Hi,
I recently purchased a 2008 Mini Cooper S , manual transmission, with 68,000 miles on it. I noticed that the coolant water level in the reservoir was low so I topped up between the high and low marks and took the car for a spin. The next morning, the reservoir was practically empty and coolant was on the floor.
I put some more coolant in and ran the car again. On return I put a container below where I think the coolant is leaking, basically between engine and transmission directly below the exhaust. The next morning coolant was in the container.
I still have to get under the vehicle to find where everything is, ie, thermostat, water pump, oil filter etc, so hope to do this this weekend.
Any ideas where this leak could be ?.
Also, any recommendations on a good workshop manual for this model Cooper?.
Thanks in advance.

 

You're onto the right scent with the thermostat housing.

 

Thanks Eric for the quick response.
Anyone....Any links to what is involved here?. Replace housing AND thermostat?. Best place to get the parts from ?.
Is a Bentley manual the best purchase or is there a Haynes?

 

Here is a thread on NAM that may help with your questions. Can purchase the thermostat here. I'd stick with genuine. We will be uploading more, but we have some tech articles up for the R56 here for any other future fixes/repairs.

 

I think there may be a Haynes manual, but it's not going to be very good. The Bentley manual is expensive, but is the best one that we can currently get.

 

So if it is the thermostat, where does the leak typically come from, where the body mates to the side of the engine, ie, the blue seal I see on new component, is it a seam in the moulding, a crack in the body ?.Just curious as I would hate to discover it is just a hose connection.
I do get a watery substance on the top of the tranny and some residue underneath at the lowest point on the bell housing by the cat convertor.

 

I'm sure it's the thermostat housing... I've replace 2 of them already... every 45k miles.
Another crappy design!! should you expect anything less?
Didn't think so!!

 

Not yet totally convinced it is the thermostat housing, here's why.
With the coolant level at minimum level in the reservoir I did a 6 mile run. Stopped the car to do some shopping, came out, puddle under car in usual spot.
Drove home, opened bonnet and yes, some coolant on top of the tranny (manual by the way) and level had dropped slightly.
Allowed car to cool down, no obvious leaks, and filled to the max level in the reservoir. Drove 6 to 7 miles hard driving, parked up, no leaks underneath or on tranny. Turned off ignition, auxiliary pump for turbo running, no leaks. Aux pump turns off after approx. 5 mins, no leaks. I let the car cool down, checking at intervals, no leaks......??
I have a longer run tomorrow, so will see if I can reproduce the leak and get a clear look into the thermostat/tranny area.
Will update tomorrow with findings, if any.

 

The coolant can slow leak and puddle on top of the transmission. On and off when they first start to leak as its a hairline crack at first.


Great DIY here and lots of info on the locations and what to look for. I done all of these before many times.


https://www.northamericanmotoring.co...8-no-heat.html 11537534521 KT

 

Just about anyone who replies to your thread has already experienced what your experiencing. No it doesn't "always leak" because the hair line crack has only just started to leak. Heat, ambient temperatures and the temperature differences between where you are and where your going play a role in how fast this hairline crack develops.

Mine started leaking because when I left home to go to the beach it was 97F and when I got to the beach (15 miles away) it was 74F, big temperature changes like that will cause plastic to expand and contract forcing that hairline crack to stretch open and start squirting, I just hope it doesn't soak you $3000 ECU and harness right next to it! I'd be amazed if this was your first thermostat housing failure as they don't often last past 50K miles, some have replace them every 30K miles.

These Mini's have some **** poor design issues (plastic water pumps, plastic thermostats) and this is how the thermostat housing goes bad in every single Mini Cooper!

 

I can attest to this as well, as i changed my thermostat housing at 62k. Plenty of threads out there on this forum, and others, all around a 60k interval that have identical problems.

Do yourself a favor and get hose clamp pliers before you start this one up. Spent more time fumbling around with channel locks than anything else when i did my repair.

 

Great feedback!. The hairline crack description with its intermittent failure from systemlord/ecs I can identify with. As I said in my post, did a long run today and had the leak which I could see underneath the car at the classic bell housing/engine joint. Nothing on the top of the tranny, but I am assuming that has evaporated off. Will check when car cools down.
I bought the car a couple of weeks back with 67000 miles on it. no evidence of leak at the time.
Will update. Thanks to all again.

 

Yep,

It will pool on these inner fins / cavities on top of the transmission and when you drive / take off and stop , drains off under acceleration. Then that hairline crack and out side temp thing. I would order the parts and have them on hand for the repair. Go through all the other locations , do the water pump if its plastic version and change to metal , I did the thermostat , water pipe , aux water pump ( covered by MINI ) , water pump ( main one ) , oil cooler gaskets at the oil filter housing ( outside and on the block ) , oil turbo lines, and cleaned all around the engine all at the same time. Now it was a happy MINI.


looking forward to the update.

 

The coolant that leaked onto the top of the transmission has now drained off and typically drips down the rear of the bell housing as with all failed thermostat housings.

 

OK, changed the thermostat housing over the weekend. I purchased the genuine Mini part. No more leak, so thanks for the advice.
A couple of comments:
1/ Reading comments/links on this forum along with an excellent YouTube video was a great help.
2/ Recommend that you take photos as you remove parts.
3/ I tagged electrical connections as the plugs/receptacles are not necessarily color matched.
4/ use a dental pick to help get the electrical harness cover off and the tabs are not very strong so take care
5/ Took me about 4 hours, start to finish including road test.
6/ Ensure you get all the air out after filling with coolant by squeezing the hoses and using the bleed screw on top of the housing
7/ when I got the old housing out I could not see any obvious area for the leak. Also part was dated Feb 2008. The car is a 2008 with 69000 miles, so all I can think is that either the housing was replaced very early in its life, or the PO just kept topping off the reservoir.
I now await the water pump leak......

 

Glad you were able to do it.

Get the water pump done if its the plastic original housing , I did all my coolant system at once and then motor on.

Great notes and the seam the housing can have a hairline crack, barely seen, also on the seam itself, only seen when under pressure.

 

Got under the car yesterday (2008 Cooper S) to check out the water pump. Not easy to see, but no leaks.Not sure if it has plastic housing or metal. It is black . I assume the metal replacement would be bare aluminum?

 

Believe the updated pump has a metal housing and composite impeller. 11-51-7-648-827 here with images. This part number supersedes 11518604888, which I believe is a black plastic housing.

 

All listed here:

https://www.ecstuning.com/Search/SiteSearch/11517648827/






11517648827 is the newest part number , older part number was 11517550484 . The older ones that are not metal housing are black with that plastic.


All the housing are metal now from aftermarket to Genuine MINI.

The newest FEBI version has a Metal impeller also, the other ones are a composite impeller.

Hope that helps.

 

SpeedyG56,
Keep an eye on your water pump feed pipe. If it leaks again from the back side of the engine, passenger side, or you think the water pump is leaking, this pipe could be your culprit.
Since you changed your housing, you already had to detach the feed pipe and know where it is. It just pulls out from the backside of the water pump along the back of the engine. No clamps, not bolts, nothing. It's just wedged in there between the water pump and the thermostat housing. Like holding a straw between two finger tips.
I think when the engineers got together to design this engine, they really let their imaginations run wild.

 

If you're talking about the water pipe (pictured below), it is actually attached to the thermostat by a clip, which is #3 below. Yes, this item is prone to cracking and causing coolant leaks.

 

Ahh..my bad. Yeah, there is a clip on the thermostat side.
I did this job and the whole end of my feed pipe looked like it had been chewed off. I couldn't figure it out. I only found out when I removed my water pump and the feed pipe o-ring was came out with it.
I was scratching my head trying to figure out where that came from. Then Pelican Parts came to the rescue with the answer. Thanks Pelican Parts!

 

Glad I could be of assistance. Any questions you have don't hesitate to ask!

 

woops. Didn't realize this was done.

 

Our thermostat DIY is up now and can be viewed HERE.