Decemberist

Here goes, I had an ONGOING issue with oil pressure, last week the pressure dropped to zero. I changed the oil pressure sending unit/oil now I get low pressure 12 psi at idle and 35 with rpm above 1600. I noticed that i had to continuously add antifreeze about a gallon every month more, more during the warmer months. I have not noticed a jump in oil quantity when I check it but there is no coolant leaking anywhere. What do you guys think, could this be a cylinder head? It is a 2000 XJ, which apparently has had problems with cylinder heads cracking. Shouldn't this be a recall at this point??

robertj

Miles?

Decemberist

It has 112,000 on it, what do you think?

tjwalker

There is no recall. You get what you get with the infamous 0331 head. You're on your own. Chrysler didn't support this problem back then and they definitely won't support it now.

The fact that you are using that amount of coolant is VERY suspicious. You could very possibly have a cracked head. You should never be going through that amount of coolant!!!!!!!!!!

I would suggest pulling the oil fill cap and looking inside with a good light. Otherwise, pull the valve cover and take a look. The 0331 head has a casting defect between cylinders 3-4 and if the head cracks, it cracks there. Many times, the cracks are visible to the naked eye.

Otherwise, there are tests that can help including a cooling system pressure test, leakdown test, block test (sniffing coolant for the presence of hydrocarbons (oil)

If the head cracks and it isn't caught and resolved early enough, that can lead to the toasting of engine bearings, which can result in low oil pressure.

You really need a solid diagnosis of your head/engine at this point.

Rmart30

Are you having to add coolant to keep the overflow jug at the proper level?

If so you have a cracked 0331 head that has let coolant seep into the oil and has damaged your bearings.
No easy fix.... new head and rebuild your short block or a complete other motor.

Decemberist

yes, I have to add it to the overflow. I just did an oil change and did not notice any presence of anti/freeze. Would there be white smoke coming from the exhaust? If I get some of the tests done that tjwalker suggested and it is the cylinder head, how big of a job am I looking at? Should I try to dump this thing??

wahoo

I just helped a buddy replace his head on his 2000 cherokee this past weekend, he had anti-freeze in his oil. He bought a remanufactured head at Advance Auto for 350.00 plus core and has changed his oil 3-4 times since Saturday, oil pressure is staying at 35psi at idle and 55psi at cruising speed.

5150mechanic

Replace the head, plan on cam bearings for oil pressure, maybe rods and main but def. cam bearings. Cam bearings can be done in vehicle but the trans. has to come out.

Decemberist

Jesus, man...seriously?

5150mechanic

Ya, a pain but worth it. The head has to come off to do the cam bearings anyways because of the lifters. You might want to replace those too, but if you're not hearing any knocking from the bottom end or loud lifters you can prob leave those alone. Know what, replace the lifters, $50. You'll be pissed later if you have to pull the head if an old lifter starts making noise. The bottom end beaings and oil pump can always be changed later when dropping the pan.

tjwalker

You need a diagnosis before getting ahead of yourself, but yes...this is potentially serious.

Start with the VISUAL head tests I recommended. With many, I have been able to see the cracks. Then a block test (sniffing).

Gotta know what you're dealing with first.

And be absolutely sure that you don't have a leak somewhere, so you are not chasing your tail.

Rmart30

You wont hardly see anything in the oil when you dump it. I have had a couple of these with cracked heads and it was not noticable in fresh dumped oil. it did not look milkshaky at all.

You can take a clean yellow drain pan dump the oil and let it sit for a cpl of hours.....very slowly pour out the drain pan untill there is about 1/8" of oil left in bottom. The small green antifreeze droplets will shop up and almost glow when you hold a drop light under the pan.

There will be no white smoke coming from your exhaust on a 0331 head leak.
Most people when they hear cracked head think that it will. When most other engines crack heads they let coolant into the combustion chamber. A 0331 cracked head lets coolant into the oil where it mixes with the oil and wears out the bearings.

5-90

White "smoke" is actually steam, and could be caused by either coolant getting into the combustion chambers (an underside crack - not the common #0331 topside crack) or by condensation in the exhaust system being boiled off (which would happen on startup and disappear as the system heats up.)

You say you don't see any increase in oil volume - any changes in colour or consistency? The #0331 head cracking can usually be determined by the oil looking like a chocolate malt, and the crack can sometimes be seen looking straight down through the oil filler hole in the valve cover.

You may have a head gasket failing - which would let coolant into the combustion chambers without it getting into the oil. There is a chemical test kit for seeing if combustion gasses are present in the coolant - if you can't find it at the local, any decent cooling system shop or mechanical shop can do it for you for a nominal fee. A leaking head gasket - coolant to chamber - would have coolant drawn in on the intake stroke, and would force combustion gas out during compression and power (and, to a limited extent, exhaust - before the exhaust valve opens.)

A head gasket is a much simpler fix - although, if you have a 2000, you may want to go ahead and source a 2002-up #0331 TUPY head and throw it on while you've got the old head off, to save you doing it later. Generally, the early #0331 heads (without the TUPY foundry mark) have about a 50/50 shot at cracking around 150-180Kmiles.

The TUPY mark I'm referring to is cast into the top of the cylinder head, I believe it's under the valve cover. Any 2002-2006 6-242 head will be the #0331 casting, and therefore compatible directly with your 2000 (you can make the earlier 7120 or 0630 heads match up with a bit of work, if you are so inclined.)

A compression test will help you isolate which cylinder is potentially leaking into the cooling jacket, and a leakdown test will confirm it by showing air bubbles in the coolant (the leakdown test is done to further enhance the results of a compression test - the compression test will show you that there is a leak, while the leakdown test will help you isolate it without tearing the engine down...)

Decemberist

Thanks for the information, I am in the military and will be gone until march so this isssue will have to wait. When I get home I am sure that I will not have the energy to conduct compression test and leakdown tests myself so I wiil have one of my local shops do the diagnostics for me, but I hope that they give me good news about my jeep, I will get this fixed and be back on the ol' dusty trail in no time, thanks again.

tjwalker

Good luck on this and THANK YOU for your service to this country.