Mystery RV8 Oil Pressure problem

[BadgerV8]

Hello.

I'm hoping someone could point me in the right direction with my misbehaving oil pressure... I've searched the forums and not found these symptoms listed.

Its a new engine, new electronic gauge, new SD1 type oil pump. Oil pressure light behaves as it should. 20w50 oil.

On cold oil, I get 2 bar (39psi) exactly. This is regardless of RPM, at tick over and upwards, always 2 bar.

At a steady temperature of 80C water, 95C oil, a rock solid 1 bar (14.5psi).

On hot oil, this goes down as low as 0.5bar. Again RPM doesn't seem to effect it.

I've already changed the sender to be sure they are compatible, and no difference.

Soft pressure releif spring? Surely that would give the same oil pressure reading hot or cold? But anything else should see variation with RPM, wouldn't it?

Advice please! I'm (stupidly) taking this freshly built car to Italy in less than three weeks, and don't want to be worrying about oil pressure the whole way!

cheers in advance for any advice on this.

Dave

[katanaman]

Sounds very odd! Wont be a soft spring as that would still be rev dependent and you wouldn't get as high as that cold. Also your pressure switch will trip by .5 bar so that's why the oil light is going out regardless. I take it that everything sounds ok and there are no nasty noises? Where do you have your pressure sensor screwed into? Does the gauge drop evenly as the engine heats up or does it just drop at some point? I would be tempted to get hold of a mechanical gauge and stick that on, even if its just for testing. Never been very keen on electric gauges. Other thoughts are a blockage somewhere so lift a rocker cover when hot and check for good oil flow. Maybe something weird going on with the pressure relief valve but what I don't know. Could be a blockage somewhere (permanently high pressure) then as it heats the valve gives in and opens but sticks (permanently low pressure). Am really just thinking out loud here to be honest.

Sorry lots of questions in there but the more info people have the easier it is for them to get their heads round it.

[Ian Anderson]

Did you pack the pump with Vaseline for the start up?

If so the vaseline could be forming a plug at the sender and giving these wierd results

Remove oil pressure sender and check for blockages

Could also be worth asking are you running a standard filter or remote - if remote do you have the pipes connected the right way around for flow through the filter non return valve

Is there a cooler in the system? is i a reused unit? if so what caused the rebuild? It could be a cooler that has crud that moves and blocks the flow


A few suggestions

Ian

[Darkspeed]

I would check that the relief valve is seating fully as it sounds like its staying open

Andrew

[katanaman]

I would check that the relief valve is seating fully as it sounds like its staying open

Andrew

Doesn't sound like its staying open when cold though in fact it doesn't sound like its moving at all. You should never have that much pressure at idle unless the oil isn't going anywhere.

Ian might have something with the filter being connected the wrong way round if its a remote filter.

[Darkspeed]

2 bar is only 29psi which with cold thick oil should be easy to achieve at idle - it just sounds like the pressure is being viscosity led and not regulated.

A fresh engine with virtually no oil pressure when hot - sure sounds like a pressure relief staying open to me.


Andrew

[BadgerV8]

OK... I'll do some further testing this evening.

I've borrowed a calibrated pressure sensor/gauge gadget, and so will varify the pressure gauge reading with that.

So not a soft spring. I was finding this hard to beleive, and I had compared it to a spring from another pump and they 'felt' about the same.

I have checked oil delivery to the rockers... was OK... Plenty oozing out at revs. I'll check this again incase something has found its way up there tho'.

Oil filter hoses the wrong way round... I have done this before! When I remove the oil filter, the oil should squirt out of the side hole, not the centre hole, correct?

I did use vaseline a while back, but its been flushed a couple of time since then. Primed the pump with a drill down the dizzy hole last time the cover was off. Maybe worth cranking over with sensor removed, make sure something comes out the hole!

No cooler in the system at present.

I'll remove the pressure valve again, and see if it seems to still work smoothly. I probably don't have time to tadpole it before the big trip though! Urgh...

More info when I return from my garage later this evening.

cheers for the advice so far,

Dave.

[ian.stewart]

If its the pressure releif valve it may be worth swoping it for a Tadpole type plunger, they are not so prone to sticking, BTW I am getting 25psi at cranking speeds on a fresh engine,

[BadgerV8]

Borrowed digital pressure gauge fromo work... Can't switch it on! Small fuse blown inside and no replacement at home. &@$$@%!

Removed pressure relief spring... plunger seems to be going nowhere. I found the origanal cover (changed to to sensor octopus taking a whack and damaging thread), removed pressure relief spring, also seemed to be fairly stuck. Oily, but took some prizing with a screw driver to get out of the hole! Both from the same supplier.
Is this normal?? I seem to recall from my old high milage engine that plunger plopped out when removing the spring, but that was a few years ago, so I'm not sure now.

As an idea for a quick and hopefully reliable fix, I have my old-old oil pump cover... this seemed to keep the previous engine alive for 20 years quite successfully, and so maybe I should fit the tried and tested one? Any reasons not to? The pump face may be a bit worn I guess, but as long as its OK, the valve should still be fine, right? Do they tend to sieze with age, or just the ones that are dodgy to start off with?

I'll report back after removing old-old pump cover...

Dave.

[BadgerV8]

Yeap, after a year of sitting in the corner of garage, the old-old pump cover's black mucky plunger plops out with a tap. A little worn on the pump face, but I think I can live with that.

Mozzeis are starting to swarm... Think I'll swap pump covers tomorrow and see what happens.

[BadgerV8]

80's oil pump cover and relief valve appear working a treat!

2 bar cold tick over, 3 bar cold with revs, 1 bar hot tick over, nearly 2 bar hot with revs. >phew<

Thanks greatly for the diagnostic advice!

Engine noticeably sounding smoother, which raises the next question:-

How much damage have I done??? 100 gentle miles, mostly less than 3000rpm in a light weight car. I then got the gauge working and spotted the problem... There was oil going to the rockers, just not the full amount, I guess. Should be mostly OK, right?

T'was stupid, I know... going on the oil pressure light alone, but I was gagging to have it back on the road after 12 months with out... you know how it is. And I can be pretty good at being stupid...

[Darkspeed]

The Rover V8 can take an unbelievable amount of abuse oil pressure wise, we have run an old P6 with oil pressure that didn't register on a mechanical gauge and lit the oil warning light on idle and only went off if over 1200rpm - never any more than 20PSI when hot even at 6000rpm.

It smoked, it threw out oil that filled a 0.5litre catch tank in the space of 20 miles but it never seized or sounded even remotely rattly. We only replaced it because we had a spare sitting about doing nothing - I think to we would have had to shoot the bloody thing to kill it.

I think you would be very unlucky if you have done any damage.

Andy

[BadgerV8]

Exactly what I was hoping to hear! Cheers!

Think I'll wait for the rush hour traffic to thin out and go for a nice long test drive!

Happy Dave.