300CE Gearbox leak

[Adeinfrance]

Hi. Just got me car back from the mechanic who informs me that my gearbox leak is from the joint where the gearbox meets the engine. I didn't realise that this was possible. Is it as simple as changing a gasket. He also informs me that the gearbox is on its way out hence the clonking when it changes gear, so sort everything out when the gearbox goes in. A mechanic friend in England told me the box was knackered some time ago but I thought he was just saying this because he didn't want to rectify the problem. Anybody got any ideas as to whether he is correct or not, bearing in mind he is french and they prefer to bolt new bits on instead of repairing, as the car drives fine with oil in the box.

 

[mejermy]

Depending on where in S France you are I have have a great guy, Manuel Hernandez, about 20m west of Avignon. He would repair rather than fit new any time. I'm in UK for Crimble, but let me know if this is of interest.

Malcolm

 

[kth286]

clonking would normally be harsh gearchanges due to a vacuum leak somewhere.

Or

the mounts for gearbox/engine have perished.

or the clonking is from the diff or driveshaft area due to worn rubber
driveshaft couplings.

If the leak you mention happens after car has been standing for say a week
or more the fluid can drain back from the torque converter into transmission housing and start to overfill the transmission thus causing fluid to leak past
front input seal.

There is nothing wrong. Just top up and drive car again.

If however the leak is happening after every drive and getting worse, then the 'front pump' seal is gone.

It needs removal of transmission and replacement of:

* input seal

* pump O ring

* pump gasket.

If this is being done, then get the rear engine main seal done at same time whilst engine is parted from box (small extra cost).

Time to do the seals is approx 2 to 3 hours, plus the big job of R&R gearbox.

You need someone with experience of doing this stuff with your generation of Merc.

 

[Adeinfrance]

That's great advice thank you. It only loses oil when driving, for example it was topped up in the south of France and had lost all the oil by the time I reached Calais. The first I knew of it was when the smoke appeared in the rear view mirror and the oil leak had reached the point underneath where the exhaust crosses to the last silencer and was burning on there. When it has oil in it it changes gear superbly. To change the seals mentioned could a very competent mechanic do it or is it a specialist gearbox thing? Do you have an idea of cost as it might be easier to get a secondhand one from Dronsfields who have quoted me £200 plus delivery. I've owned the car 13 years now and had it totally restored and repainted 6 years ago before coming to France, it's only done about 60 miles in the last 3 years and I know it's not worth much but don't want to give up on it now. If I charge the battery after leaving the car for 8 months it still starts first time every time and doesn't miss a beat, incredible.
Forgot to ask is it worth buying the product that stops leaks for automatic transmission or is it a waste of time?

 

[Adeinfrance]

Hi Malcolm

I'm just 30 minutes north of Beziers near St. Chinian on the Herault/Aude border, 1 1/2 hours from the border with Spain. I think Avignon is 2 hours from me.

Ade

 

[kth286]

do think it might be burning oil in the engine and going out of the actual exhaust ?

I ask, because in that scenario, it could simply be the diaphragm in the vacuum unit (bolted to side of gearbox) ruptured.

The vacuum then sucks gearbox oil back to engine, where it gets burnt out through g/box. It would be good if it was just that. Check it out and report back.

 

[MR-AUTOMATIC]

The oil leak could be from the pump or torque converter both will have to be checked note the transmission can be damaged internaly if you run it to long without oil. also the oil CANNOT leak from the torque converter or front seal if the car stands for a week the torque converter can drain back but it goes into the sump pan of the transmission the car could sit for a year or more & should not leak

 

[Adeinfrance]

Hi again. It doesn't use much engine oil. When you look under the car you can clearly see, as it is totally covered in oil, that it has leaked from the gearbox and blown back along the underside of the car whilst driving, then the smoke starts when the oil reaches the exhaust pipe where it crosses from the middle to the left hand of the car. I am just trying to determine my best options to fix it, but as the value of the car is basically nothing I don't want to put a reconditioned gearbox in it. I am a builder not a mechanic, but surely if the car changes gear perfectly when it has oil in there can't be a lot wrong with the gearbox can there? Can anyone answer my question as to whether changing the pump seals as suggested is possible by a competent mechanic or would the box have to go off to a specialist?
Thanks in advance, Ade
p.s. If any of you auto gearbox mechanics think you can fix it and fancy a weekend in the south of France let me know.

 

[kth286]

The oil leak could be from the pump or torque converter both will have to be checked note the transmission can be damaged internaly if you run it to long without oil. also the oil CANNOT leak from the torque converter or front seal if the car stands for a week the torque converter can drain back but it goes into the sump pan of the transmission the car could sit for a year or more & should not leak

if the oil does drain back to the gearbox from the torque converter, it will
overfill the transmission, just like if you overfill transmission when topping up the gearbox.

Where does this excess oil go, except out via the front input seal as a leak ????

 

[300CE]

As stated by KTH, the clonking could well be the propshaft coupling as i had a knocking when i got mine. The part is cheap and isn't too difficult to change:

http://www.mbclub.co.uk/forums/engine/90411-w124-propshaft-coupling-part-number.html

 

[Will]

It you can get a decent used autobox for £200, considering the major leaks and the fact that this one clonks and has been driven whilst low on oil, my advice would be to obtain another box and get it fitted by a competent local garage.

What's the mileage on your car out of interest?

 

[MR-AUTOMATIC]

if the oil does drain back to the gearbox from the torque converter, it will
overfill the transmission, just like if you overfill transmission when topping up the gearbox.

Where does this excess oil go, except out via the front input seal as a leak ????

Behind the input seal there is a drain back hole on the pump body this is where the oil drains back through from the torque converter into the transmission. It will only drain back a litre or two the torque converter will stay at least half full when the engine is switched off. You should always check the transmission oil with the engine running & when the engine is switched off then the oil level will be above the full mark on the dipstick because of the oil draining back from the torque converter. hope this helps & answers the question

 

[Adeinfrance]

Mileage on the car is 195K. I bought it 12 years ago showing 141K with full service history from Hughes of Beaconsfield. Eventually the head gasket went and an Indy wanted £650 to replace it so I bought an 85K engine from Ebay for £50 from a company that used to supply cars to the Ant n Dec show and this engine was from an advert for Norwich Union where they crashed an estate car, and got it fitted for £400. Couldn't see the point in changing the head gasket on an engine that had done 190K when I could change the whole engine for that price.

 

[Will]

With a 195k gearbox that clunks and has been run low on oil, I'd definitely look at a good used replacement box!