Oil pressure variations
Discussion
Hi all,
Have read the many threads on 'oil pressure' and am still not sure which way to 'jump' - any comments gratefully received:
Have just had the car ('97 450) serviced where oil type was changed from MOBIL 0/50 to a 10/40. Couple of days later, at idle and around 90degrees temp., noticed the oil pressure drop through zero and hit the peg where the needle sits when the ignition is off, no oil pressure warning light though.
After initial panic, cutting the engine and then testing that the pressure warning light works I thought that the gauge was faulty. The gauge still comes up to higher pressures with revs but not as much as it used to.
Have checked / cleaned the connector to the sender - this is OK.
This may also be connected with something else that was worrying me a bit. Have noticed that the engine is noisy (big ends) on startup for approx. 1 second after a few days of non-use.
Any ideas chaps?
Cheers, Matt
Have read the many threads on 'oil pressure' and am still not sure which way to 'jump' - any comments gratefully received:
Have just had the car ('97 450) serviced where oil type was changed from MOBIL 0/50 to a 10/40. Couple of days later, at idle and around 90degrees temp., noticed the oil pressure drop through zero and hit the peg where the needle sits when the ignition is off, no oil pressure warning light though.
After initial panic, cutting the engine and then testing that the pressure warning light works I thought that the gauge was faulty. The gauge still comes up to higher pressures with revs but not as much as it used to.
Have checked / cleaned the connector to the sender - this is OK.
This may also be connected with something else that was worrying me a bit. Have noticed that the engine is noisy (big ends) on startup for approx. 1 second after a few days of non-use.
Any ideas chaps?
Cheers, Matt
it's sender/gauge related i would think, for it to do the same thing at idle AND at 90c. if pressure was really being lost like that i'd expect a BIG puddle, or a BIG cloud of smoke followed by a loud bang and the contents of your engine across your driveway.
look for a dicky connection, maybe hack the old connector off at the sender and stick on a new crimp.
don't panic yet.
look for a dicky connection, maybe hack the old connector off at the sender and stick on a new crimp.
don't panic yet.
chimtvr said:
get a new sender
Yup get a new sender.
Plus get some 15/50 oil in there - the initial tapping is your followers (cam followers - hydraulic ones) bleeding down from "thinner oil". It doesn't do any damage, but frustrating to hear at each switch-on.
It can also be the way some oil filters drain down after switch-off. Perhaps a change of filter make may stop the tapping if you also change to thicker viscosity oil.
Trev McM
Had a similar experience on mine. The gauge reads sensible figures under normal driving, but when in traffic when the water temps is up at 90 the pressure gauge drops off, not quite to the stop. I was initially very concerned but afer talking to Richard Thorpe (RT racing)and having him give the car a once over, I've been convinced that it is the gauge.
If the oil pressure is truly low the warning light would come on. Apparently this happens at around 8psi.
If the oil pressure is truly low the warning light would come on. Apparently this happens at around 8psi.
edward1 said:
I've been convinced that it is the gauge.
That doesn't sound like a gauge problem to me, sounds like the oil pressure is dropping off at idle when the oil is hot. Doesn't necessarily mean you have a problem, could be because you are using a thin grade oil, or the oil level is low (raising the oil temperature), or the pump is worn. Or it could be because the engine is worn.
Thinning oil when warm was my first conclusion.
Assuming that the oil pressure warning light is functioning as intended, and has never shown any sign of coming on with the engine running (thankfully). Would the likly scenario be a fault with the gauge/sender calibration or lack of it.
If as I have been informed the oil pressure warning would come on at 8psi and the gauge drops below 10psi down to around 5 then either the gauge must be reading wrong or the pressure can drop much lower before the warning light comes on?
Well it seemed logical to me.
Assuming that the oil pressure warning light is functioning as intended, and has never shown any sign of coming on with the engine running (thankfully). Would the likly scenario be a fault with the gauge/sender calibration or lack of it.
If as I have been informed the oil pressure warning would come on at 8psi and the gauge drops below 10psi down to around 5 then either the gauge must be reading wrong or the pressure can drop much lower before the warning light comes on?
Well it seemed logical to me.
I undertstand that I can test the wiring by shorting the connection on the sender unit to earth. This is supposed to make the gauge go to full scale.
Anyone tried this? Is it safe and won't blow the gauge up?
PS Can you believe how much those sender units are....55 pounds....sheeesh!
Cheers,
Matt
Anyone tried this? Is it safe and won't blow the gauge up?
PS Can you believe how much those sender units are....55 pounds....sheeesh!
Cheers,
Matt
Hi,
Thanks to all who contributed - thought you'd like to know the outcome....
I connected a mechanical-style pressure gauge in place of the sender unit and found 45psi at idle on start-up, falling to around 30psi at idle when warm, so looks very good.
So looks like the "change the sender unit" suggestions were correct.....thanks. This is a good way of proving your engine's oil pressure if you get your hands on a gauge (I borrowed one from a Land Rover garage).
Matt
Thanks to all who contributed - thought you'd like to know the outcome....
I connected a mechanical-style pressure gauge in place of the sender unit and found 45psi at idle on start-up, falling to around 30psi at idle when warm, so looks very good.
So looks like the "change the sender unit" suggestions were correct.....thanks. This is a good way of proving your engine's oil pressure if you get your hands on a gauge (I borrowed one from a Land Rover garage).
Matt
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