convoyduel Posted August 23, 2012 Share Posted August 23, 2012 Our 2000 Postal Puppy with the E7-300 and Allison 5 speed has some funny issues going on with oil pressure that have us and the dealer stumped. The oil pressure bounces between 60 and 90 when throttled up while in neutral and when driving, under heavy acceleration, the pressure will drop rapidly from 60 down to 30 and right back up, almost instantly. There is a noticeable change in noise that exactly matches the fluctuations on the gauge. It almost sounds like the Centrimax sound changing with the pressure. Not sure if the noise is related to the cause or a symptom of the loss of pressure. The sharp pressure drop does not occur (or at least not as noticeable) under lighter acceleration. At highway speeds, the pressure flucutates somewhat rapidly in a 5 to 10 psi range typically from 60 to 65 or 70 psi. The engine has been fully serviced with new filters, including the centrimax. The engine is a REMACK engine from June 2005. The truck has 625k with less than half of that on the new engine. They checked the dash gauge and it matches the pressure shown on a known good remote gage. The pan was dropped and a bad plunger was found in the oil pump. It has been replaced with no change. Also, a rocker arm had an odd squirt of oil coming out so it has also been replaced. Rod and main bearings have been checked and are in excellent condition. A pressure test with the pan dropped shows no unusual pressure loss at any of the bearings on the bottom end.Any ideas on another source or cause? Quote Link to comment Share on other sites More sharing options...
staxx Posted August 23, 2012 Share Posted August 23, 2012 I would check the block off plate gasket on the oil pump, its oposite of the pickup tube . this is for option to have rear sump oil pan or front. The gasket gets brittle over time and I had one I chased for two weeks just the corner of it was missing and sucking air under had accleration and heavy breaking. Also can check the assory drive gear the one that turns your oil pump for slippage they are pressed on, they get spun off when engine are over sped .Hope this helps good luck. Quote Link to comment Share on other sites More sharing options...
staxx Posted August 23, 2012 Share Posted August 23, 2012 Good looking truck by the way does it have air starter system as I remeber most of tose posts trucks had. Quote Link to comment Share on other sites More sharing options...
Frmconcrete09 Posted August 23, 2012 Share Posted August 23, 2012 Good to have guys like you around staxx... Looks like you been round these macks a while Quote Link to comment Share on other sites More sharing options...
staxx Posted August 23, 2012 Share Posted August 23, 2012 I can fix alot of things but still havnt figured out how to fix the nut behind the wheel.................. Quote Link to comment Share on other sites More sharing options...
rsb502 Posted August 25, 2012 Share Posted August 25, 2012 I can fix alot of things but still havnt figured out how to fix the nut behind the wheel..................And you never will just stop tryin! Quote "Any Society that would give up a little LIBERTY to gain a little SECURITY will Deserve Neither and LOSE BOTH" -Benjamin Franklin"If your gonna be STUPID, you gotta be TOUGH" "You cant always get what you want, but if you try sometimes you get what you need" Link to comment Share on other sites More sharing options...
mackdaddytruckfixer Posted September 22, 2012 Share Posted September 22, 2012 it might be just a simple short in the wire but you would think mack deal would find that but you have to remember people like me have work there lol Quote Link to comment Share on other sites More sharing options...
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