Hey all, been hunting down a low oil pressure issue on my XJ for a bit now. I bought it with a cracked head but it ran fine and didn't have any milkshake when I fixed it (replaced head/hardware).
Ever since replacing the head it's run like a champ. It's needed a couple sensors here and there (TPS, IAC and CPS) but the engine has been strong and healthy. That was confirmed by a compression test not long after a couple cycles of oil to clean out the block. Each cylinder was at spec.
One issue ever since then is that the oil pressure on the gauge would be fine at start up and while driving for a bit. But once it'd heat up to operating temp, it'd sit right at the first line (10psi) at idle and only go up maybe another 10-15PSI under load. Considering it had a cracked head and coolant could have ruined the bearings, I've kept a close eye on it. There has been zero noise/ticks out of the engine other than a bit of an exhaust leak because the previous owner omitted 2 exhaust manifold bolts.
Either way, to be safe rather than sorry, I've tried replacing the pressure sender but I've only tried some non-oem/mopar versions. Neither of them worked. Before spending the money for the $90 mopar version, I tried a mechanical gauge. Granted, it was a cheap one. It was reading near zero at hot idle... Thinking it was faulty, I returned it and got a bit pricier of a mechanical gauge (off amazon) and while it wasn't zero at hot idle with this one, it was at maybe 3-5 psi and 20psi under load. It's still possible the gauge was cheap/subpar but I doubt 2 gauges would be that wrong, especially since the second one had a relief valve to remove air out of the hose/housing.
Considering the potential of my bearings going out, and seeing what looked like very very fine glitter/metal in my oil, I sent a sample off for analysis at Blackstone. To my surprise, nothing came back too worrying! Definitely no major wear metals that could indicate bad bearings (lead/copper). Here's the report:
https://i.imgur.com/KzCvjI0.jpg
So, if all looks good there then would my next step be replacing the oil pump? I do have a slightly leaky oil pan gasket. And my valve cover leaks a bit more than that. Could that cause low oil pressure at hot idle? Should I just go ahead and replace the oil pump for peace of mind since it's cheap and I need to do my oil pan gasket anyways? Anything concerning on my report that stands out? What is the molybdenum from?
Side note, I've switched over to some 15w40 diesel oil and the XJ lovessss it. It's been running even better, and oil pressure has been up as well.
Ever since replacing the head it's run like a champ. It's needed a couple sensors here and there (TPS, IAC and CPS) but the engine has been strong and healthy. That was confirmed by a compression test not long after a couple cycles of oil to clean out the block. Each cylinder was at spec.
One issue ever since then is that the oil pressure on the gauge would be fine at start up and while driving for a bit. But once it'd heat up to operating temp, it'd sit right at the first line (10psi) at idle and only go up maybe another 10-15PSI under load. Considering it had a cracked head and coolant could have ruined the bearings, I've kept a close eye on it. There has been zero noise/ticks out of the engine other than a bit of an exhaust leak because the previous owner omitted 2 exhaust manifold bolts.
Either way, to be safe rather than sorry, I've tried replacing the pressure sender but I've only tried some non-oem/mopar versions. Neither of them worked. Before spending the money for the $90 mopar version, I tried a mechanical gauge. Granted, it was a cheap one. It was reading near zero at hot idle... Thinking it was faulty, I returned it and got a bit pricier of a mechanical gauge (off amazon) and while it wasn't zero at hot idle with this one, it was at maybe 3-5 psi and 20psi under load. It's still possible the gauge was cheap/subpar but I doubt 2 gauges would be that wrong, especially since the second one had a relief valve to remove air out of the hose/housing.
Considering the potential of my bearings going out, and seeing what looked like very very fine glitter/metal in my oil, I sent a sample off for analysis at Blackstone. To my surprise, nothing came back too worrying! Definitely no major wear metals that could indicate bad bearings (lead/copper). Here's the report:
https://i.imgur.com/KzCvjI0.jpg
So, if all looks good there then would my next step be replacing the oil pump? I do have a slightly leaky oil pan gasket. And my valve cover leaks a bit more than that. Could that cause low oil pressure at hot idle? Should I just go ahead and replace the oil pump for peace of mind since it's cheap and I need to do my oil pan gasket anyways? Anything concerning on my report that stands out? What is the molybdenum from?
Side note, I've switched over to some 15w40 diesel oil and the XJ lovessss it. It's been running even better, and oil pressure has been up as well.
