Hello everyone, I'm new here but I figured this would be a great place to get some insight as to what is possibly going on with my '92 940. Until recently the car had been running well, no issues.

Over the last week or so I have noticed the fan is running even after the car is off, something that never happened before. Not having any real knowledge on the mechanical side of things I didn't think too much of it until the other day when I was on the highway and had to somewhat push the engine. This is when i noticed the temp. gauge climbing rapidly, and dangerously close to the red area. Even though the fan had been running in excess, this never happened before.

I get home, open up the hood and see no coolant in the tank, so I decided to open up the cap as if I was going to put some more in when the system seemingly released a ton of pressure. Soon after the tank started re-filling w/ antifreeze and subsequently started to boil. After a few minutes ALL of the fluid in the full tank was sucked back out and into the car. Tank empty. Let the car sit for a night, go back out this morning and the tank is still empty, no excess has been removed from the system.

Has anyone ever experienced something like this? Or have any insight as to what might be wrong? Any help would be much appreciated.

 

Most everything you can think of expands when heated and contracts when cooled. Pure water is an exception as it expands when frozen. There are a few scenarios for your car. They range from very cheap to going somewhere very secluded and crying like a school girl. a. Your system is simply low on coolant and needs to be refilled to the normal level b. you have a faulty thermostat that isn't opening fully (doubtful) c. you have a blown head gasket. The HG is a common failure on over boosted cars; doesn't sound like you're hotrodding but they still blow.
NEVER OPEN THE COOLANT SYSTEM when the engine is hot!!! You can be a crispy critter in no time.
Here's what to do...
Fill the overflow bottle up with water (not antifreeze). It will continue into the radiator up to a point. Then, with the overflow cap still off, start the car. As the engine warms up, the thermostat should open and begin slurping more water from the overflow bottle into the radiator. Note the full line on the overflow bottle. It's important not to overfill (not deadly, the coolant just needs to have a place to go as it heats and expands) the overflow bottle. Half way is fine. Let the car idle until you see the gauge at its customary position. Leave the overflow cap OFF during all this. Once it's up to operating temperture, rev the engine like you stole it. 3500-4500 rpm's. You don't have to hold it up there but don't just blip it. If the water you just added to the overflow bottle vomits out like something from Alien...you have a blown head gasket. Even if it doesn't...it may still be blown; any reputable shop can do a test on the coolant that will detect combustion byproducts in the coolant. But, if it doesn't puke when you rev the snot out of it...go ahead and flush your radiator, replace it with antifreeze and hope for the best.
Like many engines, the B230 has an iron block and an aluminum head. As they are two different metals, they expand and contract at different rates. And, yet, they are bolted together! It's very easy to warp a head enough for the gasket to fail.
While you're at it, check the motor oil. If it looks like a chocolate milkshake that's another sign the head gasket is blown. Again, let's hope it was just oversight on your part and the coolant was low. Know this...your turbo is not only oil cooled but coolant runs through it as well. As turbos wear out, they can consume various amounts of coolant. White smoke coming from the tail pipe is water or coolant. It's normal to havea little bit whn the car is cold; that's condensation in the exhaust. If you have white smoke under boost or after the engine is warmed up it's not a good thing.

 

Thanks for the much appreciated input, Swiftjustice. Problem turned out to be the thermostat, so it looks like I got lucky this time. Again, thanks for your time and insight.

 

Glad to hear you dodged the bullet!!