In this video, we demonstrate the steps in removing and replacing the thermostat housing on a Generation 2 MINI Cooper S.
The unit used here is an aftermarket version of the OEM (factory original) type.

Click Here for the aftermarket thermostat housing
Click Here for the factory original thermostat housing

Questions?  Contact our MINI experts at 1-800-946-2642 or send us an email.


Hi guys its Brendan from Mini Mania and today we are again at Ryan GMW down in Auburn, CA. We are going to do a thermostat housing swap out on this Cooper S over here. It's already had a water pump replaced, but we are going to replace the thermostat housing as well. So if you want to know how to do that follow along.

This is a thermostat housing, and like I said this Cooper S already had it's water pump replaced. But we are going to replace this, we sell a lot of these thermostat housings and we are going to show you how you can do it yourself.

So you are just removing all of the intact right now? Yeah. Cover off the air box, that normally just has those rubber pins or whatever you want to call them.

One screw right there behind, and there is one screw right down in there. There is the screw that you have to remove, that's what it looks like without the airbox gone, marking the connector to where this thing goes back.

This one has to intersect with that, they will plug in on the wrong one and then you will have coolant problems, temperature faults.

Getting close, so basically any electrical connection that is keeping that harness tied down secured needs to be undone and removed so be careful and mark where everything gets plugged in and you can do that with paint pens, you can do that with toenail polish, you can do that with whatever will work. Get a pen that actually works. Get a pen that paints.

This is basically a remote house clamp wrench operated by a cable, you can lock it in place, these are made by KDTools, this comes with a bunch of adapters. Very cool. This is a same effect, hand held, its sometimes hard to reach in. So you can take, that one just doesn't fit. So I take this one from over here, clip it onto that house clamp, that's pretty tight. Oh yeah, I can see that.

As far as draining fluid from the car, you only need, we only did a water pump on this car so we had to drain all of the fluid anyway. But you can put a catch pan, it's going to continue draining and making a big fat mess, the water pump was just off and there is still residual coolant in here in the heater core, so it's almost impossible to get that empty before you attack it.

Just so you can see that was the hose right there that was removed from there and yeah its a tight fit to be able to get your hand down in there.

Even this hose is almost impossible, that is buried. Yeah it sure is. It's right under the high pressure pump. That's pretty cool, that's a nice tool. That's a nice tool to have. About $150. If you do a lot of them or just do one and don't want to take all day.

That was the hose that was removed. There's another one. We'll use these this time, you can see you can access and get down in there like that, that one's not so bad. They will self clamp like that, kind of like a blessing and a curse. Yeah, they will at least stay on the hose, but they will spring off eventually, they stay loaded on that tang, they will bite you so be very careful.

So you just removed, I just pulled the thermostat because I can't get this hose out, that clip goes to the coolant pipe that runs to the water pump, we're going to be doing that hose too so you can see where it goes and what it does and why it fails.

That should be all she wrote other than the spot of house I couldn't reach. Still can't reach. It's buried. It has a million different connections to it.

The book says that this takes two hours. That's a lot of work for two hours. Without your handy-dandy tool. You can spend a lot of time taking things apart.

If you were doing it with hand tools it would take a little bit longer. Just be methodical. You can see where it's mounted. Everything that it's connected to it, its roughly in this orientation in the car, you can see how many different things are connected to it. You some penetrating lube. To crack the hoses loose, then you will need to get a hook tool on them. Oh, and it's that one right there.

That hose is short so it really binds up. And it's actually behind it isn't it? Yeah it runs in. Believe it or not it has come free. It likes to leak out of the sensors and the housing here. You will see some staining like that, some residual, it was pouring of this end here, it was split right there.

There is the production date so it is original to the car. Make sure that they are the same, there's two different styles, they're good. They look the same.

The one that has the hose in the back here is a tricky one, it's right there, it's sort of underneath and behind, it's a tough one to get to, that was the last one that we just got rid of. Here is an original one made by Markiv, I've never hear of. They are currently changing production companies. You can see there's where it actually attaches to the engine.

So that clip that we took out earlier, holds this pipe like this, and then that goes along the back here. So we are going to extract that pipe.

These crack at this end if you pull on the thermostat without wiggling this this will crack and this will leak. It's only sealing on this o-ring and it floats between the two.

This o-ring goes into the back side of the water pump through the block, so this is pretty much the entire cooling system running on the back side and it's all plastic. O-ring, it's on the intake side so it's not too hot but these get brittle and break.

So just got to wiggle it, and really its just forced in with the o-ring, its trapped between the thermostat and the block, so it's got a couple clips on it, you really can't see what you are doing, there's a couple of retainer clips holding wiring harness' to it, just kind of gently twist and it will come free eventually.

You can kind of see it there, its just barely poking out right there in the center of the frame right there. And it runs along there. Kind of like this orientation right here.

It's impossible to demonstrate this here, that's one you are going to have to feel, just tug it, it's got a clip right there holding the harness to it, you can see the end of the pipe, it broke off.

So again this is why you are replace it, especially on a car that has been over heating, the plastic will fatigue, this gets pretty brittle, its easy to break off, your whole repair will be wasted if you don't fix every problem. That kind of has to go in first, thermostat locks this in, so you can not get that pipe out without pulling the thermostat.

Lot of work for another $70 water part, you might as well do it while you are there. Now I got to try to get that broken piece out of the backside of the housing.

So thats an inspection mirror that we are looking in from the bottom here. You can see that the hole where that rear pipe goes under the intake, we are looking at the hole to see if the end of the pipe is stuck in there but it's not. This is the only thing you are allowed to put on an o-ring, no silicone, no sealants, nothing, this is dialectric grease that will allow this o-ring to slide right into the hole, just give it a nice light coating.

So the same stuff that you would use for a spark plug boot, should have a tube of this if you are doing any repairs on your car, connectors, it's not going to damage the o-ring, it's going to make the pipes slide right in without any damage, you can lube up this side, doesn't take much. And it's not the kind of thing thats going to harm the rubber, or degrade any plastic, or wash away once the coolant flows through there for a while.

You can see how nice this just slips together. Got to key this up right there, plugs in, unplugs, trying to do that without a lube is next to impossible.

So this is just to illustrate the way this clip goes down. And it has to snap down and stay flush, it's locked in.

Now the pipe won't come out. It's kind of redundant, it's bolted in place so it won't go anywhere but this keeps this from spreading under pressure and trying to pull away, it will release. You can't push down on this one like some of these clips you actually have to remove it to get the pipe out.

Look and see the hole, got to guide it in semi-blind here. And that hole is literally on the back side of the water pump in the block. I'm in the hole, you want to get that in the hole first and then those little tabs then you want try to get it against those. So that's how it sits, just kind of chilling next to the transmission. That's it.

Ok, and that one definitely has to go in first. Absolutely, it basically lines up everything else, make sure this gasket doesn't fall out. Don't crimp it if you can help it.

Light coat of silicone spray on this to help everything flow together when you try to plug it in, it can be frustrating and time consuming.

Electrical plugs, that is fine too.

Gasket, not going to hurt it. That just helps.

Now you got to remember which hoses you couldn't get off while it was in, so this hose was fighting me cause you can't see it, the one on the back is probably the first one, its the front one here, yeah put this on right here. You still have your little remote clamp, left that one on there. Now all you have to do is just release it.

That's a pretty handle tool. That's why you pay a price. Eventually it will pay for itself if you do enough. For the shade tree mechanic, see if you friend has one you can borrow. So we've got two hoses back here, we're going to leave those alone, two more in the front, you got five hoses plus the coolant pipe and into the head, two connections with temperature sensors. My pipe fell out of the block, you've got to put it back in. It got moved. Let's put this back in.

See if we can't trap it quickly. We will bolt it in first. Keep it held, it's not going to go anywhere, the clip can always go in last. Just putting the top bolt in temporarily. Thats the easy part.

First bolt is the easy one. The other two you can't see. All the bolts are the same length, stainless steel bolts, you can't see where they are going so you have to kind of know and be able to feel. This one goes straight above this, nice and easy, don't tighten them down too tight yet. Just get them started, most of the way there.

This hole we can see from the front. You can see the bolt hole right above that hose, I can do that while I am standing here. Get all three in and then you can tighten them. Recheck out pipe. Still good, nice and trapped, no pocked out o-ring, good to go.

This clip goes in like this. It's clocked so it can only go one way, if it's not right it won't stay in there, it's kind of hard to see. Just takes some finesse and patience, line that up, both sides. It's in. You can see it right there. It's tedious, its a little tricky to get back there and get it in. Just hold onto it with your finger tips and then wiggle it down in, takes some finesse and patience and smaller hands.

Now are bolted up and just have to connect everything. We are going to start with the rear hoses. We've got these two guys, put them back where they came from. They are kind of formed, this one comes out and goes over this way, should make sense you are putting them back on.

This hose clamp was clocked wrong originally so I am going to relocate it so I can install the hose with the thermostat in. I couldn't get that off with that in. And that's ok if you have to take the thermostat off to get the hose clamps off, don't fight it, you can always relocate them like that, you can always put the worm gear clamps on too. Not going to hurt my feelings later when I have to do it over. Just like that, thats it, don't fight it.

Face it towards the outside for the next time you can get it them more easily. Face it whatever is the most comfortable for your tool.

You can do this with pliers but its really not easy, you have key marks that lines up with that so that hose needs to twist a little bit. It feels ok but they are kind of indicated where they want to be. This hose should be nice and relaxed.

Now the hose clamp is over tightened so this is locked down. So you basically have to free it. So it's got a little tang locking it in place. They like to snap all of a sudden. You can see that there is a lot of spring, potential energy. This tool will help absorb some of it's energy so that's not going to out snap these, we can take a pair of pliers and take that down like that.

Now it won't fly across the room.

With a tool like this, this is a $25 hose clamp wrench for these, this got these little floating ball cups so you can kind of go in at any angle, crimp them down till its almost over that line lock, that lock broke off when we released it, so it's no longer locking. Which is totally fine, it will still clamp. Yup, that is just for install, it doesn't effect its longevity.

That's it. It lines up with the lines back there. That's the back two. This is your rear cam adjuster, or fuel pump pressure sender. I like to take that off to free up the harness a bit. This looks nice and relaxed going in here, blue paint there.

These are the ones you mixed up in the head, gray goes to the gray sensor, green on your original one o-ring, this is now a brown sensor. Plug that in like that, I put two dots on this one. They are all marked so you can't get them wrong. Mark them. Mark them so you can't get it wrong. Those two are easily interchanged and will cause a check engine light, and you are going to know if you get a check engine light after you do this that you have probably connected something backwards. You got the two front hoses here, tighten that till it's closed, so that tang should be lose enough, we are going to slip this over the hose, it's got plenty of room, going to shove it in, line that up, line up those two white marks, pop the tool, done. That's why the factory likes these, its a little out of alignment, square it up a little bit here. That's it.

All our hoses are on, all three sensors are plugged in close to your fuel pump, back here. And no it's just question of making everything else go back the way it came.

Waste gate hoses, you've got one on the pressure side of the turbo, these go bad, these will cause no boost so you will end up thinking you have a bad turbo you just really have a bad waste gate control vacuum hose.

This is the pcb hose on the air box. That air box mostly just goes in on those little rub bits but it's also got that one screw on that side.There's that one.

I also took this off, this is your booster vacuum pump, so this clips on like that, clips on down here. If you don't have that connected you aren't going to have power breaks. That's all that is, it doesn't connect to the engine, you won't have any codes you just won't have any power breaks. So if your breaks go out this could be broken, could be unplugged, these clips can fail. It will be under vacuum the first time you pull it off pull it off nice and straight because its all plastic, clip it on like that, just push that in and pull up. It comes right off and should stay on there. Definetly going to need to get that out of the way because it's right over where you will be pulling things out. And it's got a service connection down here with a clip on the back, you've got to push on there to take it off and then the whole hose can be set aside for later.

This thing goes in upside down, that's the fresh air intake for the air box. If you guys have any cold intake set up, you may not have this, you are still going to have to move something out of the way. That's it. Break hose plugs into these little ports. That's it.

Oh it clips onto the edges of the one we just replaced, its got a little clamp to it, connects to it. Oh last thing, filling this up. There is a bleeder screw, often missed and very important, this is your bleed port, so this is sitting on your thermostat.
So you are going to want to have that opened when you fill it, it is accessible when you put it in, straight down there, you can get right to it. A lot of people miss that, so you just stick a long Philips in there, and you just want to open that up about two turns, you can feel the o-ring give up. This just has a flat face here, cut grooves so the coolant can leak past it. And that's it.

Just loosen it enough for coolant to flow out. Fill up your system, run it till it starts spraying out of this continuously and then close it up. Top of the bottle, run it with the heater full blast, 5-6 minutes or so get the thermostat to open, shut it off, let it cool down.

Double check your coolant level, you are good to go.
It's about a two hour procedure for a pro. Maybe more. Don't get frustrated. There's all there is to it.