Oil Pressure Due To Seized Oil Pressure Relief Valve - (Dec 29, 2009) Subject: Low Oil Pump Pressure due to Seized Oil Pressure Relief Valve Models: 2008-2009 Buick Lacrosse, Allure (Canada Only) 2007-2010 Cadillac CTS-V, Escalade 2007-2010 Chevrolet Avalanche, Corvette, Silverado, Suburban, Tahoe 2007-2008 Chevrolet Monte Carlo SS 2007-2009 Chevrolet Impala SS, Trail Blazer 2009-2010 Chevrolet Colorado 2010 Chevrolet Camaro2007-2010 GMC Envoy, Sierra, Yukon 2009-2010 GMC Canyon 2008-2010 Hummer H2 2008-2010 H3 Alpha 2008 Pontiac Grand Prix GXP 2008-2010 Pontiac G8 GT 2007-2009 Saab 97x with the Following Aluminum V8 Engine RPOs: L76, L77, L92, L94, L99, L9H, LC9, LH6, LH8, LH9, LS2, LS3, LS4, LS7, LS9, LSA, LZ1 The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI. Condition/Concern: Some customers may complain of low oil pressure, no oil pressure, and/or engine noise, which may be the result of a sticking oil pump pressure relief valve. In some instances, this may occur intermittently if the valve frees up when the engine cools down. Recommendation/Instructions: If SI diagnosis isolates low mechanical oil pressure at the oil filter housing and oil pressure sensor, replace the oil pump, flush the oil cooler lines (if equipped), clean the inside of the oil pan, change the oil and filter, and re-evaluate the concern. Notice: If an engine noise is noticed after replacing the oil pump, follow the SI diagnosis and repair the engine as necessary.
 
Messages
26,181
Location
MA, Mittelfranken.de
^^^This sound more like the problem. I would just swap the pump out for a Melling M355, that should take care of it if no bearing damage has taken place already.
 
Messages
595
Location
Murray KY USA
Originally Posted By: FL_Rob
The year dosen't match the tsb but i'll bet they use the same parts. Here is a TSB concerning low oil pressure from 2007 to 2010 GM Vortec family engines. PIP4158C: Low Oil Pressure Due To Seized Oil Pressure Relief Valve - (Dec 29, 2009) Subject: Low Oil Pump Pressure due to Seized Oil Pressure Relief Valve Models: 2008-2009 Buick Lacrosse, Allure (Canada Only) 2007-2010 Cadillac CTS-V, Escalade 2007-2010 Chevrolet Avalanche, Corvette, Silverado, Suburban, Tahoe 2007-2008 Chevrolet Monte Carlo SS 2007-2009 Chevrolet Impala SS, Trail Blazer 2009-2010 Chevrolet Colorado 2010 Chevrolet Camaro2007-2010 GMC Envoy, Sierra, Yukon 2009-2010 GMC Canyon 2008-2010 Hummer H2 2008-2010 H3 Alpha 2008 Pontiac Grand Prix GXP 2008-2010 Pontiac G8 GT 2007-2009 Saab 97x with the Following Aluminum V8 Engine RPOs: L76, L77, L92, L94, L99, L9H, LC9, LH6, LH8, LH9, LS2, LS3, LS4, LS7, LS9, LSA, LZ1 The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI. Condition/Concern: Some customers may complain of low oil pressure, no oil pressure, and/or engine noise, which may be the result of a sticking oil pump pressure relief valve. In some instances, this may occur intermittently if the valve frees up when the engine cools down. Recommendation/Instructions: If SI diagnosis isolates low mechanical oil pressure at the oil filter housing and oil pressure sensor, replace the oil pump, flush the oil cooler lines (if equipped), clean the inside of the oil pan, change the oil and filter, and re-evaluate the concern. Notice: If an engine noise is noticed after replacing the oil pump, follow the SI diagnosis and repair the engine as necessary.
We had this to happen to our 2003 5.3L GM engine at around 140K right after a new oil change in the wife's vehicle after I was doing some WOT take offs. I ran a half of can of Seafoam for 160 miles and it stopped. The no oil pressure was more of an issue on hot restarts than cold start ups. Doing WOT take offs when the car was not driven that way I expect moved the relief valve beyond its normal range of travel and caused it to stick OPEN. Use M1 high mileage at the 160 mile oil change and at high RPM the pressure gage jumped around when doing interstate speeds in 3rd gear for about 50 miles. After that the gauge was stable and good oil pressure on all start ups hot or cold. I see this as a stiction issue in our 2003 5.3L and are moving to Archoil AR9100 usage to try and prevent this GM issue in the future. Based on my reading at the time I think the issue is common to engines with the front mounted oil pumps. There are some good youtube info too. Folks this issue is serious. I think we got lucky that I forced the issue with WOT take offs and was working with the car. It can be a year or more between when I drive it. As for Archoil AR9100 we are adding it to all of our gas and diesel engines for better cleaning and reduced friction after buying a gallon of it. It is cheaper than many additives and our engines are from 1976-2003 with many hours/miles.
 
Messages
26,181
Location
MA, Mittelfranken.de
If this is really the issue, its serious and needs to be addressed yesterday. The last thing i would do is fiddle around with some mechanic in a can, whiz bang ceramic in a bottle or some other snake oil to address the issue. Fix it once and fix it right.
 
Messages
595
Location
Murray KY USA
Originally Posted By: Trav
If this is really the issue, its serious and needs to be addressed yesterday. The last thing i would do is fiddle around with some mechanic in a can, whiz bang ceramic in a bottle or some other snake oil to address the issue. Fix it once and fix it right.
I did not have a good way to pull the oil pump and clean the valve or replace so I went with cleaning with Seafoam that I have used for years with success I guess. Never tried snake oil but I guess regardless of the source all oil is organic in nature. Hopefully the AR9100 cleaning and anti friction traits will help prevent it sticking again. M1 HM 10w-40 is hard to beat for a lube I have learned. We now use it as cutting oil when drilling and metal sawing.
 
Top