Another oil pressure thread, this time ZEROpsi :O
Discussion
Please help...
Already searched all previous threads, but am so concerned, i want to start a thread of my own!
This evening on the short journey back from the station i noticed whilst stopped at some traffic lights the oil pressure warning light flickering. Looked towards the gauge and was shocked to see 0 psi!!! Had never done this before.
Pulled away and pressure rose. Reached about 15psi at 2000rpm and 30 at 3k (10psi per 1000rpm thereafter), and the light went out. These readings are normal for my car/gauge. When i next came to a stop, pressure went back to zero. (normally reads about 7psi at idle/900rpm)
Once home, topped up oil - it was halfway between min and max. Started engine, 7psi, gave throttle a blip, 30psi then back to 7, a bigger blip followed, 60 psi then fell to 0. Engine sounded fine and felt as smooth as always, so went for a quick drive round the block.
Pressure readings appeared normal apart from at idle, when gauge showed 0psi and warning light came on.
I know i need to check the sender and connections. i recently had a coolant hose burst which poured dirty coolant all over the engine, so it could be contaminated.
Also, i'm using Castrol RS 0/40W, so it could just be the (thin) oil getting thin when hot, which from previous threads seems to be a fairly common problem. Note that the oil has not recently been changed, so i can rule out a faulty pump (hopefully!). Might replace with thicker stuff.
I will also check the pressure release valve - i pressume i dont have to remove the oil pump?
Finally, it was asked in a previous thread if their engine was knocking. I have to say that my 4.0 pre-serp engine is incredibly smooth from 1500rpm and sounds smooth too, but at idle, it has an intermitant knock/vibration (though idle itself is fairly steady). Sometimes, it wont occur at all, but on other journies i can feel a fairly harsh knocking/vibration from the engine, through the floor and steering wheel - but it is only at idle and only every now and then. What is this and of what relevance to the oil pressure is it I am assuming it could be related since it was asked in another thread.
Cheers for your help in advance. I'm off to check my bank balance, just in case!
Already searched all previous threads, but am so concerned, i want to start a thread of my own!
This evening on the short journey back from the station i noticed whilst stopped at some traffic lights the oil pressure warning light flickering. Looked towards the gauge and was shocked to see 0 psi!!! Had never done this before.
Pulled away and pressure rose. Reached about 15psi at 2000rpm and 30 at 3k (10psi per 1000rpm thereafter), and the light went out. These readings are normal for my car/gauge. When i next came to a stop, pressure went back to zero. (normally reads about 7psi at idle/900rpm)
Once home, topped up oil - it was halfway between min and max. Started engine, 7psi, gave throttle a blip, 30psi then back to 7, a bigger blip followed, 60 psi then fell to 0. Engine sounded fine and felt as smooth as always, so went for a quick drive round the block.
Pressure readings appeared normal apart from at idle, when gauge showed 0psi and warning light came on.
I know i need to check the sender and connections. i recently had a coolant hose burst which poured dirty coolant all over the engine, so it could be contaminated.
Also, i'm using Castrol RS 0/40W, so it could just be the (thin) oil getting thin when hot, which from previous threads seems to be a fairly common problem. Note that the oil has not recently been changed, so i can rule out a faulty pump (hopefully!). Might replace with thicker stuff.
I will also check the pressure release valve - i pressume i dont have to remove the oil pump?
Finally, it was asked in a previous thread if their engine was knocking. I have to say that my 4.0 pre-serp engine is incredibly smooth from 1500rpm and sounds smooth too, but at idle, it has an intermitant knock/vibration (though idle itself is fairly steady). Sometimes, it wont occur at all, but on other journies i can feel a fairly harsh knocking/vibration from the engine, through the floor and steering wheel - but it is only at idle and only every now and then. What is this and of what relevance to the oil pressure is it I am assuming it could be related since it was asked in another thread.
Cheers for your help in advance. I'm off to check my bank balance, just in case!
definately agree, these modern super-low viscosity oils (around which modern engines are designed with a view to low oil drag and improved fuel economy)don't suit the rover engine, especially with the earlier 'dizzy' driven gear pump. Mobil 1 motorsport 15/50 (as opposed to the ordinary Mobil 1 which i think is 5w/ 40 or something) is much nearer the old 20w/50 (Castrol GTX -70's vintage, etc) which was the recommended spec' when the engine entered service. Has the oil filter been changed recently (can have very short life if lots of short journeys and engine never warming through, leading to rapid waxing up of the element and blockage). Sender units can go mad, but that doesn't explain the warning light coming on, which tends to be more reliable. If none of the above helps it needs checking out asap.
I fear the worse. Although changing the oil to 15/50 (or even 20/50 mineral oil) may improve matters it won't stop the knocking. You may have imminent main bearing failure - the knocking could be the crank - does the sound (knock) stop if you put your foot on the clutch? Does the sound change at all?
By all means change oil AND FILTER. Then get it to a garage for professional advise before the oil police catch you!
By all means change oil AND FILTER. Then get it to a garage for professional advise before the oil police catch you!
hi jsr, first to agree with other comments re oil, these engines were designed in the 60s (or earlier?) when "oil" meant mineral 20w50. The independant i use reccomend a 10w40, which I suspect is the thinnest which should be used.
Second the pressure reading, mine got very erratic but said independant had seen it all before and screwed their accurate meter straight into the block to test it, all was fine and a new sender unit later my blood pressure was back to normal. I certainly wouldnt start changing oil pump springs until you have had a simple pressure check by someone with an accurate gauge.
All IMHO, but hope this helps, dean
Second the pressure reading, mine got very erratic but said independant had seen it all before and screwed their accurate meter straight into the block to test it, all was fine and a new sender unit later my blood pressure was back to normal. I certainly wouldnt start changing oil pump springs until you have had a simple pressure check by someone with an accurate gauge.
All IMHO, but hope this helps, dean
The oil pressure switch and the oil pressure gauge are independant of each other and both are telling you that you have very low oil pressure. I would believe them and get professional help PDQ.
I think the usual advice is do not even start the engine as you are liable to be doing more damage to the engine which will be pushing the re-building bill upwards.
Always best to err on the side of caution.
Nick
I think the usual advice is do not even start the engine as you are liable to be doing more damage to the engine which will be pushing the re-building bill upwards.
Always best to err on the side of caution.
Nick
Zero oil pressure means stop the car and don't even think about starting the engine. Quite possible to scrap the engine in a few minutes. Just driving it a mile or so can kill the engine.
As to why... oil pump is a possibility. Too thin an oil is a red herring as even with a 0W30 you will get oil pressure even when hot. Could be the pressure relief spring but also the pump itself.
Big sections on this in the bible including pictures of worn oil pump gears.
Steve
www.tvrbooks.co.uk
As to why... oil pump is a possibility. Too thin an oil is a red herring as even with a 0W30 you will get oil pressure even when hot. Could be the pressure relief spring but also the pump itself.
Big sections on this in the bible including pictures of worn oil pump gears.
Steve
www.tvrbooks.co.uk
Read the section in the bible mk 2 (excellent book Steve!) - will check the pump and PR valve tonight.
Thanks for all your responses. I am fearing the worst though, mainly due to the occassional knocking. And the fact that the pressure has always been fine, but suddenly lost pressure yesterday.
Thanks for all your responses. I am fearing the worst though, mainly due to the occassional knocking. And the fact that the pressure has always been fine, but suddenly lost pressure yesterday.
When both the oil pressure gauge and the oil warning light indicate a problem - there is a problem! Especially considering that most oil warning light switches operate at around 5 psi - which means if the engine is running when the light actually comes on, the engine is already f**ked!
I suspect that the bearings were wrecked when you had the coolant leak, leading to massive localised over-heating, over heated oil and metal to metal contact within the bearings. The oil (pressure) maintains the clearance within the bearing.
If you are lucky you might be able to replace the bearing shells in situ. But if the bearing surfaces (big ends and little ends) have any sort of scarring on them it will be an engine out repair.
I suspect that the bearings were wrecked when you had the coolant leak, leading to massive localised over-heating, over heated oil and metal to metal contact within the bearings. The oil (pressure) maintains the clearance within the bearing.
If you are lucky you might be able to replace the bearing shells in situ. But if the bearing surfaces (big ends and little ends) have any sort of scarring on them it will be an engine out repair.
My last Griff lost almost all pressure "just like that". The oil pick up pipe in the sump had fractured and was drawing up "some" oil but also air. The local V8 expert said its common,in fact i explained over the phone and he diagnosed. Vibration can cause the pipe to do just that, fracture. I was lucky as i drove carefully and got away with just rocker assys as they are on the very end of the oil supply. Thats my story.
If you're refering to the bearings due to the occassional knocking i mentioned, then i should point out that this knocking has been present on the car since purchase - i just put it down to a lumpy idle. More of a judder really than a knock - it's not result of the coolant loss 3 weeks ago.
Beginning to think the pump needs priming. Have been thrashing the car recently and cornering hard, and the oil was half way between min and max, so there could be an air lock. Afterall, it does produce pressure with more revs.
Beginning to think the pump needs priming. Have been thrashing the car recently and cornering hard, and the oil was half way between min and max, so there could be an air lock. Afterall, it does produce pressure with more revs.
Yes could be the switch or the bulb for the warning light. Should come on with ignition and go out just after firing up. Warning light switch is separate to the pressure sender and located on the oil pump housing / front cover (depending whether pre-serpentine or not). If its the bulb you will need to remove the dash top to get to the instruments. i have done this recently and have got it down to a fine art, can fit / re-fit the dash top in about 5-10 mins now without wrecking the trim. If you want tips, let me know and i can give you details, but i'll spare you all this now as it'll be a bit long winded. You could check the switch with a multimeter, should be closed circuit (to earth / body) with engine off and vice versa. To check the bulb and wiring just short the lead to the switch to earth with ignition on and bulb should illuminate. 
jsr what's the prognosis? We need to know!
Hope this mighht still be in time to be some help... Bearing in mind the concern that you may genuinely have had virtually ZERO oil pressure (i.e: warning light on, which would indicate a serious lubrication problem, you should really, as Steve pointed out, really not be starting the engine at all. However that doesnt help give a diagnosis since to find out anything further you'll either have to do the oil change etc and try it or else strip the engine to investigate. Suggestions: 1) drain the old oil into a bucket and leave to settle, decant the oil slowly and see what debris remains in the bottom, Any significant metallic swarf or particles indicate problems and better drop the sump and take a look at the bearings / oil pic-up / strip the pump etc. (a small amount of very fine metallic 'glitter' may be acceptable but no more). If this is ok then do the oil / filter change (change the filter quickly, having pre-filled it - as much as one can- with oil to prevent the pump from draining). Then, asap, once re-filled, crank the engine (having disconnected coil low tension lead and preferably fuel pump relay or fuse also and ideally with plugs removed - to give good rpm). Watch the warning light / gauge, if all ok should start developing enough pressure to extinguish light and start gauge reading within say 10 seconds. This way you will not be exposing the crank journals to the impact load of firing cylinders, which if a bearing is failing, could wreck the crank. This is the method I always use after major engine work or a rebuild ( and often after an oil change if there is any delay), so i know for sure oil is circulating before firing up. The oil pump shouldn't need priming unless left for quite a while drained, then provided there isnt a pump problem and so long as the gears are reasonably oily it will develop enough suction to pull oil up out of the sump promptly. Sorry to be so verbose...Gassing Station | Chimaera | Top of Page | What's New | My Stuff