Docmichael

My C4 transmission has a pipe which seems to originate at the top of the box and then bends downwards at its end. It is an open ended pipe approx diam 7mm. It seems to be some sort of breather pipe. I have seen it on diagrams of the C4 box but can find no reference to what it actually is. When the car has been standing unused for a couple of weeks or so, trans fluid starts to drip out of this pipe in significant amounts, 50+ mls, it behaves as though some sort of siphon action suddenly starts up. Can anyone throw any light on what might be happening here and suggest a cure ? Help!

groho

Its the vent tube, as fluid gets hot and expands, it gives the tranny the ability to breath. The torque converter in the front of the tranny has about 2-3 liters of fluid. When the transmission sits for a long time that fluid will drain back into the transmission and will often overflow out the vent tube. This happens because the check ball in the pump sometime leaks or the spring is weak allowing fluid to flow backwards into the transmission. This is not a problem, just a mess. My first fix was to connect a piece of vacuum hose and secure it facing upwards so the fluid will flow back into the tranny but still let the tranny breath. I eventually fabricated a small reservoir (177ml) with a hose fitting on the bottom and a screw on breather cap mounted that on my inner fender, so any fluid that passes up the hose or into the reservoir will flow back into the tranny, but still allows the tranny to breath. Search Girling Reservoir on internet.

barnett468

check your trans fluid level when cold. if it is more than around 3/8" above full, it is too high.

Docmichael

Groho and Barnett, thanks for the diagnosis and advice, much appreciated and will act on it.