The AERA Technical Committee offers the following information regarding Lifter Noise And Low Oil Pressure On GM Engines on 1997-2013 GM 4.8L, 5.3L, 5.7L & 6.0L engines. This noise is only noticeable at idle and a slight increase in RPM will diminish the noise. The noise is also only present on a engine that has been brought to normal operating temperatures.
Low Oil Pressure
This condition may also be noted by a lower oil pressure reading on vehicle oil pressure gauges or warning lights may come on at low idle conditions. It’s been reported these engines may start to lose oil pressure after many engine temperature cycles. Reports of “suddenly the oil pressure light started flashing” have
been heard on well-maintained vehicles. On vehicles with installed oil pressure gauges, the engine idle may be lower than 10 psi.
Camshaft Thrust Plate
The cause of this condition may be a leaking camshaft thrust plate at the front of the engine. The plate is bolted to the front of the block and seals the front lifter oil galleries with a captured rubber “O” ring type seal. Over time this seal becomes hardened and loses its sealing ability. The gasket flattens out and allows
oil pressure to go into the oil pan rather than to the lifters.
To help determine if this condition is present, the observed oil pressure on a “Hot” engine will differ when measured at the top of the engine and compared to the bottom of the engine. To do so, a special adaptor is available from GM with Part # J42907 and J21867 to measure oil pressure at the oil filter base (See Figure
1). If there is a 15-30 difference in upper and lower psi readings, there are seals leaking.
Originally, GM may say that the O ring gaskets are reusable but it is good insurance to always replace those affected components.
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