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I have a great problem getting a dipstick reading on a Merc220 diesel M reg. when a reading is taken cold the level is way over the top of the level indicators, when the car is hot it is way below! I have consulted the experts who have differing opinions...''cold is right''...''no no hot is right'' 'strewth! help.
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have you got the owners manual? Should tell you conclusively, but IIRC it's usually correct to take the measurement while the engine is cold.
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Supposedly the best way is taking the level after an overnight stop and the car is on level ground. That way, all the oil in the head and journals has come back to the sump.
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Espada III - well if you have a family and need a Lamborghini, what else do you drive?
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BMWs like to be warmed up....and some Vauxhalls should be at "working" temperature..guess it varies from engine to engine.
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Would depend on how far above when cold.and how far below when hot.also.some check level when hot just after engine shutdown.that will give a false reading.should wait for a couple of minutes then check.cold I would expect a couple of mm`s over.that I would call about right.? But I dont know the car.but would think it right.
Was mech1
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Do you know the history of the car? Are you sure the dipstick is the correct one for that model?
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smart specify that the oil should be checked when the engine is up to full operating temperature (three blobs on the temp gauge). I've checked it both hot and cold and it's made no difference!
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Normally its at operating temperature (to take account of thermal expansion) and with engine shut off for a few minutes to allow the oil to drain down.
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Both my car and one bike says check after warmed up and a one minute wait. The difference between this and cold is the same as between 'high' and 'low'. I have noticed that the level takes a long time coming up the dipstick tube - I don't know if there is a restrictor or something to stop oil shooting out if you forget to replace the dipstick??.
T'other bike is wierd as it's a dry sump thingie - two dispsticks, one in the 'sump' and one in the frame where the oild is stored.
Martin
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I aired my confusion about the oil level on my diesel C class (reg) and the good people on this site have answered. Unfortunately I can gain no difinitive answer! When cold the oil level reads well over an inch over the ''maximum'' mark, when hot it reads the same below. It seems about even to the hot and the colds at the moment. Any more ideas...thanks.
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When you check the oil when the engine is hot, do you do it straight away after turning off, or approx 1 hour later?
If it\'s the former, then the oil might noy have fully returned to the sump - hence why you\'re getting a low reading.
People have made this mistake on checking the oil on their diesel Vauxhalls.
Generally you should check the oil after being stood overnight, i.e. stone cold; or left to drain back into the sump, i.e. leave parked up for approx an hour.
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Just a thought - has it got the proper oil filter fitted? Good ones have non-return valves which stop all the oil draining back into the sump when you switch off. Cheap ones often don't.
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How do you actualy check it.I think it best you explain how you do the check rather than anyone presume.there are many reasons why level may be inacurate.?
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Was mech1
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I've always been given to understand that the oil level should be checked when the engine is cold.
However, the manual for my VW Bora states to wait a few minutes after the engine is switched off to allow the oil to drain into the sump; then remove the dipstick, wipe it clean, replace it and then check the level.
It's always been a pointless exercise up to now as both my previous Jettas never used any oil (nor leaked any) and the Bora appears to be the same. The oil container for topping up intentions has never needed to have the cap taken off in the 13 months I've had the Bora.
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Take a step back for a moment here. An inch difference between hot and cold is a huge amount. Assuming that most cars have an oil capacity of around 4 litres, then thermal expansion is not going to make that much of a difference on the dipstick - assuming that the sump designer has got his sums right and that the sump is not a strange shape (consider the typical cross-sectional area of a sump...). Similarly, think about how much oil is going to be pumping around when the engine is running against how much needs to be in the sump to cover the inlet to the pump, even when cornering at high speed....
Something does not seem right - assuming that the hot and cold measurements are both taken on level ground. Points towards the above-mentioned check on making sure that the correct dipstick has been fitted, together with measuring the quantity of oil drained out at the next oil change, and a check in the handbook to determine the recommended capacity.
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>>An inch difference between hot and cold is a huge amount
I'm puzzled as I can't find any reference in these postings to there being an inch difference between hot and cold.
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PS
My car handbook is quite specific regarding topping up - if the upper hatched area marked on the dipstick has been reached by the oil, oil must NOT be added; if the area below has been reached, then the oil CAN be topped up until it reaches the hatched area.
The words NOT and CAN are in bold type.
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Way over the indicators to way under the indicators must be an inch.
But RTQ, chaps. It is over when cold and under when hot. Thermal expansion would suggest that it should be under when cold & over when hot. There is something else, bizarre, going on here.
What does the handbook say? My Merc iirc had different instructions for reading the levels when hot & when cold (or was that the tyre pressures?)
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>>It is over when cold and under when hot.
over when all the oil has sunk into the sump
and under when half of it is lying around in various parts of the engine.
Not particularly bizarre, or am I missing something ?
M.
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That was really my query. Normally a small amount of oil runs back into the sump when the engine is turned off, so the reading would be slightly higher when cold. But the bulk of the oil in circulation is held by the non-return valve in the filter. If the wrong filter had been fitted, or the valve were faulty, it would let ALL the oil back into the sump, giving an abnormally high reading. Some angled oil filters would drain completely without the valve.
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OK, Mark different approach to the same argument.
Any car I've ever checked the oil on it's higher when the oil is hot as a result of thermal expansion. If the reading is relying on the oil being stuck all around the engine then that's no way to take a reading - I should suggest - as who knows how much is going to be stuck in the different parts of the engine (as you rightly say). The oil drains back into the sump pretty quickly out of a warm engine, doesn't it? I suppose what I think is bizarre is that anybody would want to check the oil level so soon after turning the engine off - as there could be any amount of oil (unquantifiable) stuck in various parts of the engine.
By the time the engine has been off for a copule of minutes, then it is perfectly sensible to expect the oil to be back in the sump.
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By the time the engine has been off for a copule of minutes, then it is perfectly sensible to expect the oil to be back in the sump - Surely?
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stuartli asked -I'm puzzled as I can't find any reference in these postings to there being an inch difference between hot and cold.
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stuart -
look at barney100's post
"... When cold the oil level reads well over an inch over the ''maximum'' mark, when hot it reads the same below. ..."
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Cheers. Definitely a case of not seeing the wood for the trees.
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Shot in the dark here: crankcase breather blocked, therefore slow return of oil when hot (sump presurised) but dipstick registers full when cool (sump at atmo. pressure).
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Mapmaker - the differing Merc instructions for hot or cold are tyre pressures. Very good advice; when do you ever check tyres cold, its usually done at the petrol station when you have been driving all day..
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Espada III - well if you have a family and need a Lamborghini, what else do you drive?
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28 June 21:40 post refers to an inch under/over.
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The volume difference between hot and cold should not be significant, as the sump expands too, so a cold reading is more reliable, as it can be reasonably assumed that all the oil that's going to will have drained down.
I think the reason for the apparent favouring of hot measurements in car manuals is simply that most people check their oil on garage forecourts and cannot be expected to wait for the engine to cool!
The difference you are experiencing (2 inches!) suggests a problem, unless you are measuring the hot level the instant you turn the engine off!
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I think you should do an oil change, fit a new maker's oil filter, pour in exactly the quantity of oil specified in the handbook, clean all the filters and breathers, and report back.
1) what is the level hot, after say 5 minutes cooling
2) what is the level after leaving overnight.
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I think you should RTFM!
The designers may have marked the dipstick to be accurate reading the level with the engine hot. They may have designed it to be read with the engine cold. The manual will tell you the answer. No amount of guesses from us will help, as we don't know how it was designed.
At that point, I accept, the question may become: "How do I get an owner's manual for my car", but otherwise we are all just guessing, unless one of us happens to have read it.
V
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I think the problem is this: When the dipstick is in place, there is air trapped between the oil level in the dipstick tube and the where the dipstick seals at the top. When it gets hot, the air expands and some of it will bubble out into the sump. When the dipstick tube cools, the air inside contracts and draws up the oil from the sump, often to an absurd level (in the case of my lawnmower!). Conversely, if the engine is hot, you may get a very low reading (even if you leave a few minutes for the oil to drip back into the sump), because the air pressure in the dip tube has pushed the level down. This phenomenom may not occur on some cars - it depends on whether the dip tube enters the sump below the normal oil level. The solution is to take out the dipstick, wipe it and then check the oil. This lets the oil in the dip tube find its correct level, now undisturbed by the pressure of the air in the tube.
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But you are always advised to wipe the dipstick before actually checking the oil, otherwise you /could would get a false reading from oil retained on the dipstick.
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I don't know what's difficult about this. My wife's car manual states (I read it this morning but don;t have it in front of me):
"place the vehicle on level ground, run the engine for at least one minute, stop the engine, then wait one minute, remove the dipstick and wipe it clean, then reinsert the dipstick and take the reading".
My manufacturer has clearly placed the mark on the dipstick to reflect these instructions.
Equally, another manufacturer (or even the same manufacturer with a different model) might say test the oil in a cold engine with the car on a 45 degree downhill slope. Provided they have put the mark on the dipstick in the right place given these instructions, the reading will be accurate.
So, I go back to my earlier post: Read the Flippin' Manual. If you don;t have one, get one, then read it. It is utterly pointless debating, unless you happen to own the exact same vehicle and have RTFM.
V
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\"My manufacturer has clearly placed the mark on the dipstick to reflect these instructions\"
They don\'t always get it right, though. IIRC, early Austin 1800\'s (which had a transverse engine that had previously been used fore and aft) suffered from premature engine failure, until it was discovered that the dipstick was too long!
Not that Mercedes would make a mistake like that...
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I need to clarify one or two points on my oil level problem. I know on petrol cars that the oil level should be checked when the engine is cold and the car is on level ground. This is my first diesel car and the rules are not clear: on my last service i was told that the amount of oil in the sump was low, this is despite the dipstick showing a reading over the maximum level when cold. Mercedes service desk people gave differing opinions, they are either in the check it hot school or the check it cold school. Other mechanics I have asked come in both schools too. I can only repeat the cold reading is way over and the hot reading is way below. Thanks for your interest in this baffling saga.
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barney100,
As this relates to your earlier question, I'd be grateful if you could keep it within the same thread that you originally created, so as to save the moderators from having to move it.
This of course will be moved shortly into that thread, which is here ( www.honestjohn.co.uk/forum/post/index.htm?t=23275 )
DD. BR Moderator.
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Have a similar problem with my Vectra 2.0 diesel Barney.
If checked when cold the first dip shows well over an inch too high. Successive wipes and dips brings it down to the correct level.
Reading the handbook it says that it should be done with the engine at operating temperature after leaving for at least five minutes.
Strangely again on the first dip at operating temperature no oil whatsoever shows on the dipstick. The next dip shows the correct level.
I seem to recall reading on this site that Saab who use the same GM engine had issued a warning or affixed a label under the bonnet saying not to add oil until it had been dipped a couple of times to show the correct level.
There is a thread on the same theme some months ago.
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Barney and Alvin,
I think my explanation fits with your symptoms on the Vectra and the Merc. When hot, the level may appear very low (forced down by the air in the dip tube expanding) and vice versa when cold. I think that you should get a good reading with a hot or cold engine (allowing for a 5 min drain down time if hot), if you pull out the dipstick (ignoring the level completely - which may be high, low or even non-existent), wiping it and dipping again. Once the stick has been pulled out and wiped - the air pressure in the dip tube is relieved and you should then get a correct reading. I don't think it is a petrol or diesel thing - it just depends on the how the dip tube is installed on a given engine. That said, my Pug106 diesel shows the same effect - and it is very worrying the first time you see it!!!
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Anyone care to tell me why you shouldn't overfill? Sorry for such a numpty question, but electronics is my thing, not mechanics.
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PDC
Refer to thread 'Overfilling the engine oil' which started
16.10.03 which will provide all your info and more
Sorry, I don't know how to identify and attach thread reference
(Perhaps someone could explain how to do this)
AI
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Sorry, I don't know how to identify and attach thread reference (Perhaps someone could explain how to do this)
Explained here:-
www.honestjohn.co.uk/forum/post/index.htm?t=11017
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PDC Refer to thread \'Overfilling the engine oil\'
www.honestjohn.co.uk/forum/post/index.htm?t=16905
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DD
Many thanks. As I've said many times: Ignorance is 'not knowing' but 'not wanting to know'
Gratitude
Ian
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