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Coolant Expansion Tank Replacement
 
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Pelican Technical Article:

Coolant Expansion Tank Replacement

Jared Fenton

Time:

30 mins.

Tab:

$40

Talent:

**

Tools:

pliers, 10mm wrench, turkey baster.

Applicable Models:

R50 MINI Cooper Hatchback (2002-06)
R52 MINI Cooper Convertible (2005-08)
R52 MINI Cooper S Convertible (2005-08)
R53 MINI Cooper S Hatchback (2002-06)
R55 MINI Cooper Clubman Wagon (2008-14)
R55 MINI Cooper JCW Clubman Wagon (2009-14)
R55 MINI Cooper S Clubman Wagon (2008-14)
R56 MINI Cooper Hatchback (2007-13)
R56 MINI Cooper JCW Hatchback (2009-13)
R56 MINI Cooper S Hatchback (2007-13)
R57 MINI Cooper Convertible (2009-15)
R57 MINI Cooper JCW Convertible (2009-15)
R57 MINI Cooper S Convertible (2009-15)

Parts Required:

expansion tank, coolant

Hot Tip:

wait overnight so that the coolant is cold

Performance Gain:

No more coolant leaks

Complementary Modification:

Coolant flush
How to Maintain and Modify your new MINI

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 2015. See The Official Book Website for more details.

Due to an apparent manufacturing defect, the coolant expansion tank on the MINI Cooper tends to leak along the molding seam. This defect was supposedly fixed on cars from 2005-up, however it still seems to strike at random. When the car warms up, both the heat and pressure of the coolant starts to attack the seam along the edge of the tank, eventually causing it to fail and the car starts leaking coolant. The good news is that the replacement tank is relatively inexpensive and can be changed in under 30 minutes.

Take a look around the coolant tank. In some instances, you can instantly see it has been leaking. In others, you may only see a faint trace of coolant beginning to emerge from the molding seam. It's important to tackle this problem as soon as possible. Failure to do so could cause a complete loss of coolant and perhaps even engine damage.

The first step is to let the car cool down. You might want to wait overnight to make sure that the coolant is not hot If you open the coolant tank with the car warmed up, it could burn you. There is heat and also pressure in the system. When you are sure that the coolant is not hot, remove the cap and use either a turkey baster or a large syringe to siphon the coolant out of the tank. You'll want to keep siphoning until the level is just at the bottom of the tank. This prevents spinning coolant all over the ground when you remove the tank. Keep in mind that when you remove the tank from the engine compartment, the level will drain back down through the bottom hose.

Next, use a pair of pliers to loosen the hose clamp around the upper hose connection. Slide the hose clamp back over the hose. Now remove the 10mm nut holding the tank to the mounting bracket. Pull the upper hose off the tank. You may want to carefully take a small screwdriver and work it between the hose and the tank connection. Coolant hoses sometimes stick to these connections and have to be 'worked' loose. Just carefully work all the way around it and pull it off.

Now remove the coolant tank from the engine compartment. One the back of the tank, there are two tabs that fit into two holes on the firewall. Give the tank a good tug upward to free it from the holes then maneuver it out. This can be tricky because of the mounting bracket right above the tank. Once free, pull the tank up. This will drain the remaining coolant back into the bottom line. Now locate the lower hose and remove the clamp securing it to the tank. Again, carefully work the lower hose free if it's stuck.

With the tank removed, clean around the area where it has been leaking if there is any baked-on coolant. In our case, I had to chip away a good deal of it with a pick before I could clean the heat shield directly underneath the tank. Now slide the lower hose over the fitting on the bottom of the tank and re-fit the hose clamp. Carefully maneuver the new tank into place, making sure that the tabs on the back fit into the hoses on the firewall. Re-fit the upper 10mm nut and tighten it.. Slide the upper hose connection on and re-fit the hose clamp.

R50 Cooper: The coolant expansion tank is different on the non-supercharged cars. However, the replacement procedure is basically the same. Suction out any coolant inside the expansion tank and then remove the 10mm nut that secures the tank to the bulkhead next to the power steering fluid reservoir.

Next, lift the tank up from the mounting slots on the bulkhead. Once free, loosen the hose clamp holding the lower coolant hose to the tank and pry off the hose. Now place the hose on the new coolant tank and tighten the hose clamp in place. Re-fit the new coolant tank in the mounting tabs on the bulkhead and re-install the 10mm nut holding it to the bulkhead.

R55/R56/R57 Cooper and Cooper S: On the later R55/R56/R57 cars, the coolant tank sits at the front of the engine compartment. Like the earlier cars, replacement is easy. Like before, use either a turkey baster or a large syringe to siphon the coolant out of the tank. Once the coolant has been evacuated, use a pair of pliers to remove the hose clamp at the top of the tank and also remove the 10mm bolt holding the tank to the lock carrier (See Figure 11). Now pull the tank up and rotate it over to access the hose clamp holding the hose on at the bottom (See Figure 12).

Now on both the early and later cars, fill the tank with coolant until it registers in-between the MIN and MAX lines molded into the tank. Start the car and let it warm up. Now recheck the level and add coolant if it has dropped. Pop the cap on the new tank and that's it!

Shown here is a new coolant expansion tank with cap for the MINI.
Figure 1

Shown here is a new coolant expansion tank with cap for the MINI. It has been suggested that the newer tanks have been re-worked to prevent the seam from failing; however I couldn't find any noticeable difference between the two tanks.

As you can see, this coolant expansion tank has failed along the manufacturing seam (green arrow) This is unfortunately an all to common problem with the MINI.
Figure 2

As you can see, this coolant expansion tank has failed along the manufacturing seam (green arrow) This is unfortunately an all to common problem with the MINI. This is due to a manufacturing defect that seems to strike at random. You can see the baked coolant on the heat shield directly below.

Use a turkey baster or large syringe to siphon out the coolant inside the old tank.
Figure 3

Use a turkey baster or large syringe to siphon out the coolant inside the old tank. You don't have to get it perfectly dry, but just enough to where the level is at the bottom of the tank. When you lift the tank up and out of the engine compartment, the remaining coolant will drain back down through the lower hose.

Next use a pair of pliers to remove the hose clamp on the upper hose connection.
Figure 4

Next use a pair of pliers to remove the hose clamp on the upper hose connection.

Remove the 10mm nut holding the tank to the firewall.
Figure 5

Remove the 10mm nut holding the tank to the firewall.

Pull the upper hose connection off the old tank.
Figure 6

Pull the upper hose connection off the old tank. It may be helpful to take a small screwdriver and gently work it in-between the hose and the plastic, working all the way around top free up the hose.

Connect the bottom hose to the bottom of the new tank and slide the hose clamp back on.
Figure 7

Connect the bottom hose to the bottom of the new tank and slide the hose clamp back on. Maneuver the new coolant tank into place, making sure that the two tabs on the rear of the tank fit into the holes on the firewall. It will take a little effort to get the tank in as it's tight fit.

Connect the bottom hose to the bottom of the new tank and slide the hose clamp back on.
Figure 8

Connect the bottom hose to the bottom of the new tank and slide the hose clamp back on. Maneuver the new coolant tank into place, making sure that the two tabs on the rear of the tank fit into the holes on the firewall. It will take a little effort to get the tank in as it's tight fit.

Re-fit the upper hose connection and install the 10mm nut holding the tank to the bracket.
Figure 9

Re-fit the upper hose connection and install the 10mm nut holding the tank to the bracket. Once in place, fill the tank with coolant until it registers between the MIN and the MAX marks.

(R50 Cooper): The R50 Cooper uses a different kind of coolant tank then the R53 models.
Figure 10

(R50 Cooper): The R50 Cooper uses a different kind of coolant tank then the R53 models. However, it is easily changed as well. Siphon out all of the existing coolant, and then remove both the upper 10mm nut holding the tank to the firewall (green arrow) and pull the tank out of the holding brackets.

(R50 Cooper): Once removed, pull the return hose off the tank at the bottom (green arrow).
Figure 11

(R50 Cooper): Once removed, pull the return hose off the tank at the bottom (green arrow). You may find that it is difficult to remove the bottom hose. It may need to be "walked off" NOTE: the power steering fluid reservoir has been removed for additional space in thisPicture.

12 (R55/R56/R57 Cooper and Cooper S): The coolant expansion tank sits along the front edge of the upper support panel on the R55/R56/R57 MINI Coopers.
Figure 12

12 (R55/R56/R57 Cooper and Cooper S): The coolant expansion tank sits along the front edge of the upper support panel on the R55/R56/R57 MINI Coopers. Remove the hose clamp and hose going to the tank shown here (green arrow). Also remove the 10mm bolt holding the coolant tank in place (purple arrow).

(R55/R56/R57 Cooper and Cooper S):Rotate the tank up and out of the engine bay.
Figure 13

(R55/R56/R57 Cooper and Cooper S):Rotate the tank up and out of the engine bay. Use a pair of pliers to remove the hose clamp holding the hose to the bottom of the tank. Now lift the tank out and install the new one.

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Comments and Suggestions:
Marvin m Comments: 17-12-2-754-231-BOE
Hose to expansion tank to radiator,
Im replacing my expansion tank due to the expansion being plastic and not very sturdy i bought the tank and the hose to the radiator, how do you install that?
August 26, 2016
  Followup from the Pelican Staff: Follow the hose to the other end, disconnect it, then rettach and fill and bleed system. - Nick at Pelican Parts  
Ferd Comments: Hello. Do you have the part # of the hose on the bottom of the expansion tank? When doing an oil change, removing the filter, noticed it was leaking there. It losses coolant over a two week period and there are no other visible leaks nor coolant in the engine.
2008 Mini Cooper S 6 speed.
Thank you.
October 8, 2015
  Followup from the Pelican Staff: I’m not the best with part numbers.

Give our parts specialists a call at 1-888-280-7799. They can figure out what part or repair kit you need.
- Nick at Pelican Parts
 
Carstock Comments: How is the coolant level in the metal expansion tank checked for a 2008 Mini Cooper?
June 21, 2015
  Followup from the Pelican Staff: I have to assume this is an aftermarket component, I haven't seen a metal tank on a Cooper model. I would check with the manufacturer of the tank. - Nick at Pelican Parts  
MINIJCW07 Comments: Doing a expansion tank replacement on my 07' JCW. I came across the part GROMMET that is used for the bottom insertion of the reservoir, it points out to the front. My question is where does the grommet go into? Is it necessary? And whats the grommet used for? I feel that when I pulled off the reservoir I might of pulled it off a bit to hard and the grommet fell down. I've added a picture for a better view of the question I'm asking?
June 1, 2015
  Followup from the Pelican Staff: There is a plastic pin at the bottom of the reservoir, this pin sits in the rubber grommet at the base, in the radiator support. - Nick at Pelican Parts  
brewpoint Comments: Where are the bleeder valves on an R56 2008 Cooper?
December 11, 2014
  Followup from the Pelican Staff: There aren't any. you either bleed it with the heat on or with a vacuum bleeder. - Nick at Pelican Parts  
karlito Comments: Battery issue was the cause of my problems. Fan not kicking in at correct temperature and this was due to the battery being the wrong amp per hour it was a 41 amp battery
I replaced battery and fan kicking in at 112'C where it had been kicking in at 117'C. At 117'C the coolant was being forced out the expansion tank. Now the fan is kicking in it 112'C stays on until the temp cools to 108'C. The battery wasnt out putting enough power amps to switch the fan on at the correct temp. I'm assuming it had something to do with the resistor that controls the fan and without the correct voltage or amps going across it it wasn't kicking in. Ie voltage = amps x resitance. V÷amps = resistance etc.
July 29, 2014
  Followup from the Pelican Staff: Thanks for the feedback and additional info. We appreciate it.
- Nick at Pelican Parts
 
karlito Comments: I'm having the coolant being forced out of the expansion tank by popping the cap and sometimes just coming out with the cap still on. I have been topping up with coolant and water but unsure of the mixture %. Is the 50-50 mix essential and as I'm not using it is this causing my problem?
I've looked at the articles and tried checking those I'm able to rule them out. I noticed that another reason for this is the fan not kicking in. Mine kicks in but I'm not sure of it's a stage one fan or stage 2. I used the diagnostic test to check the temp and when the fan kicks in and it comes on at 117'C. I think this maybe stage 2 as I assume it should kick in earlier to stop overheating. So at what temp should stage one kick in?
My car is a 02 Cooper.
July 28, 2014
  Followup from the Pelican Staff: The fan turns on at 105°c and high speed kicks in at 115°c.

Coolant mixture will not cause this issue. - Nick at Pelican Parts
 
chris Comments: i want to know the cooland expantion tenk if i lost the cap how can i seal it till i can find one and how tight must it be and what is the purpose of that tenk and what pressure is in it???/
June 13, 2014
  Followup from the Pelican Staff: You'll need a new cap. Give our parts specialists a call at 1-888-280-7799. They can help you find the right part.
- Nick at Pelican Parts
 
Laura Comments: I recently had the tank replaced and next day it over flowed from cap. If I remove some coolant will it be ok or is it ruined?
December 15, 2013
  Followup from the Pelican Staff: Check this article, it shows how to check the coolant level when filling.

http://www.pelicanparts.com/techarticles/MINI/20-WATER-Coolant_Change/20-WATER-Coolant_Change.htm - Nick at Pelican Parts
 
oded Comments: I have been told that you will need to bleed the coolent to avoid air bubbles after replacing the expension tank, you did not mantion that in this article , my question is : do I or do inot have to do so?
Thanks
August 2, 2013
  Followup from the Pelican Staff: I suggest bleeding it. This tech article should help you: http://www.pelicanparts.com/techarticles/MINI/20-WATER-Coolant_Change/20-WATER-Coolant_Change.htm - Nick at Pelican Parts  
Tom S. Comments: Recently replaced my R53 tank and purchased genuine mini coolant to replace what was removed / lost. New coolant was dark blue while, what I believe is, original coolant was green as well as all coolant I see in the tutorials. Was mixing the two perfectly ok? I thought all BMW / mini coolant should be the blue type. There is endless contradicting/ vague information on coolant types on the Internet and want to be certain of type to use when I do a coolant change. Thanks
July 10, 2013
  Followup from the Pelican Staff: If you purchased genuine MINI coolant you can mix it. The coolant in your vehicle may look darker due to age. - Nick at Pelican Parts  
A Mini Driver Comments: Excellent how-to! I would suggest also replacing the hose clamps. In the past, I've had the spring type not hold as tightly after they've been released. So any time I work on hoses, I go ahead and change the hose clamps for the style with the screw.
November 4, 2012
  Followup from the Pelican Staff: I agree, replacing spring type hose clamps is a good idea. - Nick at Pelican Parts  

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