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The water level in my mini is draining slowly, but I am not sure where it is leaking. I don't see any water laying on the ground. I attached a few photos of some stains I am seeing on the engine. I am not sure if this is radiator fluid that is dried up or something else.
I would guess the infamous cracked thermostat housing. Or a leaking o-ring on the housing. What year? More info on model year and S or non-S would be helpful. I would put a pressure-tester on the cooling system, and see where the coolant comes out of.....
The easiest thing to check is the coolant reservoir. remove the one screw holding the reservoir to the radiator support, and look on the bottom of the reservoir for any colored residue and cracks.
I agree with the other comments that the thermostat housing is probably leaking. It is on the driver's side of the engine block, and the leaks normally get trapped on top of the transmission. The trans case has ribs on the top that hold the coolant. Take a flashlight and look behind the oil filter, see if you can see some wetness. The thermostat housing is black plastic with several hoses and electrical connectors going to it. It is known to crack and leak, generally after 4-5 years.
Think I see coolant pooling on top of the transmission right under thermostat housing , you have leak from the connection under the expansion tank, or the expansion tank has a hair line crack on the bottom.
Upper left in the pic.
Thermostat housing and expansion tank. And links to DIY.
I would guess the infamous cracked thermostat housing. Or a leaking o-ring on the housing. What year? More info on model year and S or non-S would be helpful. I would put a pressure-tester on the cooling system, and see where the coolant comes out of.....
It is a 2009 Mini Cooper Hardtop. Is there a way to pressure test it myself. Not sure if I can rent the tester from the auto store, or is it easier to just stop by a shop.
Originally Posted by mbwicz
The easiest thing to check is the coolant reservoir. remove the one screw holding the reservoir to the radiator support, and look on the bottom of the reservoir for any colored residue and cracks.
I agree with the other comments that the thermostat housing is probably leaking. It is on the driver's side of the engine block, and the leaks normally get trapped on top of the transmission. The trans case has ribs on the top that hold the coolant. Take a flashlight and look behind the oil filter, see if you can see some wetness. The thermostat housing is black plastic with several hoses and electrical connectors going to it. It is known to crack and leak, generally after 4-5 years.
Mike
I'll take a look behind the oil filter and see if there is any dampness.
Originally Posted by ECSTuning
Think I see coolant pooling on top of the transmission right under thermostat housing , you have leak from the connection under the expansion tank, or the expansion tank has a hair line crack on the bottom.
Upper left in the pic.
Thermostat housing and expansion tank. And links to DIY.
Yea, you should be able to see the drip or the pool of coolant on the transmission or track down the residue on the transmission housing. Reach you hand down there and feel for coolant / or if its wet.
We have a large amount of literature on possible DIY repairs pertaining to leaks on your vehicle. If you do locate it, take a look around the tech articles here and see what help we may offer you in your repairs.
Adding to the conversation...
what about the water pipe between the pump and thermostat? It's also plastic. I know it has o-rings to seal, but it just never felt secure.
Also, pressure testing. I have a Stant 270 tester, which is great on my old cars, but I haven't found a thread-on adaptor for my Minis.
Yea, you should be able to see the drip or the pool of coolant on the transmission or track down the residue on the transmission housing. Reach you hand down there and feel for coolant / or if its wet.
Good luck.
added some more detailed photos that shows a pool of water. The water is dark because I had an earlier oil leak from the tensioner, which I tightened. Its not clear where the water leak is coming from, but it might be the thermostat housing as mentioned before. Not sure how I can tell exactly.
Originally Posted by chimivee
At the risk of stating the obvious, check that the bleed screw is not loose.
I was thinking about that. Is there a bleeder screw that might leave water in the area of the photo?
I was thinking about that. Is there a bleeder screw that might leave water in the area of the photo?
Yes, the bleeder screw is at the top of the thermostat, so if it were loose, coolant would dribble down the thermostat and drip below it the same as if the t-stat itself were leaking. It's a 5 second check, so do that before replacing the t-stat (which is probably leaking). I'm sure there's info here somewhere on where exactly the bleed screw is - it' hard to see if you don't know. But it's right against the driver side of the engine, about inline with the spark plugs, and maybe 6" down.
Yes, the bleeder screw is at the top of the thermostat, so if it were loose, coolant would dribble down the thermostat and drip below it the same as if the t-stat itself were leaking. It's a 5 second check, so do that before replacing the t-stat (which is probably leaking). I'm sure there's info here somewhere on where exactly the bleed screw is - it' hard to see if you don't know. But it's right against the driver side of the engine, about inline with the spark plugs, and maybe 6" down.
That would be nice. Now the hard part if finding the bleeder screw. I checked online but having difficultly finding it for the N12 engine. I cleaned out the area under the thermostat with a cleaner and paper towel. I ran the engine, but nothing came down and sat in the collection area under the thermostat. I'll check it later in the week. The radiator fluid is falling from the high mark (halfway up the expansion reservoir) to the low mark in about a week and a half. That's about 150 miles in city driving.
It looks like phillips, but use a flathead. Doesn't need to be gorilla tight. If it's not loose (probably isn't), then you're probably due for a t-stat housing.
Its the hex head / phillips head screw with gasket, You can use long Phillips screw driver, the head of the phillips cant be too fat, otherwise it wont fit.
I would guess the infamous cracked thermostat housing. Or a leaking o-ring on the housing. What year? More info on model year and S or non-S would be helpful. I would put a pressure-tester on the cooling system, and see where the coolant comes out of.....
I finally saw some water accumulating in the pool area on the transmission. So it appears to be the thermostat housing. I looked at a diagram, and noticed the water pump is right behind it. Does the gasket for the water pump need to be replaced if I change the thermostat housing?
I also noticed the water was dark, and saw some oil residue on the round silver object in the photo. It looks like that might have a leaking gasket if it holds the oil in.
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Not sure what diagram you are looking at, but the water pump is not behind the thermostat housing, and not something to do as a matter of course while replacing the housing. The only gasket you need comes with the new housing.
One tip, you can remove the fresh air pipe (the big tube running between the coolant and windshield wash buckets ) and still run/drive the car. With that out of the way you may have a better view to see whats going on re possible oil leak.
There is a good youtube video available for this job (search for it.. )
I think you have a Vaccum pump leak: The thermostat houing will leak right under it and have a pool of coolant, should be sweet smelling and have a blueish-green color.
The Water pump if on the other side of the engine ( passenger side ) near the back. The water pipe then connects the rear of the thermo housing to the water pump on the other side.
See that link above or right here that explains the set up. You have a non turbo engine, so you dont have the additional water pump up front in front of the tranmission. The vaccum pump is that leaking oil parts.
You have a non turbo engine, so you dont have the additional water pump up front in front of the tranmission. The vaccum pump is that leaking oil parts. 
