Re: [Amc-list] Low Oil Pressure when warm, 58 Rambler American

[Frank Swygert <farna@xxxxxxx>]

Mark, low oil pressure in most engines is usually due to wear in the main bearings. Sometimes it's an oil pump, but not often. You definitely need to run a compression check (pressure through the spark plug hole). If the engine has a lot of miles on it 95-100 psi will be good, but it really should be 110-120 psi. 
You didn't say what engine you have, but I assume it's a 196 flathead six, not the OHV six (which was optional in the 58 American). 

Check the oil pressure with a mechanical gauge. Unscrew the oil pressure sending unit from the block (on the exhaust side, near the back of the engine just above the oil pan) and screw in the gauge. You might want to get a "T" fitting, screw that in, then connect a gauge to one part of the T, the oil light sending unit to the other. The engine needs to produce a minimum of 12 psi once the engine is hot at idle. When you first crank it up pressure should shoot up to 40 psi or more, decreasing as the engine reaches normal operating temperature (the oil gets thinner as the engine gets hotter). You should be running 10W30 or 10W40 oil. If the engine has lots of miles on it you can run 20W50 to increase the oil pressure some. If the compression check shows 95 psi or more but oil pressure is low, add a can of STP to the oil and see if that helps. If it brings the pressure up to 12 psi with the engine hot, try changing the oil and using 20w50. It may still need a can of STP added to
  keep pressure when hot in hot weather, but don't run the STP in cold weather (when temps you will be driving the car in are below 40 degrees Fahrenheit). 

The oil pump is that thing sticking out the right side of the engine, just above the oil pan, about midway down the side (side of engine is from the driver's point of view, so right side is passenger side assuming steering wheel is on left side of car -- typical US driving position). As you can see, it's very close to the body! To remove it the engine has to be dropped down. That's not hard to do, but I've never run across one of these engines that had low oil pressure due to a bad pump. It's ALWAYS been bearings. The oil filter (if yours even has one!) is only partial flow, meaning only about 20-30% of the oil goes through it at any one time. The rest continues to circulate through the bearings. This usually isn't a problem, but oil must be changed every 3000-3500 miles, or at least once a year, no matter what. That's where the oil change places get the 3000 miles interval from -- old technology! New cars with computer controlled fuel injection and full flow oil filtering (A
 LL oil goes through the filter before recirculating) can easily go 5000 miles between changes.

Feel free to ask any questions you have here on the list! Sounds like you are new to working on cars much as well as new to Ramblers. You really need to invest in a TSM (Technical Service Manual -- the dealer repair manual) for your car. It's only $29 + shipping from http://www.faxonautoliterature.com/ (search for 1958 AMC) for a reprinted manual. That will save you hours of questions and puzzling over how something comes off, and will help some of us to help you when you refer to a page number. 

I do hope you enjoy the Rambler, they are fun collector cars, and are still very affordable! Some other make of the same year would cost a lot more. The Rambler has its "quirks", but many of us here are familiar with them and can help you overcome any problems. All the mechanical parts are available, though some can be hard to find. We can help there too! Anybody can pick up a catalog and "fix up" or restore a Ford or Chevy, it takes a real car nut to fix a Rambler!

---------------
Date: Tue, 26 Feb 2008 22:11:00 -0500 (EST)
From: "Mark Dominesey" <LostWater@xxxxxxxxxxxxx>

Hello All, New list member here as well as new Rambler owner.

My 58 Rambler American has low oil pressure after it warms up (at least
the low oil pressure light comes on once the car has warmed up).

I have not checked oil pressure with a gauge through the spark plug holes,
but that is the next task.

My question is, if my pressure is indeed low when warm, what is problem? 
Someone told me either bad pump or bad bearings.  I am hesitant to think
that it could be bad bearing as it runs really good.  Bad pump is
something I may agree with.

I will first check the pressure on the cylinders, if they check out ok,
then I will look at the sender, then the pump.

It could just be a bad sender, maybe? Or old/bad wiring to the gauge?

If it is the pump, where is the pump located on this engine?  Is it behind
the oil pan like other engines?  If so, how do I get it out to replace it?

I am hoping someone can help!  Thanks!

-- 
Frank Swygert
Publisher, "American Motors Cars" 
Magazine (AMC)
For all AMC enthusiasts
http://farna.home.att.net/AMC.html
(free download available!)


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