My, just bought, 2005 Chevy box van 4.8 L Drops In Oil Pressure When Driving and starts making a rapping noise

Matthew Monteith

Asked by Feb 17, 2015 at 08:38 PM about the 2005 Chevrolet Express Cargo 3 Dr G1500 Cargo Van

Question type: Maintenance & Repair

When I Stop the van, shut it off and check the oil it is fine. When i start it back up it runs fine at normal pressure. Then, 15 min later, the oil gradually drops to almost zero, and eventually starts to make a rapping noise again 30 min after. I have already changed the sensor sending unit. I'm very frustrated because it has just had a oil change, filter, and lube! The oil pump looks relatively new. I'm guessing gunk build up, and i need an engine cleaning, but i was trying to avoid that because of possible oil leaking afterwards. Please help! I need to know if i should put a stop payment on my check, LOL!!!   

P.S. Bought this van today, and the dealer mechanic already said he fixed the problem. The test drive which was only was 15 min had no signs of the problem!!

1 Answer


If the crankcase is overfilled it will do that. The oil will foam and cause the oil pump to suck air instead of oil. So the oil pressure will drop. If this is not the case and the van has high mileage try using a thicker weight high mileage oil. This may help. HTH. -Jim

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