Why do worn bearing affect oil pressure?

[Smcatub]

So I was reading a thread here about a car showing low oil pressure. The idea some posters had was that maybe the bearings were worn. I've heard this before as well - that worn bearings will cause low oil pressure. Why is this? I don't get it but would like to understand. As far as I know, it's the pump that's picking up and pressurizing the oil, isn't it? All the bearings seem to do is splash around in the sump. So why do worn bearings show up as low oil pressure?

 

[Pop_Rivit]

Wikipedia's Answer

 

[Kuato]

Imagine your garden hose with a kink in it. Pressure is higher. Remove the kink, pressure is lower. Same theory in the bearings; when new there is a small clearance. When worn, the larger clearance has less resistance to flow.

 

[Smcatub]

Thanks for the quick answers! I never realized there were oil passages in cranks - I thought bearings just got lubricated from oil flying around after getting splashed out of the sump. Now it makes sense!

 

[NHGUY]

In the old days it was splash lubrication.Later on it became full pressure lubrication.Some used external copper lines to bring oil to the heads.

 

[MolaKule]

Here are some other illustrations: http://what-when-how.com/crankshaft/crankshaft-lubrication/ http://www.tpub.com/engine3/en3-54.htm

 

[bubbatime]

Originally Posted By: Smcatub

All the bearings seem to do is splash around in the sump.

LAUGHING MY FREAKING BUTT OFF HERE!!! Do you have any idea what engine bearings look like? They sure don't "splash around in the sump" like a bunch of ball bearings rolling around in the oil, as you seem to indicate. This is what a common engine bearing looks like. When the metal wears away, the clearances become larger. When clearances become larger, the oil easily squirts out the sides , thus oil pressure drops. Common engine bearings

 

[MolaKule]

More explanations and background: http://www.machinerylubrication.com/Read/779/journal-bearing-lubrication http://www.bobistheoilguy.com/forums/ubb...tor#Post3312122 http://www.epi-eng.com/piston_engine_technology/crankshaft_design_issues.htm

 

[Smcatub]

Originally Posted By: bubbatime

Originally Posted By: Smcatub

All the bearings seem to do is splash around in the sump.

They sure don't "splash around in the sump" like a bunch of ball bearings rolling around in the oil, as you seem to indicate.

This is the 'splashing' I was talking about:

 

[Srt20]

Proper oil level should be below the crankshaft anyway. If it's not it creates pressure, foaming, and hp loss. Windage plates are common in oil pans.

 

[nitehawk55]

Pay no attention to Bubba , he doesn't realise that some do not know how an engine operates .

 

[wsar10]

Originally Posted By: nitehawk55

Pay no attention to Bubba , he doesn't realise that some do not know how an engine operates .

X2..... Now that you have a better understanding of oil passages (in a pressurized system) it should make sense why sludge is a MAJOR issue in engines. FWIW; allot of "small engines" still use splash lubrication, therefore if your ever shopping for a garden tractor or some other peace of equipment spend the extra coin and buy a quality machine with an oil filter (indication of a pressurized lubrication system).

 

[Chris142]

http://en.m.wikipedia.org/wiki/Chevrolet_straight-6_engine maybe the op is more familiar with the 216 chevy?