Ford Focus 1.6 Zetec 2007. - Driveshaft oil seals

Honest John Back Room » Technical matters
What is life like with your car? Let us know and win £500 in John Lewis vouchers | No thanks
View Threaded
Mon 18 Jul 2016 11:18
Ford Focus 1.6 Zetec 2007. - Driveshaft oil seals - argybargy

General question.

I believe that on my car at least (perhaps on all cars, I don't know) the gearbox end of the driveshaft rotates within a fixed oil seal which has no moving parts.

If so, why is the rubber seal not melted by the heat created by the friction of the rotating shaft?

Had some problems with driveshaft oil seals recently, and just wondering how they work.

Thanks.

Reply | Report as offensive | Link
Mon 18 Jul 2016 13:13
Ford Focus 1.6 Zetec 2007. - Driveshaft oil seals - Wackyracer
The same as most oil seals for the last 30+ years. the part that seals on the rotating shaft has a tiny lip that rubs against the shaft and will be lubricated and cooled by the oil that it is stopping from escaping.
Reply | Report as offensive | Link
Mon 18 Jul 2016 13:25
Ford Focus 1.6 Zetec 2007. - Driveshaft oil seals - focussed
Rubber lip seals are lubricated by the fluid that the seal is retaining, ie gearbox or differential lubricating oil. The "lips" of the seal should also be pre-lubricated with grease at the time of fitting as should the "land" or surface of the rotating shaft which the inside of the seal is running on.
If you have a problem with the seal running too hot are you sure that the internal size of the seal is correct for the size of shaft?
Reply | Report as offensive | Link
Mon 18 Jul 2016 23:18
Ford Focus 1.6 Zetec 2007. - Driveshaft oil seals - argybargy
Thanks for the responses.

I've had the seal replaced twice recently. The first time it was replaced after the existing seal started leaking about 18 months after a clutch change. Subsequent to that I had another seal and a recon shaft fitted after I was informed that the reason for the poor seal was that the original shaft was damaged, possibly by the person who did the clutch.

It occured to me to ask whether there are any moving parts in a seal because it didn't seem feasible to me that a fixed piece of rubber could accommodate a rapidly rotating metal shaft without leaking. It is the right seal for the shaft; of that I'm sure.

You've answered my question, and thanks again.
Reply | Report as offensive | Link
Tue 19 Jul 2016 00:12
Ford Focus 1.6 Zetec 2007. - Driveshaft oil seals - focussed
"It occured to me to ask whether there are any moving parts in a seal"

Yes and no - the inner part of the seal where the lips of the seal are, have a little bit of flexibility relative to the outer part which is rigidly fitted into the housing so the seal can cope with a very small anount of side to side shaft movement, depending mainly on the seal material's hardness and the type of material.

Oil seals are a very complicated subject,

I was involved in a warranty job on some hi-power diesels years ago.
The rear crank seals leaked after about 5-6 hours test running.
We kept replacing the oil seals with the genuine part - three or four times- a lot of expensive work to get to the seals.
Nothing was amiss, the 6 inch diameter seal land was perfect the seals were lubricated at fitment, the seals were square in the housing, the housing was concentric with the crank, the crank bearings were good etc.
In desperation we put more tension on the loading spring by removing the spring and cutting about a quarter inch out of the spring and reassembling the spring on the seal.
It worked and didn't leak again in service. The design department was not amused.
The service department were pleased.

Reply | Report as offensive | Link