low oil pressure reading

[3.2_fordy]

The oil pressure instrument reading on my wifes 964 is reading very low

When the car is first started from cold, gauge reads about 4 bar, after taking the car for a short run I have a reading of between .5-1 bar sometimes the oil light comes on if its a warm day this all at tick over.

Had the car checked out by a independent he said it could be the sender unit after he had checked the pressure straight off the engine this was at 5000 rpm and read 6 bar+.

Just this min got back from the independent fitting the sender unit to the car, after the short run home found that there was still low pressure on the gauge after phoning him up he said it may be the instrument thats at fault

Not sure if he is right when the light is coming on as well
What should it read at tick over?
The pressure steadily rise`s with the revs right up to max reading but I`am still worrying so can someone please help

 

[oldtimer]

At 830 rpm tickover I think you should get 1bar at least when hot , increasing by 1 bar per 1000 rpm ie linear , the 3.2 engine should have similar characteristic...also the oil viscosity rating has an effect ,for example an 0-40 will give lower hot tickover pressure than a 15-40. I guess the reading and the warning light are probably working off the same sensor

 

[3.2_fordy]

Thanks Oldtimer/Maurice
For your comments, I think I will change the oil as you said maurice to 5-50 cannot harm .
My independent did say he thought the gauge was reading about 1 Bar lowTo rule out the pressure gauge has anyone got a spare one for sale or one that I can borrow will pay all p/p and insurance for said return of gauge

 

[Shaun Leahy]

Graham

I recently had similar problem, after coming off a track day: when engine was hot and the revs dropped for idling, the idle speed was approx 800rpm but oil pressure light came on. From then on it would go out when revved above 2000rpm for several seconds, then on again when stopping etc where idle revs were down to 800rpm and pressure dropped below 1 bar. Stayed like this for over a week, tryed reseting the DME by disconnecting the battery and spiritied driving but still, if the revs were too low, but it came back immedaialty. Presseu when starting and when revving high would go up and be OK and the oil temp was not a problem, so oil type was not relevant

Nobody was able to help and an independent specialist thought the revs were fine but it might need rebuild.

SOLUTION:
on further investigation, it was a small blockage in a pressure or pressure release valae in the oil system, prob caused by the high revs on track day and high pressure for a long time. I forget the actual name of valve now. After £300 spent, it is now back to normal and the guage goes up and down but always above 1 bar.

FWIW I use 15-50, apparently slightly thicker oil best for older engines (not had a rebuild).

 

[3.2_fordy]

Shaun
Had a good look at the manual that I have on cd, there is only one pressure relief valve and a safety release valve which looks a sod to do,
looking at the under side of the car the relief valve looks easy to do should only take about 10 min to change so have orded all the new parts for it, under £20 so fingers crossed
By the way on my quest to get the parts I spoke to two independents thay both said it could not be this in X number of years thay had not changed one, but when I look at the manual it should be the frist thing I should of changed, its constantly working all the time if it sticks open or is worn low pressure
Changed the oil to Mobil 1 15w50 only made a small change so will keep you in formed

 

[Shaun Leahy]

Graham

I hope this went well, let us know. The guys at GT-One spent several hours checking the preseure with a manual guageand on cheking out the sytem. I am sure this caused all the cost of the repair. I am surprised some guys claim never to have done it, only because my car went from under 1 bar at low revs back to full health now and over 1 bar always, just from cleaning up some valves in the oil pipes, (forgotten the paperwork with the precise valve names). I got the feeling they were between the themostat and the filter but that could just be where they instered the manaul guage as easiest to get to.

Your theory seems good as it is relatively easy and cheap thing to check first and your wife's car has same engine and oil system as my car which was cured.

Certainly I hope a rebuild is not called for. There seem to be varying views of the inevitability of this procedure for these cars and if you has a problem with the bearing s at the bottom end then a repiar might have to be justified as an increase in investment as Gordon Brown says

Shaun

 

[Guest]

On the 3,2, the pressure guage and the warning light do not operate from the same sensor.

The warning light's switch is a common failure on the 3,2 that causes the light to come on at idle, then at higher revs, and then (if ignored) it blows itself to bits with oil spraynig all over the place! (Contrary to rumour, it can be changed with little hassle.) The sender for the guage seems to be much more reliable and gives reassurance when the warning light comes on.

I do not know if the same applies to the 964.

Alistair

 

[3.2_fordy]

Shaun
It taken me 10 days to get the right spring from the OPC now I have the right one I
changed the pressure relief valve and spring, it looked a bit worn and the spring was 5mm shorter.
It`s put the start up pressure from cold up to 4.5 bar but after a long run at the weekend the pressure is still only 1 bar when warm (no oil light on this time )
Will have to look deeper in to this, will have to change the oil gauge to rule that out first if I can get one

 

[Shaun Leahy]

Graham

glad to hear problem is (prob) resolved. There is little info on low revs' oil pressure, apparently Porsche info ifs mostly for oil pressure at high revs. Your cold start pressure look s good at 4.5 bar and the new spring has upped the warm idleing oil pressure to where the oil lght is off, so I would be happy that the problem is now within Porsche's design limits. Seems you did the right thing in bypassing the independents you metioned to get the fix. Well done.