Intermittent loss of oil pressure
Discussion
Hi all,
Slightly bizarre one. So I’ve had the oil pressure light flash up a few times, however I’ve taken it with a pinch of salt as I know that the mechanical gauge works off a separate signal, all well on that front. That is, until today.
The car is still pretty much cold, I flash my eyes down to the dials and the oil pressure light has come on. I then swiftly realise that, for the first time, the dial gauge has also dropped off the map, no oil pressure!! I killed the engine pretty damn quickly, let it settle for a few seconds and then restarted. Immediate 70psi, no oil light, gingerly continued and was fine for the rest of the journey.
This evening I jump back in the car, maybe 2 minutes into the journey and it happens again. No oil pressure on gauge and warning light. Again, I kill the engine, restart and we once again have perfect oil pressure for the rest of the journey. The level is fine although I do have a fairly mean oil leak, which I suspected front cover but could be oil pressure switch? Would a leak from here trigger the oil light as I believe it is fed through there?
And how can the car intermittently and genuinely lose oil pressure? I can only imagine it could be the oil pump...? God forbid.
Car is a 4.2.
Slightly bizarre one. So I’ve had the oil pressure light flash up a few times, however I’ve taken it with a pinch of salt as I know that the mechanical gauge works off a separate signal, all well on that front. That is, until today.
The car is still pretty much cold, I flash my eyes down to the dials and the oil pressure light has come on. I then swiftly realise that, for the first time, the dial gauge has also dropped off the map, no oil pressure!! I killed the engine pretty damn quickly, let it settle for a few seconds and then restarted. Immediate 70psi, no oil light, gingerly continued and was fine for the rest of the journey.
This evening I jump back in the car, maybe 2 minutes into the journey and it happens again. No oil pressure on gauge and warning light. Again, I kill the engine, restart and we once again have perfect oil pressure for the rest of the journey. The level is fine although I do have a fairly mean oil leak, which I suspected front cover but could be oil pressure switch? Would a leak from here trigger the oil light as I believe it is fed through there?
And how can the car intermittently and genuinely lose oil pressure? I can only imagine it could be the oil pump...? God forbid.
Car is a 4.2.
Oil light on and low-pressure means to me don't drive until resolved.
I'd put a mechanical gauge where the pressure sender is, remove fuel relay and crank engine to see if engine pressure builds and stays at pressure.
I'm new to cerbera but had the same issue on my chimaera 450, that was due to a stuck oil pressure relief valve, it would only increase in pressure when revving. I don't know if these cars have them.
If you've a mean oil leak then time to fix.
Certainly not worth the risk of starving it.
I'd put a mechanical gauge where the pressure sender is, remove fuel relay and crank engine to see if engine pressure builds and stays at pressure.
I'm new to cerbera but had the same issue on my chimaera 450, that was due to a stuck oil pressure relief valve, it would only increase in pressure when revving. I don't know if these cars have them.
If you've a mean oil leak then time to fix.
Certainly not worth the risk of starving it.
Anyone got any photos of an AJP8 sump? I'm led to believe there's more than one version too. I suspect a lack of baffles in an early version might cause of erratic oil pressure reads when cornering/braking abruptly. Location of the oil pickup within the sump would be interesting too.
When the oil pressure relief valve spring failed on my car this caused a progressive drop in oil pressure.
However it didn't recover by itself, except slightly after the engine cooled. This was because the spring fractured and ended up in several pieces.
When oil pressure is truly intermittent, the most likely cause is that the Auxillary Shaft Woordruff Key has failed, so the Oil Pump hub spins on the shaft (no pressure) until the key debris causes it to partially seize again (pressure returns).
This is the AJP8 Achilles Heel.
If you're very lucky something else is happening, but since both pressure switch and gauge confirm there is no oil pressure, and you have confirmed the the oil level is correct, that seems unlikely.
However it didn't recover by itself, except slightly after the engine cooled. This was because the spring fractured and ended up in several pieces.
When oil pressure is truly intermittent, the most likely cause is that the Auxillary Shaft Woordruff Key has failed, so the Oil Pump hub spins on the shaft (no pressure) until the key debris causes it to partially seize again (pressure returns).
This is the AJP8 Achilles Heel.
If you're very lucky something else is happening, but since both pressure switch and gauge confirm there is no oil pressure, and you have confirmed the the oil level is correct, that seems unlikely.
So maybe capillary tube bllock then?
Q: Does the shaft pass into the timing/front cover? Is the oil pump built into it?
If so changing that gasket and checking the gear gaps, woodrufs etc is an exercise well done.
My car overheated through faulty front cover gasket that led to the oil spring getting stuck.
Op this may be of interest
https://www.pistonheads.com/gassing/topic.asp?t=13...
Q: Does the shaft pass into the timing/front cover? Is the oil pump built into it?
If so changing that gasket and checking the gear gaps, woodrufs etc is an exercise well done.
My car overheated through faulty front cover gasket that led to the oil spring getting stuck.
Op this may be of interest
https://www.pistonheads.com/gassing/topic.asp?t=13...
Beyond the pressure relief valve, any work on the oil pump and its drive is an engine out job.
Mine sheared the end of the shaft off inside the drive sprocket within the timing cover, so there was no confusing issue of oil pressure coming and going, it was quite clear cut.
Good luck..
Mine sheared the end of the shaft off inside the drive sprocket within the timing cover, so there was no confusing issue of oil pressure coming and going, it was quite clear cut.
Good luck..
ukkid35 said:
When oil pressure is truly intermittent, the most likely cause is that the Auxillary Shaft Woordruff Key has failed, so the Oil Pump hub spins on the shaft (no pressure) until the key debris causes it to partially seize again (pressure returns).
I had two similar oil pressure drops as the OP. UKKIDs description was pretty much the cause of mine. Mine used to do it all the time when going round a fast left hand corner when the revs were low. When the revs were above 3k it would be fine going round a left hander.
Check the oil level, I had it have it on max, anything below and it would drop all the time. I don't know how accurate the dipstick markings are.
Check the oil level, I had it have it on max, anything below and it would drop all the time. I don't know how accurate the dipstick markings are.
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