V8 low oil pressure

I

Ian M

New Member
Hello, I’m wondering if anyone could give me advice on a problem with a V8 engine in a 3500s that is now running with low oil pressure.The engine has always run with good pressure 30-45 psi, however on a recent short trip the pressure gauge dropped to around 15psi with the warning light coming on at idle. There is also tappet noise from the engine.

I took the car to a local garage where they ran an engine flush through it and changed the oil (20/50) and filter along with the oil pump pressure relief valve. The oil pump is not suspected nor the oil pickup. Pressure test confirms that it is low and not a faulty instrument gauge. The issue was not resolved and have been advised that the problem is probably bearing related and an engine rebuild or new engine will be required.

The main bearings were replaced 20 years ago (less than 10K miles ago – current mileage 70K) along with the cam & followers. The car is serviced regularly, although it did have to sit unused for a period over lockdown.

Just wondering whether anyone with experience of such V8 issues could help shed any light on this. I’m just trying to work out potential next steps.

Many thanks for any help or advice.
 
Hi, The V8 is very tolerant of low oil pressure, However for your piece of mind it might be an idea to drop the main bearing caps, because they are the first port of call, to see what the shells are like and similarly the big ends. While the sumps off, check the oil pick up screen to see if it's blocked and whether there's a lot of baked oil sludge in the bottom of it.

Colin
 
Thank you for your reply. The oil pressure has usually been very good on my engine – up until now. I'll try and see if I can have it checked out as you suggested. Thanks.
 
Had the same problem with mine except I didnt get tappet noise. Couldnt sleep at night thinking about the dash light that came on at idle.
I started by dropping the sump , which had now collected an wonderful array of sludge.
I then replaced the oil pump with the later SD1gears from Real steel or the likes. Its taller than the P6b gears and creates more oil volume
My oil pressure is steady on 50psi and that annoying dash light hasnt made an appearance at idle.
Im not a mechanic but was motivated to do the exchange oil pump by myself and wasnt a problem when talking it through step by step with all these guys on here.
Have fun
Gerald
 
Thanks for your information, that's useful to hear. I had some quite pronounced tappet noise earlier this year, but it went away. The oil pressure problem is a new one to me – coupled with tappet noise again, makes me wonder if there is possibly a blockage somewhere. The sump might be a good place to start. I'm not a mechanic! Thanks again.
 
Along with checking the sump for sludge, I would make sure the pickup screen is clear. It would also be useful to check the valve rockers and shafts for wear - oil is pumped up there through the head, and with the rocker assembly off you could check that oil gallery. When I got my car it was a little bit tappety, so I pulled the rockers and replaced the shafts and rockers - the mileage I do will never wear out even cheap aftermarket parts.
This is one of my shafts....you need to replace shafts and rockers together. I knocked out the end plugs of the shafts, and there was plenty of sludge inside.
 

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Thanks again for the replies, that's very helpful. The garage rebuilt the oil pump pressure relief valve but there was no improvement. I'll try and look into the sump pickup and the rocker suggestions. There is a bit of tappet noise from the engine as well as the low oil pressure.
Many thanks.
 
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