Low Oil Pressure

[zcacogp]

Sounds more extreme than mine, but if I drive hard on a hot day I can see the oil pressure drop down to 1 bar at idle. Manual says anything above 0.5 bar is OK. What oil are you running? Oli. ETA: Are you sure it is genuinely low pressure rather than a faulty gauge/sender? If so, how?

 

[Hairyarse]

Just as I arrived at my destination in the car today (only about 15 mins drive) I noticed my cruise oil pressure had dropped to about 2.5-3 (usually about 4.5 from memory.) When I pulled up the oil pressure dropped right down on engine idling and the red oil warning light came on.

This has happened on the way back too (started return journey with cold engine) It seems to be after about 10-15 mins of driving (once engine is hot I guess.) My oil level is ok, there's no mayo anywhere and no oil leaks and I'm not using any oil either.

Texting with Rob Wright today so far we've identified possible causes as oil pressure relief valve o-ring (I have one but not fitted yet, as pressure gauge used to flick up and down a little so thought this might fix it) OPRV itself and crank pulley bolt.

Has anyone else had similar and know a potential cause/solution? The engine is running sweet as a nut with no strange noises or anything unusual happening other than the pressure dropping on the gauge and showing the red light as mentioned.

Any help appreciated.

Regards
Andy

 

[pse_SC]

...hot day I can see the oil pressure drop down to 1 bar at idle. Manual says anything above 0.5 bar is OK.

I would suggest it’s the heat - they can run pretty low and still be OK. It’s probably had a shock (like everyone else at the moment), in that there is actually some heat in the air.[]

 

[edh]

Sounds unusual after just 15 mins of driving - should be ~4bar @ 4k rpm OPRV is a very expensive part - nearly £300! I have just swapped mine for the opposite reason as it appeared to have stuck shut twice at Bedford, causing a lovely oil slick.

 

[edh]

The gauge on my turbo used to drop slightly when on boost - after testing with a separate sensor and gauge, we decided that it was actually a dash wiring fault, so as the boost gauge rose, it affected the oil pressure gauge. The OPRV is supposed not to be rebuildable, although not sure why. I've kept my old one in case anyone ever decides that they are...

 

[tref]

Sounds exactly like the symptoms of a loose crankshaft pulley bolt to me, and right kind of figures for it too, but that doesn't mean it couldn't be anything else!

 

[DC911SC]

this is a must read: [link=http://forums.pelicanparts.com/porsche-924-944-968-technical-forum/757457-months-repair-few-weeks-problem-free-now-low-oil-pressure-ugh.html]pelican low oil pres[/link] long story short my money is oprv either seal or something blocking it! also if your lifters sound a little rattley at idle it rules out any sender fault - do they?

 

[Hairyarse]

Thanks for all of the thoughts chaps! [8D] Oil is 10W/40 semi-synth from memory. There is no rattles or any other unusual noises. I'd be surprised if it's a weather/temp issue I think. I've not had similar on hot days before and this morning I only drove for 15 minutes and it was warm but still cooler than other hot afternoons I've driven in. I've been around to Rob's and borrowed a flywheel lock - I'll check the pulley bolt in the morning plus he happens to have a spare OPRV (it may not be the same as mine) to swap over and try if it's not the crank pulley bolt. I already have the O-ring for the OPRV so that's good! Well it looks like the MK1 Golf wont get a look-in tomorrow, will investigate the 944 and update [] Thanks again Andy

 

[chrisg]

Good luck with the Flywheel lock...... BTW it could actually just be a duff sender unit, this happened to me and a quick swap out fixed it ! I think Rob is doing whats called sub contracting....

 

[Frenchy]

If it was the crank pulley bolt you would have the same readings from start up i would have thought as the tapered drive would not be engaging hot or cold with a loose crank bolt, i would have a guess at wiring, does the gauge show low and the light come on together ? Oil pressure sender ?

 

[Hairyarse]

ORIGINAL: chrisg Good luck with the Flywheel lock...... BTW it could actually just be a duff sender unit, this happened to me and a quick swap out fixed it ! I think Rob is doing whats called sub contracting....

Sorry Chris - I did mean to say some thanks to you - Rob did say it was yours - I hope you don't mind the subcontracting, it will be taken care of [] Ref the sender, I thought if this fails then the gauge reads 5 bar all of the time? The oil pressure light only comes on when symptoms have started and the car is at idle, otherwise when driving the pressure is lower than usual - 2.5-3 bar but the light does not come on

 

[robwright]

Guys the pressure sender has two functions. It is a variable resistor to indicate actual pressure on the gauge and also a switch to indicate low oil pressure. They will normally fail high. Besides it is probably as easy if not easier to change the OPRV seal and hence check it at the same time as it is to change the sensor. At least by doing simple and let's face relatively low cost or even free checks first like the o ring and the crank pulley he can eliminate all of these things before he needs to shell out any real cash, or perhaps even find the problem. If the crank pulley bolt was loose and not completely undone as in your case Frenchy it could feasibly be slipping and still provide some but not maximum drive to the oil pump. It could feasibly rise but still read low.

 

[Frenchy]

Keep us posted on your findings Rob, hopefully something simple, usually is (fingers crossed)

 

[Hairyarse]

Well I just thought I'd try the theory about the weather. I sat on the drive, turned the engine on and let it get up to temp. Then sat idling for about 10 minutes. Oil pressure started at 3 bar then eventually started to drop to 2 bar, then a bit lower. Then the needle would intermittently flicker up and down between 1 and 2, sometimes lower and the red low pressure light flickered on so I turned off. It's still warm out, but not that warm. Oh and I checked I use 15w/40 not 10w/40 oil! Will be trying crank pulley bolt then OPRV first thing in the morning then!

 

[Hairyarse]

Well a bit of an update so far. The crank bolt wasn't finger loose at least, it seems tight but I will check the torque on it just to be sure. I removed the OPRV and it's the old 3-piece type.

Worryingly when I went to undo it I didn't need any force - I couldn't unscrew it with my fingers at any point when trying to take it out but I needed very little force applied to the ratchet so maybe it wasn't tight enough in the first place? It wasn't leaking any oil out though. I'm going to turn the eninge over with the valve out to check oil is coming out, re-insert it, check the crank pulley bolt then run the engine again to see if it's cured. Maybe the OPRV has just had it, I've read that the springs can go weak over time

 

[pse_SC]

Worryingly when I went to undo it I didn't need any force - I couldn't unscrew it with my fingers at any point when trying to take it out but I needed very little force applied to the ratchet so maybe it wasn't tight enough in the first place?

It shouldn’t need any force - doesn’t need to be ridiculously tight. It’s similar to when people do up the filler and drain plugs on gearboxes, often silly tight (and the next time they can’t undo them).

 

[Hairyarse]

No it really was not tight at all, I re-tightened to 45NM and it wasn't that tight to undo. Anyway, after about 8+ hours stuck under the car, I don't feel any further forward [] Here's the update of what I've done since the last post this morning; 1. Turned the engine over by hand with OPRV out, no oil came out the hole. 2. Put OPRV back in and turned engine over with coil lead and DME removed, no oil pressure 3. Removed oil filter and primed the oil pump (Poured oil in filter housing and turned engine over by hand backwards.) 4. Fitted new oil filter 5. Locked flywheel and checked crank pulley bolt. Torque was ok at 210NM I then started the engine and it fired up ok, instantly went to about 3.5 bar oil pressure. Prior to starting with ignition on, oil pressure showed 0 and oil light was on. Then I left to idle and after engine was warm, about 10 minutes later oil pressure started to drop - same symptoms as yesterday. I'm not sure if this helps diagnose anything but I took one wire off the oil pressure switch, with ignition on it still showed 0 and red light on. Then removed the other wire and with ignition on it reads 5 bar. I took this to mean that switch is ok, but then I guess that may not be so as there's no switch connected to the circuit at that point. So after a long day under the car I guess I've at least checked some things but no solution still. My next plan is to change pressure switch, if that does nothing then change OPRV. Elliot, I'll be PM-ing you in a mo!!

 

[zcacogp]

Andy, Two thoughts; 1. Is it possible for the oil pump to fail in such a way as it is not pumping efficiently and hence is not producing the pressure in the first place? (This may be a stupid question, in which case I apologise!) 2. Do you happen to have the dimensions for the OPRV seal? Mine leaks and I don't know what size washer to replace it with. Oli.

 

[Hairyarse]

Hi Oli Ref 1, I hope not as really don't want to have to be doing that! I'm guessing though if the oil pump fails, it just goes completely so I'd have no pressure at all. The engine still runs as good as ever and no strange performance or noises - I'm hoping it may be the sender although it's not usual symptoms for that. Ref 2, mine doesn't have a seal - it's the early 3-piece one which doesn't have a seal. The later one has an O-ring which is approx. 10mm dia. I'd guess. You can get them from OPC still, I think it was only pennies? Cheers Andy

 

[Hairyarse]

Well I'm very surprised but very chuffed tonight! Picked up a replacement sender today (cheers Elliot []) and problem solved!! Really wasn't expecting that but so pleased I don't have to take the sump off or anything daft like that! Happy days! [] Thanks again for everyone's help []