the old oil pressure question!
Discussion
I test drove a nice s3 today all seemed good apart from the petrol guage not working and the oil pressure guage reading around 0-5lbs at idle and only around 30-40 when under stress. It seemed to fluctuate a lot, is this indicative of a faulty guage,sender unit, or horrors such as bearings etc. Also car blew no smoke and idled happily although seemed a little hesitant under acceleration from low speed,fuel starvation? thanks for your thoughts Guys!
How long / far was the test drive? If it still drives ok after a hard 20 miles,with no rattley sounds or smoke, I would guess at a faulty sender unit.
Dip the oil & check for clarity, viscosity ( rub between your fingers, does it feel slippery? ) & whether there is any evidence of water or fuel mixed in.
When I bought my S1 in Aug 2011, oil pressure was reading very low, but the engine sounded sweet & was smoke & rattle/rumble free after a decent drive, so I took a punt. After a steady 200 mile drive home, I knew it had to be an indication fault.
A new universal sender from Hose Fittings UK at a cost of less than £15 inc pp, and all was well. A reassuring 60 psi / 20 psi hot idle. Nice.
But you do have to run an earth wire to the nearby chassis terminal.
But that's just my experience. There are no guarantees in this life.
But I do know where you can buy a 2.9 V6 Efi engine for £300 if you're quick.
Dip the oil & check for clarity, viscosity ( rub between your fingers, does it feel slippery? ) & whether there is any evidence of water or fuel mixed in.
When I bought my S1 in Aug 2011, oil pressure was reading very low, but the engine sounded sweet & was smoke & rattle/rumble free after a decent drive, so I took a punt. After a steady 200 mile drive home, I knew it had to be an indication fault.
A new universal sender from Hose Fittings UK at a cost of less than £15 inc pp, and all was well. A reassuring 60 psi / 20 psi hot idle. Nice.
But you do have to run an earth wire to the nearby chassis terminal.
But that's just my experience. There are no guarantees in this life.
But I do know where you can buy a 2.9 V6 Efi engine for £300 if you're quick.
Has anyone ever had a knackered 2.9 engine in an S? The only one I recall was Nicks when anti roll bar rubbed through the sump due to saggy engine mounts.
I don't recall any others, which when you consider forums are generally full of problems with cars is pretty amazing.
If I were buying an S today the engine would be the least of ny worries, everything else warrants close attention though!
I don't recall any others, which when you consider forums are generally full of problems with cars is pretty amazing.
If I were buying an S today the engine would be the least of ny worries, everything else warrants close attention though!
During my S2 ownership I have purchased two from the bay which at motorway speeds never gave me anything more than 32 ish but last year I decided to purchase one from davidgeraldtvr and although more expensive I now get 52-55psi and 30 ish on idle.
I would say with the electrics being such a lottery on these cars perhaps the only way to be sure would be a plumbed in gauge.
I would say with the electrics being such a lottery on these cars perhaps the only way to be sure would be a plumbed in gauge.
phillpot said:
glenrobbo said:
But I do know where you can buy a 2.9 V6 Efi engine for £300 if you're quick.
Think I could "find" one for £299 if you miss that one 
The same guy who was a tvr fanatic had an engine [46000 miles]and other bits for sale.
He phoned me a week or so after i purchased the gearbox saying no one had shown any interest in the engine and i could have that for £50.00 if i wanted.
When i sold my S3 i included the spare engine and gearbox in the sale, at no extra cost.
I had got them both cheap enough off a fellow TVR enthusiast so i felt obliged to do the same.
Interesting to note regarding oil pressure:
Almost all piston engines use fluid film bearings (plain bearings). This is true for the crankshaft and sometimes the camshaft, although often the latter runs directly in the engine structure.
Fluid film bearings operate by generating, as a by-product of the relative motion between the shaft and the bearing, a very thin film of lubricant at a sufficiently-high pressure to match the applied load, as long as that load is within the bearing capacity. As the speed/load goes up so does the pressure. This is not the oil pressure you see on the gauge but is what is called hydrodynamic pressure which is very much greater.
So provided you have enough pressure to keep the bearings supplied with oil the bearing should look after itself.
Bit of a simplified explanation, google “hydrodynamic oil pressure” if your sad enough to want to read more.
Rob.
Almost all piston engines use fluid film bearings (plain bearings). This is true for the crankshaft and sometimes the camshaft, although often the latter runs directly in the engine structure.
Fluid film bearings operate by generating, as a by-product of the relative motion between the shaft and the bearing, a very thin film of lubricant at a sufficiently-high pressure to match the applied load, as long as that load is within the bearing capacity. As the speed/load goes up so does the pressure. This is not the oil pressure you see on the gauge but is what is called hydrodynamic pressure which is very much greater.
So provided you have enough pressure to keep the bearings supplied with oil the bearing should look after itself.
Bit of a simplified explanation, google “hydrodynamic oil pressure” if your sad enough to want to read more.
Rob.
I think what you're saying Rob, is the that the oil pressure reading on the gauge is a measure of resistance to flow. A high reading can mean a very efficient pump, or restricted flow to the oilways, or close tolerances on the bearing surfaces or oil that is too thick.
A low reading can mean a worn pump, excessive bearing clearances, oil that is too thin, or a faulty gauge or sender.
As long as the bearings are receiving a healthy supply ( flow ) of fresh oil, all should be good.
As mentioned by Barcychoc, our old Ford Cologne V6 motors can take a fair bit of punishment and still live to a ripe old age.
Regular oil & filter changes are the best course,. & always keep an eye on the temperature.
No secret recipe, just common sense.
A low reading can mean a worn pump, excessive bearing clearances, oil that is too thin, or a faulty gauge or sender.
As long as the bearings are receiving a healthy supply ( flow ) of fresh oil, all should be good.
As mentioned by Barcychoc, our old Ford Cologne V6 motors can take a fair bit of punishment and still live to a ripe old age.
Regular oil & filter changes are the best course,. & always keep an eye on the temperature.
No secret recipe, just common sense.
glenrobbo said:
I think what you're saying Rob, is the that the oil pressure reading on the gauge is a measure of resistance to flow. A high reading can mean a very efficient pump, or restricted flow to the oilways, or close tolerances on the bearing surfaces or oil that is too thick.
A low reading can mean a worn pump, excessive bearing clearances, oil that is too thin, or a faulty gauge or sender.
As long as the bearings are receiving a healthy supply ( flow ) of fresh oil, all should be good.
As mentioned by Barcychoc, our old Ford Cologne V6 motors can take a fair bit of punishment and still live to a ripe old age.
Regular oil & filter changes are the best course,. & always keep an eye on the temperature.
No secret recipe, just common sense.
Exactly what I was trying to say.A low reading can mean a worn pump, excessive bearing clearances, oil that is too thin, or a faulty gauge or sender.
As long as the bearings are receiving a healthy supply ( flow ) of fresh oil, all should be good.
As mentioned by Barcychoc, our old Ford Cologne V6 motors can take a fair bit of punishment and still live to a ripe old age.
Regular oil & filter changes are the best course,. & always keep an eye on the temperature.
No secret recipe, just common sense.
Rob.
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