Fordnatics List Archive

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Mail From: "Michael T. Stolarchuk" <(email redacted)>


I just want to find out if anyone else has had
any problems with oil pressure switches, and which
ones they use. I'm using one of the summit ones,
and it seems to be from the old volkswagen brake
system pressure switches...

But here's the story. I live near lots of country
roads, and last week, before I went on vacation,
I took the ERA cobra out since I wasn't going to
be around for a week, and cause of how nice of a
day it was...

On the way back, after passing someone, I noticed
the oil pressure drop from about 90 to 60, at 3500 rpm,
so I knew I had a problem. I didn't worry too
much since I was only about a mile away from home,
AND cause I've got one of the lube tubes which
open from the cockpit at the flick of a switch,
AND cause I know there are some three quarts of oil
in there...

Not knowing what the problem was then, and seeing
blue smoke on the right side of the car was alarming,
but I kept on saying, only xxx more feet to go...

The pressure never dropped below 60#.

And when I stoped the car in the garage, I say
the puddle underneath, and knew I didn't have too
much more time left till I would have bled the
car to death.

After I came back from vacation, I poured
four quarts in, then started the engine.
The car up on jacks, and looking underneath,
the DAMN oil pressure switch was squirting oil!

I ordered a new one from summit, and they said
they've never had any problem... it came,
and today I put the car up on jacks, and found the
oil pressure switch was loose... replaced it anyway.

Then tested the old switch with an air compressor
and yep. Air passed right through it. It had
failed...

Anyone else have a better source for an oil
pressure switch? I've got a feeling about this...

mts.

This read-only message was archived from a public mail list.
Mail From: (email redacted) (Scott Griffith, Sun Microsystems Lumpyware)

On Aug 3, Michael T. Stolarchuk wrote:

> Anyone else have a better source for an oil
> pressure switch? I've got a feeling about this...

I use the 20psi version from Pegasus. It looks a lot like the VW
hydraulic pressure switch, but it has a significantly different
diaphragm arrangement. I've never had a problem with mine, but a
sample size of one isn't particularly meaningful. And my tired old
motor never kicks out more than 80psi even with dead-cold oil (Mobil 1
15W50). If you're holding up 90+psi hot at 3500rpm, who even _knows_
what you're making with cold oil. That almost sounds like too much, to
me...

All of the diaphragm-style senders, whether they are switches or
resistive gage senders, have this exposure. None of them are immortal,
but they are close enough to it to be treated that way. I've had one
stock Ford oil pressure gage sender punch out its diaphragm and begin
leaking, but not at a high enough rate to present a hazard.

I'd say just proof-test the Summit sender to 125-130psi, or to
whatever your highest expected pressure with cold oil is going to be,
with about a 30psi safety margin added in. Some of the 20psi switches
were never designed to hold up to the 100+psi spikes that you'll see
with cold oil, a tight motor, and a high-pressure pump like the one
you must have!

-skod

- --
Scott Griffith, Sun Microsystems Lumpyware
expatriate SCCA New England Region Flagging/Communications worker
(and driver, of anything that turns both right and left,
and can pass tech...) Return Path : (email redacted)