AdamR
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| posted on 16/10/10 at 07:27 PM |
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V8 oil flow (or lack thereof)
I'm running a 3.9 RV8 with the post '94 intermediate timing cover with crank driven oil pump. I'm seeing good oil pressure of around
40psi at idle, but I'm suspicious about oil flow as I seem to have very little oil arriving at the rockers.
I've not run the engine for more than a few minutes, but all I see is a couple of drops of oil oozing from each of the small notches in the
rockers. So the shaft is getting at least some lubrication, but the pushrods and the valve stems and everything else is staying bone dry. Which surely
can't be right?
I'm using a remote filter - and I did think that I may have connected it the wrong way round, but tried swapping the connections earlier and it
didn't appear to make any difference at all, either to the oil pressure or flow at the rockers. This itself is confusing me as I've read a
lot about filters having non return valves - so I would expect to get no flow & pressure at all if connected incorrectly.
I'm also running a modified sump and oil pickup, but I don't think this can be causing the issue as if the pickup was sucking air
I'd wouldn't expect to see such a healthy oil pressure.
I've also had the pressure relief value out, but looks and feels fine, with no sign of sticking.
Any thoughts? I'm a bit stumped by this.
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v8kid
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| posted on 16/10/10 at 07:55 PM |
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Is the cylinder head gasket on the right way?
You'd be surprised how quickly the sales people at B&Q try and assist you after ignoring you for the past 15 minutes when you try and start a
chainsaw
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v8kid
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| posted on 16/10/10 at 07:58 PM |
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What revs is the oil pressure at? I get 10psi per 1k revs - Are you just running at fast idle?
You'd be surprised how quickly the sales people at B&Q try and assist you after ignoring you for the past 15 minutes when you try and start a
chainsaw
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RichardK
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| posted on 16/10/10 at 08:27 PM |
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My first instinct is to say either wrong head gaskets or head gaskets on the wrong way round causing the galleries to be blocked.
I have no knowledge of the rv8 but from the symptoms you describe, that's where I have a bet at.
Cheers
Rich
Gallery updated 11/01/2011
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AdamR
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| posted on 16/10/10 at 08:28 PM |
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I've not had the heads off, and whilst it's possible the previous owner could have had them off and got the gaskets wrong, I don't
think it's likely.
I get 40psi at a fast idle with a cold engine. I've not run it up to full temp yet, so not sure if the pressure will drop as the oil warms up.
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AdamR
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| posted on 16/10/10 at 09:14 PM |
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Other than looking at the rockers, is there anything else I can do to verify that oil is circulating properly?
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nitram38
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| posted on 17/10/10 at 12:58 AM |
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Oil pump has a spring to control pressure, is this too weak/broken? Maybe change this anyway.
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AdamR
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| posted on 17/10/10 at 08:21 AM |
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quote:
Originally posted by nitram38
Oil pump has a spring to control pressure, is this too weak/broken? Maybe change this anyway.
Thanks nitram. I checked the pressure relief valve - seems to be fine.
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AdamR
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| posted on 17/10/10 at 10:15 PM |
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Right, I've been looking at this problem again today - but I still can't figure out what going on.
Here's where I'm at:
- Oil pressure reading 40psi at idle, but hardly any oil getting to rockers
- I've checked the rocker shafts are correctly fitted so that the flow is not obstructed - they are correct
- I've removed a rocker assembly to check that I'm getting oil from the feed hole, but still only see a steady oozing of oil from the hole
- certainly not squirting out as I'd expect
- I've tried the remote oil filter connected both ways - but this makes no difference to the measured pressure or observed flow (this may be an
important symptom as the filter is supposed to have a non return valve and flow oil in one direction only)
- I've had the oil pressure relief valve out, but it seems fine and is not sticking in it's bore
- I've removed the oil cooler port blanking plugs to check they're not obstructing the oil ways internally - they're not
- I've checked the oilway to the rockers is not blocked but it's fine
- Finally I thought I'd cracked it when I worked out that my cut n' shut pickup was only about 1 or 2mm from the bottom of the sump and
that perhaps this was restricting the flow. So I spent a hour or so modding it to increase the gap and then put everything back together - No cigar!
So all in all I'm more confused than ever! Any ideas at all?
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