Temperature Gauge Reading & Coolant Bleeding

[GearHead]

Hi folks

I have a question on Temperature Gauge Reading and Coolant Bleeding

Since the beginning of the year, the Temperature Gauge on my 03 X5 3.0 started to behave strange. Fortunately it did not read HOT but as the engine warms up, I see the needle on the gauge gradually creep up. It sometimes stays dead center but in most cases, it drops down gradually and fluctuates.

While searching around for answer, the possible causes I have found are
1) possible trapped air and needing possible coolant bleeding
2) possible stuck Thermostat

Before going down the path of replacing the Thermostat, I tried bleeding

Base upon the various instructions, this was what I did
a) Remove the reservoir cap from the expansion bottle,
b) Remove the bleeder screw (next to the expansion bottle
c) Turn the key to position II (did not start engine)

Before I could do (d), coolant was gushing out from the area where the bleeder screw was. It was so bad that it appeared like a fountain with coolant gushing out

BTW, (d) was to be turning the interior temperature gauge to high temperature to open up the valve to the heater core

I am very stumped.

I will like to validate whether trapped air within the coolant before going to the dealer to replace the thermostat

Any ideas?

Many thanks

Jeffrey

[bastereo]

Umm. You are a bit off from how I do it.

Cap off
Key on, hvac temp up to max
Then LOOSEN not remove bleeder screw, just watch for the stream of coolant into the bottle

But unless you are leaking coolant it is very unlikely that you got an air bubble into the system randomly.

[simoespoir]

i had the same issue , bleeding the system didn't help . i replaced he thermostat and flashed the system .problem is gone .
my mechanic said that it was a lot dirt on the lines preventing the thermostat from opening or closing properly

[GearHead]

I guess I have no choice, my x5 and 3 series have been a money pit lately requiring numerous repairs

As for the fixing the fluctuating temperature gauge, If I'm understanding correctly, the only way to fix this is to replace the thermostat

The bleeding instruction I used was from the searches I did within the forum

Thanks for all the help

[bastereo]

Well the thermostat is a pretty common failure and the most likely problem.
And you own 2 BMWs, I would plan on them being money pits all the time, then no surprises for the budget.

[JCL]

Originally Posted by GearHead

I guess I have no choice, my x5 and 3 series have been a money pit lately requiring numerous repairs

As for the fixing the fluctuating temperature gauge, If I'm understanding correctly, the only way to fix this is to replace the thermostat

It is not correct to say that the thermostat is the only way to fix this. It depends what is broken. It could be the thermostat, a temperature sender problem, or an instrument cluster problem. The thermostat is just the most likely cause.

Air in the system would have been a more likely cause if the system had been opened recently, and air introduced (ie after a coolant change).

[GearHead]

Well, I'll plan to schedule for thermostat replacement and hopefully that will resolve the problem.

Thanks for all the help

[SlickGT1]

My thermostat went, but it gave me a code, P0128. 4.8is thermostat is only $55 with the sensor in it. 3 bolts and one hose. Going in there to replace my rattly tensioner anyway, so no biggie.