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1994 GMC Sonoma engine noise

Tiny
JMAC77
  • MEMBER
  • 1994 GMC SONOMA
  • 2.2L
  • 4 CYL
  • 2WD
  • AUTOMATIC
  • 17,000 MILES
My truck has a fluctuating oil pressure it goes really low to really high back to medium. When its real low pressure the knocking noise is louder but when oil pressure is high its not as loud but you can still hear it. It uses no oil and still runs good while driving. Dosent skip or miss. But what is wrong with it? Idk?
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Tuesday, April 8th, 2014 AT 5:03 PM

1 Reply

Tiny
CARADIODOC
  • MECHANIC
  • 33,871 POSTS
We know it's not a defective sending unit because the engine noise tells us the oil pressure really is going low intermittently. Two common causes are debris in the oil pan blocking the pickup screen, and debris in the pressure relief valve in the oil pump, or a broken spring in it.

I don't think this applies to your engine, but on older GM V-8 engines, the pickup screen can swivel or pivot, and lift up enough to draw up air instead of oil. Aerated oil can compress and will result in low oil pressure. Most engine rebuilders braze the tube to the oil pump body to prevent this from happening.
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Tuesday, April 8th, 2014 AT 5:49 PM

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