Odd Pressure issue me thinks....
Discussion
Finally got the correct pressure sender which turned out to be a Stewart Warner one used on very early Griffs.
Wired it up all works a-ok.
At start up it hang fire about a second and then climbs to a steady 50psi and hovers around there all day long - A bit like the last one before it went bang. Has been working great now for about a week.
Anyhow have recently noticed however that at tick over when hot the low pressure warning light starts to flicker (sometimes) even though the pressure reads around 40-50 psi on the gauge.
Do these pressure warning switches ever go tits up?.
MikeB
Wired it up all works a-ok.
At start up it hang fire about a second and then climbs to a steady 50psi and hovers around there all day long - A bit like the last one before it went bang. Has been working great now for about a week.
Anyhow have recently noticed however that at tick over when hot the low pressure warning light starts to flicker (sometimes) even though the pressure reads around 40-50 psi on the gauge.
Do these pressure warning switches ever go tits up?.
MikeB
I'd be surprised if your engine really was holding such high oil pressures at idle especially when hot. I think it's more likely that the sender is wrong for that gauge and it is over-reading. It's quite common for the oil pressure to dip far enough to start tripping the oil warning switch at hot idle.
Well the funny thing is that the car was behaving itself really well up until a month ago.
Where upon I changed the oil. A week later the oil pressure sender goes up the creek along with shortly after the issue with the warning light.
I replace the sender and it reads and behaves and moves exactly like the last one did when it was working with almost identical readings - although slightly less erratic and more steady.
I have had it on very, very good authority that the sender that i have replaced my old one with is an exact replacement, not to mention looking exactly like the last one along with the exact same markings, part number stamps etc. I would therefore summise that the sender is working ok.
When the red warning light starts to flicker at tickover the pressure gauge is reading reasonably high at least nowhere near 7psi although obviously lower then when reving the car when it goes back up to around 40-50psi
I have checked all the leads and earths etc but do these oil switches fail, has anybody else had one go?. It just seems funny to me that the pressure sender should go at more or less the same time.
And one seems to contradict the other.
MikeB
Where upon I changed the oil. A week later the oil pressure sender goes up the creek along with shortly after the issue with the warning light.
I replace the sender and it reads and behaves and moves exactly like the last one did when it was working with almost identical readings - although slightly less erratic and more steady.
I have had it on very, very good authority that the sender that i have replaced my old one with is an exact replacement, not to mention looking exactly like the last one along with the exact same markings, part number stamps etc. I would therefore summise that the sender is working ok.
When the red warning light starts to flicker at tickover the pressure gauge is reading reasonably high at least nowhere near 7psi although obviously lower then when reving the car when it goes back up to around 40-50psi
I have checked all the leads and earths etc but do these oil switches fail, has anybody else had one go?. It just seems funny to me that the pressure sender should go at more or less the same time.
And one seems to contradict the other.
MikeB
GreenV8S said:
I'd be surprised if your engine really was holding such high oil pressures at idle especially when hot. I think it's more likely that the sender is wrong for that gauge and it is over-reading. It's quite common for the oil pressure to dip far enough to start tripping the oil warning switch at hot idle.
Agreed, mine does when hot.
Maybe a gap in the market for an air valve that opens when the oil light comes on, to raise the idle speed...? 
mikeb said:
Well the funny thing is that the car was behaving itself really well up until a month ago.
I may have misunderstood, but you're saying you have 40-50 psi at idle with old and new senders? In that case I'd say they're both wrong. They may just be wrongly calibrated for the gauge rather than faulty.
GreenV8S said:
I'd be surprised if your engine really was holding such high oil pressures at idle especially when hot. I think it's more likely that the sender is wrong for that gauge and it is over-reading. It's quite common for the oil pressure to dip far enough to start tripping the oil warning switch at hot idle.
I agree with the sender but to me, tripping the low pressure switch at hot idle indicates a problem. I have experienced it on other old knackered engines such a A series minis but not on a Rover V8.
The pressure switch is normally rated at 5-7 lb/in and if tripped does indicate a very low pressure indeed. I would put more faith in the oil pressure light than the guage. What idle speed do you have? If this is too low, then this can lower the oil pressure enough. Solution is to tweek it back up again.
The idle is around 900-1000 but lumpy and at the momennt seems to hunting a little - have cleaned or changed the usual suspects.
Blip the loud pedal and the flickering light immediately goes out and then intermittantly flickers back on again a minute or so later. then just flickers on and off until you pull off again.
I might take it someplace with a 'proper' oil pressure meter - how easy is this to get a true reading of the pressure, is it just screw in a hose and read off the pressure off a dial type of affair??
Perhaps try running a different oil as the symptoms seem to have started after I changed and flushed the oil a few weeks ago? At the moment running Valvoline VR1 20-50w
MikeB
Blip the loud pedal and the flickering light immediately goes out and then intermittantly flickers back on again a minute or so later. then just flickers on and off until you pull off again.
I might take it someplace with a 'proper' oil pressure meter - how easy is this to get a true reading of the pressure, is it just screw in a hose and read off the pressure off a dial type of affair??
Perhaps try running a different oil as the symptoms seem to have started after I changed and flushed the oil a few weeks ago? At the moment running Valvoline VR1 20-50w
MikeB
This has to be worth a try
An unusual choice but not one that should cause any problems of this nature.
This seems to be the most likely
2 bar (26psi) at 2000 revs is normal per TVR handbook and experience of most. 40-50 at tickover is not right at all. The RV8 is a high flow design not a high pressure one.
I agree with Steve.
nick heppinstall said:
Are you sure the gauge is OK? I've had my gauge read a constant 40-50psi and also a constant 0 !! Both times a good clean of all the earths cured the problem and returned the gauge to it's normal working condition.
mikeb said:
I changed and flushed the oil a few weeks ago? At the moment running Valvoline VR1 20-50w
An unusual choice but not one that should cause any problems of this nature.
This seems to be the most likely
GreenV8S said:
You're saying you have 40-50 psi at idle with old and new senders? In that case I'd say they're both wrong.
2 bar (26psi) at 2000 revs is normal per TVR handbook and experience of most. 40-50 at tickover is not right at all. The RV8 is a high flow design not a high pressure one.
I agree with Steve.
shpub said:
You have a problem.
Uuummm try replacing the low pressure switch ? they're only a few quid, and yes they do go as the spring inside gets cooked over time and yields giving a false reading. As I've changed mine in the past due to this very reason ( oil pressure checked with mech gauge before though)
Matt
Matt
That was I was thinking. I will change the pressure switch as you mentioned these only cost a few quid. See if the issue re-occurs then go to plan B.
Did have a look at the invoice for the £8,500 engine rebuild and blueprint job that the car has had and the oil pump was changed for a high pressure, high capacity oil pump. Would this make a difference?.
MikeB
Did have a look at the invoice for the £8,500 engine rebuild and blueprint job that the car has had and the oil pump was changed for a high pressure, high capacity oil pump. Would this make a difference?.
MikeB
Mike
On my 4.5 BV (Ex chim / seac engine ) the oil pressure was reading 17 - 18 for at idle and would hardly rise at all. I then put in a mechanical gauge and managed to get a steady 20.
I thought this was low, so spoke to a guy at my local TVR dealer and he said that it was running at about the right pressure.
So if your running at 40 - 50 psi I would be a bit weary about popping things like gaskets etc !
On my 4.5 BV (Ex chim / seac engine ) the oil pressure was reading 17 - 18 for at idle and would hardly rise at all. I then put in a mechanical gauge and managed to get a steady 20.
I thought this was low, so spoke to a guy at my local TVR dealer and he said that it was running at about the right pressure.
So if your running at 40 - 50 psi I would be a bit weary about popping things like gaskets etc !
The engine has had one mother of a rebuild and blueprint job done on it by the looks - according to the bill!! 
Everything has been changed for high compressions this, polished that, uprated this, racing spec that. I ain't worried about the pressure just more concerned about the recent lack of it.
The gauge may be incorrect but at least the new pressure switch ain't tripping the warning light at tickover.
I would like to get the thing mechanically tested with a proper pressure tester but the engine has had so much work done on it that I am not sure what is supposed to be normal and not anymore.
Everything seems ok at the moment though and besto of all goes like shite off a shovel though...
MikeB
Everything has been changed for high compressions this, polished that, uprated this, racing spec that. I ain't worried about the pressure just more concerned about the recent lack of it.
The gauge may be incorrect but at least the new pressure switch ain't tripping the warning light at tickover.
I would like to get the thing mechanically tested with a proper pressure tester but the engine has had so much work done on it that I am not sure what is supposed to be normal and not anymore.
Everything seems ok at the moment though and besto of all goes like shite off a shovel though...
MikeB
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