Floor jack & jack stands, 8mm and 10mm wrench, socket set, screwdrivers
R50 MINI Cooper (2002-06) R53 MINI Cooper S (2002-06) R52 MINI Cooper Convertible (2005-08) R52 MINI Cooper S Convertible (2005-08)
New hoses and clamps
Use quality jacks and jack stands
Allows easy access to radiator, alternator, supercharger and other engine components.
This article is one in a series that have been released in conjunction with Pelican Parts' new book, How to Maintain and Modify your new MINI. The book contains 240 pages of full color projects detailing everything from performance mods to changing your brake pads. With more than 500+ full-color glossy photos accompanying extensive step-by-step procedures, this book is required reading in any MINI owner's collection. The book is due to be released in late 2012. See The Official Book Website for more details.
Check out some other sample projects from the book:
Proper maintenance of your cooling system will go a long way towards extending the life of your car. The cooling systems on most cars are often neglected, as most owners don't know much about how it works. The most vulnerable components in the entire system are the radiator and the heater core, as they tend to be damaged by corrosion and electrolysis. Poor maintenance of the system can result in the build-up of corrosion elements in both the radiator and heater core, creating clogs and leaks that decrease cooling performance. If the engine overheats, the additional heat from the coolant can also damage sensitive plastic attachments and components.
When replacing your radiator, you want to make sure that you replace it with one that meets or exceeds the OEM cooling standards. The cooling system in the MINI is prone to overheating due to a design fault in the coolant expansion tank. Therefore, it may be a wise idea to install a new tank at the same time. The tank is relatively inexpensive and is easily replace. Its also recommend to replace your water pump and thermostat at the same time. (See our projects on replacing the coolant expansion tank and water pump removal for more info).
The first step in replacing your radiator is to remove all of the coolant from the system. Unfortunately the MINI Cooper S does not have a radiator drain plug like on most cars. To drain the coolant, you must remove the lower radiator hose. In the case of the MINI, you first have to remove the front bumper cover and carrier to gain access (See our article on front bumper removal for more info).
The MINI Cooper has a unique design on the front of the car called a modular front end. Due to the limitations of space, the engineers came up with a way to extend the front bumper several inches forward to allow access to some of the engine components with having to remove the radiator, hoses or drain the coolant. However, in our case, we will be removing the radiator and hoses.
Once the bumper cover and carriers are removed, locate the two plastic retaining pins at the top of the radiator on each side. Use a screwdriver to pry out the center pin, then remove the outer pin. These pins secure the radiator to the mounting frame, but will also allow you to gain a little more free room by rocking the radiator back and forth.
In front of the radiator is the A/C condenser. This is secured to the front of the radiator by two 10mm bolts on both the left and right sides (See Figure 2 and Figure 3 ). Loosen but do not remove the bolts. Now look at the front of the intercooler, you will see that the top radiator hose is held to the front with an 8mm bolt. Remove the bolt and let the hose hang freely (See Figure 4).
The front panel of the car has two mounting holes in which BMW specifies the use of two special rods to allow the frame to slide on. However, these rods cost over $100 each and is a special order part. Instead, you can use two M8 x 100 bolts with two fender washers (See Figure 5).
Thread the bolts into the holes and look up on the front driver’s frame rail. Remove the 10mm bolt that holds both the A/C port and the bracket containing the wiring harness for the radiator fans. Remove the bracket and disconnect the harness (See Figure 6). Remove the two 10mm nuts holding the A/C condenser and carefully lay it down off to the side of the radiator frame. Now slide the whole radiator frame over the two bolts until it stops (See Figure 7).
At this point, set up a drain pan or some other collector directly under the lower radiator hose where it attaches to the radiator at the bottom. Take the cap off the coolant expansion tank and remove the hose clamp on the lower radiator hose. The hose may be stuck on the neck of the radiator, so you may have to use a screwdriver to carefully walk the hose off the neck. Keep in mind that as soon as the hose is free, coolant will start flowing out (See Figure 8 and Figure 9 ).
Let the system drain itself. This could take several minutes. At the same time, look at the upper hose. There is a small plastic section with a bleeder screw incorporated into the top. Loosen and open the screw. This will help to remove any remaining coolant still in the system. Now remove the hose clamps and remove the upper connection to the radiator (See Figure 10).
At this point, you can remove the whole radiator frame from the front of the car for access (See Figure 11). Now, follow the lower radiator hose up to the water pump and remove the hose clamp and the hose (See Figure 12). At this point, you can install the new lower radiator hose.
Removing the upper radiator hose and accessing the thermostat is a little more complicated. From the front of the engine, you can see that the upper radiator hose snakes in between the water pump and the air bypass valve (See Figure 13).
Refer to our article on cold air intake installation and remove both the air feed hoses and the airbox itself. Once these items are removed, you can access the hose clamp holding the upper radiator hose to the thermostat housing (See Figure 14). At this point, if you are not replacing the thermostat, simply put the new hose on and re-assemble the front end of the car.
Replacing the thermostat is a bit tricky as it is a tight fit within the engine bay. Begin by removing the electrical connection to the MAP sensor as well as the oxygen sensor on the small bracket next to the valve cover (See Figure 15). NOTE: in our case, the plastic retaining lug holding the O2 sensor harness to the bracket was broken. You may find the following steps easier if you remove the harness from the bracket although it is not required. Next remove the two Allen head screws holding the MAP sensor to the bracket. Remove the MAP sensor and pull it out of the hose underneath (See Figure 16 and Figure 17 ).
Underneath the bracket are two 10mm bolts that both hold the upper part of the thermostat housing and the bracket itself to the cylinder head (See Figure 18). It may help to use a socket with a universal joint to remove them. Once the bracket is removed, you will see the final 10mm bolt at the bottom of the housing as well as the rear hose connection (See Figure 19). Remove both the hose and the bolt then pull the housing off the cylinder head (See Figure 20 and Figure 21 ).
Below the housing, you will see the thermostat and gasket sitting in the cylinder head. Now, in our case, the thermostat had been replaced before and someone decided to add a layer of sealant to the gasket (See Figure 22). This is not something that you want to do. It’s likely that the previous mechanic used the sealant to hold the gasket to the cylinder head while the cover was installed. As long as the mating surfaces are clean and straight, there is NO reason the use sealant here. You risk 'squeezing' the sealant inside the housing, which then could break off and clog other parts of the cooling system. If there is sealant on yours, clean the sealing surface with a razor blade.
The hose layout for the MINI Cooper is a bit different from the supercharged Cooper S, The lower Radiator hose runs from the end of the water pump to the lower port on the radiator. The upper radiator hose runs from the upper port on the radiator, through a plastic connector hose with a bleeder screw to another radiator hose that runs behind the intake manifold to the front of the thermostat housing cover. This hose is also secured in place with a small plastic hook molded into the intake manifold.
The thermostat on the Cooper is located in the same location with a different cover incorporating a filler cap. You’ll first need to remove both the battery box and air filter housing to access the thermostat cover. Please refer to our article on Replacing Engine and Transmission Mounts for more info.
Once you have access to the filler neck/thermostat cover, remove the hose clamps on the large and small hoses and remove the hoses. You may need to “walk” them off with a screwdriver depending on the condition of the hoses. Once the hoses are removed, remove the three 10mm bolts that hold the cover to the engine block. Once free, the cover should just pull off. Underneath, you’ll see the thermostat.
Insert the new thermostat into the lip on the sealing gasket. Orient the thermostat so the small bypass valve in the thermostat faces up. Once the thermostat has been replaced, you’ll need to re-fill the coolant and bleed the system. Please refer to our article on Coolant Replacement for more info.
Remove the retaining pins at each side of the top of the radiator (green arrow). Use a flat-head screwdriver to pry out the inner pin, then remove the outer pin.
Remove the 10mm bolt securing the radiator fan electrical connection at the front of the driver's side frame rail (green arrow). Once removed, unplug the connection and set the connector and bracket aside.
Unfortunately the MINI Cooper S does not have a radiator drain plug. You need to remove the lower radiator hose in order to drain the system. Place a drain pan or other suitable container under the hose then pull off the hose and let it drain. Make sure you also remove the cap on the coolant expansion tank and also open the vent valve on the upper radiator hose.. This will help the coolant drain out quicker.
Remove the electrical plug from the MAP sensor (green arrow). Also disconnect the oxygen sensor wiring harness (purple arrow). Remove the harness from the mounting bracket by turning it counter clockwise (yellow arrow) NOTE: On our car, the mounting lug was previously broken.
The thermostat housing bolts also hold the MAP sensor bracket to the cylinder head. Remove the two upper bolts holding the bracket on (green arrow). NOTE: the right mounting bolt is not visible and can be a bit tough to reach (purple arrow).
In our case, it appears that the thermostat was replaced before due to the sealant material that has dried on the thermostat inlet. This is something that you don't want to do. As long as the mating surfaces are clean and straight, there is NO reason the use sealant here. You risk 'squeezing' the sealant inside the housing, which then could break off and clog other parts of the cooling system. If there is sealant on yours, clean the sealing surface with a razor blade.
Fit the new sealing gasket over the thermostat. Make sure that you install the thermostat correctly, using the old one as a guide. The thermostat itself is offset and the new one must go in the same way.
(R50 Cooper) Shown here is the thermostat cover for the R50 Cooper The procedure for replacing the thermostat is basically the same as the R53 engine. Cut the hose clamp holding the temp sender wiring to the filler neck (green arrow), then remove the upper radiator hose connection (purple arrow) and also the hose leading to the heater core (yellow arrow). Once the hoses are off, loosen and remove the three 10mm bolts holding the cover to the engine block (red arrows). The thermostat is directly underneath.
Comments: Hello, I discovered that my coolant hose was hanging from my 2007 mini cooper S and all the coolant drained out, so I temporarily clamped to stay together. It stop draining but then my car began to over heat and the guage raised to 120 , would it be the Thermostat that needs to be changed?
April 15, 2014
Comments: We have had three heater cores fail in our 2003 Mini S in the past year. All develop leaks. Have replaced with both factory and after market units. Same result. Is there a problem in the system causing these failures or just bad luck wit replacement parts?
April 1, 2014
Followup from the Pelican Staff: Where are the units failing (leaking from)? Could be bad luck or electrolysis. - Nick at Pelican Parts
Comments: Is it OK to use the existing gasket if you only need to replace the thermostat cover?
February 3, 2014
Followup from the Pelican Staff: No, you should replace the gasket. - Nick at Pelican Parts
Comments: Is the Mini water pump - original equipment - substantially better than most after market product - reason for inquiry is that labor on replacement is so substantial. thanks
January 2, 2014
Followup from the Pelican Staff: I always prefer to use OEM parts when I can. I would suggest doing so if you are at all concerned about longevity. - Nick at Pelican Parts
Comments: Thanks for the quick response, on 07 Mini going to change the water pump and thermostat and all the hoses. I am hopeful that I will be able to do the job because of the great pictures and detail that you show. Thanks Charlie.
December 22, 2013
Followup from the Pelican Staff: Thanks for the feedback, let us know it works out. Glad we could help.
- Nick at Pelican Parts
Comments: I have a Mini Cooper 2007 S model, Lately I been getting my over heating light coming on and off. There is coolant in the overflow tank. Any ideas?
December 22, 2013
Followup from the Pelican Staff: Check if the thermostat or water pump is failing. How long does the engine run before it overheats? - Nick at Pelican Parts
Comments: I am getting lukewarm heat inside my 2003 Mini S. I have had the thermostat replaced. All hoses have been checked and they are producing heat, but very little inside cabin. The car has Climate Control system. Suggestions?
December 18, 2013
Followup from the Pelican Staff: If there is hot coolant going into the heater core and no heat. The heater core may be plugged. Check if the outlet hose is hot or cool. this will be a good indicator of the flow of coolant through the heater core. - Nick at Pelican Parts
Comments: Any chance you guys could post a full tutorial of the coolant hose cluster install?
November 25, 2013
Followup from the Pelican Staff: if we get the chance to perform the repair, we will document it and get it online. - Nick at Pelican Parts
Comments: Anybody have a reliable way of installing a drain spigot here?
August 9, 2013
Followup from the Pelican Staff: I would say no. I opened a post in our forums. A Pelican community member may be able to answer your question. - Nick at Pelican Parts
Comments: BMW are replacing power steering pump failiar on a good will gesture free of charge on models between 2001 and 2005. Just had my 54 plate replaced. In America, warrenty has been extending to 13 years from new. 10 years in Engkand . Need to check if your model is included. good luck
August 9, 2013
Followup from the Pelican Staff: Thanks for the additional Info. We appreciate it. - Nick at Pelican Parts
Comments: I need to replace the thermostat, my mini is a 2008 Mini Cooper S - R56. Is it easy to change a thermostat?
July 1, 2013
Followup from the Pelican Staff: It depends on what you consider easy. if you are experienced when ti comes to servicing your own vehicle, you should be fine. - Nick at Pelican Parts
Comments: I have a mini one year 2003 petrol 1600cc I had a noise like the radiator overheating as continued when stopped as well as driving even a short distance. The garage said the radiator needs replacing so they did this and connecting tubes £600 but now I have got a noise every time I turn the steering wheel the garage said I need a new power steering part nearly £400 including fitting is it possible they have damaged this when doing the radiator or is it just a coinsidence its gone wrong immediately the same day we picked it up from the garage. I have used this garage for years a family owned garage.
June 12, 2013
Followup from the Pelican Staff: The power steering pump may have been overheated when you overheated then engine. This could have caused it to fail. The PS pump is on the opposite side of the engine, it is unlikely the mechanic damaged it during the repair. - Nick at Pelican Parts
Comments: hi i replaced te thermostat radiator bled evrying my car was stil running hot took ou the thermostat cooked on the stove it only opens .05 of a mm not good eough for god cooling i took it back to the agents they said they have had similar problems can i run my without it ??
June 8, 2013
Followup from the Pelican Staff: The engine will run without a thermostat installed. Keep in mind, you have to use the gasket and frame of the thermostat to seal the housing. Also, fuel economy and performance may be decreased. - Nick at Pelican Parts
Comments: Hello, would you please let me know if there are different steps if I were to perform this process on a 2007-R56 Base Model? I was quoted $1100 or $900 MINI club connection by the MINI dealer to fix a coolant leak issue due to the seal. Looking at your tab, I would rather do it myself.. Thank you for posting these awesome guides!
May 22, 2013
Followup from the Pelican Staff: Teh thermostat on R56 models is a little different. It is still mounted to the left side cylinder head, but the hose and electrical connections are not the same. - Nick at Pelican Parts
Comments: Interesting that you have no discussion of changing the thermostat to a 180 deg ....
I have used them in all my street and race cars and the vehicle as you would expect just runs cooler ..
May 1, 2013
Followup from the Pelican Staff: Most people are going to want to keep the factory thermostat installed to maintain lower emissions and proper fuel economy.
Thanks for the feedback and tip. I think for the right situation it makes sense, ie a track car. - Nick at Pelican Parts
Comments: For anyone who might have a heater problem where only cold is blowing out,i suggest you check the cable connection as mine had popped out of the control linkage that operates the vent.This is easily acessed by removing the right hand compartment tray.Found this out after checking thermostat,heater hoseswarm,and for any interior leaks from heater matrix.
October 19, 2012
Followup from the Pelican Staff: Thanks for the great tip. - Nick at Pelican Parts
Comments: Ecxellent article. Thumbs up for the one responsible. Excellent pictures as well.
August 16, 2012
Followup from the Pelican Staff: Thanks for the feedback. - Nick at Pelican Parts
Check out some other sample projects from the book:
Applies to: R50 MINI Cooper (2002-06) - R53 MINI Cooper S (2002-06) - R52 MINI Cooper Convertible (2005-08) - R52 MINI Cooper S Convertible (2005-08) - R52 MINI Cooper S Convertible (2005-08) - R56 MINI Cooper (2007-) - R57 MINI Cooper Convertible (2007-)