oil light flickering

[gwebb]

My 200tdi has 300,000 klm's on it and I change the oil every 5,000 klm and have done so since I bought it at 220,000 klms. After I change the oil I have no problems but after around 3-4,000 klms, when the engine is hotter then normal, 4wd'ing or towing, the oil light flickers at idle. When I rev the motor the light stops. After the engine cools down the next day no problem. What could be the cause of this?? I usually use Shell Delvac oil but I have also used Penrite oil and the same thing happens.

Guy

[Leo109]

Hi Guy,

As per the similar thread currently doing the rounds on this Forum, you would be well advised to get your 200Tdi to a mechanic quick-smart and have an oil pressure gauge temporarily fitted to see what the actual pressure is.

At 300K km, things must be expected to be wearing out. Might be just an on-the-way-out pressure switch but it might be a well-worn oil pump or failing pressure relief valve. If it's the latter, it won't get any better and will eventually kill the engine if the pressure continues to fall.

About I week ago I witnessed a famous spanner-wielder (initials JC) who frequents this forum check out a Td5 with similar symptoms. The workshop gauge confirmed the switch was telling the truth - very low pressure at idle.

First suspect was the infamous oil pump bolt but after the sump was off the bolt was found to be firm (just, and no sign of Locktite). Next the relief valve was checked. The spring was intact but The Guru thought he could see something wedged in the valve plunger. When it was pulled out, a fragment of die-cast metal fell out - presumably a tiny part of the original pump body casting that had been waiting to cause mayhem since the vehicle left the factory. If the owner had ignored the oil lamp flickering on at idle, his very expensive Td5 engine may well have expired prematurely.

Ian

[JDNSW]

The immediate cause is that the oil pressure is below the switch-off pressure of the sender - but I don't imagine that this is the answer you are looking for.

There are a number of factors that will give this result, and the answer is probably a combination of them.

1. hot oil with reduced viscosity
2. Clearances have increased with engine wear so for a given oil viscosity pressure is less at a given rpm - both effect of wear on the pump and on the bearings
3. Pressure drop across the filter increases as the mileage increases since the filter change.
4. Some of the oil molecules break up, reducing oil viscosity for a given temperature
5. Oil temperature is higher because of scale on the oil cooler and reduced cooling efficiency due to other components ageing.
6. Idling speed slightly down from spec perhaps
7. Switch-off pressure of sender is likely to have increased slightly due to wear on contacts.

Probably a few others I can't think of. Items 3&4 are reset at each oil change, which is why it takes a few thousand kilometres to start doing it again. My view would be that there is nothing to worry about, just an indication that the engine is showing some signs of wear and age.

John

[87County]

Just reviving this thread (after searching) -

We don't know how the original poster got on, but my 300tdi at 220000km is doing the same thing - oil light flickering at idle when hot (but not overheated). JD's points in post#3 are logical and I'm wondering what steps other tdi users have taken to rectify the problem.

The oil pump is a bugger to get at and as I've replaced the timing belt recently I'm reluctant to go straight to the oil pump if something as simple as an oil light sender/switch replacement can settle the issue.

Views, experiences and thoughts welcome......

[vnx205]

The first thing I would check is the oil pressure switch. It is cheap, quick and easy to determine if that is the problem.

Three times on three different vehicles in the last 50 years I have had an oil light flicker on idle when the engine warmed up. In each case it was just the switch that was failing. The most recent incident was the Defender, about a year ago.

[Blknight.aus]

pull the lead off the switch, if its oily the switch is stuffed.

[87County]

pull the lead off the switch, if its oily the switch is stuffed.

Thanks Dave, I had looked at that and there's no oil seeping through...

I'll have a replacement sender tomorrow and I'll try it.

[Reads90]

Most of my experience with diesels and oil lights flickering on tick over. Which I happen to add my new 200tdi disco does too. I that it is crank case pressure

I am taking it that mine is crank case pressure. Caused by worn values, rings or something along those lines.

To check this start the engine and take of the oil filler. If is chugging like Thomas the tank engine then there your problem. The other way is when it is running take out the dipstick. If it covers you in oil then you have crank case pressure.

This will also cause oil leaks as there pressure in the engine is finding ways to get out of the engine. A defender I had a few years or so ago did this and ended up blowing oil out the rear main oil seal.
BTW all the time through this is did not blow blue smoke or show any other signs of bracketed rings or values hence why I do not look here first.

Ali

[Blknight.aus]

or check the crankcase breather gear for blockage.

[justinc]

DO NOT jump to conclusions until a proper gauge is connected and testing procedure performed!


JC

[87County]

DO NOT jump to conclusions until a proper gauge is connected and testing procedure performed!


JC

I understand what you are saying Justin, but on my reading of the manual (I'm very happy to be corrected) the operating oil pressure is listed as 25-45 lb/sq in - a huge range? I could find no notation for idling oil pressure.

Obviously if you (or anyone else) can advise me on correct expected oil pressure idling and operating for a 300tdi I would appreciate it.


And thanks too Reads90 and Dave, I will check crankcase pressurisation.

[Judo]

G'day.

Most likely your scenario is different to mine, but here it is FYI. My 300TDI has 150,000kms on it.

Some time ago now, I had the oil light flicker on a really hot day, after a freeway hill climb I pulled over to use my phone, with the revs dropping when the air con came on. Without the air con, the revs were still high enough. The lesson here I think is that only a small drop in revs can be enough to bring on the oil light. Something to consider.

Another hot day I was sitting in traffic, air con on, and it was happening again. A few grams of weight on the accelerator was enough to stop it.

I started a thread about it and big end bearings were suggested if mileages was circa 300,000kms. At the time I was running 5W-40 oil. Since I've changed to 15W-40 and currently 15W-50 penrite. Haven't had it happen since. Far from conclusive proof, but it's worth considering too...

So to end my long post with a question, what oil are you running?

[Spel1]

A while ago I was trying to track down an oil leak in the area of the filter housing on the 300TDI (was an o-ring eventually) but in the process changed the oil pressure sender. Not long after the oil light flickered on idle when hot, nothing else changed to create the symptom. I took the new sender off and compared it with the old one, I found that on the new sender the hole where the oil enters was much smaller than the old one. I put the old one back on as it was not the cause for the leak, just to see if it went away. No more oil light flickering. The part number was right but it was aftermarket. I'm not sure if this was the reason but it was 50K km ago and its been OK with the old sender. So if you do change the sender compare the two first so you are not at an immediate disadvantage. Simon

[TonyC]

Most of my experience with diesels and oil lights flickering on tick over. Which I happen to add my new 200tdi disco does too. I that it is crank case pressure

I am taking it that mine is crank case pressure. Caused by worn values, rings or something along those lines.

To check this start the engine and take of the oil filler. If is chugging like Thomas the tank engine then there your problem. The other way is when it is running take out the dipstick. If it covers you in oil then you have crank case pressure.

This will also cause oil leaks as there pressure in the engine is finding ways to get out of the engine. A defender I had a few years or so ago did this and ended up blowing oil out the rear main oil seal.
BTW all the time through this is did not blow blue smoke or show any other signs of bracketed rings or values hence why I do not look here first.

Ali

Ali,
How can low oil pressure be the result of high crankcase pressure?
They are both symptoms of a worn engine.

Tony

[Reads90]

Ali,
How can low oil pressure be the result of high crankcase pressure?
They are both symptoms of a worn engine.

Tony

Yeah seem your point but last time I had a flickering oil light was on a 2.5 N/A 90 and it turn out to be crank case pressure which ended up blowing oil out the rear main. Total engine rebuild was done


But as for the flicking oil light on my 200 TDI disco. I thought another rebuild was in order. Not that I was too worried as it is a cheap disco and has 450,000 on it. So you have to be realistic.

. But after buying a new oil pressure switch for $15 it has gone now and no oil light flickering. Still runs sweet as a nut.

[Blknight.aus]

Ali,
How can low oil pressure be the result of high crankcase pressure?
They are both symptoms of a worn engine.

Tony

it doesnt, it causes oil leaks.

a severerly restricted air filter (garbage back sucked into the airbox horn) can cause low pressure at idle as the crank case pressure is reduced by the scavanging system.