View Full Version : 93-98 V8 Rear Main Seal & Oil Pump Replacement

07-07-2004, 09:00 PM
Estimated time: 4-6 Hours

Tools Needed:
10mm-19mm Assorted Sockets/Extensions and Wrenches
Oil Filter Wrench
Screw Drivers, Flat head variety
Drain Pan
Air Tools if you have them

Brake Cleaner 2 Cans $5
2” Cleaning Discs (For air tools, not required) $2
New Fasteners for Exhaust (not required) $7
Oil Pan Gasket Mopar P/N 53005650 $35
Rear Main Seal Mopar P/N 04778228 $15
Oil Pump Mopar P/N 02806270 (recommended) $60
Black RTV/Silicone (Right stuff or Mopar) $6
Loctite 514 $3
Oil and Filter Castrol Syntec, Fram Filter $35
Exhaust Doughnut for stock manifolds or Collector Gaskets for Headers $7
Red Line Assembly Lube (not required) $15

Needless to say after 150K on the clock the rear main oil drip was unbearable anymore. Doing this on your back must suck to say the least, so once all the parts are gathered get it organized and get ready.

First things first, I wiped down all the old oil that I could as to not have it drip in my eyes while looking while working.

Disconnect battery, and Remove Dip Stick, Then remove the Exhaust Crossover pipe and set aside. Disconnect Starter wires. Unbolt and remove starter (2bolts~16mm socket), set aside. Remove nut holding Tranny cooler lines to oil pan (11mm socket). Remove the bolts holding the Flex plate Dust Shield (4bolts~11mm socket), inspect shield for Dents or Warping, if it is found that the Shield is indeed bent, simply pound with hammer until straight again. Drain Oil from Pan entirely (plug 16mm socket). Remove all bolts holding the Oil Pan in place (12mm socket) and slowly lower the pan, be cautious not to bash the oil pump pick-up screen.


Remove Oil Pump Bolts (2 bolts~16mm socket) Careful this is messy !
Remove Rear Main Cap (2 bolts~19mm socket) & Loosen the Second to last main cap.

Once the items are removed, clean thoroughly.

VERY gently push the ORANGE Rear Main Seal around the Crank Shaft with a Flat head screw driver, DO NOT SRATCH THE CRANK JOURNAL. Pay Attention as to which direction the seal is facing as to reinstall correctly. Also remove the Orange seal from the Main Cap.

Clean/Prep the Block surface with Razor Blade and Brake Cleaner to remove old gasket material and oil contaminates, also clean the Main Cap where the Seal seats in it. DO NOT REMOVE MAIN CAP BEARING.
Thoroughly LUBE the seal and slide into Main Cap. Also wipe the Bearing with CLEAN CLOTH and apply assembly lube to TOP ONLY as seen in picture below.

Lube the other half of the Rear Main Seal, Reinstall the seal into the block so the lip on the seal matches the lower seal and GENTLY push it with a flat head screw driver until it’s all the way around like picture above.

Reinstall Main Cap with just a DAB of Loctite on the Cap to Block surface and Torque Bolts to 85ft lbs as required. Before installing new Oil Pump, remove pick up tube from the old Pump, and reinstall it into the new pump, mine was 4 ˝ Turns and then just level it to the oil pan. Pour oil into new pump from the top side, while spinning the pump shaft. See picture below…

Silicone all four corners of the front and rear seals, (the round parts of the oil pan). Drop New Oil Pan Gasket onto the Oil Pan, and lightly silicone the top side of the gasket in the same areas. Reinstall the Oil Pan with all the bolts and torque to 18ft lbs each. Reinstall the Dust shield and Starter (wires too). The tranny cooler line mount and Oil Filter and Oil Pan Drain Plug. Reinstall all exhaust that was removed.

All clean… Time to double check everything that was removed. Refill with new Oil and check Dip stick.

I also suggest that you run the vehicle for a while to check for any leaks, Oil/Exhaust. Now you know what I say it must suck to do this on your back. LOL


07-08-2004, 09:39 AM
On my back... in the rain/snow.... cold as balls... getting dark.. Yeah it was a wonderfull experience. Great write up though!

05-14-2005, 09:59 AM
So do you HAVE to remove the oil pump? It kinda looks like it but I don't know, never done it.

Swamp boy
05-14-2005, 11:29 PM
You dont have to... But its the perfect time to replace it... Its only about $50 for a Melling high volume pump and why not change it now before your pump goes out and you have to do it later... :mrgreen:

05-15-2005, 01:36 PM
I'm using this writeup today. Installing new oil pump and rear main while the motor is out.


05-15-2005, 05:48 PM
I would have thought to stay away from a high volume pump only because of the nasty angles the motor ends up at along with the rest of the truck. Would you not be filling a valve cover up faster then it could drain while off camber?
I may be wrong, but it seems like a good way to end up with a empty oil pan at times.

Swamp boy
05-15-2005, 06:51 PM
Never had a problem with it... But I did install a baffle in the pan as well..

Not that that would really matter in Off camber... But So far no problem...

Been over 2 years..

05-15-2005, 07:52 PM
I bought a Mopar pump from Kolak.

05-15-2005, 11:06 PM
Thanks guys. I will only do the mopar unless it is just way outragous.

05-15-2005, 11:26 PM
Mine was 67 from Kolak I think.

02-11-2006, 06:24 AM
If anyone needs mopar parts I can get them at 10% over cost plus shipping to you.

03-05-2006, 12:24 AM
I would avoid the High Volume pumps FWIW... at high angle they "could" drain the pan to fast on ya. Just a thought.

03-05-2006, 01:44 AM
i'm running a high volume pump, didn't think about that :(

07-23-2008, 02:35 AM
Do I have to go with a mopar oil pump or would something from partsource/NAPPA be good enough. I don't want to cheap out I am just not sure they will be able to get it in in time for me. I guess I could finish most of it up tomorrow and let her sit. Let me know what you guys think.
Thanks for the info guys.

07-23-2008, 11:22 AM
I went with a pump from NAPA back when I did this in October, been doing fine ever since.

07-23-2008, 12:00 PM
how much did the napa pump run you? If I can't get one from mopar in time or for a decent price I will go with one of the part store pumps:smt024
Also is there anything I should be paying attention to when I put the pump back in? I know I have to pre charge it with oil but is there anything else interms of mounting I should worry about?
Thank you very much for the reply, I know this is kind of newb ish but I just want to get it right the first time:)

07-23-2008, 12:07 PM
how much did the napa pump run you? If I can't get one from mopar in time or for a decent price I will go with one of the part store pumps:smt024
Also is there anything I should be paying attention to when I put the pump back in? I know I have to pre charge it with oil but is there anything else interms of mounting I should worry about?
Thank you very much for the reply, I know this is kind of newb ish but I just want to get it right the first time:)

When I put the oil pump in my stroker I packed it full of vaseline. Oil will run out but vaseline won't. Also, I haven't had any problems with my high volume pump and I have several thousand miles on my stroker now.

11-02-2008, 11:36 PM
Make sure the new pump is correctly seated before you torque it down. If it's not seated you can get it tweaked when you torque the pump down.

If your ZJ is at stock height you'll have to disconnect most of the front axle suspension, basically everything except the control arms and driveshaft. You can probably leave the steering hooked up too. Otherwise you can't get the pan past the front axle pumpkin.

11-03-2008, 11:34 AM
fyi, i started this last night on my 95. it has the 6cyl in it not the v8.

for 6cyls you dont need to take out the starter and/or exhaust. im running 3" of lift, so i just jacked up the front on the truck a little with my hilift and was able to get to everything and got the oil pan out no problems. all i got done last night was removal of everything, took about an hour. i need to hit the parts store on the way home to get the new seal and pump.

also, when i got the main seal cap off the bearing didnt come with it, and as i was looking at it it fell off and hit the ground. no visible marks or damage. so i guess i can just clean it off, oil it up and stick it back in right?

the reason i had to do this was the jeep was leaking oil so bad when sitting idling, i found out what an added problem to that was that my oil pan gasket was torn from the last time i put it in, it was torn right at the curve where the rear main seal is at. so thats another reason why it was dripping so much... :(

11-06-2008, 08:31 AM
well, a little update for anyone interested.

after finally getting some time to work on the jeep, it was about 8:30 and totally dark last night. but i still got alot done. the top part of the seal was a little tricky to get out, but when i finally did i oiled up the new one and tried to shove it up in the top, and that was even harder. you cant exactly do it by hand. so i had to use a pair of pliers and be careful as to not ruin the seal. then just muscled it in there. swapped out the oil pump, the pickup doesnt screw in, its just pressed in. it came out of the old one with a few twists back and forth, to get it into the new one though i had to tap it with a hammer.

but i finally got both pieces of the seal in, got the rear cap back on and torqued down. got the new pump in and bolted on.
only thing left to do is clean the oil pan up, and the mating surface, then bolt it back up.

im glad this didnt take me near 15 hours to do. i wasnt looking forward to it at all, which was why i kept putting it off. i have maybe 4 hours into it so far (most of it in the dark)

11-07-2008, 12:36 AM
I know on the 4.0 It helps to have someone turn the motor over by hand with a socket on the crank shaft bolt while you press out the old seal and press in the new one

Most of the time you can just push them out but if you get one thats been in there for 200,000 plus they are a real bitch. Done 5 of these so far and everytime i say never again lol

02-01-2010, 09:15 AM
Did this over the weekend, and had an issue where it felt like the oil pan seal wasn't seating correctly on the back of the motor. Torqued it down and fired it up, and now it is leaking worse. In the FSM they recommend making dowels out of bolts and putting the gasket on the block 1st. Tried that, but the gasket kept falling down. So I just dropped the gasket on the pan and bolted it up. I did use a new pan, as mine had a major dent in it from a rock. Any suggestions?

02-01-2010, 10:04 AM
Bad gasket? Is it at the pan seal or where the rear main seal is?

02-01-2010, 10:19 AM
Bad gasket? Is it at the pan seal or where the rear main seal is?

Not sure, as the oil is coming out between the flexplate and transmission right next to the stud for the starter. The gasket seemed like the curved area that rests in the groove of the main bearing cap was to long. I will probably try a new gasket 1st. The gasket was a Mopar gasket.

02-06-2012, 06:16 AM
i know that this post is old... but can somebody help me with the pics!? plx!

02-06-2012, 10:44 PM
i know that this post is old... but can somebody help me with the pics!? plx!

Just click on AW's picture link, then reload this page. Should pop up with the pictures you need.