Lousy oil pressure = bearing replacement?

[Careful34]

Here's my story - 89 wag, 360 with around 150K on it. My oil pressure at idle is 0, traveling is 30-40psi with oil warm (I put it in neutral when at a stop). I'm running 20w-50 with thickener. I replaced the pump gears, and pressure spring with out much improvement. I checked the gear tip to case clearance and it seems to be under .020" at least (I didn't check the end clearance yet, but it doesn't seem bad), so the pump is OK? Does this mean I've got worn bearings? Reading past threads seems to indicate either main, or cam bearings would be the biggest cause. Haynes doesn't even describe how to do cam bearings, but it sounds like a fairly major job. Main bearing can be done with the engine in place, with out too much disassembly right?

My big question to those who really get into engine guts: Would it be worth it to replace just the main bearings? Or can you think of any thing else I should try?

As alway, big thanks in advance!

[mandoneer]

chack the lifters first , a dead lifter(s) will also give bad oil pressure and as far a the question about the main berings being replaced with the motor still in the truck it can be done but it is a pain cause you still have to pull the tranny off the back to get the rear main - the rod bearings and cam berings are the only ones that can easily be replaced with the motor still in the truck and for the cam you will need to pull the front clip and rad. . hope it is just a lifter . also have you put a mech gauge on it to see if your pressure is really bad - it could be a faulty gauge or sender and ya really dont have bad pressure

[Stuka]

is the engine loud when your at zero psi? The stock guages SUCK! I dont rely on them at all. My J10's reads 30psi cold, and zero warm, but the engine is quiet. If I indeed at zero psi, the engine would be rather loud. Which is what aftermarket mechanical guages are for.

[L.D.]

I've got one with low oil pressure like that,0 at idle. The engine runs quit and I checked it with mechanical guage and the electric guage is correct.

How can a lifter cause low oil pressure?

L.D.

[mandoneer]

basicly it is because the pump itself isnot what gives pressure it is only for flow ,the pressure is created by the resistance in the clearances of all the moving parts so if a lifter was overpumping and leaking alot of oil that will cause a lack of resistance ,and due to any pressurized system fundamentals the oil will all go to that one area first and easier therby dropping the pressure in the whole system I.E not oiling the rest of the system and not pressurizing the sender for the gauge

[Careful34]

I do have a mechanical guage on it, and it comfirms the pressure (should have mentioned that first). Is there any way to check part, lifters bearings, or what, is the culprit?

[mandoneer]

for the berings use plastigauge , for the lifters a visual inspect is usually good but also make sure the cups are moving and if they are than make sure they dont raddle when ya shake the lifter (they are sprong loaded)

[Bobbo]

These things have oil pressure?

[jeepsr4ever]

I have compiled some great info on AMC V8 oiling here

http://www.bulltear.com/forum/viewforum.php?f=25

[tgreese]

Usually rod bearings will wear out before main bearings. If you get that far, check the mains clearance with Plastigage before you do anything drastic.

Personally I think you haven't been thorough about measuring the timing cover and oil pump cover clearances. It's Occam's razor - look in the most obvious place first. Reading this page http://www.jedi.com/obiwan/jeep/wagoneer/401/timingcover.html it's the gear end clearance that's critical. Unless you know what the side and end clearance is with total certainty, I think it would be a mistake to start thinking about less likely reasons like main bearings.

BTW our friends from BJ's Off-Road assure us that the quality problems with the replacement covers, mentioned on the site above, have been corrected.

JMO :cool: Tim

[ December 20, 2003, 12:24 PM: Message edited by: tgreese ]

[mandoneer]

I keep forgeting the "standard "amc V8's have that funky oil pump/timing cover/dizzy housing setup, but he did say that his clearance was good in the pump gears so I was thinking that that would not be the most likely place where he is loosing pressure but it might be I dont know but on a side note :are the pushrods hollow or not because on motors with hollow pushrods an easy way to see a leaky lifter is by looking at the rocker and the oil will actually be squirting rather than Just pumping out of the rod or it will well up the lifter bore and pool in the valvetrain

[Stuka]

My J10 has a 258, not sure of any oiling problems with them, except most only run about 12-18psi when warm from what I have seen.

[Al Johnson]

If you actually have anywhere near .020 side gear clearance in the oil pump, it's shot. Read the http://www.jedi.com/obiwan/jeep/wagoneer/401/timingcover.html site listed above, if you haven't already. It's got good info. My rebuild had .006 side clearance on the (scored) pump cavity walls, I flattened and smoothed the pump cover surface, replaced the pump gears and deburred them, and most importantly, reduced the end gear clearance to .002". I did that with EXTREMELY careful filing on the pump housing surface, and finished it off with carborundum sandpaper on a very flat steel block. I now have 25-30PSI at hot idle, and 65PSI at anything above idle, running 5W30 dino oil.

Good luck!
Al

[jeepsr4ever]

Thats site lists a factory spec that is wrong

end of gears to cover is .004-.006 and that depend on your gasket

Most newer sets only contain .010 gaskets

gear side to wall is max .005

[jeepsr4ever]

sealed power only offers a .0085 gasket now

side gear factory spec is .002 to .006 sorry about the 5 thats my limit

[Traveler111]

This seems to be a common problem. My '88 GW had 132000 miles on it and was blowing oil in every direction. It also had zero pressure at idle when hot and around 20 when on the road. At least one cylinder was weak as well. I didn't diagnose it too much further since together, these symptoms added up to serious problems.

I bit the bullet. I went for a total rebuild. Could have done it myself but didn't have the time. I farmed the whole job out to a rebuilder shop.

It now has about 900 miles on the engine and the only problem is one slightly ticking lifter. The shop will fix it when I bring it in for the first oil change.

Oil pressure is now about 40 at idle, maybe a little less when it's real warm out and the engine is hot. It's running at just about 50 lbs. on the road. That's on the factory gauge.

Overall, I am very happy with the result. I know I would never get my money back if I sell the beast but I plan to use it, not sell it.

Also, I had heavy-duty valve train and a "stage 1" cam put in. I asked for an "RV" cam and that's what he called it. It's definitely peppier but maybe that's just because of good compression etc.

[Careful34]

I'm sorry, side clearance was under .002, not .02, I'm a little new to this feeler gauge stuff :rolleyes: . Haynes list the required clearances of .0005 - .0025 for side, and .004 - .008 for end. I figured since the allowable clearance is greater for the end it wasn't as important. Obviously, I'm mistaken. I still haven't measured the end clearance, and in fact already packed the thing with vasaline, and put it back together :rolleyes: (again). I guess I'll be taking it back apart! I suppose I should run it awhile to clear out the vasaline. I understand that using a priming tool would be better, but I don't really want to yank the diz. Wouldn't the priming tool be spinning in an unlubricated pump though? Thanks Jeepsr, and Al for great links! I book marked both of them!

Another question: I'm thinking running synthetic oil would be a good idea. Would it be worth the extra price?

[jeepsr4ever]

synthetic oil is definately worth it if you go on longer drives, it may leak between the first and secind oil change untill the seals swell

[Al Johnson]

Be really careful how you measure the end clearance of the pump gears, if you take it apart again. Some of the books tell you to measure how far the gear sticks out of the pump cavity with no gasket, and some other places you will read about measuring the clearance between the cover and the gear with the gasket in place. Just use caution and be sure you know what you're looking at and measuring. If you've run it more than a few seconds, the vaseline is dissolved in your oil, and no longer in the pump.

I didn't really want to say this, but if you have 150K on the engine, you will most likely be looking at a full rebuild soon anyway... Ouch, I know!!

[grimgaunt]

why does everyone rebuild at these low mileages ?
All 3 of my jeeps have over 220 K mi on them and dont use ANY oil. I change oil once a month no matter what kind of miles I put on them. Oil pressure is good (aftermarket VDO gauge)
AMCs are good engines, admittedly not as durable as Mercedes diesels (I buy them used at 240 kmi plus and run them for another 200 k typically)

[Al Johnson]

I don't know about everyone, but I rebuilt because I needed an engine, I had one, it had 128K on it, and it was badly in need of rebuild. It had 2 flat cam lobes, 16 concave bottom lifters, 1 broken ring and the cylinder wear to match. The bearings weren't bad, but lots of other stuff was. Now if the previous owners had treated it to the TLC yours is getting, it probably would have lasted well past 200K as well. I sure plan to get that kind of mileage out of it this time around!!

:D
Al

[Crazy_Jeepman]

Yea I don't much pull and keep any AMC engine with more than 90K. At that point I would not bother an engine swap without going inside it. 111K on my J10 and the POS 360 in it, I only hope it lasts till spring........Nice running Caddy 500 awaiting its new home. ;)

[Matt in AZ]

At 150 K miles, I'd expect the center cam bearing to be partly broken out. It's a big job. I'd remove, clean, and replace the pressure relief spring first.

Unknown maintenance by a prior owner can be a problem, and sometimes, I think the center cam bearings were just bad to begin with, on some engines.

[jode]

Originally posted by mandoneer:
...it is a pain cause you still have to pull the tranny off the back to get the rear main...AFAIK, this is not correct on AMC engines. You thinking bout Chevies again? You can drop the oil pan and access the rear main seals, and all the other crankshaft main bearings on AMC 360s. It is not a very big deal (compared to an engine rebuild). But it is a big deal if you do it and it doesn't solve your problem.

[Knucklehead]

Do what tgreese said and check out that link. It has good info.

The gasket should be a white plastic wrapper like material. This very critical in getting the end clearence set up right. This type of gasket does not compress much and allows for tight tolerances. Harley uses them on there oil pumps.

If fixing the oil pump don't fix it I would run 60 wt. or gear lube (joking). I've done it for a year. motor was really tired though. with that many miles I would consider a rebuild in the near future. I see engines listed on here quite abit. There is a 401 listed in the "for sale" section, rebuilt for 500$ in Reno. I might have a 360 with about 10,000 on a rebuild, this summer.

Good luck

Jon

[mandoneer]

AFAIK, this is not correct on AMC engines. You thinking bout Chevies again? You can drop the oil pan and access the rear main seals, and all the other crankshaft main bearings on AMC 360s. learn me sumpin new please, because I just dont see any way of doing the rear bearings on ANY motor without dropping the crank some , that is to say that I am sure that you can wedge them in but not without damaging the bearing surface or cleats/tangs the seals yes but I dont see the upper bearing going in without the surface getting mangled