Thread: Chugging and Erratic Oil Pressures

Crikey, when do you get time to watch the road, LOL, I would try a new sender unit and work from there, Regards Frank.

wonder if when the oil gets dirty if it starts changing the pressures? it needs oil change pretty soon anyway so might do that first and if problem still there i'll try new sensor.

makes sense to change the two at same time though as i need to drain oil to do sensor. in which case i'll never know answer to my first question if the problem goes away.

Originally Posted by Fausto79

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makes sense to change the two at same time though as i need to drain oil to do sensor. in which case i'll never know answer to my first question if the problem goes away.

You shouldn't NEED to drain the oil to do the sensor, but it makes sense to change the sensor when you drop the oil.

FWIW: my Tdi basically has erratic oil pressure.
I don't really watch it like a hawk(so to speak), but the 1Gauge logs all the sensors connected.
oil temp and pressure are two that I've used.
I have logs to go by, and looking at the graph, oil pressure isn't steady.
It may stay steady for a few mins, but then spikes up and downwards more than remaining steady.
There is a correlation between load(on engine) and oil pressure too.
Using the MAP(manifold pressure) reading as my gauge for engine load, it's easy to see that when turbo pressure is peaking so does oil pressure too.
(ps. I'm not a rev head either, so I'm not referring to massive turbo pressure due to 4K revs!).
The peaking and dipping of the graph is subtle tho, I doubt that I'd notice it even if I did keep eyes on the gauges.
The only reason I see this (now) is due to your thread, and now me graphing my logged data.
It's hard for me to post a pic of the graph data tho as there is a technical issue between my 4K screen and the software used to make the graph.
Font's are tinier than teeny-weeny! .. close to impossible to read.
if you were curious as to my logged data, it'd be better for me to send you the csv log and a link to the software for you to view the log directly .. it'd make much more sense(to you) than if I posted a posted a pic of the graph.
But for sure, higher engine load = more oil pressure.

And I'd also probably change the oil pressure sender unit at the next oil change too.
Curious as to what brand/model oil pressure sender unit the Madman uses?
The 1Gauge uses the VDO 360.002 unit.

Hi,
my 300tdi oil pressure has also become more erratic--it is a VDO gauge and now sometimes goes to 80psi when started and stays for a while, then drops back to around 50psi as my normal reading when driving but has always gone down to about 10psi or even lower when at idle and hot. Once the gauge did not register at all. Motor was rebuilt about 100K kms ago and goes very well but the pressure readings do seem strange. Does anyone think it is just the sensor?

Originally Posted by alan48

.... Does anyone think it is just the sensor?

Possibilities would(or could) be:

sensor(or sender).

wiring and or connection to sender and or gauge.
has the wiring come through from engine bay to compartment via a bare unprotected hole drilled in the firewall and it's cut the wiring? ... etc.

gauge itself(??)
Whilst the gauge is unlikely to be the issue, we had a C1300 International back in the day which had an erratic temp gauge, and after much mucking about was finally diagnosed as "maybe the gauge is playing up"
Another gauge was temporarily connected and bingo!

ground connection of the sender. again, why it'd be something like that would be inexplicable. corrosion maybe .. who knows.
simple fix would be to remove and refit, hoping that the ground would be disturbed and then properly connected again in the process.

eg. I'm currently having on again off again issues with my auto temp sender(the LR one, not one of my own fitting).
The process is the trans temp warning light comes on, I remove the plug, it fixes itself and the process starts again.

i am aware of the correlation between engine load and pressure. the engine has always sat on 49-51 whilst under load or at cold idle.

on warm idle usually 25psi roughly. less with ac running.

the thing that scared me is that the madman is set to have the alarm at 80psi and lately its gone off a few times. never happened before. when under load it usually never went over 55psi. it seems to be at weird times when going round a corner and changing gear. which is why i thought sensor issue. when you think about it now, happened twice when i was turning left, changing gear. maybe as the sensor is on the right of engine oil get pushed up against it.

pretty far shot but who knows. id say the sensor hole is too small for any such pressure from gforces to have an effect.

PS, i have a VDO gauge. not sure exactly which, but has a range of 0-100psi i think.