Thermostat question

[Peter D]

Guys,

The temp gauge in my '04, 3.0, X5 always stayed at the mid point of the gauge winter or summer (110k on it)...

At the end of last winter i noticed that the temp gauge wasn't going over 1/4 after 25+ miles of driving on a cold morning (never got to 1/2) and that i had a bit of milky sludge on my oil filler cap because i wasn't warming up. Spring and summer came and the X went back to normal (no milky sludge, no coolant loss) for the warm months, but now that fall it here, the 1/4 gauge is repeating

My thought is that it is a bad thermostat but then i noticed its got an electrical plug on the housing. Is this electrical connector from a sensor that reads, or is the thermostat electrically controlled meaning that i may have an issue other than a bad thermostat.

I am planing to replace coolant, thermo, WP and serp belts due to milage but I don't want to replace the thermostat to only find out I may have a computer or other sensor that controls the thermostat problem.

Who has best prices, real OEM and ECS seem the highest

[i-want-in]

There are no electronicly controlled thermostats. That is a sensor. Usually there are two or three. One is exclusive to the dash panel guage, usually located in or around the thermo housing to give an "after coolant going thru the engine reading" to the guage so it will display the highest temperature seen in the system, which is after it has circulated thru the engine.
Another after the radiator usually in the lower hose or bottom of radiator to control the fans. And sometimes a third to give a reading to the ecu. Sometimes one is shared.
They are not very expensive. I would recommend replacing all that you can get to while in there, and always go oem thermostat and water pump if possible. Not oem replacement, just oem.
Check the radiator. If you see any signs of seepage around the plastic tanks replace it too. I would recommend an all metal(copper,brass) unit. Yes they are heavier and sometimes a bit larger for the same cooling capacity, but if it leaks you can get it brazed. If it gets clogged, you can get it rodded out. It will be the last one you buy. And probably cheaper than an oe replacement. The ultimate would be an all aluminum version with aluminum end tanks, but expensive and not need in a stock application.
Buy a GATES brand belt at yur local store. Dayco sucks. Remember to use the corect sealant which is gray water pump and thermo housing silicone, comes in a small tube at the parts store. Coolant safe.
Be sure you dont put the thermostat in there facing the wrong direction.

[rayxi]

Originally Posted by i-want-in

They are not very expensive. I would recommend replacing all that you can get to while in there, and always go oem thermostat and water pump if possible. Not oem replacement, just oem.

Welcome to the board! Looks like you got in.

If you replacing the WP and belts anyway. Have a good look at your hoses too. If there is any doubt about their condition replace those too.

[eracer61]

I'm in the process of doing he same thing, plus changing out the (dreaded) failing oil separator.

I split my order between RMeuropean and AutohausAZ. They're both great to deal with, have the best prices I've found, and they ship quickly.

[Peter D]

Sounds good, now that i know its not an electric stat i can proceed as planned.

Will try AutohausAZ for the parts but how much coolant should i buy