every other week something new
 

quick recap
in oct 2016 change water pump then 1 week later radiator upper neck crack
put in new radiator. 3 weeks ago change tstat as the housing was leaking coolant since the it has
been running fine then today bam it over heats. WTF got code for coolant temp sensor low input something like that gauge peg in corner.got it tow home
4 hours later re-fill cooling system took 1 3/4 gallons did the bleeding all seems good drove it for 5 minutes came back took cap off coolant a tad low but no leaks what so ever
the only thing i saw is from time to time coolant work come out from radiator cap even though it was tight. so where is some of the coolant going if not leaking or smoke from tail pipe

I think the only thing you can do is check all of the hose connections and the expansion tank, and also check the temp sensor. The temp sensor leak is hard to see, but it can leak quite a bit.

To be honest, when doing the water pump, the tstat should done too. Depending upon how many miles you have, and time since it was last done, I'd do the hoses and temp sensor while doing water pump and tstat. It's not much money, and when one of those goes, they all tend to go.

I think when I did the tstad I didn't bleed it the right way press for time I bleed it with cap off not thru bleeder screw .yes that day I can say I was a dumb ass.LOL

"drove it for 5 minutes came back took cap off coolant a tad low"

If you had the engine up to temperature, you should not have been able to take the cap off without blowing coolant all over the place. I would recommend you perform a cooling system pressure check since it sounds like you have a potential coolant loss somewhere else.

2002 X5 3.0 317,000 miles
2014 428i 24,900 miles

2004 325i sold at 123,600 miles
2001 325i sold at 66,000 miles

1970 Firebird - Under restoration

I've forgotten to use the screw in the past as well. air gets trapped, and you overheat.

hope that's all it was for you.

i hope so too doing it the right way from what i read
take out bleeder screw fill system until no more bubbles come out put screw back on top off expansion tank start car with cap off put heat on highest temp blower 3 notches up let run until temp goes up toward normal then open bleeder screw a tad until all air is out and only fluid comes out then close it
top off expansion tank again put cap on take it for a ride until heat feels normal
temp is in the middle crack open bleeder screw again until no more air sound is heard close it let it sit until is ice cold the refill one more time put cap back on should be good i'll know by tomorrow if ok.

by the way anybody knows where the Temperature sensor water/oil is located
i know it has 2 one on oil filter housing for oil temp then the other one for water is where.?? thanks

Do you mean coolant temp sensor? If so, it's on the lower radiator hose. There is an electrical plug on top. Push in the wire, and it comes off.

Then, you squeeze in the tabs on the sensor, and pull it out. The sensor has a little green o-ring around it that degrades over time. When you hold a new one next to the old, you see right away why it would leak.

Look around that plug location to see is there are drips. It usually leaks out the sides of the sensor where the tabs are.

ok here is an update
after bleeding it on monday had the old lady drive it yesterday to do errand locally she said heat was blasting,temp stay in the middle. when i got home from work she just had gotten home 5 minute before me i lifted the hood saw coolant around expansion tank frame and around abs housing and air box housing. then i could hear air coming thru radiator cap even though it was real tight.so it seems that the radiator cap has gone bad and under pressure coolant is seeping out just order a new one and to be safe a new temp switch too.

borrow a pressure tester from mechanic at work here pics this is for 10 minutes then while
still with pressure i started it there was no miss firing or smoke or coolant smell out the pipe.