Strange oil Pressure behaviour
Discussion
Last week after a drive up to aylesbury and back giving it few more beans then i usually would. Even in the nearly four years that i have owned it i have never heard the change up buzzer, still haven't although on the particular day i believe i was close.
Nearing the end of the journey stopping at Miller and Carter restaurant in Ruislip for some dinner my SPA dual gauge started flashing red. I have the warning set at about 20-25 for low pressure, looking at it i was seeing 14/15 but would jump back to normal within a second. A few revs, and was fine. Same happened on the way home after dinner.
Oil level was spot on, having just topped it up prior to the trip.
Any way onto today, having not used the car until i could investigate further. I brought a mechanical oil pressure tester a clarke one and fitted it to my sandwich plate at the filter, checked the level again having left the dip stick out, started car, instant pressure, both gauges reading the same.
Warmed the car up, oil temp around 70 degrees, water 80, pressure idle 30, pressure with revs up to 65-70, so again could not answer why it had done it.
As a precaution, i have done a oil and filter change relief spring, which was changed two years ago, and looked about 1-2mm short and the fuel filter, not related but not sure if its been done before, cars covered less then 30000, but when the warning come on, the typical pound signs start coming up, but all seems well, haven't driven it yet, will tomorrow to check it is all okay.
Just a little vid to show, both the SPA gauge and the test gauge.
Nearing the end of the journey stopping at Miller and Carter restaurant in Ruislip for some dinner my SPA dual gauge started flashing red. I have the warning set at about 20-25 for low pressure, looking at it i was seeing 14/15 but would jump back to normal within a second. A few revs, and was fine. Same happened on the way home after dinner.
Oil level was spot on, having just topped it up prior to the trip.
Any way onto today, having not used the car until i could investigate further. I brought a mechanical oil pressure tester a clarke one and fitted it to my sandwich plate at the filter, checked the level again having left the dip stick out, started car, instant pressure, both gauges reading the same.
Warmed the car up, oil temp around 70 degrees, water 80, pressure idle 30, pressure with revs up to 65-70, so again could not answer why it had done it.
As a precaution, i have done a oil and filter change relief spring, which was changed two years ago, and looked about 1-2mm short and the fuel filter, not related but not sure if its been done before, cars covered less then 30000, but when the warning come on, the typical pound signs start coming up, but all seems well, haven't driven it yet, will tomorrow to check it is all okay.
Just a little vid to show, both the SPA gauge and the test gauge.
Is the vid showing the normal behaviour or do you think it is still low?
I bought my car (also a 4.5) with no oil pressure which turned out to be a faulty gauge but before firing the engine up with a test gauge attached I had changed the oil, relief spring and filter. The pressure on mine reads 80PSI at idle on start up, 90PSI if I rev it. Once hot (when sitting in traffic for a while) the idle is 65PSI and goes back to 80 PSI if I blip the throttle or move off. I have never seen mine below 65PSI which does seem high compared to your readings. I have confirmed my reading with a test gauge (surprisingly it is within 1PSI of the rebuilt TVR gauge) and have checked the oil level is correct. The new relief spring was the same length as the old one but much firmer (you can't compress it in you fingers, the old one you could slightly).
Maybe my oil pressure will get lower with age as new the relief spring wears or maybe your relief spring was slightly shorter but shouldn't all 4.5 AJP engines be roughly the same?
I bought my car (also a 4.5) with no oil pressure which turned out to be a faulty gauge but before firing the engine up with a test gauge attached I had changed the oil, relief spring and filter. The pressure on mine reads 80PSI at idle on start up, 90PSI if I rev it. Once hot (when sitting in traffic for a while) the idle is 65PSI and goes back to 80 PSI if I blip the throttle or move off. I have never seen mine below 65PSI which does seem high compared to your readings. I have confirmed my reading with a test gauge (surprisingly it is within 1PSI of the rebuilt TVR gauge) and have checked the oil level is correct. The new relief spring was the same length as the old one but much firmer (you can't compress it in you fingers, the old one you could slightly).
Maybe my oil pressure will get lower with age as new the relief spring wears or maybe your relief spring was slightly shorter but shouldn't all 4.5 AJP engines be roughly the same?
Hi Peter
I seem to recall you renewed your oil cooler a few years ago and you mentioned the pipe diameter on the new cooler was smaller than the one it replaced.
Early 4.2 cerberas did suffer with the same problem you mention and the factory fix was to put bigger diameter oil pipes on to the same spec as the 4.5 s
When fitting your new cooler you may have invertley restricted your oil flow.
It's just a thought I had when seeing your post. But if I've got my wires crossed and your oil cooler is the right spec please ignore ever thing I've just said
I seem to recall you renewed your oil cooler a few years ago and you mentioned the pipe diameter on the new cooler was smaller than the one it replaced.
Early 4.2 cerberas did suffer with the same problem you mention and the factory fix was to put bigger diameter oil pipes on to the same spec as the 4.5 s
When fitting your new cooler you may have invertley restricted your oil flow.
It's just a thought I had when seeing your post. But if I've got my wires crossed and your oil cooler is the right spec please ignore ever thing I've just said
Edited by Gray_101 on Monday 19th May 20:13
My oil pressure used to get very low after a long hard drive or trackday session, better oil grade fixed that, original had been spec'd wrong I believe. Now running 15/50 and new spring, 80psi cold, 65 ish hot, at idle, up to 80/90 when driving. Only drops to 30 after a session on track now.
There is a chance eith the spring has gone weak or your going beyond the oil grade and it's cracking.
What oil/grade you using?
Darren
There is a chance eith the spring has gone weak or your going beyond the oil grade and it's cracking.
What oil/grade you using?
Darren
Vee8ight said:
My oil pressure used to get very low after a long hard drive or trackday session, better oil grade fixed that, original had been spec'd wrong I believe. Now running 15/50 and new spring, 80psi cold, 65 ish hot, at idle, up to 80/90 when driving. Only drops to 30 after a session on track now.
There is a chance eith the spring has gone weak or your going beyond the oil grade and it's cracking.
What oil/grade you using?
Darren
This is too high, you are using oil that is too thick and risking your engine as a result, flow is as important as pressure, probably more so, an AJP should run about 65 cold idle, 35-40 hot idle dropping a bit after a real spanking like a track day, about 60 hot running at 2500 rpm or so. The relief valve opens at 85psi and you should only reach that if you have a blockage some where.There is a chance eith the spring has gone weak or your going beyond the oil grade and it's cracking.
What oil/grade you using?
Darren
I believe the handbook says switch off if oil pressure drops below 10psi on hot idle.
Have a look on the Opie oils web site about why they don't recommend 60 grade oil, it makes interesting reading.
Edited by gruffalo on Tuesday 20th May 00:02
gruffalo said:
This is too high, you are using oil that is too thick and risking your engine as a result, flow is as important as pressure, probably more so, an AJP should run about 65 cold idle, 35-40 hot idle dropping a bit after a real spanking like a track day, about 60 hot running at 2500 rpm or so. The relief valve opens at 85psi and you should only reach that if you have a blockage some where.
I believe the handbook says switch off if oil pressure drops below 10psi on hot idle.
Have a look on the Opie oils web site about why they don't recommend 60 grade oil, it makes interesting reading.
It was said oil supplier that supplied me with incorrect oil for the engine and my diff, but did replace it FOC, when questioned.I believe the handbook says switch off if oil pressure drops below 10psi on hot idle.
Have a look on the Opie oils web site about why they don't recommend 60 grade oil, it makes interesting reading.
Edited by gruffalo on Tuesday 20th May 00:02
The handbook says 15/40 or 5/50, and doesn't mention max oil pressure, I'm not the only one running this pressure when having replaced the spring.
I'm not using 60 weight oil.
Darren
Darren
[/quote]
This is too high, you are using oil that is too thick and risking your engine as a result, flow is as important as pressure, probably more so, an AJP should run about 65 cold idle, 35-40 hot idle dropping a bit after a real spanking like a track day, about 60 hot running at 2500 rpm or so. The relief valve opens at 85psi and you should only reach that if you have a blockage some where.
Flow is definatley more important than pressure. I would think max of around 65 to 75 @ 2K when stone cold dropping to 45 to 55 when hot. The valve spring should be regulating the pressure so the only drop is caused by the viscosity change of the oil.
My engine changes by about 10psi between stone cold and hot. I'm running 10w 50.
pmessling said:
I'm using 0-40 oil as stated in the hand book the last generation of handbooks
Was fearing the woodruff key but currently everything checks out.
I am running 5-50 oil which might explain why mine is higher. I used to run 0-40 in my old Cerbera and that would be around 60 cold and 30 hot idle.Was fearing the woodruff key but currently everything checks out.
My understanding with oil pressure changes is the time to be worried is when you see the pressure dropping during acceleration. So long as it rises during acceleration and doesn't fall too low at hot idle then it is probably fine.
In all the times my pressure has dropped I have never seen the low oil pressure light in the rev counter come on.
Only the low pressure reading on my SPA gauge.
Although the sensors are £100 I think worth changing just in case
Or am I just kidding myself knowing its worse and engine out.
What is the original pressure switch set to?
Only the low pressure reading on my SPA gauge.
Although the sensors are £100 I think worth changing just in case
Or am I just kidding myself knowing its worse and engine out.
What is the original pressure switch set to?
Sender changed and still the same pressure. Fine whilst idling and raving. As soon as it's driven drops.
I'm going to fit an analog gauge with a longer hose and go for a drive with that attached to see that again the SPA gauge.
After that I've ran out of things bar it being the oil pump drive.
If it is. It will have to wait till I move and be carried to the new house where I can remove the engine in the garage.
I'm going to fit an analog gauge with a longer hose and go for a drive with that attached to see that again the SPA gauge.
After that I've ran out of things bar it being the oil pump drive.
If it is. It will have to wait till I move and be carried to the new house where I can remove the engine in the garage.
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