No Signals Posted May 9, 2022 Share Posted May 9, 2022 Or more to the point, the lack of it. Not by choice, but I did a ten mile run up the motorway the other day. When I came off I had to stop, as I had a traffic light against me, and I noticed the oil pressure drop down to zero, or maybe +5. I revved the engine to see if it recovered any and it did, a bit. When I got moving again it went back up to 40 (ish). Is this something that I should get investigated or is it something to associate with old jeeps? The engine was professionally rebuilt a couple of years ago, maybe 2000 miles? Quote Link to comment Share on other sites More sharing options...
Nick Johns Posted May 9, 2022 Share Posted May 9, 2022 (edited) What grade of oil are you using ? a long thrash on the motorway will get the oil really hot and thin, the wrong grade will give low pressure when very hot Edited May 9, 2022 by Nick Johns Quote Link to comment Share on other sites More sharing options...
No Signals Posted May 9, 2022 Author Share Posted May 9, 2022 SAE 40 (sorry about putting it in the wrong section, no idea what I was thinking 🙂 ) Quote Link to comment Share on other sites More sharing options...
phil.c Posted May 11, 2022 Share Posted May 11, 2022 Had similar problem, used Castrol 20/50 classic and tick over pressure is fine now. Probably is as Nick said your oil getting thin when hot. Quote Link to comment Share on other sites More sharing options...
G506 Posted May 11, 2022 Share Posted May 11, 2022 I've had this happen to me. In my case it was the oil pick up pipe in the sump. Air was being sucked in at the pivot of the pick up. On speaking to other jeep owners they advised slightly overfilling the sump oil got around the issue. Thd proper solution was a new pick up, but then they weren't readily available, not sure about these days? Quote Link to comment Share on other sites More sharing options...
ferretfixer Posted May 12, 2022 Share Posted May 12, 2022 16 hours ago, G506 said: I've had this happen to me. In my case it was the oil pick up pipe in the sump. Air was being sucked in at the pivot of the pick up. On speaking to other jeep owners they advised slightly overfilling the sump oil got around the issue. Thd proper solution was a new pick up, but then they weren't readily available, not sure about these days? Or if pushed. Remove sump pan to gain access to pick up pipe. Remove pipe & the pin hole, or split. Could then be repaired by brazing. Dosent have to be a neat job, as it wont be seen inside the engine! Quote Link to comment Share on other sites More sharing options...
No Signals Posted May 12, 2022 Author Share Posted May 12, 2022 Thanks for the observations and input guys. Quote Link to comment Share on other sites More sharing options...
Ian J Posted June 29, 2022 Share Posted June 29, 2022 Another possibility is your relief valve stuck in the open position. When the engine is cold, remove the relief valve cap nut and spring, With a flexi magnet pull the plunger out and give it a gentle polish with very fine steel wool. I strongly advise you to use 20W/50 oil as the viscosity between hot and cold is far more consistent than straight 40 weight. 47 years of experience with MB's 😁 Cheers 1 Quote Link to comment Share on other sites More sharing options...
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