Low coolant warning light

[ac427]

I think E46 M3's are great but christ almighty it's beginning to try my patience.
I noticed that the temperature gauge was a little to the right of the middle mark.
I didn't think much of it because it has strayed slightly before.
That was a couple of evenings ago.

I started it up tonight reversed off the drive and the low coolant warning light came up on the dashboard.

I opened up the bonnet but what can you really see unless the expansion tank has failed. It's reasonably new.

Sure enough the float was well down. Luckily i had 5 litres of G48 in the garage to top it up. It probably took 0.5 litres at the most.

What are the usual failure points in the cooling system?

[gabylonfive]

stuff i have personally seen fail:

- vent line from the expansion tank can become brittle and crack
- leak from the lower rad hose connection or temp sensor seal
- cracked plastic end tank on rad
- cracked expansion tank

I've heard of weeping water pumps and tstats but dono how common those leaks are. the above are definitely more common from my experience.

[dukeofchen]

I would think that if it's leaked that much there are residue marks somewhere that should make it pretty easy to pinpoint, whether you need to stick your head in there or get under the car.

[ac427]

I would think that if it's leaked that much there are residue marks somewhere that should make it pretty easy to pinpoint, whether you need to stick your head in there or get under the car.

I agree to a point but with most of the cooling system under the air box apart from the radiator and the underneath covered by panels it's not the easiest diagnosis to carry out.

Not knowing how long it has taken to lose that amount of coolant is another factor.

[Estoril]

If you can't see i under the hood, then pull the undertray and look for a leak.

[ac427]

If you can't see i under the hood, then pull the undertray and look for a leak.

That would be the obvious next step fellow Estoril owner.

I've just got an endoscope, so that may yield results.

[ac427]

Does the pipe that always gets pushed aside when changing a starter motor, from the engine bay and consequently weeps a bit of coolant. I was told not to worry about the slight leak because it seals under pressure.

That's BS though isn't it?


I'm referring to the rubber pipe that connects to the metal pipe with the coolant temperature sensor in it.

[oceansize]

I think E46 M3's are great but christ almighty it's beginning to try my patience.

Welcome to thug life.

Your car:

[timpnw]

My water pump leaked and was starting to make some noise before I replaced it. It did make a bit of a mess around the plastic guards, but it wasn't obvious until I took a flashlight to it.