gilles Posted July 11, 2008 Report Share Posted July 11, 2008 Hello, Is anybody here can help me on the followings : 1/ what should be a normal oil pressure on the TR4A IRS : * just after ignition (at idle) * after let say 30 minutes of driving time 2/ should the pressure increase or decrease after a short period of driving (15 to 30 minutes) ? 3/ what should be the temperature * just after ignition (at idle) * after let say 30 minutes of driving time thank you very much for your kind help best regards gilles (from France) Quote Link to post Share on other sites
MikeF Posted July 11, 2008 Report Share Posted July 11, 2008 Hello, Is anybody here can help me on the followings : 1/ what should be a normal oil pressure on the TR4A IRS : * just after ignition (at idle) * after let say 30 minutes of driving time 2/ should the pressure increase or decrease after a short period of driving (15 to 30 minutes) ? 3/ what should be the temperature * just after ignition (at idle) * after let say 30 minutes of driving time thank you very much for your kind help best regards gilles (from France) Bonjour Well in theory the oil pressure is the same hot or cold, after 2 minutes or 200, and at high or low revolutions. That's because the oil pressure relief valve controls the pressure to be always the same. IN practice things are different, the control is only on the high pressure not on the low and is not perfect. A cold engine can be a higher pressure than a hard driven hot one and if your idling speed is set too low then the oil pressure can be low or jump around a bit. You should find though that the pressure is around 70 psi, maybe a little high at start and after a long run perhaps a little lower. 30 minutes ordianry riving should not effect it. Of course the gauge could be a little out after several years of use, as could the adjustment spring and so on. Probably more important are sudden big changes from the needle's normal place on the dial. Problems then could be simple like: needs an oil top up. More complex like a stuck control valve, or totally disatrous like the engine bearings have gone. Any sudden downward change is a cause for stop!! and immediate investigation as the possible consequences of running with no oil pressure are very severe. If teh gauge is constantly low this is also a csue for concern as it is a possible indicator of a wordn engine and impending disaster, especially if accompanied by knocking or rattling sounds and smoke from exhaust etc, Sometimes the low pressure at idle is disguised by setting the idle speed high. A usual idle speed would be no more than 800 rpm Genuine experts may refine my numbers. What is reason behind the question? Mike Quote Link to post Share on other sites
Allan Westbury Posted July 11, 2008 Report Share Posted July 11, 2008 Hello, Is anybody here can help me on the followings : 1/ what should be a normal oil pressure on the TR4A IRS : * just after ignition (at idle) * after let say 30 minutes of driving time 2/ should the pressure increase or decrease after a short period of driving (15 to 30 minutes) ? 3/ what should be the temperature * just after ignition (at idle) * after let say 30 minutes of driving time Hi Gilles, We are talking about 40 year old cars that probably have had a fair bit of work done to them - for instance a reconditioned oil pump, changed water pump etc. - but which probably still have the original temperature & oil pressure gauges fitted. The point of this being that they will all read differently and i guess actual readings are less important than what happens at different stages of the driving cycle. At start up on my 4A the oil pressure at tickover is around 50 psi rising to 70 psi under acceleration or higher revs. I have just changed the oil filter head however as I have converted to a screw on filter. The old head would give a higher reading of up to 90psi at high revs when cold but this was purely a function of where the pressure release valve was set . Perhaps of more importance is the readings after say 30 mins when the engine & oil are warm. Under these conditions the pressure can drop to 25-30 psi on tickover but will still rise to between 50 - 70 psi at higher revs. I have never known the actual temperature indicated by my temperature gauge & have always judged it by the position of the needle on the gauge. Once again this will vary with the condition of the gauge itself, the temperature sensor, the effectiveness of the radiator & water pump & the accuracy of the bypass thermostat. Mechanical & electrical fans will also vary as will the position of the temperature sensor for an electric fan. After a few minutes my own car used to run 'normally' just on the hotter side of mid way on the temperature gauge when I was running with a standard radiator & original fan. fitting an electric fan did not really change this, it just stopped the gauge going into the red when driven really, really hard. I know other people had cars that run just cooler than mid way on the gauge but this was probably just a difference in the reading rather than the cars running at different temperatures. I have now fitted an aluminium radiator & the 'normal' running temperature shown on the gauge is lower than before. Now if the water pump & thermostat were working properly this should not have made any real difference under 'normal' conditions. It would however make a difference when the car was driven hard as the radiator is able to handle higher heat loads. I am sorry if this is a bit confusing , but I think both areas need to be taken as complete systems. High or low oil pressure or temperature can be caused by a number of factors & the actual reading could well be less important than the change under different conditions. I hope this helps. Quote Link to post Share on other sites
ChrisR-4A Posted July 12, 2008 Report Share Posted July 12, 2008 Hi Gilles, my 4A is similar to ollies, I have never adjusted the relief valve but do have a spin-on oil filter. On short journeys of 5-20 miles pressure is 50-70psi and 30 on tickover. After 200 miles pressure is still about 55-60psi at 3000 rpm in od top and about 50 around town at lower revs, at tickover, which is slower when really warmed up it is 25-30. What will make a difference is the oil you use. A good 20/50 seems best and I have used Duckhams and Halfords Classic and noticed no difference except in the price, locally a can of Duckhams was £12 earlier this year. Hope this helps. Chris Quote Link to post Share on other sites
67_gt6 Posted July 28, 2008 Report Share Posted July 28, 2008 Hi, my 4A when hot is 65 -70 PSI at 2000 RPM+, and 10 - 15 PSI idling at 700 RPM. The idling pressure used to bother me but it has never changed in 7000 miles. andy Quote Link to post Share on other sites
North London Mike Posted July 30, 2008 Report Share Posted July 30, 2008 Hello, Is anybody here can help me on the followings : 1/ what should be a normal oil pressure on the TR4A IRS : * just after ignition (at idle) * after let say 30 minutes of driving time 2/ should the pressure increase or decrease after a short period of driving (15 to 30 minutes) ? 3/ what should be the temperature * just after ignition (at idle) * after let say 30 minutes of driving time thank you very much for your kind help best regards gilles (from France) Gilles Happy to confirm the same basic info. 70psi above 2000 rpm, 50 psi at 800 rpm idle. 20/50 oil (Halfords UK shop chain, good value) 70 drops to 65 when hot, idle stays at 50psi Temp 185 controlled by electric fan +/- 10 degs Hope this is what you wanted to hear Quote Link to post Share on other sites
67_gt6 Posted July 31, 2008 Report Share Posted July 31, 2008 On a sidenote, if my engine is showing 70PSI at about 2300 RPM when hot, but 15 PSI idling hot at 700RPM, would this tend to indicate that the pump output is a bit low at idle? It is noticeable also that above 2300RPM the relief valve opens and pressure drops briefly to 50PSI before climbing back up to 70. andy Quote Link to post Share on other sites
ianc Posted July 31, 2008 Report Share Posted July 31, 2008 The most important thing is oil FLOW, for it is the flow which ensures that metal to metal contact does not occur and that heat is removed from the bearing surfaces. The removal of heat by the oil is just as important as this action by the coolant circulating round the liners and through the cylinder head. Oil pressure is solely an indication that the pump is likely to be generating a healthy flow, but is only an indicator - not actually a true indication of flow. So - don't get paranoid about oil pressure, as long as it's reasonable, you should have nothing to worry about. In the 1960s, my TR2 would cruise the M1 at 4200 in overdrive top (3.7 axle, so around 100 mph), with oil pressure sinking to about 45 psi at that speed. When I came off the M1 and the car was ticking over, oil pressure was less that 10 psi. However, despite the fact that clearances must have been huge (very evident went the car started on a cold winter's morning - it rattled for a few seconds until oil pressure built up!), it was utterly reliable and amazingly fast for an unmodified, low-port, TR2. Given good conditions it would wind up to about 114 mph with windscreen fitted - and could stop, because it was fitted with disc brakes! Ian Cornish Quote Link to post Share on other sites
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