lnichols

I know I need to replace the main bearings in the 2001 4.0 engine. Probably need to either do a complete overhaul or get a rebuilt engine. The engine just started losing oil pressure at idle - down to zero and the check gauges light comes on if I don't maintain 750 to 1K RPMs. The problem is that I'm 1,000 miles from home. I've been running 10w30 oil. Can I use something thicker, like 10w40 or 20w40 to get home and then decide what to do with the engine?


Thanks, Leni

bigbadon

Yes you can but it won't solve your problem. You may increase pressure a LITTLE with thicker oil but more pressure will not give any more life to a tired engine. What is your pressure at cruise speed? A engine does not need alot of pressure at idle. If it is not making noise your fine till it does.
FYI my DD has had the same low pressure symptoms for years. I run 15-40 wally world fleet/diesel oil.

Burwood69

Although I'm not well versed with Jeep yet, my experience with low oil pressure tends to be plugged oil pick up strainers. It could be an internal leak but if it only gradually happened there's a possibility of simply not enough oil getting to the pump.

I'd suggest trying the cleaning the pick up and retesting long before replacing bearings.

dmill89

Before you do anything have you verified the pressure with a mechanical gauge? The XJ oil-pressure sending units are notoriously unreliable and excessively low or high readings are often a failed sender.


If the oil-pressure is verified as low look into Burwood69's advice(always start with the "cheap" "simple" stuff). Since you have an 01 a cracked 0331 head and damaged bearings from coolant contamination of the oil is a possibility so check for signs of a cracked head (milky oil, mysteriously disappearing coolant, etc.).


Like bigbadon said thicker oil isn't going to fix the problem and would have little if any affect on the pressure. Though 4.0L I6s have been known to run a long time with low or no oil pressure at idle.

lnichols

Thanks for the responses. I'm not looking to "solve" the problem. I'm looking to make it 1,000 miles to home, and I'll solve the problem there. Oil pressure at cruising speed is 50-60 lbs. I had the oil pressure verified. We replaced the sending unit and it's slightly improved. Meaning the pressure gauge doesn't immediately drop to zero the instant RPMs go below 750. Now it takes a few seconds. Unfortunately, it is making a tapping noise. It's worse at idle, but verified to be main bearings with a stethoscope. There is no loss of coolant, oil is clean and clear, and there is no burning of oil and no oil leak. Engine has 193K miles on it. I've kept maintenance up well, but I have no idea how it was maintained for the first 140K miles.

dmill89

Also, what oil filter are you using? Certain brands (especially Fram) are known to cause pressure issues.

freegdr

Try new filter first could be that simple .

thatXJguy

I have the same problem on the new 2000 I just bought. Turns out there was some water in the oil, and I bet the head suffered a crack, as there was stop leak in the system when I bought it.

Well, now oil pressure sits at about 2-5 when idling. Even with a mechanical gauge. We even put new rod and main bearings in with a new high-volume oil pump and found that it made no difference. The engine is worn and we're just going to run it until it gives.

lnichols

Oil filter is Mobile 1. Same brand of filter I've been using since 1999. No problems before now, but I may go ahead and change it. Thanks.

dmill89

Mobil1 are generally good filters (not sure if they are worth the price, but decent none the less) but any brand can have a defect so an new filter is worth a shot.


If you are looking for something cheap, easy to find, and good quality a Motorcraft FL-1A (probably the best <$4 filter you can buy) and its cross-references (Purolator L/PL30001, WIX 51515/NAPA 1515, etc.) will work (it is larger than stock and will increase oil capacity by approx. 1/4 qt.) and these are a common "upgrade" due to increased capacity and ease of availability (virtually every older ford Truck/Van used these as did many other vehicles so pretty much everyone has this size in stock).


WIX/NAPA (WIX makes NAPA filters), Purolator, Baldwin, Bosch, Hastings, Motorcraft (made by Purolator) or another Mobil 1 should all be decent filters.

Radi

You should get home OK.

Fred/N0AZZ

In the future instead of the Mobil 1 (paying more for the name) filter consider a NAPA Gold (Wix) instead, I have used both the NAPA is a better filter IMHO.

For the 1k trip I would just go easy on it and use a good 30wt. oil or even a flat 50wt. In fact if you were here I would give you some Mobil 1 15-50wt. Syn Racing Oil that I run in the summer. Its supplied by a sponsor along with all my filters. I'm no longer racing full time but checked the other day and still have 65 cases of oil and 128 NAPA NASCAR Racing oil filters on hand. Oil (8 qts.) and filters were changed after every race and at times filters were pulled and cut open in between rounds to see if there any ware issues with the engine depending on the pass made.

I'm not a cheerleader for NAPA or Wix filters, but if you cut open a lot of different ones and look inside its not hard to tell who has the best and the very cheapest filters. BTW I only used Mobil 1 oil in my race cars because it was supplied by them through NAPA.

Good luck till the overhaul.

bigbadon

If you have 50-60 psi at cruise speed you don't have anything to worry about!
With that much pressure I would not suspect bad mains. The pickup is not clogged b/c if it was oil pressure would drop on the high rpm end. Many 4.0s (especially 2000 & 2001) have low pressure issues and they run forever....mine has, and it only has 20 psi at cruise.

lnichols

Changed oil from 10w30 to 10w40 and installed a Napa Gold filter. Oil pressure at idle now stays at about 10 psi and the check gauges light doesn't come on. Starting to sound like a diesel, but since the pressure is staying higher, I'll start the 1,000 mile drive home tomorrow.


Thanks, Leni

freegdr

Good Luck.