Club 80-90 Forums

Oil Pressure and Temperature Question.
Had a recurrent buzzer of doom going off, so I temporarily earthed the signal from the dynamic oil pressure system and just relied on the red light.
I have now installed VDO gauge with a twin sensor added between the cylinder heads on LH side of engine.

The started specification value we should see is 2 BAR at 2000 RPM with an oil temp of 80 deg C, so having also installed the required VDO tachometer I'm just missing the oil temperature value. I have just done an oil change with 10W/40 Mineral Oil and a Mann filter as advice also stated to only use Mann or Mahle filters if you have a suspected low oil pressure. Engine has approx. 130,000 KM on the clock.

On start up with cold oil is see 3.5 to 4 Bar, but when the engine is warm with the coolant gauge just past the centre point on the gauge where it normally operates, I get about 1 Bar at tickover, which is quite high on my LPG vehicle at approx. 1500 rpm. I need to get to about 3000 rpm to see 2 bar. What is my likely oil temperature here at operating temperature, do I need to fit an oil temp gauge as well to see that I'm not operating at too low an oil pressure, and if I am, what is the resolution?

From the values I'm seeing, the buzzer of doom was going off correctly, but also that doesn't have an oil temperature input.

the oil temp makes quite a lot of difference, you could fit a temp gauge or you can just poke a thermocouple down the oil filler tube, you can buy thermocouples reasonably cheap some multimeters support them too. I was not happy poking it in witb engine running.

I got mine hot, switched it off, poked the thermocouple down tube, waited for it to fall to 80, removed thermocouple, then started and measured

for the buzzer to go you have to be under 0.9 bar for a few seconds and above 2000rpm, that is really low pressure even with stinking hot oil.

I use 20w/50 oil in the warmer months.
I find this keeps my pressure at 1.4 bar (20 psi) at 90 deg. C @ 850 rpm
It's then changed for the winter to 15w/40.
Cold starts see 4.5 bar @ 850 rpm and 4 bar at 3000 rpm (hot)

In my experience thinner oil caused my pressure light to flicker at 800 rpm., this thinner oil also reacted quicker to coolant temperature changes. During a long climb the oil pressure dropped alarmingly as the engine worked harder and gained heat.
I am sure this issue could have been resolved by fitting an oil cooler but a thicker oil was the cheaper option while I save up for it
In the US the hotter states use 20w50 in their Vanagons.

does your 2.1 on pierburg have the standard oil cooler/warmer Kev?

What would cause the buzzer to sound at exactly at 2200 RPM after a long run? It only buzzes at this RPM and will turn off when I accelerate above 2200 but if i let the van slowly drop below it remains on until I blip the throttle but If I am slowing down quickly it turns off. It is fine at constant speeds above and below. (2.1DJ on carb)

Buzzer only sounds above 2000 rpm, remember the circuits are old and probably never exact in the first place so 2200 it is ( or perhaps the rev counter us a bit in accurate too)
once above 2000 the pressure at the high pressure switch must be below 0.9bar ( assuming you have a grey switch) to trigger buzzer

If ypu test this by removing switch wire the buzzer does not come on for a few seconds so it won't buzz if you get a small duration low pressure.

once triggeredhow long it stays on for after pressure rises above 0.9 bar or revs fall below 2000 I don't know but it sounds like it's working correctly.

After a long run in summer yur oil temp could be up at 120 degC which makes it very thin and pressure drops.

Having said all this your engine is tired thats why it's happening, mine did this, I got a few more years with 2050 oil and an oil cooler, when I stripped it one cam bearing was disintegrating.

Thanks Itchy, That probably confirms what I was thinking.

itchyfeet wrote:does your 2.1 on pierburg have the standard oil cooler/warmer Kev?

Yes.

I might well be doing the wrong thing but I have used 20/50 mineral oil for a number of years since My oil light took to momentarily flickering when my engine got unbelievably hot and started faltering on tick over in a summer traffic jam. In the event the faltering "went away" * but I stuck with the 20/50 anyway. Before then I used to fit oil pressure gauges in all my vehicles but stopped doing it because I became obsessed with oil pressure at tick over.
CS
*As do some problems of their own accord or because you unknowingly did something apparently not related.