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Oil Pressure

 
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Joe



Joined: 01 Jun 2006
Posts: 453
Location: Hephzibah,Ga


PostPosted: Fri Jun 27, 2008 2:55 pm    Post subject: Oil Pressure Reply with quote

Beetle Bug is doing strange things. When driving she keeps about 40lbs. and every time I stop or slow way down the needle bottoms out and slowly comes back up to about 20 and then goes up to 40lbs.

Oil temp. doesn't get above 170

What could it be.
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Clyde



Joined: 03 Jun 2006
Posts: 855
Location: Athens


PostPosted: Sat Jun 28, 2008 12:09 pm    Post subject: Reply with quote

It's normal for oil pressure to change along with engine speed. A general rule is to have about 15 psi at idle when warmed up, and add about 10 psi per thousand rpms as the engine speeds up.

The factory idiot light comes on at about 5-7psi, screaming that the idle is way too low, and/or the bearings are shot. I remember my idiot light blinking at idle, but it would go out when I depressed the clutch (massive end play).

A lot of things effect oil pressure- bearing clearances, end play, oil pump gear end clearance (remove the pump and sand the face of it 'til you have .001 or less clearance), pickup tube fit and length, and the weight of the oil are a few. When it drops to zero, I assume it's sucking air in? An engine without an additional sump can do that if you corner hard enough (sloshing all the oil to one side of the engine, leaving the pickup tube dry).

Maybe see if it does it when the car isn't moving?
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Joe



Joined: 01 Jun 2006
Posts: 453
Location: Hephzibah,Ga


PostPosted: Sat Jun 28, 2008 1:41 pm    Post subject: Reply with quote

Jim Skelton went through the motor just before it went in and got everthing back in tolerence.

Nothing is factory in the car, no idoit lignt just oil temp and pressure gauge.

This just started in the last couple of days. I started her up Thursday and just let it idle and the pressure would drop then come back up. Last night it drop every time I slowed down but today it is running normal.

Could it be the pressure relief valve sticking?
I'm also running a Fram oil filter and I had an old truck that would knock when it would first started up then quit. Come to find out it was the filter, resticted to much oil.
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Clyde



Joined: 03 Jun 2006
Posts: 855
Location: Athens


PostPosted: Sat Jun 28, 2008 8:39 pm    Post subject: Reply with quote

I didn't think of the pressure control valve. There could be a piece of grit in it. I just checked the Bentley manual, and it says if it sticks, there would be too much pressure? This is the one closest to the clutch.

The oil filters also have a bypass valve that could go bad as well. I don't know what it would do if it messed up though Rolling Eyes

It's 50/50
I'd change the filter first, and see what happens.
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Joe



Joined: 01 Jun 2006
Posts: 453
Location: Hephzibah,Ga


PostPosted: Sat Jun 28, 2008 9:19 pm    Post subject: Reply with quote

Thanks Clyde
I herd that Fram filters don't have the bypass, but I I'm going to change it tomorrow and put on a machanical (sp) oil pressure gauge and see what happens.
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Joe



Joined: 01 Jun 2006
Posts: 453
Location: Hephzibah,Ga


PostPosted: Mon Jun 30, 2008 5:33 pm    Post subject: Reply with quote

The oil pick up tube was coming aloose at the case. Took a hammer and drift pin and knocked it back on. So far so good. Cool

Thanks Clyde for the advice.
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