BMW E46 Lower Radiator Hose Leak at Temperature Sensor – M54 – E39 X5 X3 Z4 Z3
Replaced a bunch of parts, one is the lower radiator hose when doing a belt replacement. It is leaking at the sensor connector. Replaced the sensor and it is still leaking with new. Here is a reply from Mike at BMW CCA. Do you have some additional recommends? “The new style hoses have a plastic quick disconnect mechanism that uses an o-ring seal. This was in response to the fact that the engine compartments are incredibly tight nowadays, and there’s no room to get in there with a hose clamp tool. Of course, the new style means it’s easy to break the brittle plastic and you have to think about the o-rings. Anytime you see an o-ring, you should take it off, inspect it for cracks or deterioration under a light, and if none is found, lubricate it with Vaseline before reinstalling. If the o-ring breaks when you take it off, it needed to be replaced anyway. I doubt the problem is the hose itself. I would say the connector is either not snapped in completely, the o-ring is shot, or the plastic is cracked..
I have a new hose and the temp sensor, here at my desk. All appears to be as I would expect. This is actually a fairly common issue when either the hose or the sensor are replaced, on the M54 engine applications. The o-ring compresses adequately as the sensor is installed in the plastic fitting at the hose end. During actual installation, I would lubricate the o-ring with some Vaseline. I agree with Mike, that the sensor is likely either not plugged in fully or that the o-ring is not seated properly or is damaged. Remove it one more time, inspect the o-ring, if it’s OK, lube it and re-install. Make sure that both snap clips are fully engaged. Please let us know what you find.