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New member with bbc problem

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BoneStock02

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I just signed up to get some help with my "new to me" truck. It's an '84 GMC C2500 with the 7.4L big block. Anyway, my oil pressure gauge dropped to about 4 or 5 psi the other day. So I tested the gauge and it's just fine. Then I replaced the oil pressure sender, and that didn't fix anything. I hooked up a mechanical guage to the block and it didn't register any pressure, I even open the valve on the other side (oil should have came out of it) and no oil came out. At this point I'm leaning towards replacing the oil pump, but I wanted to see if you guys have any suggestions on this problem before I go drop $60 on a new pump and put it in.
 
Low oil pressure like this is VERY rarely the fault of the pump.

Did you recently replace any gaskets, maybe using RTV?
 
I haven't changed anything on it but the oil pressure sender and I'd never use rtv on it. However I did just chage the oil in it, and when I pulled the plug out of the pan to drain it there was some thread-locker on it from the previous owner, I cleaned it off. Perhaps some got in there and is pluging up something?
 
It really takes quite a bit of crud to clog the screen on a Chevy V8 (small or big block).

If your oil pressure is reading right and there is nothing blocking the pickup screen, its probably bearings going bad.

The only real way to check either of these is to drop the oil pan (which, lucky for you is really easy on an older Chevy like this) and see if anything is suspect. If the screen isn't obviously clogged, start checking the main and rod bearings.


Again, weak/bad oil pumps are SUPER rare.
 
Was the oil pressure low when you bought the truck or was it fine and all of a sudden the pressure went away? Like was said, it is RARE for the oil pump to be the culprit. Low oil pressure is almost always the fit between the crank and bearings or the cam and bearings. There is an off chance though that if oil pressure was lost all of a sudden that one of the front three oil galley plugs came out and fell into the oil pan.

There is one other thing that commonly happens to BBC's and that's the oil pick up screen can fall off if it's not tack welded like they were from the factory. I have no idea why this phenomena doesn't happen to SBC's since the screens attach just like the BBC's. :dunno:
 
The oil pick-up can fall off even if its tack-welded.
I know this from experience :mad:
 
Yeah, it broke for sure.
But now i've got three tacks on it, so it should hold up three times as long :wink1:
 
4X4HIGH said:
Was the oil pressure low when you bought the truck or was it fine and all of a sudden the pressure went away? Like was said, it is RARE for the oil pump to be the culprit. Low oil pressure is almost always the fit between the crank and bearings or the cam and bearings. There is an off chance though that if oil pressure was lost all of a sudden that one of the front three oil galley plugs came out and fell into the oil pan.

There is one other thing that commonly happens to BBC's and that's the oil pick up screen can fall off if it's not tack welded like they were from the factory. I have no idea why this phenomena doesn't happen to SBC's since the screens attach just like the BBC's. :dunno:
Click to expand...

The pressure was fine, I put about 100 miles on it getting it home, and it gave me no problems, and it was good for for about a week . Then I was driving home from work one day and noticed the gauge was real low and that's when my prolems started. I'm hoping it's going to be an easy fix, but I'm not going to tear into it untill this saturday.
 
I would start by removing the timing cover and looking to make sure the three oil galley plugs above the cam are still in place.
 
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