Rear main seal or Concentric slave cylinder

BlakeS94

Changed the oil and filter on my 2010 Mondeo, mileage is just over 122k miles. Noticed this under the engine where the gearbox sits against the engine (flywheel area)

I've seen that with this vintage mondeo what can happen is the clutch slave cylinder takes a sh1t before the clutch plate or flywheel are ready to go.

Not losing brake fluid, I changed it last week along with the master cylinder cap and the level is the exact same, engine oil level was the same, checked it before I drained the oil.

No visible leaks from the top end, or loss of fluid at any time and I check all fluids on a weekly basis bar the gearbox oil for obvious reasons.

The leak in the picture isn't dripping, and nothing more has come out when I revved the engine at idle, or pressed the brake pedal down hard.

Just seems fresh which is concerning.

Clutch pedal feels soft but it returns well enough, bled it when I did the brakes it made a small difference but not much, car drives and pulls perfectly fine. If it was a failing clutch slave cylinder I don't think it would give a warning and it would just pop one day while out driving.

Any thoughts?

blackbox

Have you confirmed that the leak is hydraulic fluid rather than oil?

BlakeS94

I don't know how to confirm that?

Toyotafanboi

Looks like there's another oil sweat higher up too?

That's engine oil IMO, it's jet black and if you'd lost that much brake fluid you'd know about it, the level would be low and you'd be losing the pedal.

BlakeS94

So rear main seal?

BlakeS94

The bit of oil higher up is from the oil filter dripping down, its in an awkward spot under some wiring and above the air con compressor so oil leaks down when changing the filter

BlakeS94

After some further research I have a feeling it could be the transmission input shaft seal that's gone, reason being is that I am not losing a drop of engine oil or brake fluid

CoBo55

Can you check the gearbox oil level? Are you certain it isn't spillage from the recent engine oil and filter change? It looks far too dark to be gearbox oil. What does it smell like?

BlakeS94

I didn't get any of that distinct gearbox oil sulphur smell. Although I didn't exactly stick my nose to it either, I could just remove the fill plug on the gearbox and check if oil comes pouring out, I guess it is possible that engine oil could have dripped down and collected at the furthest down point which would be the gearbox where I took the photo. I'll have a closer look when the weather clears up

If there is no any oil leak from top of the engine, then your options is very limited. Slave cylinder (no lost fluid level), rear main seal (no lost oil level) or gearbox oil seal (not checked).

CoBo55

https://www.boards.ie/discussion/comment/118569852#Comment_118569852

You don't have to stick your nose in it, just put some on your finger and see does it smell/feel like engine oil or gearbox oil. Is there anything else above that spot that could be leaking? Steering rack etc?

BlakeS94

What's above that is the engine oil filler neck, it could have been someone missed a good bit and it would have flowed fown and collected there on the gearbox I think

BlakeS94

What I think I'll do is clean it off, leave it few days and re-inspect

CoBo55

Good idea, it could all be about nothing (hopefully)

BlakeS94

Yeah I just saw the "leak" in that area of the gearbox and I panicked and went with first and worst case scenario, hopefully all is well.

BlakeS94

Cleaned the black *unknown* fluid off the bottom of the bell housing, will come back in a few days with an update.

I think I can rule out gearbox oil because it doesn't really smell.

Also rule out brake fluid because im not losing any, and it would never be that black even if it was very old.

so that leaves engine oil, or the possibility that its spilled oil from a long time ago and it was never cleaned up, which is why it's so black. I noticed quite a lot of black oil around the oil cooler/filter housing. And some very slight seeping from the filter itself, I only just changed it with a Ford filter, put the O-ring in the correct place, lubricated it before installing and torqued to the specified 25nm.

That's a good bit away from where the bell housing leak is, time will tell, I'll update for anyone who's interested in my troubles.

The car is still driving quite well.

Once I seen the car where was only 0.5l oil including oil inside oil filter (refill capacity 4l). It droves too well, if it is possible to say so.

BlakeS94

Yes but I'm checking the oil level, it's stayed at 3/4 of the way between the two marks on the dipstick.