Re: my high oil pressure.
I don't mean to be a stickler, but remind me of things like how
fresh the bearings are, when the problem arose, etc. I can't
seem to find the original message on this subject. If, for instance,
you just put in 40-under bearings on a 20-under crank, we'd know
what the problem is... if the problem started recently on a well
used but still sound engine, that's another story entirely.
Last night I found the oil pressure relief valve. [. . .]
(i.e. will removing it drain the oil for me :-) ?
No. It's above the level of the sump, so while you'll certainly get
some oil on the side of the block, there's no way you can drain the
oil unless you pull it while the car is running. However, for reasons
I will address shortly, it's probably a good idea to drain the oil
anyway.
I am beginning to think there is a problem. With the oil cooler out, the
pressure is still too high until the engine is hot (I think the oil cooler
kept the oil cool and thus the pressure high.) I still haven't ruled out
a faulty pressure sensor, since it may have gotten banged up a little during
the installation of the oil cooler (detaching the old hose from the back of
the block was a b*tch!).
Which kind of sensor do you have? It might be easier for you to test
the sending unit and gauge to make sure they're not feeding you false
information. Hook up a mechanical gauge with the right kind of
fitting -- I've got one in my garage (where is meaddata.com, anyway? :-)
It's the best way to determine whether you need a new engine or a new
gauge or sending unit.
It's been my experience that MG engines are about fifty to a hundred
times more reliable than Lucas gauges. Chew on that thought while you
contemplate rebuilding your bottom end.
Assuming the pressure relief valve is bad, will I be able to get it out?
The pressure relief valve is nothing more than a sort of bullet-shaped
plug of steel with a spring behind it and a bolt holding the spring
and bullet in the block. Basically, when you remove the bolt, the
spring will try to fly out of the block and get lost under your parts
car.
How the PRV works: The spring holds the bullet against a restriction in
the oil passage. It only allows a certain amount of oil to flow through
the restriction, based on the amount of pressure that the spring applies
against the bullet. The typical failure mode is that the spring weakens
or breaks and there is insufficient pressure against the restriction.
This causes the gauge to read lower than normal. In the best of all
possible worlds, you're still getting oil flowing at the same volume
and you don't blow your crank into itty bitty pieces.
Someone mentioned it might be stuck. Let's say I get it out, cleaned up
and it no longer sticks so I have a nice 70 psi oil pressure. Something
still bothers me. It seems to me that a bypass valve isn't supposed to
open all the time. What I mean is, it doesn't seem that I should always
have 100 psi brought down to 70 only by the bypass valve. It seems that
something is wrong making it run at 100 psi in the first place.
Actually, this bypass valve *is* supposed to open all the time. That
is, the spring is designed to press the bullet against the restriction
all the time, whether there's oil in the engine or warm beer. If your
oil is 100 psi, it's either because the spring is too stiff or something
is holding it in too tight.
What's happening is that the bypass valve is *closed* all the time (or
at least when you've got 100 psi), and only opens to its correct state
when the oil warms up.
If there is crud in the oil passages that is causing the pressure to run
high is there anything I can do to get it cleaned out (short of ripping
the engine apart and having it hot-tanked)? Maybe a good snake oil?
Um, well, you could try running a 25% mixture of good old Marvel Mystery
Oil. If it doesn't clean the crud out, at least it will wear down your
bearings to the point where you'll have sufficiently low oil pressure. :-)
(Not really; about the worst it will do is speed up any leaks, as long as
you stick to a quart per sumpful.)
Doctor Fisher prescribes the following treatment for your MG:
1. Put a reliable gauge on the engine and see if it's a problem
with the engine or with the gauge. If it's with the gauge,
then troubleshoot the gauge. If it's the engine, continue.
2. Start by cleaning the bypass valve. Drain the engine of oil
and clean the bypass valve, its socket, and the passage that
you can reach through the hole with Brakleen and a Q-tip.
(That's why you want to drain the oil first, I don't think
Brakleen will do your oil much good.)
3. If the engine still runs with too high a pressure, run a quart of
Marvel Mystery Oil through the engine for a day or two. MMO is
mainly just a light oil with a lot of detergents in them; it will
help clean some of the gunk out of your passages if that's your
problem. (I often run a quart of MMO through the car during the
last couple of days before an oil change, for just this reason.)
BTW, I'm running Castrol 20W-50. I suppose I could switch to a lighter
oil but this seems like it would only treat the symptom.
20W-50 shouldn't be too high, unless it's really cold where you are.
p.s. In the meantime it is just too nice out, so I've been driving it
anyway watching for an oil well to sprout in front of me.
Keep the faith!
--
"Do you ever wish you had a joystick with a big red button on it so
you could just nuke the person when you send a reply?" -- Kim
Scott Fisher/sfisher@wsl.pa.dec.com/DEC Western Software Labs/Palo Alto, CA
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