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Low oil pressure?

Tiny
FDXORF
  • MEMBER
  • 1999 CHEVROLET SILVERADO
  • V8
  • 4WD
  • AUTOMATIC
  • 112,000 MILES
On cold starts it takes 15-30 seconds before the oil pressure builds. "Oil pressure light" comes on and engine starts making a "clanking" noise. Any ideas? I use Castrol 15W30(conventional) and I change oil regularly.
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Wednesday, February 18th, 2009 AT 6:08 PM

33 Replies

Tiny
MMPRINCE4000
  • MECHANIC
  • 8,548 POSTS
Check oil pressure with a mechanical gauge, if no pressure or low (below 10psi) turn off engine immediately.

Replace oil pump.

Recommended oil for all engines except diesel is 5W-30.

Always use recommended oil, higher viscosity oils can cause engine damage, especially main and cam bearings on cold startup.
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Thursday, February 19th, 2009 AT 8:28 AM
Tiny
2CP-ARCHIVES
  • MEMBER
  • 4,540 POSTS
  • 1999 CHEVROLET SILVERADO
  • 150 MILES
No oil pressure indicated but oil was just changed. It is clean and level full. Engine runs quietly. What's up?
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Thursday, September 3rd, 2020 AT 11:23 AM (Merged)
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,755 POSTS
If there is no noise, then chances are the sending unit is bad. You can just replace it, or get a mechanical gauge to see if there is actually oil pressure. If there is no knocking or ticking from the engine, you have oil pressure.
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Thursday, September 3rd, 2020 AT 11:23 AM (Merged)
Tiny
AFREDERICK
  • MEMBER
  • 2 POSTS
  • 1998 CHEVROLET SILVERADO
  • 18,188 MILES
Can you please tell me what else could cause the oil pressure to get low it's also making a tappin noise I change the oil pump and clean the screen. It's acting like it wants to cut off and the oil pressure is below 30 it's a 5, 7L engine
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Thursday, September 3rd, 2020 AT 11:23 AM (Merged)
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,755 POSTS
If you hear a tapping noise, you need to confirm that the pressure is low. In some cases, the oil sending switch will send a bad signal to the gauge. Replace the switch, problem fixed. However, if you hear a ticking, that leads me to believe there is a problem with the oil pump.

You can rent an oil pressure gauge at most parts stores. It will be mechanical. Using that, you can see exactly what the pressure is.
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Thursday, September 3rd, 2020 AT 11:23 AM (Merged)
Tiny
AFREDERICK
  • MEMBER
  • 2 POSTS
Thanks alot
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Thursday, September 3rd, 2020 AT 11:23 AM (Merged)
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,755 POSTS
Let me know what you find. If there is ticking or knocking, I wouldn't drive it until we determine the problem.
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Thursday, September 3rd, 2020 AT 11:23 AM (Merged)
Tiny
SCOOBYDOO25E5
  • MEMBER
  • 1 POST
  • 1998 CHEVROLET SILVERADO
  • V8
  • 4WD
  • AUTOMATIC
  • 151,000 MILES
I have a chevy silverado k 1500 1998 I step on the gas and the exhaust got louder I also had no oil pressure the engine died and it would not restart I stopped the vehicle I saw the oil coming of the oil pan. Would this be a blown oil gasket? Or a thrown rod?
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Thursday, September 3rd, 2020 AT 11:24 AM (Merged)
Tiny
HMAC300
  • MECHANIC
  • 48,601 POSTS
If you have a hole in the oil pan you probably have thrown a rod, especially since you said there was no oil pressure. Get a flashlight and look inside you should be able to see some damage.
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Thursday, September 3rd, 2020 AT 11:24 AM (Merged)
Tiny
TOMGREGORSKI
  • MEMBER
  • 1 POST
  • 1998 CHEVROLET SILVERADO
  • V8
  • 4WD
  • AUTOMATIC
  • 120,000 MILES
My daughter recently purchased the subject pickup. Under load (pulling a trailer) and after getting hot, upon acceleration the engine knocks and at idle the oil pressure drops very low. Is this due to bad main bearings? If so, can they be replaced without removing the engine? Thanks
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Thursday, September 3rd, 2020 AT 11:24 AM (Merged)
Tiny
MASTERTECHTIM
  • MECHANIC
  • 4,749 POSTS
Well unfortunately the oil pan needs to be removed and inspect the connecting rod bearings and the main bearings. These engines have problems with the intake manifold gaskets going bad and coolant getting into oil causing engine damage. Realistically most likely nothing short of overhauling the engine is going to work if indeed there is bearing failure. Also these flywheels have been known to crack where it bolts to crankshaft making a noise that appears to be engine bearings.
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Thursday, September 3rd, 2020 AT 11:24 AM (Merged)
Tiny
CWATSON79
  • MEMBER
  • 1 POST
  • 1998 CHEVROLET SILVERADO
  • V8
  • 4WD
  • AUTOMATIC
  • 185,000 MILES
2 days ago on my way home from work I noticed a small minor tapping noise. I checked my oil everything was good, I was preparing to take it into the shop. Drove it home and on the way home the knocking (which sounds to me in the upper part of the engine) got worse and louder. Also as I come to a idle my oil light comes on and I notice my oil pressure is bottoming out. Is this an oil pump problem or do I have bigger issues?
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Thursday, September 3rd, 2020 AT 11:24 AM (Merged)
Tiny
JEEPFAN
  • MECHANIC
  • 135 POSTS
It sounds as if your oil pump is going out the noise you were hearing is at this point only lifters rattling do not run the engine until you fix the pump as it will damage the engine
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Thursday, September 3rd, 2020 AT 11:24 AM (Merged)
Tiny
BAN1
  • MEMBER
  • 9 POSTS
  • 1994 CHEVROLET SILVERADO
  • 5.7L
  • V8
  • 4WD
  • AUTOMATIC
  • 1,532,558 MILES
I just started getting low oil pressure on my truck. Literally yesterday. Truck runs fine there is a small oil leak after running it after a little while, usually four or five drips. I am curious as to what could be causing this. I have general idea. I am going to replace the pick up hose because it looks dry rotted and then I am going try a new sending unit on it.
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Thursday, September 3rd, 2020 AT 11:24 AM (Merged)
Tiny
HMAC300
  • MECHANIC
  • 48,601 POSTS
It may be the oil filter as they can cause problems like this, but the age of truck may have a lot to do with it as well. It would not surprise me if bearings may be problem. Manually check pressure with a gauge.
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Thursday, September 3rd, 2020 AT 11:24 AM (Merged)
Tiny
BAN1
  • MEMBER
  • 9 POSTS
Im hoping it is some thing none costly the drips do seem to be coming from around the oil filter somewhere but not directly from it sometimes the oil pressure is fine for example I drove the truck all day yesterday with no drops in oil pressure
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Thursday, September 3rd, 2020 AT 11:24 AM (Merged)
Tiny
MORRIS072807
  • MEMBER
  • 1 POST
  • 1994 CHEVROLET SILVERADO
  • V8
  • 4WD
  • AUTOMATIC
  • 136,000 MILES
I had a low oil pressure gauge when I bought the truck a month ago. Oil was crappy so I changed it with 10w-30 full synthetic with an a/c delco filter. Now when I start it the oil pressure is at 40 and once it warms up it's between 30-30 while cruising and down to just above the red mark at idle. Engine does not make noise oil level is perfect. Could it be a worn pump that needs to be replaced, wearing bearings?
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Thursday, September 3rd, 2020 AT 11:24 AM (Merged)
Tiny
RASMATAZ
  • MECHANIC
  • 75,992 POSTS
Check the oil pressure with a mechanical gauge if normal replace the oil pressue switch abnormal could be the oil pump and engine bearings.
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Thursday, September 3rd, 2020 AT 11:24 AM (Merged)
Tiny
NINJA181
  • MEMBER
  • 3 POSTS
  • 1994 CHEVROLET SILVERADO
  • V8
  • 4WD
  • AUTOMATIC
  • 379,000 MILES
I've been getting low oil pressure for about 2 weeks now. For the most part on the highway it is a little low, approw 25, but at an idle goes to almost 0 and the light comes on. In the morning it would take about 10 seconds to get any pressure. Changed the sensor for the gauge and checked with a mechanical gauge no help. Did an oil change and got pressure right away, and good pressure but that went away after an hour on the highway I got off the pressure went to about 2 but when I got into the gas it would go up. So I pulled the oil filter and the new oil was very dark and thin but the oil on the dipstick still looked new. Engine was running good when in the gas and was ideling OK.
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Thursday, September 3rd, 2020 AT 11:24 AM (Merged)
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,755 POSTS
When you used the mechanical pressure gauge, did it read low too? Also, when you changed the oil and got good pressure for a short time, did you also change the filter at that time? Have you tried an engine flush? I'm a little confused as to how the oil could be dirty when drained, but clean on the stick.

When the pressure drops to 0 or very low, do you hear any ticking or knocking in the engine? Finally, is this the original engine with 379K on it?

Let me know.

Joe
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Thursday, September 3rd, 2020 AT 11:24 AM (Merged)

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