Hi all, I know this is a super common issue but I havent found an answer still!

My 2000 Cherokee Sport has 120k on the stock 4.0 and suffered from loss of coolant and low/no oil pressure at idle, engine ticked. I've been researching and troubleshooting the issue FOREVER and still haven't fixed it, so frustrating! Finally decided to nut up and join the community for some help.

Replaced the head, lifters, rockers etc. to fix the coolant and ticking issue but the oil pressure is still dropping to 0 when the car is warmed up at idle. I've used the mechanical gauge and ran the cluster test as well.

Replaced the sending unit (a couple times), various oil filters, main bearings, rod bearings, oil pump, rear main seal, made sure the pickup was clean etc. Fired her up last night and STILL no oil pressure when warmed up. Oil barely seems to reach the valve cover, rockers look too dry. This is really throwing me for a loop...WHAT THE HECK IS IT?!?!?!

I'm hoping its not the cam bearings, I don't have a hoist in my garage. Any ideas??? Thanks!

 

Im running into the same problem right now.

 

1. What is your idle RPM
2. What is your pressure at 2000 RPM
3. How did you old bearing inserts look
4. Did you mic or plastigage new bearings (possibly used wrong size)
5. Did you replace main bearing #4 (thrust)
6. What is the noise level when first started in am
7. what type oil and filter
8. do you get oil to rockers when you increase rpm to 1000? Normally they do not get alot of oil at idle but they get SOME
9. Are all rocker arms getting oil
10. How long have you been losing coolant
11. what type of antifreeze has been run in vehicle while it was losing coolant

Answer these questions. Without data your just another person with an opinion

 

I agree with all the above and can only add:
The AF is abrasive and will quickly destroy the bearings. It will also wear the bearing journals. Did you check the crankshaft and camshaft bearing journal diamaters? Please post your measurements here.

 

Thanks for taking interest in my quote

 

you for got cam bearings. that is usually the first set of bearingsto go since the cam spinds at twice the rpm.

 

WRONG Camshaft spins at 1/2 of engine speed. However,you are correct that the cam bearings could be the cause.

 

1. What is your idle RPM - 500-700RPM
   1. 500 is too low should be 650 and steady
2. What is your pressure at 2000 RPM - 30PSI
   1. Not great but adequate
3. How did you old bearing inserts look - Not great, trying to attach a pic
   1. which were worn more rods or mains?
4. Did you mic or plastigage new bearings (possibly used wrong size)- Yes, all sizes were correct
5. Did you replace main bearing #4 (thrust)- Yes, size was also correct
6. What is the noise level when first started in am- Noise level low, started great
   1. Good
7. what type oil and filter- Always used Mobile1 synthetic with NAPA Gold filter. Just used switched to Valvoline to cut cost for most recent start up since I'm on my 5th-some odd oil change at this point. Always ran 10-30. Did one run with 20-50 prior to chaning bearings etc just to try.
   1. Good
8. do you get oil to rockers when you increase rpm to 1000? Normally they do not get alot of oil at idle but they get SOME- Maybe a little bit?? Expected a little pool in the rocker but nothing there and nothing splashed against oil cap.
   1. Normally won't splash out oil fill hole but you should see oil flowing to drain hole
9. Are all rocker arms getting oil- Not sure, everything is new up top. Will have to take off valve cover to see.
   1. Need to remove cover and make sure all rockers are wet
10. How long have you been losing coolant- Drove it for probably a year off and on and coolant loss was very gradual. Not until it started mixing into oil that I stopped driving right away.
    1. How gradual? How frequent were the oil changes?
11. what type of antifreeze has been run in vehicle while it was losing coolant

• Prestone 99% of the time, may have mixed in PEAK at one point.

•  
  • Prestone “any make,any model” (OAT) is silicate free which is a good thing since silicate eats bearings. The OAT coolant will still destroy bearings because it interferes with the lubrication but it is still more bearing friendly. If you have coolant leaking into the oil the best antifreeze to run is Amsoil propylene glycol because it is a better lubricant.

•  
  • How did your lifter bores look? A damaged bore will bleed off oil pressure. Did you prime the lifters?
  • The cam bearings can be seen when oil pan is removed but all you can do is visually check to see if one has “walked” out of its bore. A good test is to use compressed air where the sending unit is and then look and listen to see where the most air is escaping.
  • Low pressure is usually a matter of excessive clearance...and that can be accumulative. For example; if ALL your bearings were worn only .001 your engine would still be within factory specs BUT your oil pressure would be LOW
  • Another thing is temperature. If your running around 220-230 it will have an impact on pressure.

 

I was having this issue and it was the wire on my oil pressure sensor. It was old and cracked. It was touching my oil dipstick tube. I taped the whole wire with black electrical tape and the problem was fixed. Hope it helps.

 

Or as I read this a little more. You replaced the head. I have heard this problem with severe oil passage blockages caused from head gasket up side down. Good luck

 

xjtimbo- I'm pretty sure the head gasket cannot go upside down on this model. There is a lug that comes up from the block that ensures the gasket and the head are on the right way. I'll take a closer look at the wire leading to the sender. Good work on that rebuild btw

@bigbadon:

3. which were worn more rods or mains? Mains
10. How gradual? How frequent were the oil changes? Gradual as in 1-2 years. Oil changes @ 3K

Bores looked OK (I think, learning as a I go) and I primed all the lifters.

If it is blowing through the cam bearings when engine is warm and not when it is cold, wouldn't a thicker oil keep pressure with the engine warm? How thick would I need to go to mimic the cold 10/30 oil?

 

At this point I'm thinking about dropping in a crate motor. If I'm going to go through the hassle of pulling my engine out to access the cam bearings I'm thinking this project is going to take me who knows how long. Plus my noob skills may or may not get it back together properly. My buddy at NAPA is saying he can do a full long block for $2,100 with 100,000mi and 7yr warranty. Thoughts?

 

Yes and no IF you were sure all bearing clearances were on the loose side thicker oil will help by supplying oil with a thicker film strength.
Cam bearings do not operate under the intense load as the rods and mains do. I would suggest 15-40 fleet oil like Rotella ( I use wally world 15-40 diesel oil). Don't expect the thicker oil to help much....the viscosity of 40 vs 30 wt. at 210 degrees is almost identical. Do not worry about the oil pressure..as long as you are getting enough flow to keep the lifters pumped up oil will be getting to everything else. Look under the oil fill cap and see if oil is flowing, if it is I would continue to drive it and save up for a crate motor.
Mine has the exact same symptoms as yours and I have been driving it a long time.

 

Thanks for the advice bigbadon

 

Heck u can get one at slawtozone for 1500$ brand new