Engine oil leak opinions?

[450fab]

Hi all,

I've just bought into the Mercedes community with a fifteen year old W203 C180. It has around 130,000 miles on the clock and has been owned by myself for around a week.

I bought this car to try and expand my mechanical experience beyond my current competency of simple things like oil and fluid changes, brake changes, and chain and sprocket-type work on motorcycles.

Anyway, this morning I've found my first problem-project; what appears to be an oil leak. After sitting all night, and running the engine for around 15-20 minutes to run a pump for the tyres (another problem for another thread), I find a significant puddle of oil under the engine. I've only a hydraulic jack to hand at the moment, so haven't been able to get underneath to give a good look, but the engine looks to be covered in oil.

Here are some snaps taken from the vantage point of the right and left front wheel arch, and also into the engine bay from above.

https://imgur.com/a/yqZoN

I've checked the dip stick, and there's oil on it (might be slightly too much actually), and I did a computer check of the oil when the engine was slightly warm on a flat driveway, and got a thumbs-up; no issues.

When I bought the car last week the computer did say it wanted 1L of oil which was promptly provided; w10-30.

My plan of action now is to wash the engine bay down to clear the crud in there, let the engine run for 15min and see how quickly the oil forms on some cardboard underneath.

Next I'll see about getting some UV fluid so I can see with my UV torch where the oil is coming from.

Then, when they arrive, jack the car into some stands and have a close look with the torch.

My very uninformed feeling is the oil pan gasket on the underside of the engine may be leaking and require a replacement. Total stab in the dark though. How much work does that involve?

What does everyone think of my analysis so far; have I missed anything? Does anyone have any thoughts/suggestions?

 

[bob6600]

First thing to check is the sump bolt. Loose or with a re-used collapsible washer could be an easy fix. Next obvious as you said is sump gasket. You do really need to get underneath it.

 

[markjay]

If the engine breathers are blocked, pressure will build up in the crankcase and seals will blow. The cam cover seal other the rear crankshaft seal are often affected.

If the breathers are cleaned the oil leak might stop without having to replace the leaking seals, but not always.

But ultimately this might be any seal, best thing would be to wipe the engine dry and then check regularly for leaks. This should help pinpoint the source.

 

[grober]

As above ^^^ lots of breather pipes on the M271 motor. Worth checking them all.
Haynes do a manual https://www.amazon.co.uk/Mercedes-C-class-Petrol-Diesel-Service/dp/1844257800&tag=amazon0e9db-21

 

[450fab]

Update:

I monitored the oil over the Christmas period, and I was losing probably just over a teaspoon or-so of oil a day from what I could eyeball on the cardboard I left underneath. Not a scientific measurement, but the dip stick never changed, and the computer wasn't complaining of no oil.

I was able to book some time on a lift and carry out a service I was planning to do: oil & filter change being the relevant servicing.

There was no oil around the sump bolt, which was on nice and snug. The oil appeared to make a big appearance behind the auxiliary belt.

Here's a photograph Oil buildup seen from underneath and behind front grill - Album on Imgur

I didn't have time to get a proper look as it's very cramped in there, and I think I'd need to remove the radiator or something to make space.

I carried out my oil service regardless, added some 10w-40 and a tin of Wynn's Engine Stop Leak, swapped the filter for a new one and replaced the seal.

Half a week later and I've not seen any leaks since. I've just given it a spirited drive, got the oil to around ~70 deg c. and parked it over some clean cardboard for 20 minutes with the engine running and not a drop!

Do you think the Wynn's has rejuvenated some seals somewhere, or might the oil filter have played a part in this (the case didn't seem oily when I was handling it)?

 

[grober]

Location of the oil would indicate a leak around the timing case area. One candidate would be the main crankshaft front oil seal behind the crank pulley. Over time at high mileage a lip is worn on the crankshaft leading to a poor seal. On older cars this can be solved with a new seal repositioned to bear on an unworn section of the shaft. However removal of the crank pulleyand seal can be problematic so most people live with the leak unless its excessive.