Coolant Level Low indicator

[ungcj]

I have a 2000 4.4 -101,000 miles. I have had to add coolant about 5 times over the last 12,000 miles. It never shows that it is overheating. The bottom of the fill cap (the part that holds the float straw in place) desintigrated. I guess the little plastic parts just went into the tank. I don't know why it desintigrated. I wouldn't have known it except about 1/4 of the ring was attached to the cap. I rubbed it with my finger and it fell off so I know that the other 3/4 must have just gone into the tank. I use the BMW raditor fluid. I bought the car used, but it was always dealer serviced. I usually add about a quart of 50 / 50 mix when it shows low coolant.

I think it could be 3 things, but it could be others:
1. Leak in head gasket? But NO white smoke.
2. Faulty water pump? But no overheating.
3. Stuck Thermostat? But no overheating.

I parked at the airport one time and there was water from the radiator underneath the car (maybe 2 cups), but I have never seen any other signs. It was just that one time.

Any ideas as to what is causing the low fluid?

Thanks in advance!!

[ViperMX]

...the coolant expansion tank. I've never experienced it, but many here have had issues w/ it cracking/leaking. Some will change it out as a precautionary measure (...like me next week.) Good luck

[Bimmer360]

check the following:

The drop - coming from the radiator or expansion tank side? The leak could be from one of the hoses, radiator, valley pan, or expansion tank. Checke each one and you should be able to see.

[FSETH]

I had the same issue twice. Fisrt time it was the water pump and the valley pan gasket. The second time it was the expansion tank. Both times the coolant would leak out very slowly and I wouldn't have to add any for a significant number of miles. The expansion tank was more obvious because the leaking coolant left a white color residue on the hood liner and some other plastic engine components. I would have the cooling system pressure tested if you can't determine the cause of the issue easily on your own. Beter safe than sorry. You don't want to let the engine overheat if you aren't paying attention.

[supersteve]

+1 on the expansion tank. Mine split at the seam. This was on my 2001 4.4 X5 at about 110000 miles. It was also a good time to flush the system.

[justintmn]

I had the same problem and replacing the expansion tank fixed it.

Justin.

[fast4d]

yes, it's either the expansion tank or valley pan. one easy to fix and the other one about a day's work.

[ungcj]

Thanks to all who responded!!!!!!!!!!!!

[X5Kiwi]

I had the same problem just last week, turned out to be a split heater hose between the engine and firewall.