'97 5.7 Vortec Low Oil Pressure

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Jacob Hendrix

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In my '97 C1500 Silverado, I'm getting the check gauges light and low oil pressure. I had thought at first that it was the actual gauge cluster since those tend to jump around anyway, but after driving for a week or 2, I started noticing a slight clacking noise. To me, it sounds like something valve related.

Is it common for the oil pumps go bad on these trucks? If not, what else typically causes this?
 

SAATR

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SBC oil pumps are a gear type pump in an iron housing, and typically only "fail" or stop producing pressure with cavitation wear on the teeth of the gears or more commonly scarring of the housing or bottom plate. Pretty low on the list of possible causes, though. More likely is sludge restricting the pickup tube, wear in the cam bearings, or wear in the rod and main bearings. Before removing any parts, I would install an accurate mechanical gauge and verify that the pressure is indeed low ( factory spec is something like 5-8 psi minimum at hot idle) and then go from there. If you find good oil pressure, then you probably have an electrical issue, either the sending unit or the cluster. Everything else requires at least partial disassembly, and likely a rebuild. In that case, I would pull the intake and inspect for sludge. If you have a sludge issue, it may have already toasted the bearings. You can clean the engine out thoroughly (oil pan included) and install a fresh pump and see what happens, or get a short or long lock and be assured that the bearing clearances are right and go on your way. It all starts with verifying the pressure reading.
 

Supercharged111

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If you have lifters clacking, you likely have a no **** low oil pressure scenario and a low probability of an easy fix.
 

RawbDidIt

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All true. My "check gages" light is on constantly after warmup and the oil warms up. Helped a bit to move up to 40 weight, but even with 30 weight it was above the low spec, and it's well above 10 psi/1000 RPM which is not great, but acceptable from my understanding. How does it behave? Does the oil pressure dip on acceleration or increase immediately. Dip then rise issues means low oil level, rise immediately means the pump is at least working and not completely fried. But as mentioned this should be done with a calibrated meter at the oil pressure sending unit. I have a video on YouTube showing where it's at, it's somewhat hidden behind the distributor.

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Awest623

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^^^ Wisdom.

The only thing I can add to that is that earlier oil pressure sending units were extremely prone to failure, as are the aftermarket replacements. But the Vortec engine should be using a different design.

Kinda off-topic but I had my oil pressure sender break not too long ago. The who thing just shattered and started puking oil out of the hole.
 

stutaeng

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Here is the special socket for removing the sending unit:https://www.amazon.com/Lisle-13250-Pressure-Switch-Socket/dp/B0002SR2RY

I've got the same issue on a '99 4.3. The instrument cluster gauge always reads lower than the actual pressure. The dash is more like a "high" and "low" reading similar to what Fords had.

Does the SBC pickup tube have an o-ring like the later Gen III? I was going to suggest looking into that, but now I'm remembering that the design is a press fit?
 

RawbDidIt

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Here is the special socket for removing the sending unit:https://www.amazon.com/Lisle-13250-Pressure-Switch-Socket/dp/B0002SR2RY

I've got the same issue on a '99 4.3. The instrument cluster gauge always reads lower than the actual pressure. The dash is more like a "high" and "low" reading similar to what Fords had.

Does the SBC pickup tube have an o-ring like the later Gen III? I was going to suggest looking into that, but now I'm remembering that the design is a press fit?
If i remember correctly, it's a press fit, but it's been over a year since I've pulled the oil pan. I'm sure somebody else here knows with more certainty than me.

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SAATR

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The pickup tube is press fit. Racers have been known to tack weld them to the pump to prevent the tube from moving or falling out. A cracked pickup tube is certainly possible as well, but falls into the "unlikely" category. You can overfill the oil by a quart or two to verify, but I wouldn't recommend driving it like that unless you have no alternative. Getting the oil level too high will allow the rotating assembly to whip the oil, causing aeration and excessive windage on the crank. Both can lead to bottom end destruction.
 

Pinger

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Presumably these motors have an oil pressure relief valve - not seating properly due to dirt or soft/broken spring?
 
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