00exjay

2000 xj good oil pressure at cold idle (40) at hot idle it slowly sinks to 10 than check gauges light comes on. Has a new in cracked head and new high vol. oil pump. New mopar filter and 6 qts of 15x40 rotella. The sending unit is good I check with mechanical gauge. Should I add another quart of oil? Cus it's a high vol. pump. Need some advice thanks guys

bigbadon

sounds like you might not have caught that cracked head in time??
Any noises? You can drop the oil pan and check the bearings....you can have a worn main and it will not make noise, worn rod bearings will sound off around 2000 to 3000 rpm. If it isn't making noise I wouldn't be overly concerned until it does. Mine does the same thing (4psi) and I have been driving it for about a year. Year 2000 seems to be the dominant year for this problem.

00exjay

I'm debating wether or not to add another half quart. Would that hurt anything u think?

scottmphoto

A high volume pump is not the same thing as a high pressure pump. Now, I don't know about the XJ (cause I haven't had to replace one yet) but on my Power Wagon, they offered the two different pumps. I opted for the high volume pump over the high pressure one.

jebmccall

there is no need at all for an extra quart. you can run an xj on 3.5 qts of oil and still get oil pressure. the oil capacity has to do with a number of things such as cooling... when you get on a hill the pick up tube can still get oil, etc.

over filling only causes reduced fuel economy.

now lets say you switch to a large capacity oil filter then yes add another half quart, but as long as there is 5qts in the 4.0 it will maintain good oil pressure if nothing is excessively worn or thinned out.

more than likely you have worn mains from the cracked head allowing coolant to mix with the oil causing the bearings to wear.

jebmccall

also i have heard of the oil filter adapter getting plugged with gunk over the years causing oil pressure to drop off at the sending unit.

another thing is the gasket where the oil pump mounts to the block if it got torn during install it would cause a loss in pressure.

00exjay

But wouldn't worn mains cause low pressure All together? It's at 45 when cold than it heats and it drops

tjwalker

No. Cold oil is always going to have a little higher pressure than hot oil.

Unfortunately, the odds are quite high that you have internal bearing wear because of the cracked head that you replaced.

I always verify low oil pressure though. Use a mechanical gauge which can be rented from many parts stores.

Good data = good decisions.

00exjay

Just checked with mechanical gauge and it's reading at 5psi at warm idle

bigbadon

Welcome to the low oil pressure club! Any noises? There is no guarantee how long it will last but it could go another 100k like that if you don't hotdog it. Reference your noise level and oil pressure and then monitor it. Any changes will be the alert to do something.

00exjay

It makes a little noise. Not sure if it's normal I haven't driven it much since we put the head back on 2 days ago. I'm wanting to add another quart of oil but I don't want to hurt anything

bigbadon

More oil won't help and could make things worse. All 4.0s make noise, if you have to strain to hear it you probably don't have a problem yet. When you replaced the head you also contaminated the oil so change it. I don't think you have an oil pressure problem...you have a wear problem.

cruiser54

Read this.

http://www.jeepforum.com/forum/f19/4...fixed-1304679/

00exjay

Tried cleaning the hole for the sending unit and letting some oil squirt out and still no luck. How about an extra capacity oil filter? Would this help anything?

cruiser54

No.