Oil pressure release valve?
Discussion
Does anyone know about them? I noticed the other day that when the engine is cold there is plenty of oil pressure, also when the engine is hot and running at mid to high revs there is the usual amount of pressure, but as soon as the revs drop below 2-2.5k rpm the pressure just drops to nothing! From what I have read either my oil pressure release valve has got stuck open or the sender is knackered. What I was wondering is......do you normally have to replace the valve, just clean it or, as some people have suggested, replace the whole pump base?
The oil light doesn't come on either as the bloody bulb doesn't work, something else I've got to fix.
Any advice would be greatly appreciated.
Sorry, should have mentioned it's a 4ltr Pre-Cat engine.
>>> Edited by dougal on Tuesday 11th December 14:14
The oil light doesn't come on either as the bloody bulb doesn't work, something else I've got to fix.
Any advice would be greatly appreciated.
Sorry, should have mentioned it's a 4ltr Pre-Cat engine.
>>> Edited by dougal on Tuesday 11th December 14:14
If you are getting zero oil pressure... do not drive the engine and get it checked immediately. If you drive on zero pressure, there is a big big chance you will scrap the engine.
Check the obvious things like oil level. It could be the oil pressure valve but it caould also be a worn oil pump or engine. Hopefully it will be something simple like a duff sensor and the pressure is fine but until you know, assume the worst as getting this wrong is very very expensive. Like new engine expensive.
Steve
www.tvrbooks.co.uk
Check the obvious things like oil level. It could be the oil pressure valve but it caould also be a worn oil pump or engine. Hopefully it will be something simple like a duff sensor and the pressure is fine but until you know, assume the worst as getting this wrong is very very expensive. Like new engine expensive.
Steve
www.tvrbooks.co.uk
Thanks Steve, haven't dared touch it since I noticed. I don't think it is engine wear as it was absolutely fine on the way to see a friend (10 miles), but it started on the way back. I always look at the guages regularly during every journey. The oil level is on the button. Surely if the pump was worn it wouldn't have adequate pressure at all, or at least read lower?.....but I am treating it as worst case senario, just in case.
Just bought a copy of your book and read up on the priming of the pump etc. You don't happen to know if the Pressure rel valve is a standard Rover article or have TVR bunged a stronger/weaker spring in to change the pressure?
Just bought a copy of your book and read up on the priming of the pump etc. You don't happen to know if the Pressure rel valve is a standard Rover article or have TVR bunged a stronger/weaker spring in to change the pressure?
There are many many different types of oil pressure valve and spring so can't tell you which one is fitted. Take it out and match it or get one from a TVR dealer. They are not expensive IIRC.
Steve
www.tvrbooks.co.uk
Steve
www.tvrbooks.co.uk
quote:
I got the same problem with my 500. When the engine is hot the oil pressure drops to just above zero on tickover and is up to 30psi as soon as the engine speed picks up. Been like it for a few thousand miles now and everything still seems fine....
Have you looked inside the engine to see how much wear is being caused by non-existent oil pressure? A new engine is 5-7000 pnds so I think checking it out is prudent. I know of several TVR engines that have died prematurely due to low oil pressure being ignored.
In parctice it is normally a sensor issue and everything is fine but you don't know until it is checked. I would not risk it. But it is your car and upto you.
Steve
www.tvrbooks.co.uk
quote:
Thanks Steve, haven't dared touch it since I noticed. I don't think it is engine wear as it was absolutely fine on the way to see a friend (10 miles), but it started on the way back. I always look at the guages regularly during every journey. The oil level is on the button. Surely if the pump was worn it wouldn't have adequate pressure at all, or at least read lower?...
I was down at Tower View when they were sorting out a similar problem and the vanes on the oil pump were in pretty bad shape and could not maintain pressure. Typically the pump is capable of higher pressure nut the oil pressure relief valve controls the pressure. If the pump is worn, the valve does nothing and the pressure is purely dependent on how good or worn the pump is. If the Oil pressure valve is jammed open I suspect it would not be reaching 30 lb pressure at all but it could just be sticking. Until it is checked you just don't know...
Steve
www.tvrbooks.co.uk
'they all do this don't they ?' - I thought low oil pressure at idle was a characteristic of the Buick/Rover v8. My 4.0 (when warm) just registers at idle, and immediatley picks up to middle of the dial if you raise the revs a bit (either stationary or moving). Sounds smooth/quiet (under bonnet) and runs well. Dealer specifically warned me re this, not to be alarmed. No major trouble in 15 months/12K miles, just a dead starter motor.
Modified motor in my MGB V8 has mechanical gauge, I guess nice modern TVR's have electric gauge ??
Anyway, engine is pre-SDI 3.5 block, oil cold = 42psi, hot oil = 25psi. I don't know the spec of pump and relief assembly but suspect more or less standard.
Previous correspondant is quite correct, 'High volume, low pressure' system. RPI's web site has plenty of advice on oil pressure problems, their web address is in the "oily pages"
Anyway, engine is pre-SDI 3.5 block, oil cold = 42psi, hot oil = 25psi. I don't know the spec of pump and relief assembly but suspect more or less standard.
Previous correspondant is quite correct, 'High volume, low pressure' system. RPI's web site has plenty of advice on oil pressure problems, their web address is in the "oily pages"
On my V8S the oil pressure guage sits at about 25-30psi almost all the time (it creeps up under hard acceleration). However when everything gets really hot after a long run, or a long time crawling through town traffic, the needle drops to about 10-15psi at idle. If I squeeze the throttle to get the revs up to 1000rpm then it jumps back to 25-30psi (doesn't the bible give the pressure at a specific rpm?). I've had the car for 4 years, but when it first happened I was straight on the phone to Fernhust who said it was perfectly normal. I mentioned it before the first service and they replaced the pressure relief valve but this has never made a difference, so I haven't mentioned it since. After four years and 20,000 miles I had almost stopped worrying about it - until now!
Similar story on my V8S too. On start up the pressure is about 35-40 psi, but can drop when oil is hot and engine idling to about 10ish psi. Rang up RPI who said oil pressure for a rover v8 should be 27 psi at 2000rpm which is about what mine reads. Interestingly they suggested considering an oil cooler as Tivs they said have a reputation for getting hotter than most under the bonnet, anyone any thoughts? At the risk of stating the obvious choice of oil is going to affect oil pressures...20W50 is what they recommend, I have 15W40 in at the mo but will try the thicker stuff next time.
There are a few other sort of related threads going on this topic now. For info I checked out my copy of the "Leyland student training notes" for the MGB GT V8, dated 1973 (found it again whilest having a sort out at home.......). It states oil pressure should be 42psi cold 32psi hot, but doesn't state the rpm. Choice of oil is an interesting one, as brand/viscosity makes one hell of a difference to pressure and temperature. Off thread a little, but see this quote from Keith Calver, tech expert of Minispares : -
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Use good quality oil. Valvoline 20/50 Racing mineral oil is very good in Minis at a very reasonable price. Torco 20/50 mineral oil is exceptional, 5/50 synthetic better, 20/50 absolutely brilliant - but all a bit more expensive. Most established brand named multi-grade oils are OK. Torco’s whole range of oils are the best at heat transfer I’ve ever come across, Red Line a close second but they only do full synthetic racing oils so are relatively expensive. Mobil 1 was the first real fully synthetic oil, but I've always found it poor at carrying heat away from major components (like crank and cam). I've had the same reports from other users in various fields of motorsport used in a wide variety of engines. Simply going from Mobil 1 that I used for a couple of years, necessitating a very large oil cooler to be used, to Torco 5/50 I saw such a huge drop in oil temperature I could run with NO cooler, and still had 10 degrees better temperature. And that was in a 1430cc, 150bhp, LSD equipped tarmac racer!
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For the full article see www.calverscorner.com ->engine ->lubrication - temperature critical.
The training notes say 20/50 is the thing, modern oils developed for new engines are generally thinner, the stuff developed for Ford Zetec for example is 5/40. This is way too thin for old-tech engines, like Rover V8 and A-series, unless in severe cold climates.
I use Silkoline Pro-4 (which is actually a bike oil) in my Mini, it's fully synth at 15/50 and is fine. The MGV8 is currently on regular Castrol GTX 15/50.
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Use good quality oil. Valvoline 20/50 Racing mineral oil is very good in Minis at a very reasonable price. Torco 20/50 mineral oil is exceptional, 5/50 synthetic better, 20/50 absolutely brilliant - but all a bit more expensive. Most established brand named multi-grade oils are OK. Torco’s whole range of oils are the best at heat transfer I’ve ever come across, Red Line a close second but they only do full synthetic racing oils so are relatively expensive. Mobil 1 was the first real fully synthetic oil, but I've always found it poor at carrying heat away from major components (like crank and cam). I've had the same reports from other users in various fields of motorsport used in a wide variety of engines. Simply going from Mobil 1 that I used for a couple of years, necessitating a very large oil cooler to be used, to Torco 5/50 I saw such a huge drop in oil temperature I could run with NO cooler, and still had 10 degrees better temperature. And that was in a 1430cc, 150bhp, LSD equipped tarmac racer!
--------------------------------------------------------------------
For the full article see www.calverscorner.com ->engine ->lubrication - temperature critical.
The training notes say 20/50 is the thing, modern oils developed for new engines are generally thinner, the stuff developed for Ford Zetec for example is 5/40. This is way too thin for old-tech engines, like Rover V8 and A-series, unless in severe cold climates.
I use Silkoline Pro-4 (which is actually a bike oil) in my Mini, it's fully synth at 15/50 and is fine. The MGV8 is currently on regular Castrol GTX 15/50.
I had the exact same problem with mine 30lbs cold and would drop to between 5 and 10 when hot at tick over, but a blip of throttle back up to 30. well I decided to rebuild the bottom end. on the way to the workshop I got stuck in traffic and the temp of the car went up and up, the oil pressure fell to zero.
on dismantleing, I found that the bearings had all worn to the copper, but evenly and withoud causing damage to the crank.
The cause of the problem must have had something to do with the fact that I had lost 3 lobes off the camshaft!
engine rebuilt and runs on Castrol RS now, constant 45lbs, and sometimes pops up to 55 when cold. so there is your answer, I think that I would blame the mobil One, I personaly think that it is shite!
Paul.
on dismantleing, I found that the bearings had all worn to the copper, but evenly and withoud causing damage to the crank.
The cause of the problem must have had something to do with the fact that I had lost 3 lobes off the camshaft!
engine rebuilt and runs on Castrol RS now, constant 45lbs, and sometimes pops up to 55 when cold. so there is your answer, I think that I would blame the mobil One, I personaly think that it is shite!
Paul.
. The other valve is in the oil cooler if you have one... 
Thanks for all the help chaps, just thought I'd let you know, checked the release valve and it was fine, so changed the pressure sender and hey presto, loads of pressure on tickover! So it was OK all along. Also changed the oil pressure warning LED as it had stopped working, have the part numbers if anyone needs them.
quote:
If you are getting zero oil pressure... do not drive the engine and get it checked immediately. If you drive on zero pressure, there is a big big chance you will scrap the engine.
Check the obvious things like oil level. It could be the oil pressure valve but it caould also be a worn oil pump or engine. Hopefully it will be something simple like a duff sensor and the pressure is fine but until you know, assume the worst as getting this wrong is very very expensive. Like new engine expensive.
Steve
www.tvrbooks.co.uk
Mine had exactly the same condition! I changed to Castrol RS and the pressure upped 10Lbs on tick over, but the true cause of the low pressure was a couple of badly worn lobes on the Cam!
change the oil and see how you do, if no real improvement get the sender looked at, if OK look inside the Engine.
change the oil and see how you do, if no real improvement get the sender looked at, if OK look inside the Engine.
You could also try an uprated relief valve spring; Rimmer Bros. amongst others can supply for a couple of quid.
I just rebuilt my V8 and fitted an uprated spring; claimed to give another 10 psi of oil pressure. I get 3 Bar (45psi-ish) cold at idle and about 2.8 Bar hot, above 1800RPM. To be fair, I haven't tried refitting the original spring to see how much it drops by, but what the hell!
W.
I just rebuilt my V8 and fitted an uprated spring; claimed to give another 10 psi of oil pressure. I get 3 Bar (45psi-ish) cold at idle and about 2.8 Bar hot, above 1800RPM. To be fair, I haven't tried refitting the original spring to see how much it drops by, but what the hell!
W.
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