YACT...Low oil pressure when cold

[Sluggo]

My work truck, a 99 Chevrolet (with a 5.3 and auto) has trouble keeping up the oil pressure first thing in the morning.

I think the issue started since it is colder in the mornings. For the most part the pressure is OK, it has the most trouble at idle. After the truck is driven for 5 minutes or so, the oil pressure all returns to normal, and everything is fine until the next morning.

Its not a huge issue, just have to keep the RPMs up at stoplights to keep the oil pressure from dropping to zero until it warms up, but if there might be an easy fix I'm all for it.

Any ideas? It might have more to do with old age (160,000 miles) and abuse more than anything.

 

[InlineFive]

160k seems like a heck of a lot for a native vehicle...

 

[Zim Hosein]

Originally posted by: Sluggo
My work truck, a 99 Chevrolet (with a 5.3 and auto) has trouble keeping up the oil pressure first thing in the morning.

I think the issue started since it is colder in the mornings. For the most part the pressure is OK, it has the most trouble at idle. After the truck is driven for 5 minutes or so, the oil pressure all returns to normal, and everything is fine until the next morning.

Its not a huge issue, just have to keep the RPMs up at stoplights to keep the oil pressure from dropping to zero until it warms up, but if there might be an easy fix I'm all for it.

Any ideas? It might have more to do with old age (160,000 miles) and abuse more than anything.

Try a lower viscosity engine oil. What grade are you using now Sluggo?

 

[Pepsi90919]

Originally posted by: PorBleemo
160k seems like a heck of a lot for a native vehicle...

not really.

and sounds like it could be a bad gauge.

 

[herm0016]

the temp will do that, you may want to switch to a senthetic or a blended oil, they seem to pick up faster,. also the 5.2 is a very loosly built engine, the best thing to do is to let it warm up before you start going anywhere, which you should do with every car and truck, makes everything last longer.

 

[Zim Hosein]

Originally posted by: Pepsi90919

Originally posted by: PorBleemo
160k seems like a heck of a lot for a native vehicle...

not really.

and sounds like it could be a bad gauge.

I didn't think of that!

Also, what is the ambient temp in the AM Sluggo?

 

[Sluggo]

Originally posted by: Zim Hosein

Originally posted by: Sluggo
My work truck, a 99 Chevrolet (with a 5.3 and auto) has trouble keeping up the oil pressure first thing in the morning.

I think the issue started since it is colder in the mornings. For the most part the pressure is OK, it has the most trouble at idle. After the truck is driven for 5 minutes or so, the oil pressure all returns to normal, and everything is fine until the next morning.

Its not a huge issue, just have to keep the RPMs up at stoplights to keep the oil pressure from dropping to zero until it warms up, but if there might be an easy fix I'm all for it.

Any ideas? It might have more to do with old age (160,000 miles) and abuse more than anything.

Try a lower viscosity engine oil. What grade are you using now Sluggo?

The morons at the Kwik Lube place continue to put 5W/30 in it, even when I tell them I want 10W-30. They have a short attention span.

I have been thinking the heavier oil would help with the amount of miles.

 

[Kalvin00]

Originally posted by: herm0016
the best thing to do is to let it warm up before you start going anywhere, which you should do with every car and truck, makes everything last longer.

Not really...unless the temp is below 10 or something..

 

[Sluggo]

Originally posted by: Pepsi90919

Originally posted by: PorBleemo
160k seems like a heck of a lot for a native vehicle...

not really.

and sounds like it could be a bad gauge.

The gauge seems to act fine, it responds instantly with more pressure when you bump the RPMs up a bit. It seems to function flawlessly the rest of the day.

As far as temps, it hasnt really dropped much below 25F here yet.

Yet another EDIT:

I do let it warm up a bit in the mornings, just idle in the drive for 5 minutes or so. As soon as you drop it into gear the oil pressure plummets.

 

[Zenmervolt]

Colder oil will run higher pressures... My cars peg out the guage until the oil warms up and the pressure drops to 30-40 PSI at idle. You should see 70 to 80 PSI at idle with cold oil...

It actually sounds like the oil pressure relief valve is sticking open until the metal and seals heat up and allow it to move freely.

ZV

 

[Sluggo]

Originally posted by: Zenmervolt
Colder oil will run higher pressures... My cars peg out the guage until the oil warms up and the pressure drops to 30-40 PSI at idle. You should see 70 to 80 PSI at idle with cold oil...

It actually sounds like the oil pressure relief valve is sticking open until the metal and seals heat up and allow it to move freely.

ZV

Hmmm, the morons at Kwik Lube asked it I wanted to replace the PCV valve last time. I figured they were just selling crap, and I really didnt need it and even if I did and really didnt want to buy it there anyway.

I had meant to pick one up, but forgot, Will pick one up tomorrow, it more than likely needs one anyway.

 

[mattgyver]

Could be a bad Oil Pressure sending unit. Have seen it several times.

 

[natto fire]

Originally posted by: Sluggo

Originally posted by: Zenmervolt
Colder oil will run higher pressures... My cars peg out the guage until the oil warms up and the pressure drops to 30-40 PSI at idle. You should see 70 to 80 PSI at idle with cold oil...

It actually sounds like the oil pressure relief valve is sticking open until the metal and seals heat up and allow it to move freely.

ZV

Hmmm, the morons at Kwik Lube asked it I wanted to replace the PCV valve last time. I figured they were just selling crap, and I really didnt need it and even if I did and really didnt want to buy it there anyway.

I had meant to pick one up, but forgot, Will pick one up tomorrow, it more than likely needs one anyway.

PCV is positive crankcase ventilation, and shouldn't affect oil pressure, it is basically a one-way valve that allows crankcase fumes to go into the intake manifold. The pressure relief valve that ZV speaks of is a valve that bleeds off excess oil pressure into the pan, usually. If this sticks open, it can release pressure too soon (at idle) instead of it's designed operation to bleed excess pressure in the higher RPMs. Since oil pumps are usually directly driven off the crank, this valve allows the engine to maintain normal oil pressures in higher RPM engine events.

 

[Zenmervolt]

Originally posted by: Captain Howdy

Originally posted by: Sluggo

Originally posted by: Zenmervolt
Colder oil will run higher pressures... My cars peg out the guage until the oil warms up and the pressure drops to 30-40 PSI at idle. You should see 70 to 80 PSI at idle with cold oil...

It actually sounds like the oil pressure relief valve is sticking open until the metal and seals heat up and allow it to move freely.

ZV

Hmmm, the morons at Kwik Lube asked it I wanted to replace the PCV valve last time. I figured they were just selling crap, and I really didnt need it and even if I did and really didnt want to buy it there anyway.

I had meant to pick one up, but forgot, Will pick one up tomorrow, it more than likely needs one anyway.

PCV is positive crankcase ventilation, and shouldn't affect oil pressure, it is basically a one-way valve that allows crankcase fumes to go into the intake manifold. The pressure relief valve that ZV speaks of is a valve that bleeds off excess oil pressure into the pan, usually. If this sticks open, it can release pressure too soon (at idle) instead of it's designed operation to bleed excess pressure in the higher RPMs. Since oil pumps are usually directly driven off the crank, this valve allows the engine to maintain normal oil pressures in higher RPM engine events.

DING DING DING! Winner!

ZV

 

[Sluggo]

Originally posted by: Zenmervolt

Originally posted by: Captain Howdy

Originally posted by: Sluggo

Originally posted by: Zenmervolt
Colder oil will run higher pressures... My cars peg out the guage until the oil warms up and the pressure drops to 30-40 PSI at idle. You should see 70 to 80 PSI at idle with cold oil...

It actually sounds like the oil pressure relief valve is sticking open until the metal and seals heat up and allow it to move freely.

ZV

Hmmm, the morons at Kwik Lube asked it I wanted to replace the PCV valve last time. I figured they were just selling crap, and I really didnt need it and even if I did and really didnt want to buy it there anyway.

I had meant to pick one up, but forgot, Will pick one up tomorrow, it more than likely needs one anyway.

PCV is positive crankcase ventilation, and shouldn't affect oil pressure, it is basically a one-way valve that allows crankcase fumes to go into the intake manifold. The pressure relief valve that ZV speaks of is a valve that bleeds off excess oil pressure into the pan, usually. If this sticks open, it can release pressure too soon (at idle) instead of it's designed operation to bleed excess pressure in the higher RPMs. Since oil pumps are usually directly driven off the crank, this valve allows the engine to maintain normal oil pressures in higher RPM engine events.

DING DING DING! Winner!

ZV

OK, I'm going to assume that is an internal part of the oil pump?

If thats so, it looks like I will be living with it for awhile. According to my book here, changing the oil pump requires tearing down the front of the motor and possibly dropping the oil pan.

It seems the oil pump is driven off of the crankshaft at the front of the motor, under the timing chain cover, with the pick-up tube running back into the oil pan.

 

[thedarkwolf]

Put a real gauge on it before freaking out. The stock gauges are crap. My van will show 0psi when its hot at idle and if I hop out and smack the oil pressure sender around a bit the gauge jumps all over the place.

 

[TitanDiddly]

Block heater.

 

[shekondar]

My truck (2000 Ranger) has also started doing this - if the temp is below 30 or so, the oil gauge will hang around zero for a few seconds, then jump between zero and the middle of its range for the next couple of minutes. It started doing this the last time I changed the oil (a couple weeks ago). Once it warms up the pressure is fine.

 

[Vette73]

Also change the oil filter to something OTHER then fram. If you have been using a quick lube shop they are probable using a Fram/Honeywell filter.

Put on a ACdelco, stp, Purolator, Wix, Supertech, etc... and also go to the 10w30 Mobil7500 and see if that helps.

 

[radioouman]

I'd check the sending unit.

It could be a stuck open pressure relief valve.

 

[Zenmervolt]

Originally posted by: Sluggo
OK, I'm going to assume that is an internal part of the oil pump?

If thats so, it looks like I will be living with it for awhile. According to my book here, changing the oil pump requires tearing down the front of the motor and possibly dropping the oil pan.

It seems the oil pump is driven off of the crankshaft at the front of the motor, under the timing chain cover, with the pick-up tube running back into the oil pan.

It's not integral to the pump on the cars I've worked on, but it's definitely some labor to get at.

This is NOT something you want to "live with". The Oil Pressure Relief Valve (OPRV) by-passes the oil filter first of all, and if it sticks open completely, you won't ever get proper oil pressure and you'll damage the engine. If it decides to stick closed someday, you'll get too much pressure and will blow the gasket out of your oil filter and lose all your engine oil.

ZV