1998 110 - Oil pressure light

[pvp89]

Hi all

Having some oil pressure light issues with the 1998 110 300tdi I am currently attempting to nurse back to health.

The car has done about 290,000kms. I did an oil/filter change a couple of hundred kilometres ago and did not appear to have any immediate issues. I'm not sure what oil was used in the vehicle previously but I swapped it out for Penrite HPR Diesel 15 15W-50 (http://www.penriteoil.com.au/engineoils-products.php?id_categ=1&id_products=8).

A couple of days ago the oil pressure light started coming on and off. It comes on for a couple of seconds after ignition then goes off. Seems to be fine as long as the revs are kept up but when idling (e.g. at traffic lights) or if the revs drop (e.g. going up a hill and having to change gear) it seems to come back on and off. Sometimes it is clearly on, others it seems to flicker and is very faint. Once you put the foot down and the revs pick up it seems to go away. However last night I took it for a 10 minute highway run and after a few minutes at the same speed (i.e. not accelerating) it started to light up. I guess that this means that the pressure is being lost as the oil heats up.

After reading a number of threads on the various LR fora it seems as though the oil pressure switch might be faulty - would this be the first port of call? Some guys in the UK seem to think that the 98 300tdis in particular were fitted with a bad batch.

Could it be a problem with the type of oil I put in? Alternatively I suspected that there might not be enough oil after the change, but the dipstick is showing near full.

Hopefully this is not a terminal sign; I'd really like to avoid blowing the engine up (wouldn't we all).

Thanks for the help.

[Judo]

The gauge is certainly the first thing to check as it's the easiest fix.

If the gauge is correct, then I would suspect big end bearings. The Penrite oil you've used is fine and I use exactly the same in my TDI.

I'm unsure if you can "test" the big end bearings. It might be a case of having a look, which means taking the sump off and looking from there.

Lastly, if the gauge is correct and you are losing oil pressure, I wouldn't like to be driving AT ALL. Bad things will happen!

[vnx205]

I don't know how common it is for oil pressure switches to fail. All I know is that I have had three fail on three different vehicles in the last 40 or so years. Coincidentally, one of them was a 1998 300Tdi.

They are cheap and easy to replace, so I would suggest you start there.

I think some of them leak a tiny bit of oil when they fail. That might be a clue.

[steveG]

I could well be a faulty pressure switch, which is a 5min job to replace. A long reach socket will help to change it as its difficult to swing a normal sized spanner.

Being a '98 and 290K, I'd be checking the big end bearings anyway (even if you find a new switch sorts the light issue out) as it seems quite common for the upper shells to delaminate. Just replaced them in my '98 build 130 at 320K and they were looking pretty sad.
Bearings are cheap (about $45 a set) so drop the sump and check them out. Unless they are perfect I reckon just replace them.
You'll need a torque wrench for the nuts on the caps, a 15mm double-hex/12point socket and some sealant for the sump.
A new o-ring for the oil pickup and gasket for the oil return tube would be nice while you have them off but not critical IMO.
Note that its the upper shell that has issues, so don't just pull the big end cap off and think everything is OK if the lower shell is fine.
If you're concerned about doing the bearings but happy to do the crappy job of pulling the sump off and putting it back on again there's likely someone nearby that would lend a hand for suitable liquid repayment ;)
Bit far for me :angel:

Steve

[ted44]

I would also be wary of new pressure switches I had the same problem, bought a new switch, the best one they sold OEM, or what ever and it still flickered under low revs, thought engine was shot, pressure tested it all good, bought new switch cheap after market one and all's been good! 300Tdi 1996

[rick130]

A '98?

As Steve said, big ends would be my guess too, late '98's have poor shells which de-laminate.
Do a search for one of bearing threads if you'd like to be suitably horrified. ;)

A mechanical gauge plugged into the sender port will tell all.

Big ends are doable in situ.

[pvp89]

I just went out and had a closer look at the sensor and it does seem to be weeping oil. Hopefully this is the culprit but I will order a new one and see. Thanks for the replies.

[pvp89]

Update:

I removed the oil pressure switch and put a gauge on this afternoon to see what readings I would get. Got consistent readings of 35 psi at idle and around 40 psi with the revs up. From what I've read online this seems to be in the correct band of 25-55psi (please correct me if I'm wrong here).

The switch itself had a bit of gunk on it so I cleaned that off with a rag and put the switch back on after I'd taken the readings over a 20-30 min period. I also topped up the oil. It also seemed to come off quite easily when I removed it so maybe it was loose.

The light is lighting up at ignition but is now staying off. I went for a 5 minute test drive and the light didn't come on at all.

Hopefully this means that it was the switch causing the issues. Or alternatively I have replaced the switch incorrectly and am getting no reading at all, thereby putting myself on a collision course with disaster.