help, advice about oil leaks in differential area

[deQuincey]

hello

I would appreciate some help on this problem

atecedents:
1- I had no leaks in the past in this area,
2- I changed oil using 80w90 in november 2009
3- some time after that (aprox february) i started seen one or two small drops in the floor at that rear area of the car
4- little by little two drops increased to 4, 8 ,....,
5- I have no leaks in the rest of the car

a fact: when the car is not moving from the garage, no drops appear, only after a ride some drops in the floor appear, and after that, it stops

the issue:

1- last tuesday I cleaned the differential case, and checked the oil level (it was ok), I found a lot of dust mixed with oil, and dirty in the case and the sorrounding elements, and I cleaned almost everything with a cloth wet on gasoline

2- on friday it was hot weather and I drove the car 200 km,

3- when on saturday I checked the floor, I found this:

this is the size of the spill in a protection paper that I put under the car

the red arrow represents the point from which the oil drops fall into the protection paper in the floor, that part is a structural member, the transmission tree that passes through the mentioned structural member is dry (no oil on it)

all the blue area has no leaks or drops falling from it, neither the blue arrowed conection points to transmission tree and to the wheels

the strange thing is that the dropping point is situated frontwards relative to the differential, in a structural member of the rear suspension, and in the way of the transmission tree I can not appreciate any oil or leaking (i.e. the possibility of the leaking differential conducting the oil frontwards through the mentioned transmission tree), the rear braking deposit is dry, and the brake fluid level is ok

can anyone help ?

additional information: on saturday I cleaned that area again with a dry cloth, I drove the car 20km, return home and put the protection paper to check any spill. the result was: no drop on it, nothing

regards

 

[JhwShark]

With the case you present, first thoughts would be a compromise in the upper edge of forward diff. seal. Possibly with enough turns (driving distance) you get it leaking out and then down onto the member it drips from. Low distance not enough movement to get fluid up and out...??? Interesting, usually drips presenting in the manner you indicate are seals but you see nothing on the seal area and nothing is picked up with a dry towel when you wipe the upper area??

Put it up on jack stands bring a good light and look as well as feel the top of the shaft above the floor drip rear-wards to the input shaft, use some latex gloves...touch the top look at hand repeat until you have felt the area in question...you should find and trace where the fluid is coming from and the whole drip route.

Was the oil you replaced in the diff same brand and model; i.e.: classic vs. synthetic? Synth's into previous classic for some gaskets and seals will not expand as much into the gasket material. Thus a the gasket/seal does not expand as much eventually compromising the g or s. Your case does not sound like this though.

Jon

 

[61porsche]

Mystery leak

From the amount of oil forward of the diff it appears to be trans/ forward related and turbulence/ raceway back to the diff area. The emergency brake cables, etc. Selector seal, reverse light switch, vent, etc. Clean really good, pressure wash if you can. Maybe tape a piece of carboard to the center bearing support and a quick trip might reveal the real source.

 

[deQuincey]

From the amount of oil forward of the diff it appears to be trans/ forward related and turbulence/ raceway back to the diff area. The emergency brake cables, etc. Selector seal, reverse light switch, vent, etc. Clean really good, pressure wash if you can. Maybe tape a piece of carboard to the center bearing support and a quick trip might reveal the real source.

hello

let me understand your text

the mechanism of movement trans/forward seems impossible for me, can you please explain a little bit ?

I assume that when diff oil leaks from the front gasket, that oil will be touching a cylinder (transmission tree) that rotates at high speed, so the oil will be given an angular speed, and when the mass of the oil drop reaches a certain speed will depart from the transmision tree following an helicoidal trajectorie facing backwards (due to the car moving frontwards), ...

if this is the case I can not understand how the oil drop can move frontwards

please tell me your ideas

thank you for your help

regards

 

[Arde]

I think the question is it is possible that the oily fluid is either engine oil or transmission oil pushed back rather than from the differential forward.

 

[61porsche]

Mystery oil leak source

There is an oil leak in front of the differential. The source is therfore in front, forward or ahead.

You say the car doesn't leak while sitting; only moving. The trans can do the same thing as the differential.

Air movement is likely blowing oil from the transmission or engine onto parts. ( Rear frames don't leak, parking brake cables and wire retainers, etc. and that's what clue i'm reffering to. )

Your oil spot on the carboard doesn't look radial ( from a rotating part) with a solid line. Looks like a drip from oil hitting a secondary area.

Is there radial evidence on the spare tire area?

 

[deQuincey]

thank you both for following this item with your interest and advices,

there is no evidence of oil projected radially in the spare wheel, and no oils drops from that area

I get your point of oil from the transmision, (i imagine that you are speaking about the gearbox, right ?), so I can assume that either oil is comming out from the engine or the gearbox (both located in the front side of the car), and doing its way back through the transmission tree until the point in which it it touches the mentioned suspension element,

but, here it cames the doubt: how can this be possible without unless a tiny drop in the mentioned path from the front to the rear ? as there is no evidence of that drops in the floor carboard I can not understand

another clue is that even if the transm tree is a hollow tube, you have an intermediate point in which it stops and connects the next part of it through an hexagonal rubber element, if some oil would have been comming from the front, it will certainly accumulate there and eventually drop from there

also if there is a oil leak in the engine or gearbox, the origin point would be the best possible point for a vertical oil drop when the car stops

remark: engine camshaft seals (both front and rear) were changed in november 2009

I agree with the sentence: mystery leak !! :-D

many thanks and regards

p.s. I ordered CASTROL classic oil for gears (EP90) from england (not available in spain), my intention is to change the diff oil a.s.a.p.

 

[deQuincey]

some additional information

i have been taking a detailed look to that area:

here you can see the diff and frontwards the cardan of the transmission tree, the illuminated part in front position is one of the silencer of the exhaust

in this pic you can see (looking upwards) a "reservoir" that covers the cardan, if you look to it in detail you can see very wet oily and dust adhered to the walls, also you can see a clean (without oil) conexion to the differential, apparently no leaks

and here it comes "the spreading and conducting" mechanism, in my opinion, there must be a sort of leak somewhere around that upper area of the differential, then the cardan may act as a "fan", possibly suctioning the oil drops that spin off until they touch the walls of the mentioned reservoir, then the "V" form of the walls act as a conduction to the lower central point, and there is the leak concentrated

agree ? any other ideas ?

regards

 

[61porsche]

mystery oil leak location

Try this.....
"Important: If the final drive looses a lot of oil, this may be
caused by an air bleeding pipe forced in inadequately.
Note that air bleeding holes (E) must be at a right angle to
the crown wheel." from the manual.

If you recently change oil and the level is a bit higher or in your case sprited driving up and down the beautiful northern mountains of Spain, the inclines and oil levels could cause oil to come from this vent which is on top.( Apparrently LS do it more according to the factory back then) The gearbox has a vent too.:wink:

Looking at your new pic 2- the dark oil streak above the pinion flange which is most noticable is the clue there.

Try draining just a pint out to lower the level. If it stops leaking- you know why.

 

[blumax]

61 Porsche echos my thoughts--

Overfilling the diff is the likely cause or major factor in your mystery leak. Overfilling will force an overflow of excess lube following spirited runs from the relief valve located on top of the diff. Solution--only fill according to specs--and only fill until the lube level is at the bottom edge of filler hole--allow any excess to drain off before installing the drain plug.

 

[deQuincey]

hi

I appreciate your advise,

I did not made the lube change myself, so I can not tell about the final reached level,

As I am not happy with the lube they used (80w90 instead of the prescribed 90), I am going to change it again (with Castrol Classic lube EP90) and this time I will do it myself, so I will check the adequate level precisely

also is my intention to have that area cleaned thoroughly to avoid grease and dirt deposits that avoid showing the critical areas when leaks happen

thanks and regards