N54 coolant filler cap, and cooling system leaks

[Kkuba]

So, I've had the car (08 135i MT) for exactly a year.

On Saturday, for the second time, I had a low coolant notification come up.

I noticed when filling it, that the cap did not "click" when I replaced it. Thinking back, I don't remember it ever doing this. I imagine this to be like the fuel filler cap. Instead, the cap just turns until it hits a stop, and the arrows are aligned.

Is it supposed to click, as stated on the coolant filler cap? I thought this was perhaps the reason for the accelerated coolant consumption.

Then, on Sunday, I went for a long, spirited drive through the hills. After leaving the car for over an hour at the top of the mountain, I came back to go home, and was given another low coolant light, a day after filling it. Two minutes after departure, I pulled over on the shoulder to help another motorist. Half an hour later I moved my car elsewhere, and came back. Someone pointed out a trickle that appeared to originate from my car where it was parked on the shoulder. Touched it, it felt like coolant. Now I am worried. Ended up at home 2am this morning, so was not able to investigate further.

To help my fiture investigations, are there any common coolant leak locations that I should be looking for?

I know that the coolant filler cap seals a pressurised chamber, but is it possible that after an hour of cool-down, and then only two minutes of driving, a poor seal here could cause a trickle? Doubt it.

I will fill it up again today, and see if I get another trickle.

Water pump was replaced about a month before I bought the car, and is the only bit of work done on the car by non-BMW, as car was stranded in the middle of no-where. Possibly a poor job...?

Have not noticed any strange (sweet) smells.

Also, got CEL or SES (iDrive: half engine symbol "reduced power") twice on the way up, but I suspect this is unrelated, and instead due to the JB4, as I got this multiple times after install, and have not fully nutted this one out. Still trying to decipher the fault code the in-dash JB4 menu spat out from the video I took: 030F, no record of it online.

Thanks in advance.

[yawn]

I'm not sure about your coolant - might be a good idea to get it checked out. The coolant cap I don't think screws on tight like the oil filter cap does. Mine doesn't either just sort of lightly clicks past a certain point with minimal resistance.

With regards to your code I've never seen that one before. More likely than not I think it would be 30FE or 30FF - both boost related. Might want to check your boost lines. Good luck.

[Kkuba]

Originally Posted by sharkatron

I'm not sure about your coolant - might be a good idea to get it checked out. The coolant cap I don't think screws on tight like the oil filter cap does. Mine doesn't either just sort of lightly clicks past a certain point with minimal resistance.

With regards to your code I've never seen that one before. More likely than not I think it would be 30FE or 30FF - both boost related. Might want to check your boost lines. Good luck.

Thank you for your response, that will be extremely helpful re the code.

Small update: after a drive today, I noticed some drops of, what I assume to be coolant, hanging from the centre of the trailing edge of the front bumper. Need to get the car up onto stands and have a closer look. Also, another low coolant light..

[froop]

If you keep getting low coolant lights then you likely have a leak but any fluid you see underneath the car should be greenish in colour. If it is just clear then most likely it's condensation from the air con system.

As for the lid, it doesn't exactly click shut but hits a stop and the arrows align. It's not completely pressurized as it has overflow valves designed not to let the whole expansion tank explode if you overheat.

I have a coolant leak in mine from the turbo coolant line and if you are parked flat it puddles up on the undertray. It's only if I tilt the car towards that corner will it spill out and I'll notice a puddle of coolant. It's bright green so there shouldn't be any confusion.

Are you sure you have filled it up correctly?

[Kkuba]

Originally Posted by froop

If you keep getting low coolant lights then you likely have a leak but any fluid you see underneath the car should be greenish in colour. If it is just clear then most likely it's condensation from the air con system.

As for the lid, it doesn't exactly click shut but hits a stop and the arrows align. It's not completely pressurized as it has overflow valves designed not to let the whole expansion tank explode if you overheat.

I have a coolant leak in mine from the turbo coolant line and if you are parked flat it puddles up on the undertray. It's only if I tilt the car towards that corner will it spill out and I'll notice a puddle of coolant. It's bright green so there shouldn't be any confusion.

Are you sure you have filled it up correctly?

Yes, I realised now that any puddles/dripping I was seeing was coming from the edges of the tray.

No confusion about coolant/condensation.

Not sure what you mean by that last question. I poured it into the correct orifice, if that is what you mean.

Another update, I took the under-tray off, and noticed there is a leak coming from above the water pump. It runs down the water pump body, and drips from there. Not sure what next.

I suppose I will have to take the pump off and investigate further. Does this require dropping the subframe and rack? As walkthroughs for LHD vehicles don't mention this (only ARB), but the receipt for the pump change 12 months ago does...

Just need to work out how much time to put aside.