DoubleFrame Posted June 22, 2019 Share Posted June 22, 2019 Help please, I just did a oil change as I normally do. I filled up my oil filters and all and then I cracked up the truck and noticed oil pressure dropping to zero on the gauge and immediately the Truck shuts down as I am in the cab. I noticed that my oil filters are extremely hot, I let the truck sit a little and changed the filters again... thinking that the filters may have been bad. Now I cranked the truck back up, everything seems to be running ok but still notice that the filters are really hot and oil pressure is at 25 psi. Which it would normally be around 50 psi in a cold start. What do you guys think this could be? Engine is a 2007 Mack Aset 427 Quote Link to comment https://www.bigmacktrucks.com/topic/57800-low-oil-pressue-after-oil-change/ Share on other sites More sharing options...
Rob Posted June 22, 2019 Share Posted June 22, 2019 Sounds a bit like the oil pressure relief opened for a spell for some reason. The oil pressure gauge transducer, (sending unit) is downstream and if this relief is acting only a portion of engine oil pressure is reaching this transducer. Why a sudden blockage in your engine or filters I cannot answer for but the filters getting hotter than normal is usually from the relief valve doing it's job. It is directly part of the oil pump and oil gets hot when oil is passed through this type valve. If the relief valve is not seated it could be passing a portion of engine oil right back into the oil pan instead of routing it through the engine which would give a low oil pressure indication. Regardless if you have changed the filters again and the oil pressure is consistently lower than normal, I would verify your oil pressure reading is correct with a known good mechanical gauge, or replace the sending unit wholesale. If the oil pressure still reads low, the oil pan probably needs to come off for oil pump work/replacement. This is a very limited diagnosis as there really isn't a lot of information presented and I'm not there. The "hot" oil filters are a pertinent factor however lending suspicion to the oil pump itself. Quote Plodding along with no job nor practical application for my existence, but still trying to fix what's broke. Link to comment https://www.bigmacktrucks.com/topic/57800-low-oil-pressue-after-oil-change/#findComment-425940 Share on other sites More sharing options...
DoubleFrame Posted June 22, 2019 Author Share Posted June 22, 2019 (edited) Thank you for the response. Update- it ran fine for about 30 minutes. Oil pressure was at 30 psi on idle and 60 psi @1400 RPM. Suddenly the oil pressure dropped to 20 psi and then 0 psi and engine shut down again. So I'm back at where I started. Update- I got a code.. 1-1 oil pressure sensor fault. I'm going to change it out now. Edited June 22, 2019 by DoubleFrame Quote Link to comment https://www.bigmacktrucks.com/topic/57800-low-oil-pressue-after-oil-change/#findComment-425941 Share on other sites More sharing options...
1965 Posted June 22, 2019 Share Posted June 22, 2019 If me; I’d put a mechanical gauge in & see. Probably bad sending unit if you service it regular Quote Link to comment https://www.bigmacktrucks.com/topic/57800-low-oil-pressue-after-oil-change/#findComment-425942 Share on other sites More sharing options...
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