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H2Onut
03-13-2002, 08:36 AM
Got a ?, BIG DISCUSSION, 2 guys here have just had there rear seals changes on ther 4.0 litre. THere oil pressure is now around 30-35 at idle and 45-50 crusing, They feel ther numberes are too low, Some guy is feeding a line of crap saying that 30lbs at idle is going to smoke there motor, I say what the frick, 30lbs at idle is PLENTY. They both claim oil pressure reading were higher prior to rear seal change. The one guy was told DONT DRIVE IT, your going to blow it up. They also claim oil press was never below 50, prior to rear seal change.
woodco
03-13-2002, 08:48 AM
Nut.... They're jus blowin smoke... 30 lbs at idle is more than
adequate.
H2Onut
03-13-2002, 08:51 AM
Tell me about it... They dont know a piston from a rod, yet they both tell me I am crazy...go figure.
woodco
03-13-2002, 01:45 PM
Just let them think what they want ;) Makes for a good laugh :D http://www.truck-insurance-mart.com/smokin3.gif
B.Leonard
03-13-2002, 02:57 PM
Rule of thumb is 10 psi for every 1,000rpm.

-BL
Rickracer
03-13-2002, 10:10 PM
10 PSI for every thousand. And that's under racing conditions, normal use with less won't hurt. :cool:
NPW
03-13-2002, 10:40 PM
Have them check with Jeep dealer,seems like was TSB to change releif spring to lower pressure..to keep from blowing rear seals!!
B.Leonard
03-14-2002, 08:30 AM
I've seen healthy SBCs idle with 10psi with stock pumps. No problems.

It is also a function of where you're putting your sensor. I think there is 5psi diff from the rear to the front of the block. Every 90* can knock psi down as much as 5psi. So where does that leave the front rod bearing! :eek:

Sometimes High pressure pumps just aerate the oil. All those air bubbles reduce the oil pressure.

-BL
Rickracer
03-14-2002, 09:15 AM
...and the only thing I came up with pertaining to rear main seals was one for installing a rubber plug in the a cast hole block to keep dust and dirt out of the seal area. What years and models are they?
H2Onut
03-14-2002, 09:22 AM
95 Wrangler, 4.0 motor.
Rickracer
03-14-2002, 09:49 AM
...pertaining to oil pressure or rear main seal.
Streamer
03-14-2002, 10:01 AM
The 4.0lt engine does not have a p.c.v. valve, it has what they call a p.c.v grommet, that can plug-up, causing high crankcase presure's and leaks and check the breather hose's from the air box to rocker cover they get soft and collapse, most of the high mile 4.0lt that I have seen, all have bad blow-by, but still run ok.
H2Onut
03-14-2002, 12:23 PM
recap, 2 guys both jeeps, both 4.0 both 95, within 3 months of each other they had rear seals replaced because of excessive leakage. Both immediately noticed a drop in oil pressure. They are freake dout thinkin motors are goin to blow with 30 psi at idel, they said it used to be 45.
People are telling them "Dont drive it, you'll blow it up.

I keep saying thats PLEANT, dont worry, But they want to see hard evidence. well what the frick, DOnt drive it then, go pay another 600 bucks and have the oil pumped changed then....

Thanks for all your input guys, Remeber you can lead an idiot to water, and then it's best to drown them, oops I mean can't make him drink:D
Rickracer
03-14-2002, 12:54 PM
Straight from AllData. :D
PARKER RABE
03-14-2002, 01:15 PM
OH GREAT I JUST BOUGHT A GRAND CHEROKEE , I WONDER IF IM GONNA HAVE TROUBLE ....
woodco
03-14-2002, 06:01 PM
Nice info Rick...... Maybe with the sandy coditions in Fl is why
the seals are going prematurely....

I've seen motors gain oil pressure with oil changes mainly
due to filters being clogged or not changed on a regular
basis......