Re: oil light food for thought
This might be of interest to all. Hope it isn't too much.
The 03 DII came in for general service as it had just been purchased, amongst the things to check was a flickering Oil Warning Light (OWL), at idle. We decided to check the pressure. The first time the engine was cold and it had good oil pressure 10-14 at idle and it raised to 30 when revved slightly, (the factory specs are 15 min at idle and 50 max at 2000 rpm) so we replaced the switch. After doing other repairs I drove my usual 5 minute test route, on returning to the lot the light came on again! We tested it again hot, the pressure had now dropped to 10/12 PSi, going up only slightly to about 15 at acceleration. We tried a different gauge, this time we had almost no pressure; we then tried without a gauge, ie the hose going straight to a container, it came out in spurts, first nothing and then a blast of oil then nothing. We decided to remove the Oil Pressure Relief Valve (OPRV) but it was stuck, we turned over the engine to see if a little pressure would help push it out, IT DID! It blew oil everywhere!!! we had good pressure, and a shop floor and clothes covered with oil, meaning, the pump was capable of delivering pressure. We cleaned and adjusted the valve and retried, again we had low pressure. Clearly something was wrong internally so we removed the oil pan to investigate, all looked OK. We then removed the timing cover to examine the pump, the gears were perfect, no sign of damage or wear. What do we do?? We decided to strip the cover completely and check for an internal fault of some sort. We discovered it had another pressure relief valve on the opposite side. We then traced the oil flow and were surprised, the diagram shows the flow from the pump, out the bottom of the timing cover to the oil cooler via a hose then back to the right side of the cover. It then goes through the oil filter to the engine via the OPRV channel. This other valve appears to be a by pass in case the filter becomes blocked! An Oil filter By pass Valve, (OFBV) was common on many cars in the 60?s, it permitted oil flow to the engine in an the case of a full flow filter becoming restricted. Most systems included a separate red warning light indicating that the filter was blocked or restricted. Our oil circuit HAS NO COOLER! This changes everything. The oil does not exit the timing cover, it cannot, so where does it go ! By now we are puzzled, how is this engine getting oil? Well, the pressure build up is virtually the same as a blocked filter, the OFBV then opens at its set pressure probably around the 15PSI range, diverting the flow via a channel into the main gallery feeding the engine. This is interesting as if the pressure were lower than that set pressure the OFBV would not open, if that were so the engine would be virtually starved of oil at idle! Also as the filter is now by passed the oil delivery is unfiltered! Now what! We thought all we have to do is fit a cooler, perhaps someone had removed it. But there was no sign that one was ever fitted. I have since checked, and although my technical data system shows an oil cooler, the D2 never had one fitted, although, the Range Rover version of the engine did! We then thought of having a hose system made to connect up the two blanked fittings on the cover, opening the correct oil flow route. But of course we weren?t 100% sure of our diagnosis. We then realized that if we removed the OFBV we could have oil flow directly to the engine at all times. We did, we removed the valve portion refitting the spring and a spacer in order to hold the plug in position. We now carefully turned the engine over without the ignition relay, we had pressure. We then started the engine, at idle we have 10 to 12 psi, at 2000 rpm we have 35psi and at 3000 rpm we have 55psi . We now have better and consistent oil pressure throughout the rpm range albeit lower than the factory data requires. Where do we go from here, the vehicle is now drivable, I did so for about 50 miles on a very hot Sunday (discovered that the Electric fan did not work) in Los Angeles with an oil gauge connected and attached to the windshield wiper. The light still flickers at low idle with the vehicle in gear and AC on but it goes off instantly. Previously it was going off as the oil built up to its max around 15PSI now it goes off and the pressure increases with RPM. Now what do we do? The engine has obviously suffered from the oil starvation and its life has been reduced but in fact it is not noisy and drives quite well. But we need to find a better solution which probably means fitting a cooler of some sort. Or are there other options, do we have the wrong front cover, it is possible that someone previously replaced it. I went to look at a new one and it appears to be exactly the same externally. I would be happy to hear comments not only on this case, But on the possibility there are many other vehicles out there with the same problem!
