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oil pressure is low


Boinker Man
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Last week my car started to read low oil pressure. It would sit between the middle line and low line. Car has oil in it I run 20 50w oil. Some say it can be the oil sending unit? And other said engine is losing compression what can it be?

 

Has anyone used a Duralast oil sending unit before?

 

Or where i can find one for the car?

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Verify actual pressure with a mechanical gauge. There is a threaded plug just to the right of the oil filter where you thread it in. I believe it's bpt. I think Mitsu still offers the oem sending unit also. I bought one maybe less than a year ago
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The hole in the block is 1/8" BSPT. British Standard Pipe Taper. Your gauge will be NPT. National Pipe Thread. NPT is the standard pipe thread in the US. So you need 1/8" male BSPT to female NPT 1/8" or 1/4". Whichever your gauge fitting size is.

 

 

Unless verified with a mechanical gauge, all the stock gauge tells you is you have some pressure. Once you have a proper gauge on the block then you can see what's really going on.

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That should work.

 

If you are just screwing a gauge into the block you may want to also use a 45 degree fitting so you can see the gauge easier. That's what I had to do. But if this is for a sending unit for an interior gauge then you don't need the extra fitting.

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If you get a sending unit from Autozone keep in mind they are listed backwards. Of the two, the one they say is for your car, isn't. It's the other one. At least that's the way it was for an '87.
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A sudden change in any dash gauge reading is bad news: SOMETHING changed. Either the gauge itself or it's sending unit could be bad... or whatever it measures could be bad. The stock oil pressure sending unit is not very well calibrated... you can install two brand new dealer sending units and get vastly different dash readings. So just replacing the sending unit most likely won't make your oil pressure gauge read like it used to... you'll still have the question "is it just the difference in two sending units or is my oil pressure actually bad?" A true direct-reading oil gauge (aftermarket) is the best answer. Of course you don't know what your pre-problem oil pressures were but a safe bet is something like 70 to 90psi at 3000 RPM when running 20W-50 oil... that's the ballpark others with stock 2.6 engines have seen. 11.4psi is the minimum spec at idle but most StarQuests far exceed that.

 

Low oil pressures (actual oil pressure) is typically caused by:

1: bearing clearance on one or more bearings suddenly getting too large. The upper balance shaft bearing is the most common cause for this as it's a) up pretty high so it gets delayed initial lubrication on engine start-up and B) the balance shafts spin at twice the crankshaft RPMs so those bearings continually see high RPM wear. Contaminants in the oil (gas or water/anti-freeze) can quickly clobber engine bearings.

 

2: issues with the oil pump pick-up tube or the o-ring that seals the tube to the oil pump body. Basically the pump can't work at full strength and/or air gets into the pick-up from holes or a leaking o-ring. If metal shards get picked up from the oil pan they'll grind away at the oil pump gears & housing leading to excessive clearances and thus loss of pressure.

 

3: There is a small half-moon shaped key tying the oil pump shaft to the little timing chain gear... it's easy for that key to slide out of position when re-assembling the engine if one isn't paying attention. So if your engine was recently rebuilt or had a timing chain replacement this might be the issue.

 

4: there is an oil pressure over-pressure relief valve near the top of the oil pump; if this jams it could be stuck in the "bleed off pressure" position leading to lower pressures.

 

5: one (or more) of the piston cooling oil squirt jets fell out or busted. It'll be bouncing around inside the oil pan.

 

6: and the obvious issues: low oil quantity so the pick-up gets a bit of air, a blocked or crappy/cheapo oil filter, etc.

 

mike c.

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