GRUWEZ

After a spirited drive I noticed the oil level gauge in the dash of my 993 TT was in the red. So I thought it was time to top it up. I did the usual routine: engine fully warmed up, car sitting level, engine running. With one eye on the gauge I started topping up through the filler tube in the engine compartment. Before I knew it, oil was overflowing out of the filler tube into the engine compartment and onto the heat exchanger. Yes, that was a very nice mess I got myself into. By that time, the oil gauge was about at the 1/2 mark (needle horizontal). But when I looked into the filler tube, the oil was nearly at the rim. Still with the engine running, I used the dipstick to check the oil level. The dipstick reading was at maximum. I know many members advice to keep the oil level lower than maximum on the dipstick reading, but still, I have never seen a situation where the oil level is so close the rim of the filler tube.

Just to be sure, I drained the oil tank and measured the amount of oil that got out. That was about 7.7 liters or a little more than 8 quarts. The Porsche instruction manual says that the oil capacity without a filter change is about 8.5 liters (8.9 quarts).

I am quite puzzled by this. What am I looking at? A malfunctioning oil level sender in the tank? Also the fact that the dipstick says "full" and not "overfilled", but still I have oil all the way to the rim of the filler tube makes me wonder. Any ideas?

ca993twin

I don't know why your oil level is at the top of the fill tube: blockage in the fill tube? There is a "pullout" extender in there which can deteriorate over time, and perhaps clog that filler tube? Get rid of that thing if you can reach in and get it out. Perhaps you were pouring the oil too fast? These are not easy cars even for something simple like adding a quart. Or checking the oil level... see below.

The dipstick tells the true story of the amount of oil. It is good to calibrate your gauge with the dipstick for your convenience. If they are way out of whack, the gauge level can be adjusted by removing the oil level sender in the tank. It has a little "float" thing on an arm. The arm can be adjusted up or down by bending it a little bit until its right. I'm not sure, but I hope the sender is above the oil level in the tank, so you don't have to drain and refill with every adjustment.

Overfilling the oil tank can lead to smoke and oil draining into the turbos, that is why we normally keep the oil level in the lower 1/3 or lower 1/2 of the "full" markings.

Basal Skull

I average about 8L without filters and 9L with filters. Don't trust the gauge, always confirm with dipstick prior to adding oil. The fill tube has a retractable tube in it that can be extended to help with the fill but due to its design, restricts the oil during fill and if you fill quickly, it will back up and spill... If you didn't extend it, it will definitely slow the oil and you need to fill very slowly. If you would have given it a few seconds, the oil in the tube would have drained into the tank.
hope that's helpful.

Basal Skull

^ what ca993twin says, (typing too slow on the iPhone ...)

GRUWEZ

Thanks for the feedback. I removed the pullout extender and checked it for clogging. Everything OK there. Even with the pullout extender removed, I can see the oil stand about 2cm below the rim of the filler tube. Meanwhile I have read quite a few posts here on Rennlist regarding the oil gauge and the dipstick. I will drain some oil until my dipstick reads halfway the spiral and perhaps recalibrated the gauge afterwards. Funny, I have owned this car for ten years now and this is the first time this happens.

x50type

You need to fill the oil tank very slowly, stopping to let the oil get into the tank, otherwise you get an air block and and incorrect reading with possible over flow.

Patience is a virtue.

Take your time...

x50type

Grewez said, I have owned this car for ten years now and this is the first time this happens.

Perhaps it's time to move on to a Fiat 500!

Quadcammer

very unusual. fwiw, i haven't looked at my dipstick in 3 years, i go solely by the gauge.

mongrelcat

You sure the car is level when you're checking/filling? If not, that could explain it. (Don't ask me how I know.)

GRUWEZ

Yes, car is level. Next plan is to drain the oil tank again, remove the plastic wheel well linings and check the tubing running to the oil tank.

Meanwhile, if anyone else has tips or hints, feel free to chime in.

OverBoosted28

When you state engine was "fully warmed up", did you check temp gauge? It needs to be at about 9 o-clock for the thermostat to open and then the level gauge "should" give a correct level reading. As long as you have pressure and check the level on the stick, I wouldn't worry about the gauge.

GRUWEZ

Yes, fully warmed up with the needle of the oil temp gauge even above the 9 o'clock position.

GRUWEZ

I did some more investigation and removed the plastic wheel well liner to get access to the oil tank and the oil tubes. After having removed the oil sender unit from the tank, I could feel inside the spiral end of the dipstick. I have my car on a lift (level) and the middle of the spiral is about 95cm from the floor level with the dipstick fully inserted. So I suppose this is what the normal oil level would be with a fully warmed up engine. The top end of the filler tube is roughly 100cm from the floor level, which means the oil level there should be about 5cm below the top end of the filler tube.

So far so good. Next thing to investigate is the resistance of the oil level sender. Remember, it used to work properly until last week. Now, all of sudden, the needle only goes up when the oil level is way too high.

One other thing I would like to check is the oil thermostat. How do I verify it is opening and closing properly?

Thanks for the input!

ca993twin

A simple check for the thermostat is to carefully watch your oil temp gauge from cold start. You should see it rise, then fall back suddenly... that's the thermostat opening. It will then rise more slowly.

GRUWEZ

Checked the oil level sender today.
Low = 3.7 Ohm
High = 38.0 Ohm

I suppose this is not what it should be? For a 964 the specs are 0 to 180 Ohm. Are they the same for a 993?