So what actually causes low oil pressure?

5spd GT

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My oil pressure (I'm pretty sure the guage is fairly accurate on mine) because it is consistent with what is going on. Anyways, I was just curious to what causes low oil pressure? Bearing clearances?

Thanks

 

srothfuss

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#2

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There are a few factors:
1) Increased clearances in bearings due to wear (probably the biggest factor)
2) Worn out Oil Pump
3) Wrong Oil weight for summer months

 

Black1987Stang

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HAHA only if i could post up a pic of one of my bearings from my worn out 302 that had 10 psi of oil pressure. Lets just say it was ALL Copper, it Should be like a silvery color and the big gouge in it didnt help either. So basically its from bad bearings clearances, cracked oil galleys in the block, worn out oil pump, clogged oil pump pickup screen. Hope this helps a little.

 

darthcual

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A Bad Cam? Just a thought.

 

HISSIN50

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Pressure is resistance to flow. If you have a given flow of water in a 3/8" hose, you will have decent pressure. Now you put that same volume of flow through a 1" hose - the pressure will go way down.

WHen a motor is tight clearance-wise, there is a lot of resistance to flow. WHen clearances open up, it is more like the 1" hose - not as much resistance to flow, ergo pressure drops.

David, I am afraid to ask why this thread was started.

 

5spd GT

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JT, all is well (well the same that it was anyways). I was just curious...I just got to thinking about it...you know me

Blowby on the rings would cause low oil pressure right?

 

B

BNAZ

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#7

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Minimum clearances between crank and bearings creates oil high oil pressure pushing oil to top of engine. Worn bearings reduce pressure as clearances increase. Just like Hissin50 explained.
Ring blowby will produce other noticeable problems: oil useage, smoke, fouled plugs. I have 143 K on mine and use a quart of Lucas heavy duty oil stabilizer
and have pretty decent pressure. My car uses 1 to 1-1/2 quarts every 3K.

 

HISSIN50

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Yep - blowby does not directly affect pressure (we could get all technical - blowby goes through the PCV and is recirculated. Oil in the chambers causes detonation, which increases operating temps, which lowers viscosity, etc). Was that a big enough stretch? I think so.

David, I do know you and know that all is well. In 'chatting' with you the other night, I can see that your ride is running like an animal (those were some cool stories!).

 

Mustang5L5

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#9

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I would hook up a "real" oil pressure gauge before making any final decisions on what to do. The factory gauge has known to be highly inaccurate.

My gauge stays stuck at 50-55PSI, even when my autometer shows i have 25psi while idling at a light.

 

The Shape

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Where is your stock gauge reading at hot idle?

 

The Shape

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^

 

Mustang5L5

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My stock gauge reads 55psi for everything. Doesn't matter engine temp or RPM.

Meanwhile my autometer shows 25 for hot idle and 55-60 when i bump the throttle.

When the engine is cold the numbers are higher as you'd expect.

Meanwhile my factory gauge never moves off 55psi

 

B

bsedwebt70-5.0

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#13

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I HIGHLY suggest a Ford Motorsport oil cooler ($120.00)to any 5.0HO owner - I just put one on and now I smile everytime I look at the oil pressure guage not to mention my temperature guage.

 

HISSIN50

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#14

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bsedwebt70-5.0 said:

I HIGHLY suggest a Ford Motorsport oil cooler ($120.00)to any 5.0HO owner - I just put one on and now I smile everytime I look at the oil pressure guage not to mention my temperature guage.

Click to expand...

Amazing how hot EFI 302's get the oil, isnt it?

 

90mustangGT

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bsedwebt70-5.0 said:

I HIGHLY suggest a Ford Motorsport oil cooler ($120.00)to any 5.0HO owner - I just put one on and now I smile everytime I look at the oil pressure guage not to mention my temperature guage.

Click to expand...

I have one, made a big difference in the oil pressure and engine temps all the way around. Many parts of the engine get real hot and don't ever come close to the coolant, such as the crank, rods, and pistons. The pressure stayed about mid-gauge no matter what temprature. This was using 5W30 Moble 1 Synthetic.

 

N

newbee90gt

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#16

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Mustang5L5 said:

My stock gauge reads 55psi for everything. Doesn't matter engine temp or RPM.

Meanwhile my autometer shows 25 for hot idle and 55-60 when i bump the throttle.

When the engine is cold the numbers are higher as you'd expect.

Meanwhile my factory gauge never moves off 55psi

Click to expand...

and to think i was worried when my gauge said 25psi(aftermarket)

 

5spd GT

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#17

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My stock guage seems to be consistent, whether accurate or not. But I do need something a bit more accurate. Autometers would be nice

So how much is an oil cooler and how is the install? Just curious if anyone is bored enough to answer

 

N

newbee90gt

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#18

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clicky here

summit 119.00 with out fan.........

 

HISSIN50

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#19

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I did not see which cooelr was linked to, so I will generically add: I would want a stacked plate design cooler (vs tube'/fin, etc). The FRPP cooler is a nice piece.

I have not done a cooler because I refuse to run rubber line to a cooler like that, and dont have cash for braided hose. But it is a great idea!