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Old 04-04-2008, 04:18 PM
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no oil pressure when coming to a stop

well i have a 350sbc in my el camino and i noticed the other day driven home from work that when i come to a stop my oil pressure drops to zero. i dont hear any noises that would be caused by loss of oil. it sits at zero for a about 10sec or when i give it gas. i was running penzoil 10w30 and i never noticed this problem. this past oil change (maybe 800miles ago) i put in valvoline (also 10w30). i never had this happen with penzoil but i didnt like penzoil because it got dirty really fast. the valvoline burns very fast but is staying a bit cleaner then the penzoil. i do not burn oil due to valve stems. i dont blow out smoke i dont smell oil being burnt the valvoline just burns fast. i have a very small oil leak but it takes about a week to form a drip on the pan so its very very slow and i drive it a lot now that im working steady. i would like to try synthetic oil a bit thicker maybe 10w40. i know the synthetic cleans the engine and makes what leaks you have worse but i can fix a leak easy if it will run better with the synthetic. so my question is do you think my loss of oil pressure coming to a stop is just crap oil to thin or what??? ive tried hard stops and easy stops it drops to zero with hard stops and maybe 2psi with easy stops. cold idle pressure is about 40psi fully warm idle is about 15psi

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Old 04-04-2008, 04:28 PM
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How many miles are on the engine?

Have you checked the pressure with a good mechanical guage? That would be my first move.


Low, really low, like yours, is not good and is usually caused by real big clearances on the mains, rods and cam bearings.

You could have a bad pump, but that is rare.


Changine brands of oil won't change the pressure. Changing to a different weight, won't change it much either. Something is wrong, either the guage or bearings.


Mark
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Old 04-04-2008, 04:37 PM
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its an ss 350 block out of a 70 camaro. i couldnt tell you if its been rebuilt but im sure it has at some point. it runs very very well. i did do a cam job a few months ago i removed the pan and it all looked ok but you cant see the clearence of the bearings so idk. if the pick up screen fell off could that cause my problem???
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Old 04-04-2008, 04:40 PM
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i experienced the same thing once, when i removed the pan the pickup had fell off the pump.
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Old 04-04-2008, 04:41 PM
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If the pickup tube is loose on the pump, or cracked and sucking air, this will cause the problem. But i'd still ck it with another guage first. And probably not drive it until you find the problem either.
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Old 04-04-2008, 05:10 PM
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Quote:
Originally Posted by elcaminodragster
well i have a 350sbc in my el camino and i noticed the other day driven home from work that when i come to a stop my oil pressure drops to zero. i dont hear any noises that would be caused by loss of oil. it sits at zero for a about 10sec or when i give it gas. i was running penzoil 10w30 and i never noticed this problem. this past oil change (maybe 800miles ago) i put in valvoline (also 10w30). i never had this happen with penzoil but i didnt like penzoil because it got dirty really fast. the valvoline burns very fast but is staying a bit cleaner then the penzoil. i do not burn oil due to valve stems. i dont blow out smoke i dont smell oil being burnt the valvoline just burns fast. i have a very small oil leak but it takes about a week to form a drip on the pan so its very very slow and i drive it a lot now that im working steady. i would like to try synthetic oil a bit thicker maybe 10w40. i know the synthetic cleans the engine and makes what leaks you have worse but i can fix a leak easy if it will run better with the synthetic. so my question is do you think my loss of oil pressure coming to a stop is just crap oil to thin or what??? ive tried hard stops and easy stops it drops to zero with hard stops and maybe 2psi with easy stops. cold idle pressure is about 40psi fully warm idle is about 15psi
There can be a lot of reasons for this, none are really very good, but my experience shows that this is almost always a sign of worn out bearings resulting in excessive clearance. One would think this is something that creeps up on an engine as it ages and you'd see it coming with steadily lower pressures over time. What I've seen, is that it usually comes on suddenly and usually looks like damn little to no pressure at idle which promptly returns to normal or closely so when the revs come up. If that's what you see think rebuild time has arrived.

Oil that gets dirty looking right away is one or both of two things.

1) It's doing what it's there for, picking up contaminates rather than letting them form sludge.

2) Some base oils and many additives turn dark brown when exposed to heat, this has noting to do with the oil getting dirty. Some brands do this immediately, some don't.

The oil filter will take the crud out if present, the filter will have no effect on color change due to reactions of heat and chemistry. I run Chevron Delo in my SBC, my Hog and Yamaha, the boat, tractor, and lawn mower; I swear it turns black as I pour it in, so don't worry about oil color as long as you stay up on changes with a filter it'll be fine.

The rate at which oil cleans an engine has everything to do with the additive package, and little or nothing with the base being mineral or synthetic.

Bogie
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Old 04-04-2008, 05:11 PM
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im positive my gauge is correct. i just knocked on the pan and the pick up is chillin at the bottom of the pan oh well. i might as well buy a better oil pump. they arent much and its another new part to cross off my list .

i dont need a high volume or high pressure oil pump so what would be a good buy??? all i ever see is high pressure 25% more oil twice as much volume. gimme the run down of a good oil pump that wont rape my wallet.
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Old 04-04-2008, 05:17 PM
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All of the engines I have pulled for rebuild that ran on Pennzoil oil were sludged up real thick including the oil return holes in the heads. Pull a valve cover and look at the oil return holes to make sure they are open. If they are partially plugged it could not let the oil return to the pan fast enough. One clue if they are plugged is when you pull a valve cover oil will run out.
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Old 04-04-2008, 05:21 PM
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Quote:
Originally Posted by elcaminodragster
im positive my gauge is correct. i just knocked on the pan and the pick up is chillin at the bottom of the pan oh well. i might as well buy a better oil pump. they arent much and its another new part to cross off my list .

i dont need a high volume or high pressure oil pump so what would be a good buy??? all i ever see is high pressure 25% more oil twice as much volume. gimme the run down of a good oil pump that wont rape my wallet.
Just get a stock Melling pump and pick-up screen.
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Old 04-04-2008, 05:33 PM
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well im gonna double check tomorrow morning that what i heard was the pick up and not me bumping something or just me thinking that its the pick up. so ill double check that tomorrow morning. but i am still positive that the gauge is correct .

hey oldbogie, if it rebuild time how long (miles approx.) can i postpone the rebuild??? i ask because work has just started to pick up so i need some time to save up money to rebuild.
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Old 04-04-2008, 06:02 PM
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Quote:
Originally Posted by elcaminodragster
well im gonna double check tomorrow morning that what i heard was the pick up and not me bumping something or just me thinking that its the pick up. so ill double check that tomorrow morning. but i am still positive that the gauge is correct .

hey oldbogie, if it rebuild time how long (miles approx.) can i postpone the rebuild??? i ask because work has just started to pick up so i need some time to save up money to rebuild.
If the enigne won't hold idle oil pressure, you're there. The real risk is the rods, at low oil pressure if they start hammering it's over big time. You might be able to pick the idle pressure up with a heavier weight oil, but this is temporary if it works at all.

Bogie
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Old 04-04-2008, 06:58 PM
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My Ford F150 (1989, 5.0liter, 120,000 orig miles) just started doing the same thing! Not always, but sometimes at idle, the oil pressure gauge (factory stock) goes below 0, off the chart. Tapping the pedal, it comes right up. Does this sporadically. The top end is starting to clatter too. Sounds like it's time for a rebuild/new motor. Correct?
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Old 04-04-2008, 07:00 PM
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Originally Posted by AntnyL
My Ford F150 (1989, 5.0liter, 120,000 orig miles) just started doing the same thing! Not always, but sometimes at idle, the oil pressure gauge (factory stock) goes below 0, off the chart. Tapping the pedal, it comes right up. Does this sporadically. The top end is starting to clatter too. Sounds like it's time for a rebuild/new motor. Correct?
Yes it's time.
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Old 04-04-2008, 07:21 PM
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Maybe if you have real beady eyes, you can peek in through the drain plug hole and see if'n it's still on the pump. Or maybe a coat hanger and fish around the pan?
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Old 04-04-2008, 07:27 PM
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Originally Posted by carsavvycook
Yes it's time.
Yeah, I thought so. Thanks for the reply. Luckily, I really don't need it again til next winter, so I'll bring it to a shop now to get it done.
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