Hi I have a 3.5 V8 in my series 3 the engine was originally from a rover P6 but I have fitted a kit to uprate the oil pump to the longer type gears.
What I am wondering is what pressure I should have at different engine speeds. Usually at idle its just over 20psi and above 2500rpm just under 40psi. But recently when above 2500rpm the pressure sometimes drops to between 20 to 30 psi and a couple of times it has been up to near 50 psi.
The engine was rebuilt about a year ago with new oil pump cover and gears so what could be causing the pressure to drop or rise?
Most likely the dreaded sticking relief valve. Dunno what you should be seeing, never actually used one of these kits myself, I prefer to fit the later front timing cover and SD1 gears. Std pressure is 35psi nominal (+ or - 5psi) at 2400rpm. If below 30 at 2400, bearing wear will shortly follow. Healthy engines normally show 10psi+ at idle. The pressure will build with rpm until it reaches the relief valve opening pressure, after this point there will still be an increase with rpm, but no longer linear if you see what I mean?
I think it must be the relief valve sticking as the pressure seems to stays between 30 to 40 psi until the engine has been up to around 4000rpm for a short time then the pressure drops.
So what makes the valve stick and what can I do to stop it sticking?
Would a stronger spring on the valve help to stop it sticking?
Also should there be oil behind the valve shuttle (around the spring)? I was wondering if oil here could some how prevent the shuttle from returning by sealing off or creating a kind of vacuum behind it or in a similar way stop it opening. Or am I wrong in thinking that it works like that?
Small burrs caused by wearing of the pump gears into the cover producing metal swarf. Tiny grit, dirt or carbon particles are the other suspects, but I've found tiny wire strands and all sorts. You need to remove the pump base and get it on the bench. Strip it completely and give it the cleaning of it's life. If there is any scoring in the valve bore, the cover is scrap I'm afraid, as any attempts to polish it will merely serve to increase the valve-to-bore clearance, allowing the valve to move around and causing more wear and also it will be bleeding off more oil past itself as well, causing low pressure at idle. If the cover is ok (check also for excessive scoring caused by the pump gears) then try a "tadpole" valve, I think JE Motors do them.
Not really, normally only a short-term fix. As the stronger spring overcomes the sticking point it causes slighly more wear each time until the deposits build up again to a level that the spring cannot overcome.
There will be oil present behind the shuttle, there isn't any pressure there as that's a return to the inlet (suction) side of the pump.
In news:dE4Zc.97285$ snipped-for-privacy@fe1.news.blueyonder.co.uk, Liam blithered:
Yes and No, it would close the valve easier but would change the pressure at which the bypass operates hence destroying the pressure relief and probably the engine by squishing any available detritous into your shell bearings under the increased pressure. Sometimes the valve itself wears, not a lot, but enough so that it doesn't remain square in the body, so it no longer sits square on the seat face. Just enough to leak and fail to maintain pressure. I don't know what they're like in the V8 I played silly buggers with them in my old Mini Cooper, a nice simple machine. You could sometimes recover them by grinding them in like a valve, but not without stripping the engine down to extract the grinding paste, which makes a really excellent lump of detritous as described above.
Now, to my v8, which I am not sure is building pressure, because I don't know if the pressure switch is working: it may be stuck, or it may be that the damned wiring is knackered round here too. I don't see a feed to the switch on any of its three terminals.
Is there a standard O.P gauge that one can get for these engines ? I'd like to know how the pressure is building as well as go/no go
IF there is no O.P, can I open a convenient oil gallery to prime the pump, rather than this buggering about with vaseline (as it were..)
I have removed the pump cover and striped the valve. Found no dirt or foreign objects, the engine has only done about 2000 miles since rebuild so everything is still very clean.
Did find a slight spot which very slightly restricted the valves movement which was easy to knock off. The bore and valve are unmarked.
Carefully cleaned and fitted it back together but it is still sticking, not as much is before, when it sticks now the pressure usually returns after a couple of minutes as if the valve is closing very slowly.
So I am thinking of getting a tadpole type valve for it, do you have any contact info for JE Motors also is there any other places that sell them?
Sorry, never used these tadpoles so don't know for sure. I don't have any dealings with JE Motors but they advertise in the comics every now and again so that'd be a starting point maybe. You might also try RPI, as much as it pains me to suggest so.
seem to know nearly asmuch as Badger (!), and I have seen the tadpole valves mentioned. Postyour query on the engines forum if you get no luck with other sources. David
Must confess, never had dealings with the 3wire sensor and I ain't got a wiring diagram in front of me for a 101.
I have a 0-100psi gauge with a quick-release bayonet fitting, brazed to a threaded connector that replaces the oil press. switch, that's what I use to check the pressures when I rebuild my engines. Can't for the life of me remember where I got it though.
Sorry, fraid not. The only thing you could try would be to remove a rocker cover, remove the rocker shaft (careful not to knock any of the pushrods!) and trickle oil down the rocker feed oilway at the front shaft support block mounting face. This would take some time and I'd bet you'd be quicker just removing the pump base and packing with petroleum jelly.
I've always primed the pump by taking out the dizzy and spinning the pump with an electric drill. I now have a number of slotted bits of rod for this purpose. Worked even when the time between building and the first starting attempt was in the order of a year or two. Never used the vaseline method.
Fair comment Beth, that's how I do it myself on all the engines I build (non-serpentine, obviously) but the poster asked about opening an oilway so I presumed they knew about the priming tool but didn't fancy removing the dizzy.
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