What Oil Pump 4.0 I-6?

[Joe]

I will be replacing my oil pan gasket and rear main seal, in the next few weeks and need to ask what oil pump should I buy.

Should I go with the stock replacement?

Should I buy a high volume pump? If so what maker?

Thanks in advance, (edited)

 

[Rafa]

I installed a Melling high volume pump, but you will need to (well, I did on my 99 4.0) to make a small dent on the oil pan to make room for it. It was hitting the pan and I don't want to make a hole in the pan from vibration.
The dent was cutting a bit on the internal baffle and hammering a dent on the pan to have eough clearance. Not a big deal, but recomended.


Rafa

 

[Joe]

Did it make a difference in the oil pressure gauge?

Do you remember the part number?

Here is what I got from the Melling website:

PART #: M167HVS
NOTES: HI VOL PUMP-20% ADD'L VOL OF OIL THAN STOCK PUMP. INCLUDES SCREEN.

 

[ChiXJeff]

I picked up a high volume pump at Autozone 4 years ago for my 94 4.0l. No massaging of the pan was necessary. Don't remember the part numbers.

 

[bigolexj]

I recommend the high pressure pump. Higher volume just means it sucks the sump dry faster. Higher pressure is better for your engine long-term, especially if you care about oil starvation (i.e. precarious positions, off-camber, etc)

 

[Joe]

Thanks I take a look at the local auto shops first and move the internet as needed.

 

[MudDawg]

Be careful with high volume/pressure pumps in a 4.0.....if the oil pressure runs above 58 pounds or so, you can damage the distributor drive gear or in extreme cases cause the cam to walk forward enough to cause lifter/cam lobe problems.

 

[rag]

so i might as well do the oilpump while im doing the rearmain and the oil pan gasket... correct? 89xj with 130k

 

[ratman572]

I recommend the high pressure pump. Higher volume just means it sucks the sump dry faster. Higher pressure is better for your engine long-term, especially if you care about oil starvation (i.e. precarious positions, off-camber, etc)

All oil pumps are positive displacement pumps, -meaning the pressure they create is not due to velocity, but rather, due to a restriction, -or orifice at the discharge.

The orifice in this case would be the bearing clearances in the engine.

There are several ways to increase pressure, mainly, -either with more flow (higher volume), or by reducing the size of the orifice (decreasing bearing clearances).

Most oil pumps are equipped with an internal PRV (pressure relief valve) that is nothing more than a spring loaded valve. This valve is simply used to protect the pump itself, the drive mechanism, -and the filter (depending on the oiling circuit).

So, in other words, a "high pressure" pump would simply have a higher PRV set pressure, -that's it.

Achieving higher pressure though depends on several things, volume of fluid, restriction, fluid viscosity, and pump speed, -and has absolutely nothing to do with the set pressure of the internal PRV.

In case you might be wondering, I'm a pump guy, -it's what I do for a living. I am not trying to bash anyone here, -just trying to educate.

My vote goes to using the stock-volume melling cast iron bodied pump. If that pump won't git 'er done, -then bearing clearances need to be addressed.

My .02

 

[Patrick S.]

I got a P4529241 from the Jeep dealer. 25% increased volume.

Was one of the best upgrades I've done. Used to get too much tappet noise with all the idling and hot weather I get on my XJ.

I do add 1/2 qt. to the oil changes to keep the pan from running low.

Don't know how may miles your xj has. Might not be the best thing to change the oil pump on a not so new engine…say more than 70,000 miles.

Patrick
1993 XJ

 

[Rafa]

To add to ratman572's comment, he is right. The use of an higher pressure oil pump will not help on a worn engine, the bearing clearances will just bleed the pressure down to what it is now; Volume will compensate for the bleeding through the bearings.
I did install a higher volume, standard pressure oil pump to help on keeping constant pressure on off-idle RPM but not affecting the PRV settings with recomended oil (10W30). I did plastigage my engine (with 86Kmiles) while doing a rear seal replacement, it was at 0.002- (which falls in the recomended range), replaced the bearings (rod and main) with the rear main seal. Pressure is 30 at hot-idle and 50-55 above 1200 RPM with a stock size oil filter.

 

[Joe]

I got a P4529241 from the Jeep dealer. 25% increased volume.

Was one of the best upgrades I've done. Used to get too much tappet noise with all the idling and hot weather I get on my XJ.

I do add 1/2 qt. to the oil changes to keep the pan from running low.

Don't know how may miles your xj has. Might not be the best thing to change the oil pump on a not so new engine…say more than 70,000 miles.

Patrick
1993 XJ

Yeah it has around 140k so that is why I was think of replacing the oil pump while I had it off.