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I have a 1996 c1500 ext cab p/u with the gm 350R engine. For the past two days on start-up, I expeienced an upper engine rattle as if a lifter was losing prime. On 10/29/04, when I started it to go home, I again experienced the problem which went away after approx 1 minute of idle time. I then proceded to go to my home. I went approx two city blocks when the check guages light came, and I noticed that I had 0 oil pressure. Upon stopping, I had oil all over the underside of the engine and front of the trans. When researching the problem, I found that the oil filter, which was a Fram filter,had blown out at its sealing gasket. At this point, I replaced the oil filter with a new TG-5 Fram filter and refilled the crankcase with new Synblend 5W-30 oil. When restarted, the engine ran fine, with no noise although I noticed that I had over 80 psi oil pressure on the factory guage. I drove home keeping the rpms as low as I could although the pressure stayed above 60 psi even at 35 to 40 mph. When I arrived home, the pressure had settled down slightly to around 35 psi at idle and 45 psi when revved to 2000 rpm. I hooked a mechanical guage to the engine and got readings within 10% of what the factory guage was showing. What is causing my high pressure readings? I recently had to replace the intake manifold gaskets and thermostat, due to both leaking. I appoligize for such a lengthy question, but am slightly stumped at this time, as I have never experienced this problem before. I consider myself an above average mechanic and have built several older small block chevys, 1 of which went approx 350k before being retired. Thanks in advance for your assistance.
Answer -
AnswerTwo things may have caused the initial problem and the continuing oil pressure symptom: 1) A stuck (or sticking) pressure relief valve; or 2) A defective oil filter. The relief valve is built into the oil filter mount and is designed to bypass oil around the oil filter if the filter should become plugged. The theory is that dirty oil is better than no oil.
Your oil pressure readings may be higher than before but they are not outside the recommended range of operating pressure.
Fram does not make a good product, in my opinion. I would try a Wix, Purolator, or Baldwin filter and see if that makes any difference in the oil pressure readings.
If you want to investigate the pressure relief system, try to find a shop manual to guide you as such repairs are not well handled by this kind of question and answer forum.
