Oil light

[Grump]

Hello can anyone help me have a rapib 2015 cayc engine 114000 miles  ive had my red oil light flash as soon as i reach 1500 revs only when warm never cold  and never below 1500 took to a garage who checked the oil pressure and was as recommended  by autodata they fitted new pressure switch took home and still the same been looking at it removed the single wire terminal off the switch and ran at 1400 revs no light on even after 4 mins  as soon as i  went to 1500 revs light came on but wire still disconnected makes me wonder if its wiring to ecu or if its even the dash insert. Any ideas

[Breezy_Pete]

Unplug the connector from the pressure switch after you've started the engine.  Get an assistant to short the loom wire connection continuously to chassis/engine/battery negative with a separate wire while you raise the revs above 1500. If the fault indication is still generated, there is a break in the wiring somewhere. If there is now no warning above 1500, the wiring is OK.

 

The switch is in conducting state (to engine metalwork) when the pressure is good/above threshold, and non-conducting when the pressure is below, so disconnected wire gives the same fault indication as actual low pressure.

 

 

Edited 3 October, 2021 by Wino

[Breezy_Pete]

59 minutes ago, Grump said:

only when warm never cold

This suggests there may be a real problem with the pressure, I fear. What pressure was measured at what rpm by the garage?

What oil is in the engine and when was it last changed, along with the filter?

[J.R.]

I think the oil pressure warning light is inhibited under 1500 rpm, otherwise even a perfect engine when hot running a thinner grade oil would have the light winking at tickover.

 

Oil change, filter change & if it remains drop the sump & clean the pick up pipe strainer.

[Grump]

Hello at idle pressure reading 11 psi 2000 revs 21 psi then  goes  up on the pressure to around 60 depends on revs. Last oil change 7mnths ago and  6/7000 miles 

[Breezy_Pete]

I think the spec for 2000rpm is 2 bar minimum at operating temp, that's about 29psi.

 

Edit: according to this page I'm wrong about that 2 bar, for this engine, it is 1.5 minimum at 2000 rpm 

 Skoda Workshop Manuals > Fabia Mk2 > Power unit > 1.6/55; 66; 77 kW TDI CR Engine > Engine lubrication > Removing and installing parts of the lubrication system > Testing oil pressure and oil pressure switch (workshop-manuals.com)

Edited 15 October, 2021 by Wino

[bigjohn]

Doesn't this engine have an oil pressure control valve?

[Breezy_Pete]

Not that I can see on wiring diagram.

[bigjohn]

4 hours ago, Wino said:

Not that I can see on wiring diagram.

 

I asked just in case as with old fashioned engines it wasn't unknown for mechanical oil pressure release valve to fail. The 1.2tsi (not this engine) can have oil pressure issues if the oil filter is mis fitted but don't think this engine is fitted with the same oil release valve.

 

Presuming monitoring is indeed correct and the oil pressure is very low then from my own experience low oil pressure when warm usually indicates something very worn in the lube circuit be it big end /  main bearings etc. It could be turbo bearing failure but I'd expect massive plumes of blue smoke out of the exhaust if that was the case. If it was a blocked oil pickup strainer I'd expect it to be worse when the oil was thicker/cold.

 

Many moons ago I had the engine fail in an old banger Datsun 100A where the big ends eventually started knocking (death rattle) when warm but worked perfectly when cold - if it's getting this bad the oil has a "distinctive" smell.

 

 

 

 

Edited 4 October, 2021 by bigjohn

[bigjohn]

Similar thread although you've already changed the switch:-

 

Edited 4 October, 2021 by bigjohn

[Grump]

Hello all update on the oil light removed battery air filter and ecu checked all connections all ok checked wiring from switch to  14 pin plug on wing checked continuity all ok rebuilt added engine oil cleaner ran for 20 mins idle went to 2500 5 mins no light  drained refilled new filters rd tested all ok no light see what happens tomorrow

[J.R.]

Engine oil cleaner ?

[Grump]

Well 40 mins ok then back to square 1 back on again

[Breezy_Pete]

I'll try asking this again; what (exact) oil is in the engine?

Is there anything to make you think the engine might be running hotter than normal? Put the A/C on and check to see if the rad fans are working.

[Grump]

5w30 mobil oil engine temp seems norm but will try air con tomorrow

[Grump]

Well switched air con on and fans run as they should  engine light still comes on as before had to go to london decided to take car as have recovery keep revs below all ok did a bit of running about light as normal 1500 revs back on came back home up m1 and no light if below 1500  no noises from engine after 430 miles  would have thought if it was the pump engine would be noisy im thinking wiring or dash insert 

[Breezy_Pete]

I described how to test the wiring in my first post on 3rd October, I had the impression you'd proved this to be OK, from what you said here: 

 

On 05/10/2021 at 15:05, Grump said:

Hello all update on the oil light removed battery air filter and ecu checked all connections all ok checked wiring from switch to  14 pin plug on wing checked continuity all ok

 

But you didn't actually do the check I suggested, which I'll repeat here:

 

"Unplug the connector from the pressure switch after you've started the engine.  Get an assistant to short the loom wire connection continuously to chassis/engine/battery negative with a separate wire while you raise the revs above 1500. If the fault indication is still generated, there is a break in the wiring somewhere. If there is now no warning above 1500, the wiring is OK."

 

 

It could instead be related to temperature increase and/or oil dilution during active regenerations of the DPF, so it might be an idea to try to spot whether there's a correlation between one of those happening and  pressure warnings appearing.