Oil Overfill?

[colinb1]

Hope someone can give me some advice please.

I have a 1990 Carrera 4 which I've owned since mid-December. Goes well and am very pleased. However, there is a slight smell of oil - particularly when in traffic. I decided to check the oil level today - first time I've done it (it had an oil change at a local specialists around 6 weeks ago) - I checked it when the engine was warm and running - and the level seemed OK but I thought I would look at the filler cap. I was surprised to see that the oil level was up to the top of the filler neck. Once it had cooled down, the level was not visible in the neck.
Does this sound like there is too much oil in the engine. Is it something I need to address? The car is running well presently. If I need to take some oil out - which is the easiest way to do it - bearing in mind I have two left feet for hands and would prefer not to do anything too complicated.

Any thoughts would be appreciated.

 

[bones]

The way to check the oil level is to warm the engine up to normal operating temperature and with the engine still running look on the dipstick for the oil to be between the hi and lo mark, don't add oil to a stopped engine unless you know what you are doing and having previously checked the oil and 'guesstimated' how much to put in.

 

[sbloxxy]

I know from recent experience that many garages simply don't know how to fill and check a 911's oil system. I had my last oil change carried out by an independent garage who allegedly look after various local Porsches. However, they let some young apprentice lad refill the car and he filled it while it was cold and not running - result was an extra 4-5 litres of oil went in. I found that a relatively easy way of draining the excess was to unscrew the drain plug under the oil thermostat.

 

[Dave Wilkinson]

Colin,

You didn't mention what the oil level gauge sits at when ticking over with a warm engine??

If the oil can be seen in the filler when warm it sounds as if it is drastically over-filled. As Pete (Bones) said, the oil level MUST be checked when the oil is really hot - at least normal running temperature with the oil thermostat open. You can tell when the thermostat opens since, as you drive from cold, you will notice the oil temperature rise steadily up to, perhaps, the 8 o'clock level and then, as the thermostat opens, the temperature will drop quite suddenly to the notch below. At that point the hitherto cold oil from the cooler will join the flow and you will need a good 10 minutes running to get all the oil to a decent temperature.

Once heated up, you should leave the engine ticking over with the car parked on level ground and THEN check the dipstick. Again, as Pete said, the level should be somewhere between the upper and lower marks. My guess is that you will find the level substantially over the top mark - and the level gauge pegged to the top of the scale!! If this is the case you should take steps to get the level reduced as soon as possible. Draining from the crankcase is probably best although it will mean removing the undertray. You can suck some out from the filler pipe but it's not recommended, particularly since the oil supply from the tank to the engine is unfiltered (it's filtered on the way back) so anything you drop in there is likely to find it's way to the bearings. A turkey baster with a long pipe can be used but make sure it's very clean!!!

With the oil level at the neck of the filler I would guess you are at least 3 litres overfilled. Failure to remove some will get you an oil contaminated inlet tract causing faulty operation of the air metering and idling.

It's not an uncommon problem, Colin - many independants (and OPCs) have been known to overfill. Again, just to reiterate Pete's advice - don't ever check the oil when cold!!!

Hope that helps.

Regards

Dave

 

[bones]

God this makes scarey reading when garages do this sort of thing.

 

[colinb1]

ORIGINAL: jace71

colin, what is your oil level on the dip stick when the car is cold?

The only oil trace I can see is about a quarter of the way between hi and low mark on the dipstick but it is difficult to see.

p.s. should there be any oil on the dipstick when cold?

 

[Dave Wilkinson]

ORIGINAL: colinb1
p.s. should there be any oil on the dipstick when cold?

Colin,

Generally, no. I believe the dipstick is located in a part of the oil tank which receives oil from the engine and hence is only relevant when the engine is running. When the engine/oil is cold the oil thermostat is closed, preventing oil flowing to the cooler in the right front wing. Only when the thermostat is open and the oil at running temperature - and, hence expanded to it's maximum - is the oil level measurement considered relevant.

I agree with you, it is difficult to tell, particularly if it's new, clean oil. If you start with a dried dipstick it helps and turn the dipstick to catch the light to reflect the oil surface. It's no surprise that Porsche fitted an Oil Level gauge since it makes the job so much easier. Some people have grown to mistrust the level gauge and with a new-to-you car you must learn to judge the relationship between the dipstick and the gauge. Once you have that trust the job is far easier since you can check the gauge on most journeys when you stop at a traffic light, or pull in to a lay-by.

It would be helpful, Colin, if you could let us know how your Oil Level gauge reacts, where it points, when it moves, how far etc. etc. The foibles of the Oil Level gauge are well known to the experienced here and it's antics can be translated without resorting to the dipstick.

Regards

Dave

 

[colinb1]

Thanks for the input. The gauge does as you mentioned - goes up to about the 8 o'clock position and then falls back a little. The oil pressure gauge is on 5 when running but drops a little when idling at hot. She's tucked away for the evening but I'll be out with her tomorrow and will pay particular attention to what the gauges are showing and will post more tomorrow.

I really appreciate your help on this. Thank you.

 

[sbloxxy]

Very well put, Dave. I think Porsche actually put that gauge there just to scare the hell out of us on a regular basis. Don't know about yours but the needle on mine dives to the bottom when you floor the accelerator or drive at high speed. Again, I've been told this is normal behaviour...

 

[Dave Wilkinson]

Steve,

It is absolutely normal behaviour - and designed that way. Because the 911/964/993 engine is "dry sumped", the oil is stored in the tank and used by the engine as required. Only when the engine is ticking over is that oil requirement at it's minimum. Couple that with the nature of oil to expand when hot, you then arrive at the requirement to have the engine hot and ticking over in order to measure the amount of oil left in the tank (which is what the dipstick and oil level gauge measure). As soon as the engine is rev'ed beyond tickover, the oil requirement increases, the tank level drops accordingly and the gauge disappears off the bottom of the scale. This oil level will constantly move up and down during a drive - exactly as intended - and the oil level gauge should be ignored completely until the conditions for measurement are met, i.e. standing still on level ground with the hot engine ticking over for at least a minute.

The great problem most people have in getting their mind around this is the natural learning process we have which associates wet-sumped engines and oil level. Different way of working, different way of measuring.

This is certainly not the first time this has come up and I'm pretty sure it won't be the last!! We all do it at first and we all have to learn.

Regards

Dave

 

[colinb1]

Just an update for you. I took the car back to the garage who did the oil change for me. They were very concerned to hear of my observations... I've used them for almost 20 years so they're keen to keep me happy.
When I got there - around 20 minutes drive away... fast dual carriageway and little roads... they checked the oil level within 2 minutes of me arriving. The dipstick level was "spot on" (I stood beside them as they did it). I asked them to look at the level in the filler neck and that was fine too. Certainly nowhere near the level I saw it at yesterday. They commented that when I had seen it like that it must not have been sufficiently hot. So I came away feeling a bit happier.
Certainly she is going very well right now. A service beckons in the next couple of months. What kind of price is normal for a 964 6,000 / 12, 000 service (or is that the cue for another thread?)
I'm interested to compare what everyone else is paying because the North East Official Porsche Centre is now offering PCGB members a 50% (Yes - Fifty Percent) discount on labour charges on cars over 7 years old. Added to the 15% off parts bought from them, it's looking increasingly possible that the car may visit an OPC again soon.

Thanks to everyone for their help and advice. It is much appreciated.

 

[Jeff Forsyth]

I agree totally with Dave-on the level with oil at temperature-equally this is a good time to do top up's with the engine running. As Dave mentioned the oil needs to get to temperature in order to gauge how much you should ultimately add, so add a small amount at a time and note how long it takes the level needle to rise, let it settle then refer to the dipstick several times before adding anymore.

Sincerely