Hello.
I have found many useful suggestions on this site before.
I have now run into a problem which I hope someone will know how to fix.
My car is a 2005 Cooper with 25,000+ miles.
Today, I drained the coolant via the bottom radiator hose, while the car was warm. I used a vacuum pump to remove the majority of coolant from the overflow reservoir.
Then, I reconnected the hose, filled the overflow reservoir with new coolant, opened both bleeder valves 5 turns, and started the car.
Within 5 minutes, the fan came on and the temperature gauge spiked.
The level in the overflow tank stayed the same.
I turned the car off, allowed it to cool down, then tried two more times, with the same result.
Can anyone tell me how to get the thermostat to open and receive the new coolant?
Thanks for your help...

 

First, don't run the car until the coolant is in there. The t-stat will not open until the water heats it enough to open. Try filling the upper hose through the bleeder with the screw out. Then close the bleeders. That should give you enough water to open the t-stat. Then shut the engine off and topp everything off again, check in the bleeder holes to see if they are topped off. Then run the engine at 2k rpm while watching the temp gauge. Once it is at normal temp let it idle for a while then shut it off. Check the level and it should be ok.

P.S. when the t-stat is open, you should be able to bleed the system through the the screws with the engine off and topping off the reservoir.

 

Thank you for your reply. That makes a lot of sense. I will try spoon feeding the top bleeder hole tomorrow. I'll post back to let you know WHEN I'm successful.
This has been driving me crazy.

 

I just checked the manual and it says you should be able to fill the system and the coolant should come out the bleed hole. Maybe you didn't have the bleed valve fully open?

 

You didn't mention having the heater on. Remove the rad. hose bleeder & fill at the coolant tank. squeeze the lower radiator hose as you fill the tankto burp/purge the air. Look how much plumbing carries the coolant apart from the heater, radiator,head & block.



When the coolant streams out the bleed hole, less screw, replace it, crack open the bleeder behind the thermostat housing,it should stream. Replace coolant tank cap. Warm up engine & check for leaks. Take a spin around the neighborhood watching the temp gage. Let it cool down a few hours & recheck tank leve & 2 bleed screws. NXT time drain the block also. A little more work & a lot bigger mess & more coolant ofcorse. Always use distilled water to mix with coolant.

 

There isn't a heater core valve, temp is set by air blend. there is no need to do this.

 

I had the same issue when bleeding the system on my MCS. The service manual states that coolant should flow out of the bleeder valve but it doesn't. I ended up running the car (and slightly overheating it). After turning it off, letting it cool a few minutes, and then back on again, the t-stat opened and coolant started to flow.

The next time I change coolant, I'm planning on doing what 002 mentioned and filling the upper radiator hose. Remember, you can bleed the system with the engine running (and heater valve open). Just make sure the expansion tank doesn't go empty.

 

Thanks 002, your right, constant flow through the heater core.

 

Thank you all for your replies.
I followed 002's instructions, by spoon-feeding the upper bleeder hole, and it worked! The thermostat opened and the levels stabilized.
Incidentally, the fluid in the overflow tank managed to migrate into the system while the car sat overnight.
And Namwob is correct - the heater needs to be on.
However, I could not find a pressure cap on the radiator; that would have made it much easier to fill the system.
I wish the block drain was easier to get to. However, I've always had good luck with my radiators by replacing 1/2 the fluid every two years, it must neutralize the Ph just enough.
A chemist acquaintance once suggested that a teaspoon of baking soda once a year would help greatly. My Dad did this on all his lumber company rolling stock and it saved thousands in cooling system maintenance costs.
Thanks again for the great help!