indoken Posted December 18, 2012 Share Posted December 18, 2012 hi all my 300 tdi has decided to show me its oil light is working but only when the engine is at normal op temp. the funny thing is the higher the revs the dimmer the light becomes untill it goes out at about 3000 revs. has anyone got any ideas as to the problem as i am stumped. p.s. there is a healthy amount of oil in it!! ken Quote Link to comment Share on other sites More sharing options...
Tetsu0san Posted December 18, 2012 Share Posted December 18, 2012 The amount of oil is not always the issue, it's the pressure that the oil is under when it's being pumped around the engine. If you are low on oil this will of course drop the pressure, but if you have plenty of oil and your oil light is showing at normal running temp then I suspect that you do indeed have an oil pressure issue. The voscosity of oil at running temperature is thinner than cold so the pressure will drop as there is less resistance to the flow of the oil. If the light goes out at 3000rpm then again I would say you have a problem because as you rev the engine in theory the oil pressure will increase because the oil pump is pumping quicker and so the pressure will be higher (like turning on a water tap a little, then increasing the opening more and more). I am sure a grown up will be along soon to say I am talking rubbish, but I think I am right. As for things that can affect oil pressure, the oil pump may be worn, the oil ways in the engine could have a blockage somewhere, the oil may be past its best. You may also have a fauly oil pressure switch. I would change that first, as this may fix the issue and that is a cheap and easy thing to do. Quote Link to comment Share on other sites More sharing options...
indoken Posted December 18, 2012 Author Share Posted December 18, 2012 hi i recently changed the head complete with a new gasket and head bolts and was very carefull to cover all oil/water ways from any contamination. thinking about it now i did'nt change the oil after i cooked the head and i wonder if the oil was affected by the very high temp the engine got to (i melted the temp gauge on the top of the head). i think new oil and filter may be a good start followed by a pressure switch. many thanks ken Quote Link to comment Share on other sites More sharing options...
Tetsu0san Posted December 18, 2012 Share Posted December 18, 2012 You cooked your head? Hopefully it is just an oil thing but if the engine got really hot then you may have done some damage on the main block. There are plenty of things that may have gone wrong in there too. But change the oil, change the pressure switch and see how that goes. Quote Link to comment Share on other sites More sharing options...
BogMonster Posted December 19, 2012 Share Posted December 19, 2012 The sender is fked. Change it and the problem will go away, 99% sure. I think I had nine newsenders in my last 300Tdi engine over a period of about 3 years. They are junk! Quote Link to comment Share on other sites More sharing options...
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