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Pelican Technical Article:

Cooling System Leak Test

Nick Czerula

Time:

1.5 hours

Tab:

$20

Talent:

**

Tools:

Cooling system pressure tester

Applicable Models:

R56 MINI Cooper Hatchback (2007-11)
R56 MINI Cooper S Hatchback (2007-11)

Parts Required:

Engine coolant. Additional parts will be determined once leak is found.

Hot Tip:

Check for leaks with engine warm and cold

Performance Gain:

Repair coolant leaks

Complementary Modification:

Replace associated hoses and cooling system seals

Pressure testing your MINI R56 cooling system is the best way to find leaks. However, not everyone has a pressure tester. I would suggest owning one if you plan to maintain your own vehicles. It can save quite a bit of time when locating a cooling system leak. You can also check for leaks without a pressure tester, but results are less accurate and the procedure is time consuming. I will cover pressure testing in this tech article, as well as some tips on checking for leaks without using one. Always start with a cool engine. If you do not find the leak, warm the engine with the pressure tester installed. At times, leaks will surface as parts expand from engine heat.

A cooling system pressure tester is used to pressurize a cooling system and hold it at a specified pressure while looking for leaks. Coolant leaks can be internal (i.e.: head gasket) or external (i.e.: radiator). It is important to take these things into consideration when looking for a coolant leak. If you are losing coolant, but not seeing any on the ground, this would likely be an internal coolant leak. Puddles of coolant found under your vehicle would be from an external leak. Remember to properly clean any coolant that gets on the ground and properly dispose of it. Place a drain pan under suspected areas of leaks to minimize coolant spills. R56 models can develop coolant leaks toward the front of the engine, in places like the radiator reservoir, auxiliary water pump and thermostat. Leaks coming from the rear or right side of the engine can be the water pump, thermostat and coolant pipe. A pressure tester is the quickest way to find these leaks.

When pressure testing a cooling system, be sure the vehicle is cool and lacks pressure.
Figure 1

When pressure testing a cooling system, be sure the vehicle is cool and lacks pressure. Then, remove the coolant expansion tank cap (red arrow).

Once the cap is removed, install the pressure tester adapter (red arrow) to the coolant expansion tank.
Figure 2

Once the cap is removed, install the pressure tester adapter (red arrow) to the coolant expansion tank.

Pressurize the system to 1.
Figure 3

Pressurize the system to 1.5 bar (21.8 psi). Pressure should not drop more than 10% over a two minute time period. If pressure drops right off, that is a sign of a leak. Look for coolant on the ground. If no coolant reaches the ground, you could have an internal leak. If you suspect a head gasket leak, you need to test the cylinder sealing via a leak down test. If coolant leaks externally, use a flashlight and follow the coolant to its source.

Coolant leaking down the right side of the engine could be the water pump.
Figure 4

Coolant leaking down the right side of the engine could be the water pump. Note the coolant at the bottom of the friction wheel (red arrow). This is a good indication of the water pump leak, when viewed from below the engine on the right side.

Coolant leaking down the left side of the engine can be from the thermostat, coolant hoses or from the oil filter stand / housing, auxiliary coolant pump or reservoir.
Figure 5

Coolant leaking down the left side of the engine can be from the thermostat, coolant hoses or from the oil filter stand / housing, auxiliary coolant pump or reservoir. Coolant leaking down the radiator could be from the radiator or a radiator hose. To check a radiator hose, pressure the cooling system, and then wiggle the hoses. While wiggling the hoses, check for a drop in pressure or a coolant leak. The red arrow points to a leaking hose at the bottom of the coolant reservoir. Note the small wet area. This vehicle was losing a small amount of coolant over time with no coolant reaching the ground. When looking for leaks at the radiator, inspect the sides on the radiator for signs of leaks or fresh coolant. Use a mirror to inspect the bottom of hoses and connections at the radiator. It can be tough when trying to figure out if the leak is from the engine or the radiator at times. Follow the wet spots upward to the source.

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Comments and Suggestions:
Ron Comments: help!! WE have replaced the waterpump on my sons 2008 Mini Cooper S 3 TIMES and it still have a leak somewhere on the right side! It appears to be seaping out just across from the bottom of the drive belt areaisn't this below the water pump and we are just befuddled at this point! Any helpful suggestions would be appreciated as we don't want to got the dealer unless we absolutely have too!!
November 7, 2016
  Followup from the Pelican Staff: Could be the plastic coolant pipe that runs along the rear of the engine. - Nick at Pelican Parts  
Rick Comments: this part is leaking on my 07 mini and I need HELP,what is this part called and were can i get it ,and the hose, no one lists this part in any place i have looked. some show the part but no part number
October 2, 2016
  Followup from the Pelican Staff: You need the hose. Give The Pelican Parts parts specialists a call at 1-888-280-7799. They can figure out what part or repair kit you need.
- Nick at Pelican Parts
 

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