My wife told me that the coolant level warning came on the other day. Sure enough, the reservoir was almost empty. I added 50/50 Blue to the Max level and we drove for some errands. We have our first bout of cold air since the summer, so we turned on the heat, and noticed that the car was blowing mostly cold air with pockets of warm/hot. I checked the coolant level a couple of hours later, and the resevoir was low, but not empty. My guess, there is air in the cooling system and particularly trapped in the heater core.

This would suggest a leak, but I've got an alternative hypothesis.
In the summer we had the intake valves cleaned by the walnut procedure and the timing chain replaced by the dealer. Does any of this require draining the coolant? If so, is it possible that an air pocket got trapped in the heater core that we didn't notice until we turned the heat this week for the first time since that work?

I looked around for signs of a leak. The cabin doesn't smell, there are no obvious signs of dripping from the engine bay or wet spots/puddles on the ground.

Any thoughts?

 

N/a

 

Sounds like a leak, I would check the thermostat housing (contain the thermostat) area first, followed by the water pump and the coolant reservoir.

I would check that thermostat housing located on the driver side, sometimes it leaks on the transmission and pools the coolant (thus you cant see anything on the ground ). When its leaking and the coolant is low enough it will not circulate enough coolant to the heater core, thus no heat.

#6 In the diagram below Thermostat Replacement Kit Part # 11537534521KT3


http://www.ecstuning.com/Search/SiteSearch/11537534521KT3/



Here is the how to link for the thermostat housings replacement if you choose to tackle it.

https://www.northamericanmotoring.co...hermostat.html


And.


Another place to look for leaks is on the main water pup on the passenger side.

Check the water pump for very small leaks right at the seal and on the plastic housing, mine had a very small drip at first that was just residue , then a week later it was a small puddle, the water pump is on the right side ( passenger ) closest to the wheel. The original pumps have the plastic housing that tends to leak.

If its leaking on or near the transmission on the driver side its the thermostat.

Water pump sets in the back corner of the engine on the passenger side.




Here is what the water pump look like , look for leaks around it.


http://www.ecstuning.com/Search/SiteSearch/11518604888/



There is a pic of the engine without the water pump installed if that helps. There is a water pipe behind it also that seals into the housing. Check that also, could be leaking near the water pump side.



[/IMG]


Also, check the coolant expansion tank is located on the driver side up towards the front of the engine and mounts to the metal cross bar. The coolant expasion tank can get small hair-line cracks on the bottom and cant be seen unless you flip it over.




http://www.ecstuning.com/Search/SiteSearch/17137823626/ES2587382/




Last but not least here is the MINI coolant ( blue ) that just needs mixed 50/50 with distilled water. Looks like you have that down, since you did that before to fill it.


MINI Antifreeze / Coolant - 1 Gallon Part # 82140031133


http://www.ecstuning.com/Search/SiteSearch/82140031133/ES196253/





If you need anything else , lets us know and hope that helps what to look for.

Thanks

 

Thanks for the comments. I just took a more careful look at the car after not being able to see the leaking spot. There is clearly coolant on the drivers side at the thermostat housing and also dripping slowly down by the transmission and exhaust biased towards the drivers side. Guess this means I need a new thermostat and housing. Question is, should I do more?

The car has 77,000. How much more work and money is it to also swap the hoses and water pump at the same time.

on my old E34 BMW, the thermostat and water pump were near each other and it made sense to replace both when going in to do one, but in the mini the pump and thermostat are on opposite sides of the engine, so this isn't as obvious. Of course doing both saves the draining and filling the cooling system twice.

I also have a gallon of BMW blue, is it the same as the mini coolant?

Also, this is the first serious repair job I'm considering doing on the mini, so any rookie hints to help me maneuver inside the tightly packed engine bay are appreciated. I've done all this kind of work on my E34 540, which even with the V8, the engine bay appears cavernous compared to the mini. Until recently my wife relied on the mini for daily commuting, so it couldn't sit around until I had the time to fix it. We just got a new Subaru outback, so its not ok for the mini to sit idle for a couple of weeks while I get the parts, and hope the weather cooperates when I have the time to do the repair.

 

N/a

 

I just wanted to update.

First, thanks for all the help in this thread and in the others on NAM.

My leak was certainly coming from the thermostat housing. I replaced it,which took me a solid 5-6 hours. I wrote up some notes and posted it in the HOW TO: thread on changing the thermostat housing, which is linked above.

Just a few quick notes I would like to add here.
1) I do not think there is a significant benefit in worrk time/effort to changing the water pump and thermostat at the same time. Most of the dis assembly needed to get to the thermostat housing would provide little to no benefit for accessing the water pump on the opposite side of the engine bay. The one clear benefit is saving draining and replacing the coolant twice. In some cars (I'm thinking of my BMW E34), the waterpump and thermostat are in close proximity, so that replacing both takes little additional time and it makes sense to do both at the same time.

2) This job isn't 'easy', but its also not 'difficult'. There is a bunch of maneuvering in a tight space. Most of my time was spent trying to figure out how to get things apart. Basically how hard and which way to wiggle/pull. Knowing this could have saved me more than two hours. That being said, this is the kind of knowledge that is hard to convey with words. If I had to do this again, it would take MUCH less time, but that's pretty typical.