I just drained the coolent out of my 91 740 T. I got a good amount out via the drain plug on the block, i only used this because i was having a tough time with the clamps on the hoses and did not want to break anything. Anyway after i drained out coolent....i went to fill my over-flow up with fresh anti-freeze. I poured some in and it went down but then it just kinda stayed full. I then ran the car around the block and the coolent was still there in the over flow tank. Now i know this car has a closed system but i know im suposed to put the coolent in the overflow tank to refill it correct? Anyway i dont want to be driving and then have something explode due to a lack of coolent. I am worried that not enough coolent will be in the car. So has anyone run into this before? Any help? Thanks guys!

 

That is the way to refill the system. Seems like you could have a big airlock.

If you have not already done so set the heater control to hot, run the engine and as it warms up massage the two big hoses to try todisperse any air pockets.

 

That sounds like it could be it. I will go do that right now and get back to ya. Thanks.

 

I did what you said, and still nothing. I am going to take a drive into town and see if it will clear it up.

 

Crack the thermostat screws and see if the coolant level in the bottle drops.

Or pull off the little hose on the top of the Radiator.

 

Thanks Tech, i drove the car a ot yesterday and it dident feel like a car that was running hot....but i will try removing the top hose today and loosning the thermostate today. Hope it works. Thanks.

 

Tech...i did what you said, and the level in the overflow remaned the same. I am going to pull the upper rad. hose off and see if i can see if there is any coolent in the rad. If not, i will fill it up from there. The main thing is, i dont want to be driving my car around in the heat and have it act fine, but in reality be hurting it because of a low amount of coolent.

 

Sure sounds like an airlock colgate. I hope you get it resolved because the engine can quickly overheat with air in the coolant system.

 

Ok guys I think I have figured this out. Please excuse my ignorance. I cannot remember if I had the heater on high when I drained the coolant or not. I only drained the coolant from the drain plug on the passenger side and in trying to figure out how to get coolant into my car I looked back into the bucket I used to catch the coolant from the drain plug and I saw that there wasn’t a ton of coolant in it. So the new coolant I put in, which was about half a gallon was enough to take the place of the coolant I drained. Here is the thing, I did it wrong. I didn’t get all or even half the old coolant out of the car. I feel like a moron. But if anyone could help me and give me step by step instructions as to how to remove all or at least most of the old coolant I would appreciate it. Thanks guys. 91 740 turbo

 

Did you loosen the coolant bottle cap when it was draining?

If not then try it with the cap off.

 

what exactly is an 'airlock'? as i recall when i drain and refill my coolant sys. assy. i start off with heater control to hottest thermo setting then drain from block with resevoir opened. then undo the bottom hose, then all else. FYI, as the coolant is drain from block I have found that when I blow in the resevoir top with my mouth, i get a whole bunch more fluid out. Anyone try that?
When all is done I refill with all hoses and run the engine to normal aperating temp and then some revving here and there 'til i'm satisfied then cap itup. never had a problem...that I'm aware of.