Yup, another overheating question

[CorvallisBMW]

I've bled the living piss out of this thing. Front end up in the air, reservoir raised above the engine, hot and cold. After driving, at idle, etc. Everything. Yet when I drive on the freeway the needle shoots up to the red zone within a mile or two. Once I coast to an offramp it immediately goes back to 1/2 exactly. It doesn't overheat around town, or at idle, or during any of the times you'd think it would. It only overheats while doing freeway speeds. I've beat my brain over this and can't figure it out. Help.

[mr.vang]

yes, that is a hard one...

[CorvallisBMW]

I almost seems like a flow issue; under load there isn't enough coolant flow to cool the engine, but once it calms down it can handle it. I'm going to try driving at 2500 rpms steady in different gears, see if I can gain any knowledge from that.

[KenC]

Is your heater working properly?

[CorvallisBMW]

yes

[Jand3rson]

Did you check the thermostat? It sounds like it isn't opening and closing properly when it should be.

[KenC]

yes, that is a hard one...

That's what she said.

[CorvallisBMW]

Did you check the thermostat? It sounds like it isn't opening and closing properly when it should be.

It's brand new, but that's my next step. Test.

That's what she said.

Good eye, I missed that one lol

[Jand3rson]

It's brand new, but that's my next step. Test.

Yep, they can still be bad. I replaced the one in this little Toyota pickup I used to have, and it was bad right out of the box. It was basically doing the same thing your car is doing. New one fixed it.

[Van Westervelt]

Thermostat sounds very likely. Sound like its stuck.

and x2 on out of the box failures.

[CorvallisBMW]

Alright, I'm gonna make some lunch then pull the bitch out, see how it does.

One more tidbit that may help: Driving around town it's great. As I accelerate on to the freeway, the temp starts to drop as the radiator gets more airflow. It dips down to almost 1/4 before starting it's rampage towards the red zone. One more thing that I think may be pointing to the thermostat

[Jand3rson]

Definitely sounds like a bad thermostat. It's not opening and closing properly.

[bmw335isturbo]

Definitely sounds like a bad thermostat. It's not opening and closing properly.

After reading all of this I would agree with his quote

[CorvallisBMW]

I've got it in a bath of water on the stove....seems to be opening and closing correctly. But I'm going to go buy another one anyways. $16 at Schucks.

[Jand3rson]

I've got it in a bath of water on the stove....seems to be opening and closing correctly. But I'm going to go buy another one anyways. $16 at Schucks.

Don't you mean at Schucks ORly? :D