[E-Type] Oil pressure drop

I recently removed the oil filter assembly from the engine block. I
did no dis-assembly of the oil filter block itself. I re-installed
it using the same style (correct) gasket. It’s now re-assembled
exactly as it was before. But now my oil pressure drops off with
engine rpm. Before I did this it maintained close to 40 psi even
at 1000 rpm idle. Now the oil pressure drops to 10 -20 psi at idle.
Since I don’t understand how the pressure is regulated with
variation in rpm I don’t know why the pressure is now dependent on
rpm. Anyone know what I could have done to cause this problem?–
George-XK120,E-Type,&XJ6
Chittenango, NY, United States
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In reply to a message from George Parker sent Wed 11 Aug 2004:

George,
40 PSI at idle is not normal. 20-30 is more like it. My guess
is your sender is going wonky on you. First thing to do is get a
good mechanical gauge, hook it up, and see what the real oil
pressure is. Typically, 20-30 at idle, 40-50 at 3000 RPM. Oil
pressure is not regulated, it’s simply limited, to something like
60-80 PSI, which you’ll only see when the oil is cold. The rest of
the time, pressure is a function of blearing clearances, and flow
rate.–
Ray Livingston - '64 OTS Santa Cruz, CA
Santa Cruz, CA, United States
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In reply to a message from George Parker sent Wed 11 Aug 2004:

George,

Possibly a speck of dirt got into the bypass valve seat, or else
the gasket did not make a good seal on some internal webs.

Or worse, you used silicone RTV seal on the gasket, and too much,
it has formed little balls or worms, and one of these is caught up
in the relief valve – or worse, the oil passages. This area is a
really bad place to use RTV, and it’s always a real danger to use
more than the very minimum.

Finally, there is always the possibility that the pressure sensor
decided to stay on vacation once it was out.

Could you clear up what readings you are getting? You say at 1000
RPM it reads 10-20 PSI, and that the pressure drops with RPM –
gee, how low does it get?

10-20 PSI is about right for idle, actually, but that would
generally be below 1000 RPM, 500 RPM is the specification.

Do you have a mechanical gauge? It’s always a good idea to plumb
one in to check the gauge. The factory gauge fails more often than
the oil pressure does, generally. The Jaguar Enthusiasts Club in
the UK sells a modern Smiths replacement that looks identical to
the original gauge, but has non-Rube Goldberg innards.

My strategy for your problem would be to open the block up again
and carefully clean out and check the condition of the relief
valve – the one inside the spigot that runs to the sump through
the external rubber hose. Parts are still available for this
valve, and it’s very often the cause of problems like yours. If it
still causes concern, then I’d check the gauge.–
Jerry Mouton
Palo Alto, California, United States
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In reply to a message from mouton sent Wed 11 Aug 2004:

Hi Jerry,
Thanks for the input. I didn’t use silicone, so I don’t have that
problem. The pressure doesn’t drop below the 10-20 range. That’s at
a 1000 rpm idle. I think the problem’s in the relief valve, and I
plan to look into that. I know that the pressure at idle was higher
before I removed the filter block.

Regards, George–
The original message included these comments:

Possibly a speck of dirt got into the bypass valve seat, or else
Or worse, you used silicone RTV seal on the gasket, and too much,
Could you clear up what readings you are getting? You say at 1000
RPM it reads 10-20 PSI, and that the pressure drops with RPM –
gee, how low does it get?
and carefully clean out and check the condition of the relief
valve – the one inside the spigot that runs to the sump through
Jerry Mouton


George-XK120,E-Type,&XJ6
Chittenango, NY, United States
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Does Jerry have some new kind of filtration system he’s using on his car??

Les…'68 2+2 (Webers/MSD/Mallory)

and carefully clean out and check the condition of the relief
valve – the one inside the spigot that runs to the sump through
Jerry Mouton

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In reply to a message from Les Halls sent Thu 12 Aug 2004:

Les,

Unless you have modified the engine, yours has a pressure relief
hose running from the oil filter block to the bottom of the sump
too.

You know, the source of that annoying drip on the garage floor?
; -)

Jerry–
The original message included these comments:

Does Jerry have some new kind of filtration system he’s using on his car??


Jerry Mouton
Palo Alto, California, United States
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Right, got it, thanks Jerry.

Les…'68 2+2 (Webers/MSD/Mallory)

From: “mouton” jerry@moutons.org
Reply-To: e-type@jag-lovers.org
To: e-type@jag-lovers.org
Subject: RE: [E-Type] Oil pressure drop
Date: Thu, 12 Aug 2004 19:36:35 +0200

In reply to a message from Les Halls sent Thu 12 Aug 2004:

Les,

Unless you have modified the engine, yours has a pressure relief
hose running from the oil filter block to the bottom of the sump
too.

You know, the source of that annoying drip on the garage floor?
; -)

Jerry

The original message included these comments:

Does Jerry have some new kind of filtration system he’s using on his
car??


Jerry Mouton
Palo Alto, California, United States
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–

Search the archives & forums - http://search.jag-lovers.org/
Subscription changes - http://www.jag-lovers.com/cgi-bin/majordomo

Search the archives & forums - http://search.jag-lovers.org/
Subscription changes - http://www.jag-lovers.com/cgi-bin/majordomo