R&R oil pump?

RogerTango

NAXJA Forum User
Location
Virginia
My oil pressure is low as a limbo bar... abt 20psi at best. I suspect it needs a new oil pump, changing oil and filter are not helping.

This engine has abt 2 monts in the chassis, I cracked my other block (please dont ask) so I dont have a full history on the current block.

What is involved in R&R of the oil pump? Something a shade tree mechanic can do on a weekend?

Thanks much for any help-
Andrew
 
have you verified that the gauge is correct. most times its just a bad sending unit, bad/dirty electrical connection, or a bad oil filter. hook up a mechanical gauge to verify if it indeed has low oil pressure
 
Ive got bad valve clatter on accel and during load around 2K to 2.5K RPM also, Im guessing the oil is not making it to the top good enough.

BTW, '93 4.0 auto.

Andrew
 
20 psi, hot oil pressure at idle is fine. Jeep spec is 13 psi minimum, hot oil at idle.

Is this a rebuilt engine or a JY pull, you said 2 months?????

I run 20W50 plus 1 quart of Lucas to keep my hot oil pressure at idle a little higher. 254,000 miles.

Sounds like you need some lifter oil additives like MMO.
 
Ecomike said:
20 psi, hot oil pressure at idle is fine. Jeep spec is 13 psi minimum, hot oil at idle.

Is this a rebuilt engine or a JY pull, you said 2 months?????

I run 20W50 plus 1 quart of Lucas to keep my hot oil pressure at idle a little higher. 254,000 miles.

Sounds like you need some lifter oil additives like MMO.

Thanks for the update... What is MMO please? Forgive me, I know SOME lingo... but not all! :flipoff:

Thanks,
Andrew
 
Uh... I *think* you mean Marval Mystry Oil.... MMO... I ran some, it only worked good for the first 5 minutes. That was with 10W30. I forget what Im running now, but I moved up in thickness, I *think* its 20W50.

Doesnt MMO thin the oil, making the thicker oil a waste of time??

Andrew
 
X2 check the gauge first, but 20psi is not bad. For the ticking I would MMO it first, cheaper and easier. As far as the oil pump, the hardest part is getting the oil pan off, the pump is not expensive or hard to replace and while you have it open you could replace the RMS if you're feeling brave...lol

I can't imagine MMO working in 5 min. It is a slow working product,prob at least 300-500 miles b-4 any diffs.
MMO has a viscosity of about a straight 5W motor oil, so I use 10-40W when doing a oil change.
MMO can replace up to 25% of your total motor oil, so I adjust oil weight to the amount of MMO being added.
 
dizzymac said:
<snip>I can't imagine MMO working in 5 min. It is a slow working product,prob at least 300-500 miles b-4 any diffs.<snip>
Well, I didnt know what to expect in the way of time frames, so Ill give it another try. Of all the additives, MMO appears to have the thumbs up all the way around.

Thanks!
Andrew
 
I'd throw in a quart of Slick 50 before pulling the oil pan. It's been my experience all that teflon will bring up oil pressure 10-20 pounds within minutes of circulating.

I theorize it reduces the bearing clearances in a nice way, which is the #1 oil pressure loser in older engines. It'll stay pumped up for years after that, and sure won't hurt.

I've gotten by with one quart of oil in the pan after using it, and have 185k on the motor with a glass sealed head gasket and some borrowed time.
 
RogerTango said:
Uh... I *think* you mean Marval Mystry Oil.... MMO... I ran some, it only worked good for the first 5 minutes. That was with 10W30. I forget what Im running now, but I moved up in thickness, I *think* its 20W50.

Doesnt MMO thin the oil, making the thicker oil a waste of time??

Andrew
I run the MMO with Lucas Oil additive. One quart of each. The high viscosity of Lucas counteracts the low viscosity of MMO so the net change in hot oil pressure at idle is nill. I have tried just MMO and Just Lucas in mine, and for the lifter / tappet clatter I find the 50/50 blend of the two (2 quarts net, mixed with 4.5 quarts of the usual oil you would normally use) is the best combo for cleaning and quieting the noise at the same time. Then 20W50 for the oil itself to get the hot oil pressure at idle increased.

I changed my oil pump to a high flow oil pump and replaced the only worn bearings I could find (slightly worn crank shaft bearings) when my 10W40 oil pressure hit 9-10 psi one day. That had almost no effect on my hot oil idle pressure.

Since then, last 2 years, I have discovered that several things seem to affect the oil pressure gauge readings. One is low voltage, and poor grounds! Low voltage and poor grounds problem is more evident as you turn on high current using devices like the AC blower for heat on high, the Electric Coolant radiator fan, head lights and brake lights and turn signals. I have also noticed that the oil pressure is extreemly sensitive to the engine idle speed. In drive the difference between 750 rpm and 450 rpm is the difference between 30 psi and 20 psi oil pressure on the gauge. Then add in the extra power loads plus low alternator output at 450 rpm and it sort of means the gauge is lying, under reporting oil pressure by maybe 5 psi, and the low rpms is actually droping the oil pump speed enough to drop the oil pressure by 5 psi.

My hot oil pressure at idle is currently 5 psi higher with my AC running, because the idle speed in drive is about 200 rpm higher with the AC running (My Renix ECU kicks in and cranks up the IAC to run at a higher rpm!!!!) .

I also recently found some old API SL Havoline 20W50 inventory that I have used twice now, and it is giving about 3 to 5 psi more pressure than Exxon 20W50 (API SL) was giving me.

On the Slick 50 sugestion, while I am a snake oil advocate, the one snake oil product I never recommend is Slick 50, or anything with Teflon in it.

Teflon has fluorine atoms which when they break down form hydrofluoric acid, which is an extreemly corrosive, agreesive acid. Teflon begins to decompose at around 700 F, so expect it to attack areas in the combustion zone over time.

I would use a product like Restore before I even considered trying Slick 50 for restoring compression, as it works the same way as Slick 50, but it uses colloidal particles made of silver/copper/lead that plate out on the cylinder walls, with out the corosive acid byproduct problems Slick 50 has.

TiRod,

How many years, and miles have you put on a Slick 50 engine with out problems? What was the mileage before you added Slick 50?
 
Last edited:
Just dropped a qt of MMO in the crank, will run it for a few hundred and see if it frees up the lifters a bit, is what I suspect.

Andrew
 
Well, 750 miles with MMO and it seams to be helping! The valve clatter is starting to diminish noticeably and the oil pressure gauge is indicating a little higher pressure from time to time.

Andrew
 
What oil are you running with the MMO? After 750 miles how dark is the oil? Dirty? Another thing to try is straight 40 weight. Also take out your oil pressure sending unit and screw in a mechanical unit to see if your gauge is accurate. It will probably very close. You will see that new oil gives better pressure also. Good luck
Ron
 
RogerTango said:
Well, 750 miles with MMO and it seams to be helping! The valve clatter is starting to diminish noticeably and the oil pressure gauge is indicating a little higher pressure from time to time.

Andrew
Even with 20# oil pressure, there shouldn't be any valve clatter. I'm thinking maybe the oil pump pickup screen may be clogged. This would give lower oil pressure and give a low volume of oil. If this is true, then the MMO might be loosening the gunk on the screen and giving more oil flow.

If the screen is indeed clogged, you'll get a very slow pressue build upon initial start-up. Instead of the needle shooting up after about 3-5 seconds, it'll take upwards of 10 seconds, maybe more, for pressure
to show on the gauge.

If a clogged screen is suspected, there are ways to clean it without dropping the pan; such as draining the oil and letting a quart of solvent sit in the pan overnight, or fishing a piece of piano wire in the oil drain hole and scraping the screen. Of course the best cure is to drop the pan and replace or clean the screen.
 
Good follow ups, thanks.

I did notice, when the engine is COLD, there is no clatter, once it warms up is when it will most happen.

Another thing I was wondering, aren't the 4.0 HO running hydraulic lifters? Im thinking/wondering if I got some sticky lifters.

Andrew
 
RogerTango said:
Good follow ups, thanks.

I did notice, when the engine is COLD, there is no clatter, once it warms up is when it will most happen.

Another thing I was wondering, aren't the 4.0 HO running hydraulic lifters? Im thinking/wondering if I got some sticky lifters.

Andrew

Yes, and Yes. The 4.0 lifters get noisy with age, and sludge and varnish build up. I think the tapets also get loose from wear, but they are not adjustable. So there is a sticking noise and a loose ticking noise. Most are noiser when cold, but that depends on what oil they are using too.
 
Back
Top