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  #1  
Old 06-20-2013, 09:14 AM
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Oil Pressure: tired oil pump?

I've got a 1990 with 360 and I think my oil pump may be on its way out...
I'm running rotella 15-40 on the recommendation of my mechanic and folks on another fsj list...which is great until I drive in temps over 100-110 F, then the oil seems to thin and sit in the pan and the pressure drops to almost nil and the dipstick reads low.

When I return to lower temps, oil pressure returns to normal. There are no leaks that I can find...

Time to replace the pump?
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  #2  
Old 06-20-2013, 10:27 AM
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tgreese tgreese is offline
 
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No or low hot idle oil pr4essure is a common problem with these engines.

The dipstick should not read low at any temperature.

Make sure your gauge is working. Test the oil pressure with a mechanical gauge.

These engines seem to suffer from very low hot idle oil pressure when they are worn out. Usually the loss of OP comes from a worn timing cover (the aluminum housing for the oil pump), or failing cam bearings. Either way, running an engine with no detectable oil pressure is very risky, and usually will result in rod bearing failure.

There are oodles of posts about this in this forum and on the net. Read read read. http://www.google.com/#sclient=psy-a...e+oil+pressure
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  #3  
Old 06-20-2013, 11:08 AM
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It's a combination of engine bearing wear and worn pump. The regulator spring collapses with heat too. One of the AMC-list guys sells new springs (not sure if BJs or Bulltear has the spring, but the midplate kit helps a lot)
The brand of oil filter you run can affect the pressure as well.
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Old 06-20-2013, 07:01 PM
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To combat low pressure I used a Wix filter, rotella 15/40 and go a quart over. The pumps leaking, the engine has mystery miles. BJs has the rebuild kit and midplate for $25 each. I hope to do mine soon. It gets low daily mileage currently. Carnuck do you have a link for the spring? Is it stock or a higher pressure?
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  #5  
Old 06-20-2013, 07:43 PM
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Quote:
Originally Posted by Carnuck
It's a combination of engine bearing wear and worn pump. The regulator spring collapses with heat too. One of the AMC-list guys sells new springs (not sure if BJs or Bulltear has the spring, but the midplate kit helps a lot)
The brand of oil filter you run can affect the pressure as well.

X2 regarding bearing & pump wear.

But "regulator spring"? According to the TSM that's a hi-pressure bypass spring, and its purpose is to prevent pump damage or timing chain cover gasket blowout (where oil it enters the blockfrom the pump) when starting up in very cold temps. Factory specs are 70 psi. If one has worn pump or bearing clearances causing low oil pressure, that spring will never lift.
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  #6  
Old 06-20-2013, 07:49 PM
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mattmopar440 mattmopar440 is offline
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Well I recommenced the BJ'S Oilpump kit there great if that doesnt fix it your bearing are gone so it time for a rebuild

http://www.bjsoffroad.com/prod-605.htm Midplate

http://www.bjsoffroad.com/prod-417.htm

I would give this a shot its your best bet
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Old 06-20-2013, 08:22 PM
Ristow Ristow is offline
 
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it's the bypass spring. stock is around 50lbs i believe. they lose their tension over time.

the bypass spring determines oil pressure. no spring,no oil pressure. it is not just a hi pressure protection device. 20lb spring=20 lbs oil pressure. 50lb spring = 50lbs pressure.

performance american style sells a green 70+ lb spring. the rebuild kits use a 50lb spring.


i'll venture a guess and say your cam bearings are delaminating and ending up in the oil pan.
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Old 06-20-2013, 08:31 PM
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Quote:
Originally Posted by Ristow
it's the bypass spring. stock is around 50lbs i believe. they lose their tension over time.

the bypass spring determines oil pressure. no spring,no oil pressure. it is not just a hi pressure protection device. 20lb spring=20 lbs oil pressure. 50lb spring = 50lbs pressure.

performance american style sells a green 70+ lb spring. the rebuild kits use a 50lb spring.


i'll venture a guess and say your cam bearings are delaminating and ending up in the oil pan.

Alright...gotta dig out my TSM on that in case my memory is delaminating...
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  #9  
Old 06-20-2013, 09:12 PM
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Quote:
Originally Posted by Ristow
it's the bypass spring. stock is around 50lbs i believe. they lose their tension over time.

the bypass spring determines oil pressure. no spring,no oil pressure. it is not just a hi pressure protection device. 20lb spring=20 lbs oil pressure. 50lb spring = 50lbs pressure.

performance american style sells a green 70+ lb spring. the rebuild kits use a 50lb spring.....

From page B-154 of the '84-87" Workshop Manual M.R.253"

"A pressure relief valve regulates the maximum oil pressure".

"The spring tension is calibrated for 75 PSI maximum pressure".

"In the relief position the valve permits oil to bypass through a passage in the pump cover to the inlet side of the pump".

...which supports my conclusion that a low pressure problem has nothing to do with the pressure relief spring. Unless of course the thing just flat out breaks in such a manner to allow constant bypass under any pressure.
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88 GW 360-.030 over/2150/727/229/Posi, e-pump, AC (broke), tow package, Monroe Air Shocks, TFI, CTO-Free, AIR-free, oil & tranny coolers, dried knuckle blood all over, GM 350 TBI in a box, waiting...
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Last edited by Rich88 : 06-20-2013 at 09:14 PM.
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  #10  
Old 06-21-2013, 01:00 AM
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Except that the factory spring was NOT rated after being heated and cooled through multiple cycles. Don't believe me? Take yours out and test it. Hundreds of others have
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  #11  
Old 06-21-2013, 04:38 AM
Ristow Ristow is offline
 
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oh i agree the spring isn't causing the 0 oil pressure. the springs do lose tension and significantly lower the max pressure.

the bearings are likely the issue,if it is actually that low.
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I LOVE how Ristow has stolen my comment about him ... "Quoted" it ... and made himself famous for being an ***hole to people. Hahahahahahahahahha!


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  #12  
Old 06-21-2013, 11:11 AM
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Carnuck Carnuck is offline
 
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Yes. Let's not forget Jeep gauges are for amusement only!
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  #13  
Old 06-21-2013, 11:43 AM
joe joe is offline
 
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Quote:
Originally Posted by Ristow
oh i agree the spring isn't causing the 0 oil pressure. the springs do lose tension and significantly lower the max pressure.

the bearings are likely the issue,if it is actually that low.
Agreed forget a spring issue. These aren't high pressure motors when new. It's easier to deal with a pump rebuild rather than likely other just but don't be shocked if it doesn't significantly improve pressure. You don't mention miles on the motor but if it's a high miler, odds are your main and /or cam bearings are worn.
As Tim mentioned quantity via the dipstick doesn't change with temp. If yours is reading lower when hot, you're not allowing enough time for all the oil to drain back down into the pan before checking.
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Old 06-21-2013, 02:36 PM
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Got a diagnosis...

It's the rear main seal. Only leaks when I'm driving at temps higher than 100-105, and since where I live rarely gets above 80, it never leaves a puddle anywhere. I guess I hadn't made it clear that I hadn't had it up on a hoist to inspect the undercarriage, which I did this am.

So... I baby it until I can take it in next week... the quote was $300-500 from the drive train guy (Pat's Gearbox in San Jacinto, CA), and $700 from the local garage.

Not great timing, financially, but could be so much worse! I'm in this for the long haul and getting to the point where I'm fully committed to seeing it through a complete rebuild.

Thanks for all of the input--I learned something!
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1990 Jeep Grand Wagoneer (AKA The Tardis)
A few pics here: http://picasaweb.google.com/10040474...0764102/Waggy#
Building a new one, one part at a time
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Old 06-21-2013, 03:13 PM
joe joe is offline
 
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Oh, I thought your thread was about a low oil pressure issue? Absolutely not related to a RMS leak. Remind your local shops you got quotes from it's an AMC motor not a Chev. It's SOP for a shop to quote a price based on one piece RMS's where you gotta pull the trans. Not so with these. These use a 2 pc RMS. Hardest nastiest part is pulling/installing the oil pan. Been awhile but you should be able to get a new RMS kit for $15-$25 plus pan gaskets. Buy two, if attention to details or cleanliness is a problem for you, you'll be glad you have a do-over in house.
On the main FSJ page in the Tech Library there is a walk through on the procedure. Before you dive in or pull out the Visa card, make sure you're not leaking oil out of the valve covers and it's running down the back of the block.
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Old 06-21-2013, 06:28 PM
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Quote:
Originally Posted by jcountryman
It's the rear main seal. ...

Oil temps would be the highest, making oil viscosity the lowest, making it easier to leak.

However, make sure your PCV is functioning and the oil filler cap screen is not plugged with crud. If PCV system and vent is not up to snuff then crankcase blow-by pressure can influence oil being blown past things like oil pan & valve cover gaskets...and the RMS.

I learned this by accident. After taking care of the above during routine maintenance (Yes, some of us actually do that), I noticed my RMS leakage was reduced significantly.
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  #17  
Old 06-26-2013, 05:24 PM
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Not the RMS...

it only looked like it was leaking. When they got it up on the rack and got all of the oil cleaned off, it turns out it was the timing cover gasket. They'll check out the chain and gears while they're in there, and check the water pump too since I had a small leak.
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1990 Jeep Grand Wagoneer (AKA The Tardis)
A few pics here: http://picasaweb.google.com/10040474...0764102/Waggy#
Building a new one, one part at a time
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Old 06-26-2013, 05:36 PM
Ristow Ristow is offline
 
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a wise man here once said he had yet to see a rear main leak actually turn out to be one.



oh yeah......it was me.

http://www.ifsja.org/forums/vb/showp...61&postcount=8
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Ristows right.................again,




Quote:
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... like the little 'you know what's' that you are.




Quote:
Originally Posted by Fasts79Chief
I LOVE how Ristow has stolen my comment about him ... "Quoted" it ... and made himself famous for being an ***hole to people. Hahahahahahahahahha!


→ Where the kids hang out...

fsjbuilder.org come for the mindless chat,stay for the hand drawn emoticons.

It's like you're unraveling a big cable-knit sweater that someone keeps knitting...and knitting...and knitting...and knitting...
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Old 06-26-2013, 06:43 PM
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