Decemberist

I had and oil pressure issue a couple of days ago, when my 2000 XJ lost oil pressure dummy light came on when at idle and went back up to 35-40 psi while driving. I changed the sending unit and give it an oil change, however, when warm and stopped or at idle the pressure is at 12psi, is this too low or is this normal?

tjwalker

You need to VERIFY your oil pressure. That way you'll know for sure. There can be some inaccuracy between the oil pressure sending unit and the gauge.

Find a parts store that rents tools and rent a MECHANICAL OIL PRESSURE GAUGE. It will come with adapters.

Temporarily install it where the oil pressure sending unit currently resides. Compare those readings to what you see on your dash gauge.

The spec. for oil pressure for the 4.0 is as follows:

*Not less than 13 psi at hot idle
*Between 37-75 psi over 1600

If you find out you do have 12 psi, I wouldn't freak out about it. That is only 1 psi lower than spec.

This engine hasn't ever been overheated has it? Coolant level okay? What I am getting at is that you have the "infamous" 0331 cylinder head, which is prone to cracking if the engine is overheated or cooling system not maintained. And if that happens, coolant mixes with the oil and can create low oil pressure and other symptoms.

Decemberist

Thank you for the reply, I have done a few oil changes on it since May and I have not noticed any oil/antifreeze mix, and it has not overheated since I have owned it...about a year. However, I have to add about a half gallon of anti freeze during the warmer months.

The closest thing that I have done to verify the oil pressure it looking through the oil filler cap and made sure there was oil getting to the top of the valves...it is. I just hope this does not turn into a major repair! I will get a mechanical guage and make sure it is right...thanks.

XJDavid

Have you noticed your oil level rising as you need to add antifreeze? Thats how I caught a cracked head on mine after owning it for about 5 months. I was adding about a 1/2 gallon every other week here in a Texas summer.

Ender

*Ouch* very interesting... I'll have to watch for that... thanks

Decemberist

No, I never thought about that, I need to add more antifreeze right now, I will check the oil level when I do...how bad of a job is changing the head on a 4.0?

XJDavid

It's not bad. Took me about 3 months to get the money together, so I broke it down in my spare time and then put it all back together in a weekend with a buddies help, just cause that head is about 80 pounds. By the way, only had 42,000 miles on it. Now sitting at 47,000 and so far so good. PM me if you like.
If your oil level hasnt gone up, check your spark plugs. If the #3 cyl plug looks steam cleaned, you might have a crack/leak into the combustion chamber. That could be the head or the gasket. Or just pull the valve cover and look for the tell-tale crack. Do a search for "0331" on here and you will find more info than you could imagine. Helped me out a lot.