Oil Pressure Issues

[Dallas Lemon]

I'm running a 401 in my CJ-7 and have occasionally lost oil pressure on steep vertical climbs. It's not often and it has to be very steep for it to happen, and the oil pressure will not return as soon as it levels out. I've had it happen on steep downhill descents, but the oil pressure returns right away when it starts to level out. The other difference is I'm usually running a higher RPM on the climbs versus pointing downhill. And I'm talking 2000 to 3000 RPM, not foot to the floor kind of RPMs. I've come to the conclusion that because I must let it set for a few minutes after losing oil pressure, the oil is contacting the crankshaft and foaming, causing this issue. I've tried running a quart over and that didn't seem to make any difference and had wondered if that could worsen the problem. This past winter, I installed a crank scraper and a Milodon pan with baffles, but not the one with the trap doors in the bottom. Well, it happened again this past weekend when I did a fairly steep climb and bounced it pretty hard at the bottom of the hill. And, of course, it happens on the steepest obstacle and the last thing you want to do is shut it down but also the first thing you want to do. As of right now, I'm considering installing an engine oil accumulator before I start tossing rods through the block. I would think cars running road race courses would experience the same oil starvation issues during times of hard cornering and racers during hard launches. Any others have experience with this issue?

Dallas Lemon

[tufcj]

You didn't say, which model Milodon pan did you add? You really need the deep sump with the extended pickup. The high clearance pan for road racing will do no good in an off-roader. The problem is that on steep inclines or drops, the oil is running away from your pickup, the pump sucks air, then needs time to re-prime. When an AMC engine runs high RPM, oil is pumped to the top end faster than it can drain back, sometimes 2-3 quarts can be in the top end of the engine.

Check your oil pickup tube. It should be centered in the bottom of the pan, and no more than 1/4 to 3/8 off the bottom of the pan. Also make sure it's not too close to the bottom of the pan. Factory had about a 1/4" spacer on the bottom of the pickup. I have seen pickup tubes crack, and suck air when the oil level drops below the crack.

Bob
tufcj

[tufcj]

You didn't say, which model Milodon pan did you add? You really need the deep sump with the extended pickup. The high clearance pan for road racing will do no good in an off-roader. The problem is that on steep inclines or drops, the oil is running away from your pickup, the pump sucks air, then needs time to re-prime. When an AMC engine runs high RPM, oil is pumped to the top end faster than it can drain back, sometimes 2-3 quarts can be in the top end of the engine.

Check your oil pickup tube. It should be centered in the bottom of the pan, and no more than 1/4 to 3/8 off the bottom of the pan. Also make sure it's not too close to the bottom of the pan. Factory had about a 1/4" spacer on the bottom of the pickup. I have seen pickup tubes crack, and suck air when the oil level drops below the crack.

Bob
tufcj

[Dallas Lemon]

It's basically the stock replacement pan offered by Milodon that has extra baffles over the top of the pickup tube. Thanks for your input on this issue, Bob. The pickup tube has been inspected and no cracks were noticed, and while the deep sump pan makes sense, ground clearance is critical making that not a good option. It is running Edlebrock heads if that makes any difference, and what you're saying makes perfect sense. So out of curiosity, would running a quart over on the oil level help the situation? Could the oil accumulator be a good remedy? Thanks again for your insight.

[tufcj]

An extra quart in the pan, or an accumulator couldn't hurt. Edelbrock heads shouldn't make a difference. If it's not doing it often, you're probably not doing any damage. You just don't want to put a lot of torque on it with low/no pressure. Let it idle till the pressure comes back up. On the last 3-4 engines I've built, I've painted the lifter valley and top of the heads with glyptal paint. It helps with oil drainback in the top end of the engine. I got out of Jeeping about 10 years ago, sold my 77 CJ7 rock crawler (it was a beast). I used to build engines for mud boggers. I still have 3 AMC cars.

Bob
tufcj

[tufcj]

An extra quart in the pan, or an accumulator couldn't hurt. Edelbrock heads shouldn't make a difference. If it's not doing it often, you're probably not doing any damage. You just don't want to put a lot of torque on it with low/no pressure. Let it idle till the pressure comes back up. On the last 3-4 engines I've built, I've painted the lifter valley and top of the heads with glyptal paint. It helps with oil drainback in the top end of the engine. I got out of Jeeping about 10 years ago, sold my 77 CJ7 rock crawler (it was a beast). I used to build engines for mud boggers. I still have 3 AMC cars.

Bob
tufcj

[Dallas Lemon]

Thank you for your expertise. I think I'm gonna do the accumulator route just for a bit of insurance. Good information you have provided. Thanks again.

[Ingrid]

I would start out by replacing the oil pressure sensor. It's a cheap enough part with a high failure rate on Audis.

If, after replacing the sensor, the oil warnings come back, you likely have a legitimate pressure problem that needs to be confirmed with a mechanical gauge.

Low oil pressure can have any number of causes, almost none of them cheap or easy to fix.

[Dallas Lemon]

It's definitely losing oil pressure as the 401 sounds like a sewing machine when it happens. And it's not low oil pressure, but no oil pressure. It quiets right down when the OP returns and climbs immediately back to 40 PSI at idle. One of these days, I'm afraid when it comes back, it's gonna read more like 10 and have a constant rattle.

[JAYDEE10]

I had quite similar problems. I'm now sorted. Thanks y'all.