1996 S850 Wagon Oil Cap problems and slow leak

[polskamafia mjl]

I'm a little confused about what kind of car we are talking about here: s80 or 850 and Turbo or N/A. If it's not a turbo there is a low chance of the PCV being clogged. Along with JackBlackBurn's idea, put your hand over the dip stick to see if their is positive pressure or a slight vacuum, or you can do the balloon test and place a balloon or something inflatable over the dip stick to see it it inflates. If it inflates on a turbo then the PCV needs to be cleaned, if it inflates on a non turbo the flame trap is most likely the culprit.

[MareJanee7]

Thanks for the advise about keeping the oil level about halfway between the bottom mark and the top mark. I guess I have been over-filling and stressing out for nothing.

MareJanee7

[mcp]

I'm curious. How far above the full mark were you filling it?

[MareJanee7]

Somewhere between the top mark and the top of that piece of metal. It was not up on the stick part. Could this be why oil sprayed under the hood?
MareJanee7

[mcp]

Don't know that overfilling would lead to oil on top of the engine, but I will guess that it might have and maybe that's the reason your mechanics thought the oil cap seal was bad and replaced it at the last two oil changes.

The marks on the dipstick represent the minimum and maximum oil levels. You are not supposed to fill it past full. Now that you are "down to the top mark", let it get down towards the bottom mark before you add more and see if it continues to leak oil onto the top of the engine.

I check the oil level on my cars with the engine cold and on a level surface. First thing in the morning after it has been parked overnight is when I usually check it. Checking it shortly after driving, say after pulling into a gas station and filling up , you will still have oil up in the engine that has not drained down into the oil pan, so a level at or above the minimum mark is fine, no need to add any.

While we are talking oil, I now use Mobil 1 10W30 in my Volvos and try to change it every 5000 miles. A lot of my driving is on the highway for around 30 minutes or more, so if I go 6000 miles or even a little more between changes I don't worry about it. I have also used Valvoline 10w30 conventional oil and Valvoline semi-synthetic 10w30. I also use either genuine Volvo oil filters or Mann, but was happy with a NAPA Gold filter manufactured by Wix when I needed to change my oil and had no time to run to the dealer 30 minutes away. On my 1996 850 with 196k miles, I usually have to add a 1/2 quart after 4000-5000 miles or just go ahead and change it when it starts dropping towards the minimum mark.

Here is a bulletin Mercedes sent to dealers in November 1995. Apparently even dealer mechanics were overfilling cars with oil.
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TO: ALL MERCEDES-BENZ PASSENGER CAR DEALERS
DATE: November 1995 (Supercedes S.I. MBNA 00/57, October 1994) REF. NO. MBNA 00/57A
Revision: Revised checking/correcting oil level procedure

SUBJECT: ALL MODELS ENGINE OIL LEVEL

It has recently come to our attention that some Mercedes-Benz vehicles are being operated with too much engine oil.

Additionally, it is important that the oil dipstick remain fully inserted in the oil dipstick tube for a minimum of 3 seconds before rechecking the oil level again. Removing the oil dipstick immediately after insertion, will result in an erroneous indication of the oil quantity within the engine.

Excess engine oil affects the engine`s drivability and performance, and may lead to engine damage.

Dealers are reminded to fill the engine with the exact amount of engine oil specified for that engine (e.g. if specified quantity is 8.5 quarts, do not fill with 9.0 quarts or 9.0 liters of engine oil). The MAX mark on the oil dipstick must not be exceeded (upper arrow, Figure 1).

Also, please remind your customers of the proper procedure for checking/correcting the engine oil level. Emphasizing that the engine should be at normal operating temperature (80 °C) and that the vehicle is parked on a level surface. The engine must not have run for approx. 2 minutes, to allow the engine oil to drain into the oil pan.

Then after removing and wiping off and reinserting the oil dipstick, allow the oil dip stick to remain fully inserted in the oil dipstick tube for a minimum of 3 seconds before rechecking the oil level again.

Ideally, the engine oil level should be around halfway between the MAX and MIN marks on the oil dipstick.

Figure 1 P01-0028-B81

Also, the customer should refrain from frequently "topping off" the engine oil level.
Never add engine oil above the MAX mark on the oil dipstick (upper arrow, Figure 1, page 1).

For approved engine oil classifications and correct viscosity grades, refer to the latest edition of the Factory Approved Service Products sheet.
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[mcp]

Just to be sure, the black plastic cap in the center of this picture on top of the engine just beneath the V in the word valve, that says "engine oil" is the oil filler cap you are having trouble with right? It should not take a special tool to get it off, just twist it counterclockwise with your hand.