Hawklord Posted June 16, 2021 Share Posted June 16, 2021 I have an issue with my oil pressure on my 300TDI Defender where starting from cold the longer I leave the vehicle between being used the longer it takes for the light to go out. For example I started it yesterday after being on the drive for 5 days and it took around 40 seconds for the oil light to go out. The oil light goes out within a few seconds when used daily, goes out immediately when re-started and doesn't come on or flicker when driving. I have have changed the switch which hasn't made any difference. Any ideas on what is the likely cause or what needs replacing. I have owned the vehicle for 19 years and it may have always done this as up until the Covid lockdowns it was used on a daily basis and I have only been aware of the issue when I drove it infrequently. Quote Link to comment Share on other sites More sharing options...
western Posted June 16, 2021 Share Posted June 16, 2021 Try a new oil filter. Quote Link to comment Share on other sites More sharing options...
steve b Posted June 16, 2021 Share Posted June 16, 2021 Just to add , good OEM quality brand Mahle etc. Steve 1 Quote Link to comment Share on other sites More sharing options...
Hawklord Posted June 16, 2021 Author Share Posted June 16, 2021 I changed the oil and filter a couple of weeks ago using a Mahle filter and the light issue was the same before and after the change. Quote Link to comment Share on other sites More sharing options...
western Posted June 16, 2021 Share Posted June 16, 2021 Only bits left then is a suspect oil pump or the relief valve Quote Link to comment Share on other sites More sharing options...
monkie Posted June 16, 2021 Share Posted June 16, 2021 Seems a bit odd as the oil pressure should be high when initially started. I think the best thing to do is get an actual reading. Get a mechanical oil pressure gauge and fit it to get actual readings just to absolutely rule out a sender/wiring issue of some sort. Quote Link to comment Share on other sites More sharing options...
hurbie Posted June 16, 2021 Share Posted June 16, 2021 31 minutes ago, monkie said: Seems a bit odd as the oil pressure should be high when initially started. I think the best thing to do is get an actual reading. Get a mechanical oil pressure gauge and fit it to get actual readings just to absolutely rule out a sender/wiring issue of some sort. not iff all the oil is drained from the oilpump , then it take's time to fill up the pump and oilways. i would go with western and look at the oilpump and reliefvalve. Quote Link to comment Share on other sites More sharing options...
monkie Posted June 16, 2021 Share Posted June 16, 2021 13 minutes ago, hurbie said: not iff all the oil is drained from the oilpump , then it take's time to fill up the pump and oilways. i would go with western and look at the oilpump and reliefvalve. Yes agreed, but before going to that trouble I think getting an actual oil pressure reading is wise to see what pressure you are actually getting. If it does read low, then time to get at the oil pump and relief valve. Quote Link to comment Share on other sites More sharing options...
Sigi_H Posted June 16, 2021 Share Posted June 16, 2021 Don't rely on the oil pressure switch. Buy a new one. If the behaviour stays the same, it's a real oil pressure problem. I had several bad switches on some vehicles. 2 Quote Link to comment Share on other sites More sharing options...
monkie Posted June 16, 2021 Share Posted June 16, 2021 2 minutes ago, Sigi_H said: Don't rely on the oil pressure switch. Buy a new one. If the behaviour stays the same, it's a real oil pressure problem. I had several bad switches on some vehicles. Yep, me too. This is why I like an actual number rather than no light/light. 1 Quote Link to comment Share on other sites More sharing options...
Snagger Posted June 18, 2021 Share Posted June 18, 2021 I agree - it could be a sticky pressure light switch, so that is a cheap and quick first item to replace before going to the trouble of the oil pump. The symptoms do sound like an oil pump that is draining back to the sump and having to prime itself each time, though, and a loss of through a bad filter or relief valve are highly plausible. It could be a failure in the oil filter housing gasket to the block joint or perhaps the timing case. This is the problem with the 300’s oil pump - while it doesn’t depend on the timing belt like the earlier engines, it isn’t immersed in the sump like the old engines’ pumps, so doesn’t self prime as easily and doesn’t stay primed if there is a leak. Quote Link to comment Share on other sites More sharing options...
Peaklander Posted June 18, 2021 Share Posted June 18, 2021 The OP says in the first post that he changed the pressure switch and the symptoms remain. 1 Quote Link to comment Share on other sites More sharing options...
Snagger Posted June 18, 2021 Share Posted June 18, 2021 Yep, missed that. I’d be tempted to fit another oil filter, just in case it’s that simple, but I suspect the pressure relief valve, which is a bigger job to get at. Quote Link to comment Share on other sites More sharing options...
steve b Posted June 18, 2021 Share Posted June 18, 2021 On 6/16/2021 at 7:50 PM, monkie said: Yep, me too. This is why I like an actual number rather than no light/light. ^^^this first - it doesn't need to be installed in the dash , just a temporary fit to see actual numbers . That said , all the tests tried so far do point to the PRV. Steve Quote Link to comment Share on other sites More sharing options...
Sigi_H Posted June 18, 2021 Share Posted June 18, 2021 5 hours ago, Peaklander said: The OP says in the first post that he changed the pressure switch and the symptoms remain. sorry, missed that Quote Link to comment Share on other sites More sharing options...
Hawklord Posted June 18, 2021 Author Share Posted June 18, 2021 I have ordered a pressure gauge to get some actual values and will report back once fitted. What fails with pressure relief valve it it is that ? Thanks for all of your replies. Quote Link to comment Share on other sites More sharing options...
western Posted June 18, 2021 Share Posted June 18, 2021 There is a spring set at a predetermined pressure & a conical valve that opens/closes to allow the pressure to relieve, the spring may be weak & the valve head & seat could be damaged, worn or something is restricting its operation. Quote Link to comment Share on other sites More sharing options...
Hawklord Posted June 24, 2021 Author Share Posted June 24, 2021 Hi I have fitted the oil pressure gauge and get the following readings, do they seem ok. Cold start idle 58psi Cold engine at 60mph 48psi Hot engine idle 18-20psi Hot engine at 60mph 28-30 psi. I don't have the readings yet for when the oil warning light takes and age to go out as I have to not use the vehicle for 4 or 5 days for this to occur. The oil which I have used for the 19 years owned is 15w40 mineral, is this the best oil to use for a 27 year old 300TDI with 201k on the clock and not having any work done on the engine. Quote Link to comment Share on other sites More sharing options...
Peaklander Posted June 24, 2021 Share Posted June 24, 2021 They are very similar to mine. The pressure relief valve operates at around 50psi I believe so that’s probably where yours maxes at startup. The test though is after those days of sitting. Quote Link to comment Share on other sites More sharing options...
monkie Posted June 24, 2021 Share Posted June 24, 2021 It's great help though to have this set of data as a comparison. Numbers are always better than an on/off light. Personally I don't see an issue with using 15W40 mineral oil. Some people will use semi synthetic. It's always good practice to regularly change the oil, even for occasional low mileage use. Quote Link to comment Share on other sites More sharing options...
Snagger Posted June 24, 2021 Share Posted June 24, 2021 That’s around what I got on my 200Tdi after rebuilding it in its entirety. The book figures are the same as on the pre-turbo engines, which I did get on my 12J, but I think they’re wrong - almost everyone has given me figures similar to yours. Ralph got the best readings I have heard of after his rebuild, and I think the Turner Engineering cam shells with smaller oil holes are the cause, preventing excess oil loss through them. Quote Link to comment Share on other sites More sharing options...
Snagger Posted June 24, 2021 Share Posted June 24, 2021 2 minutes ago, monkie said: It's great help though to have this set of data as a comparison. Numbers are always better than an on/off light. Personally I don't see an issue with using 15W40 mineral oil. Some people will use semi synthetic. It's always good practice to regularly change the oil, even for occasional low mileage use. Especially if you use vegoil as fuel - the fuel that gets past the rings polymerises the oil in the sump and turns it into a jelly. Quote Link to comment Share on other sites More sharing options...
Hawklord Posted June 24, 2021 Author Share Posted June 24, 2021 Seeing that my psi figures seem to be around normal it doesn't look like that there is anything major wrong with the engine or oil pump, which is good news. I have always changed the oil at 3000-4000 mile intervals. With the figures that I have could there still be a problem with the oil relief valve draining and causing the oil light to stay on a long while after not using the vehicle for a few days and if so how do you access the relief valve for replacement. I have never changed the oil cooler thermostat, if this is stuck open could that affect start up pressure after standing ? Quote Link to comment Share on other sites More sharing options...
Hawklord Posted July 3, 2021 Author Share Posted July 3, 2021 I started her up today after sitting for 3 days and the oil light stayed on for about 15 seconds and the oil pressure gauge didn't move until the light went out so it seems then that oil is slowly draining away from the pump when the vehicle is not being used. What do you think is the likely cause of this to happen and seeing that my oil pressure figures seem to match to other forum members can I assume that the pump itself is ok ? Quote Link to comment Share on other sites More sharing options...
Peaklander Posted July 3, 2021 Share Posted July 3, 2021 On 6/16/2021 at 6:21 PM, western said: Only bits left then is a suspect oil pump or the relief valve On 6/18/2021 at 7:48 AM, Snagger said: The symptoms do sound like an oil pump that is draining back to the sump and having to prime itself each time, though, and a loss of through a bad filter or relief valve are highly plausible. It could be a failure in the oil filter housing gasket to the block joint or perhaps the timing case. This is the problem with the 300’s oil pump - while it doesn’t depend on the timing belt like the earlier engines, it isn’t immersed in the sump like the old engines’ pumps, so doesn’t self prime as easily and doesn’t stay primed if there is a leak. These are the suggestions earlier in the thread. This is where to look. Quote Link to comment Share on other sites More sharing options...
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