Replaced Thermostat Still Overheating!?

**Ignacio328i** · 08-31-2007, 03:42 PM

My expansion tank cracked on my 98' 328i and i replaced it. After that it started to over heat one time but other than that it was good so i replaced the thermostat that was broken and now it overheats everytime, what could be the problem??

**Bluebimma** · 08-31-2007, 03:53 PM

Have you bled the system properly?

**NAe36** · 08-31-2007, 03:55 PM

make sure to get all of the air out of the system when you bleed the radiator. Also check you water pump, on average they tend to fail around 60k or so.

**Ignacio328i** · 08-31-2007, 03:58 PM

Thats what i was going to do right now, so turn the ignition on but dont start the car and fill the tank with the bleed screw removed untill it pours out without any air??

**NAe36** · 08-31-2007, 04:02 PM

i run the car when im bleeding, I don't know how you could get all of the air out of the system when the water pump isn't moving. But yea fill untill it comes out with out any air bubbles.

**NAe36** · 08-31-2007, 04:02 PM

also massage the lines to get the extra air out

**Bluebimma** · 08-31-2007, 04:06 PM

There are many DIYs on how to bleed the cooling system. You need to turn the heat to the highest setting as well so the heater core and be filled and the air throughout the whole system is pushed into the radiator to be purged out of the bleeder hole.

**Ignacio328i** · 08-31-2007, 04:49 PM

Alrite am bleeding the system and air keep on coming out of the bleed hole bt it starts coming out of the expansion tank also??

**Bluebimma** · 08-31-2007, 04:51 PM

Are you constantly pouring coolant into the expansion tank until there are no bubbles coming from the bleeder screw? Also, are you doing the above method with the engine running, or with the engine off?

**Ignacio328i** · 08-31-2007, 04:58 PM

the engines running with the heater on and am pouring it up to the Cold mark on the expansion tank it'll go down n i keep fillin it back up bt then alot of air starts coming out the bleed hole and coolant starts overflowing out of the expansion tank

**Bluebimma** · 08-31-2007, 05:03 PM

http://forums.bimmerforums.com/forum...ighlight=BLEED

^^This is a good link to how to bleed your system. Youre allowing air into the system with the way youre trying to bleed it. I bleed my cooling system with the engine off. Keep filling the coolant tank until there are NO bubbles coming out of the bleeder screw. Youre going to lose some coolant by doing so, but you will get rid of all the air in the system. Drive it for a bit and rebleed a second time for safe measure.

**Ignacio328i** · 08-31-2007, 05:55 PM

I bled the system, still overheating even at idle, what else could it be water pump..?

**Bluebimma** · 08-31-2007, 05:59 PM

Could be the waterpump, or you couldve introduced a lot of air bubbles into your system.

**Brashland** · 08-31-2007, 06:18 PM

I was having problems where my cooling fans wouldn't turn off EVER, even after the car was sitting for 6+ hours. I replaced t-stat and hoses and it ended up that the water pump was the problem. If you haven't changed the water pump to the metal empeller model then now is the best time to do it.

I think bubbles in the system would cause some problems, but not enough to cause constant overheating (not sure on this).

**Ignacio328i** · 08-31-2007, 07:07 PM

Yea i just got the water pump and gona install it see if it works

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