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CarJunky AutoAdvice

Too much oil

Showing 2 out of 15 Posts | Show 13 Hidden Posts
Question From sawl on Too much oil

Dear All,
recently I put too much oil in the engine of my Renault Master 1996, 2.5 diesel minibus (110,000 miles). At the MOT check when at high revs the van started chucking out black smoke, when the tester turned off the ignition, the engine still ran. Looks like oil got sucked up into the fuel system. The RAC repair man drained the oil out and the van went through the MOT ok. Now, the van is very difficult to start in the mornings. It takes about 2 minutes of turning over the engine and then it starts with a puff of black smoke. When started, it is fine throughout the day. Just a little more sound than normal (slight knocking). Halfords auto shop told me to drain the fuel, change the diesel filter and flush the system (not sure how). This morning, I cannot start the engine and the battery is slowly dying. Have I totalled the engine? What is my best move now? Thanks for any advice, Matt

Response From Loren Champlain Sr

Matt; I'm not a diesel mechanic, but the symptoms...dieseling after shutdown, black smoke, excessive knocking sounds like an injection pump problem. Just a guess, but might be worth looking in to.

Response From sawl

Thanks for that Loren. I'll bare that in mind. I think I'll try the fuel change first. But I can't see any access point to drain the fuel on the tank. Do you think I could syphon it out? Or drain it from a pipe that enters the diesel filter? I had a new diesel filter fitted a few months ago but I suppose there's no way of cleaning that right? Have to get another new one? Thanks again, Matt

Response From Loren Champlain Sr

Matt; I'd try siphoning as much as you can. You can disconnect a fuel line (probably at the filter) and turn the key to the "on" position and let the electric fuel pump do the rest. Bleeding a diesel fuel system, though, can be a real pain.

Response From sawl

Hi y'all,
thanks for all the help and input from everyone. The RAC said it was the faulty primer on the diesel filter housing. Letting air into the system when the engine was standing. They checked the glow plugs and they are good. After alot of hoo ha, I finally changed the fuel filter housing and filter with a brand new part from Renault. I bled the system and got the RAC to check it. This morning, it is still not starting straight away (takes about 10-20 seconds and starts with a puff of whitish smoke). So now I guess I should go for a compression test? Thanks again, Matt

Response From Tom Greenleaf

Agreed - a compression test would be informative right now. Diesels do need top compression by the very nature of them.

I'm a bit concerned about the "white" colored smoke seen? Generally white is water/coolant. Do check the coolant level now and keep it properly filled. If found low (there will be a hot/cold range) take note of that,


Response From sawl

Hi there,
thanks Tom, do you know what? I've been filling up the coolant level a bit too much recently. I noticed that it falls very quickly and when the engine's hot the water level is right up, over the max. Is this normal? The level being right up the top when hot? I remember someone saying something about oil in the coolant system? Is that possible? Why do you think the coolant is going down so fast? Thanks for any input, Matt

Response From Tom Greenleaf

sawl: Just know that normally an engine doesn't "consume" coolant. If adding it suggests a problem. It can plain leak or burn unseen thru engine head gasketing. That's what I worry about now.

Diagnosis of that can be tricky as it's an involved job and something you DON'T want to guess at and be wrong.

Note: A head gasket can leak any which way it seals. It seals coolant, oil, compressed gasses and can leak any which damn way it feels like and might only do it at certain engine temps - hair loss is part of the game! LOL

With what you just said this is now in the picture. Maybe more than that too - serious diagnostics would be pay dirt at this point - IMO,


Response From sawl

Also, if there is something wrong with the coolant system how could it effect starting in the morning? Thanks, Matt

Response From Tom Greenleaf


I'm not familiar with how your MOT tests vehicles and diesels aren't my forte either - BUT need to know how much oil was this overfilled, was there a problem before this test?

Diesels fire on "heat of compression" so excellent compression is a must. Cold starts are usually bolstered by glow plugs and some indication for operator that they are on or to wait for them.

My thoughts so far:

*If this was seriously overfilled with crankcase oil that could have caused real engine damage with a splashing of excessive oil under moving crank and the pistons. It's unknown when you might notice that - either when RPMs rise or if vehicle is running at a high angle where level could touch moving parts.

** This TWO minutes of "turning over" the engine is terribly hard on a starter motor. 15-20 seconds is a more usual max of "cranking" time without waiting a few minutes for the starter to cool or damage to starter can result.

If this extended cranking is a brand new problem after the high revs WITHOUT load (guessing) then it seems to me the damage occurred right then but still shouldn't have been overfilled.

Note: Engines in general don't do well with high RPMs especially without a load. By that I mean a "red line" on a tachometer really mean the max with engine driving - not so much just while stationary.

Last note: Black smoke is usually associated with unburned fuel and not so much crankcase oil,


Response From sawl

Thanks for that. I filled the oil up about 2 months before the test. I knew I'd put it higher than the max but thought it was not too much higher and would not be a big deal. Wrong. When they test diesels in the UK they give it full revs for about 6 seconds to test the emissions. This is when the obvious problem started ie loads of smoke and the van on full revs when the ignition was turned off. The tester said he heard crackling. I guess I put about a litre too much maybe. This was drained out at the test station and then it passed the emissions and had no more problems. After that the engine has been running fine except in the mornings when it's hard to start. I had the glow plugs done last year so I don't think it's that. Thanks, Matt

Response From Tom Greenleaf

Egad Matt! This suggests it was fine for TWO months before a test and then blew up right then? That's abuse on their part IMO but I'm not there to see just what happened or asses the situation at all.

It's near impossible to tell exactly how much overfilled is too much for any given engine. Most will take a quart (liter) or so and be fine and after two months it probably was back to a normal range reading. There needs to be a "safe" area for operation which is marked on a dipstick.

Now it's too bad you may not have a measurement of how much oil came out when changed.

Do you know the capacity for a total oil change for this engine?

The deal with oil level is too high can hit the crank and too low can act as empty when the level drops below where it gets picked up to be pumped around the engine.

An oil "Pan" is shaped for the application and hopefully it's though about and engineered to allow for operating at reasonable angles. For example when parked at a high angle the oil would set to the lower end and even while stopping and accelerating the oil can slosh around but must be available while still not hitting the moving parts. Oil is pumped thru for vital parts and gravity drains back to the pan in everything I know of.

So - If this was a liter overfilled AND was subject to extremes there's an opportunity for troubles.

Check out this generic pic as I try to explain,

The crankshaft is somewhat like pedals on a common bicycle going round and round but must clear the oil level or it would splash horribly. Imagine if you haven't (I have - laugh) riding a bicycle such that your feet are underwater - you struggle and so would the common engine designs. If you pedal slowly you can do it. If you went too fast it would slosh and fight with you or in the case of the engine the splash would probably go up under pistons and create an hydraulic lock for a split second and break something or things.

Also: The bearings of an engine like having some load on them. The load acts as a consistent pressure evenly on the bearings and pistons not intended to fly free like that. My analogy for that is try running down hill - your legs go nuts vs level or slightly uphill - similar idea.

Another bicycle example would be with your feet on pedals that were driven by going downhill going too fast for your feet as in a toy pedal car.


The point here is that this test seems to be the cause with really an unknown level of oil at that exact time. There's some fault on your part for knowing that it might have been too full of oil as well.

Now what to do? Have this engine compression tested and fully diagnosed. I suspect you'll find it may need some extensive "lower" end work meaning the block and pistons + associated parts. Full diagnosis needed to decide on the bst practical approach.


It's NOT my place to determine what exactly happened and why but I'll say if I drove TWO months with no problems and got my vehicle back after a high rev test like that there would be some heads rolling


Response From Tom Greenleaf

Hi again Matt,

Took me longer to write that so I didn't see your post done in the middle there. If it's running fine again now it might be worth changing out the fuel and a new filter would never hurt.

To me diesels make so much noise (don't own one and never did) that it's hard to tell what's normal unless it's yours. In the cold they sound like they are going to explode sometimes making noises that if a gasoline engine you would declare it junk.

It's near impossible to guess what noise is normal and isn't right now for me from here. Can you get a tech to listen to this and make an assessment on the noise?

If this problem just ceased then just cross your fingers and hope there's nothing permanently damaged which is what I feared the most.

Good luck - let's hope the trouble is just a fuel issue. Again - don't know this vehicle at all but check - it might have a drain on tank for the fuel,


Response From sawl Top Rated Answer

Thanks Tom for all your input. I don't drive this van much. When I do it's mostly quite slowly 60mph is very rare. So I reckon when full revs were on, pedal to the metal, it was a first and it blew. But the thing is, for some reason, this is part of the GB emissions test on diesels. Full revs for 6 seconds-twice. I would never thrash it but I suppose some people do and the test must be made.
I'm hoping it's just a fuel issue. I'll check the fuel tank for the drain. Thanks again, take care, Matt

Response From sawl

Don't know why but she just fired up after a small bit of ignition (3-4 seconds). Could that be due to the temperature outside, things have warmed up a bit, sun's out etc. There was a cloud of smoke and now running pretty normal, a bit more noisy than usual. What should I do now? Should I drain all the fuel? Change the diesel filter? How do you drain the fuel? Do you do it from the pipes going into/out of the diesel filter? Or from where you put the diesel in with a pipe? Should I flush the system and if so with what? I don't know what happened this morning but I'm pretty sure the diesel inside is contaminated. Thanks for your help, Matt