Low oil presure after driving for a while

Hay guys I fitted my new oil presure gauge its a 5 bar..starts at 2.5 on gauge but took it to dubbed out camp out today and on the way when I slow down or stop its dropping to 1 or even 0.5 or less and light is coming on ( light never came on before with old sensors but I believe the new one are more sensitive) when I speed up again to lol 40 or 50 it goes back upto 2 ish... so I belive it could be a bad oil pump ot any other ideas...carnt be the wiring or gauge sensor ect as it does work on start up and I believe if the oil pump is bad engine gets to hot and oil presure drops could be the timing ...also got much do you think a mechanic would charge to fit a new oil pump any help appreciated...

 

What grade of oil are you using?

 

Nothing has changed by fitting a gauge and I doubt if there is anything wrong, increase the idle revs if the oil light concerns you.

 

Sounds fine to me. 0.5bar at hot idle isn't fantastic, but is ok. The pressure switch on the dual terminal senders does operate at a higher pressure, so a false alarm.

Nothing wrong with the oil pump. A careworn engine will slowly develop lower oil pressure.

 

The VDO pressure sensor oil light terminal comes on at a higher pressure than stock hence you're likely to see the dash light come on more often. If you tee in the original oil light switch and use that instead, all your worries will go away.

 

Thanks for the reply so my original switch would connect to the tee piece above and the original wire to the old switch/sensor ..then the new sensor would just have the presure wire attached ...thanks for the reply

 

Hay guys thank for reply really appreciated ..yer so if i increase the revs at the foot pedal when stopped then the presure increases so I will increase the revs at idle thanks I will let you know how it goes

 

Castrol 15 40

 

The other way of looking at this is that the VW oil pressure light comes on to confirm what you suspect from the horrible noises you hear behind you. It's too late for a refresh type rebuild. The higher psi one on the dual sender, paired with an actual pressure gauge should potentially (depends on operator) save your engine from getting that bad?

Increasing idle revs is a good idea if they are low. Stay below 1,000rpm though.

Fitting a lower psi pressure switch to stop the low pressure light coming on doesn't sound sensible when I say it out loud. Like burying your head in the sand?

You could (I would) try 20w50 oil and the idle speed increase. I would also be thinking about refreshing my bearings and rings etc. This is ideal time to cheaply renew an engine. No immediate rush from the sounds of it, but I'd do it before you're in for piles of parts and machining. It's actually enjoyable when things are still around spec, just worn.

 

For reference, Bentley says the oil pressure for SAE30 oil at 70 degrees C and 2500 rpm should be 3 bar on a new type 4 engine, with a wear limit down to 2 bar. The oil light should open between 0.15 and 0.45 bar. I think the oil light sensor on the VDO unit opens at around 1.25 bar.

 

Thanks buddy

 

..driving my bus at 60ish (100kph) in 4th gear oil temp at 90ish engine at around 3000rpm the oil presure shows at 3bar..got these numbers for years..

 

Unfortunately I work in the normal world of UK psi units ...
My contribution would be to say that with the original VW sender the oil light comes on at around 3psi whilst the VDO unit starts to flash at 8psi . VW in their service notes say to expect a bit of flashing action on tick over after a long hard run ...
I'd certainly suggest trying 20/50 which is a thicker oil before getting too wound up about an impending disaster.

Sent from my SM-G960F using Tapatalk

 

Here is some comparison for you. My engine has only covered 15K miles or so and numbers have not changed over that time. The oil pump is the original pre-loved one.

2.5 bar = 36 psi - cold start. Mine would be exactly double that.
2 bar = 29 psi - warmed up properly. Like Arek, 3 bar = 43psi. Book says 42 psi, mine is 45 psi.
0.5 bar = 7.25 psi. Warm/hot idle. You say "or less". Mine is never below 20 psi = 1.4 bar.

The running warmed up at 2-3000rpm 42 psi is the only hint VW give for a type-4. The oil pressure relief spring/piston setup is designed to bleed off above that psi, so that's really where it should sit once you're going along as it were. 29psi is fine for now, just a sign but worth bearing in mind you have used up all the "extra" designed pressure that Arek and I are bleeding off. What would maybe concern me (I'm a stitch in time type of person) would be the possibility of the 10-13 psi loss all being at one big end and knowing how that ends up... Blimey, I sound like Mike!

 

Thanks is there any down side to using the thicker oil

 

I know you were asking Lasty but...
As a fellow type-4 engine owner - no downside. In fact, the fella that built mine and learned his trade at a big VW dealership back in the 70's insisted VW recommended, to the dealerships, to use 20W50 in type-4 engines from new. He brow beat me into putting it in mine and it was fine. I just like the thinner stuff, it seems to spin a bit easier on the starter in the winter!

 

I was made to use 20W/50 oil on a brand new engine (apart from crank & conrods) in 2018 because it was a condition of the warranty.

The engine may run hotter with 20W/50 but if it's getting worn it may not be an issue, I used to drive my first engine at 122 degrees C oil with an engine that lasted me 27000 miles while having 4psi hot idle/ 35psi hot running..

I would consider a scheduled rebuild over the next year rather than a rapid unscheduled disassembly in the next few years..

If the endfloat is reasonable keep going.

 

I had overheating and very odd oil pressure issues which I won't bore you with but learned from it , if 10/40 is getting hot and therefore thin I tried 20/50 which stayed cooler and therefore thicker for longer . I ran a 50-50 mix of the two for a while which ran much better than either so work that one out !
Others will have a different take on things as no two engines are the same but playing around with the oil viscosity gave me a good idea of how it affects the pressure and temperature.
N.B. No expensive oils were damaged in the making of this experiment....

Sent from my SM-G960F using Tapatalk

 

Would that 50/50 mix make it 15w45 oil then?

 

Really dunno but it works on mine

Sent from my SM-G960F using Tapatalk