Supplies Needed

• Phillips Screw Driver
• 13mm Socket
• Pliers
• Side Cutters, or Bull Nose Cutters, or A Rotary Cutter (Dremel)
• 2x Screw-type Hose Clamps (at least 1/2 inch)
• 3/8 inch hose barb connector
• Upper Radiator Hose (BMW Part 17127593490)
• 1 Gallon Concentrated BMW Compatible Coolant (BMW Part 82141467704)
• 1 Gallon Distilled Water
• A Clean bucket (at least 2 gallon capacity) for mixing the new coolant
• A clean funnel
• Catch Pan (at least 2 gallon capacity)
• 100% Petroleum Jelly

When To Replace The Upper Radiator Hose?

The upper radiator hose on the N52 3.0 Engine is prone to failure at the small fittings.  The small hoses are often in the way when other components on the front of the engine are serviced and can be stressed.  As the plastic components go through numerous heat cycles, they will weaken and likely start to leak before an outright failure.  The small hose that goes from where the large radiator hose connects to the Y-connector is most likely to fail as it is stressed when trying to remove the radiator fan.  If this leaks, it will likely drip onto the serpentine belt.  This hose does not need to be replaced unless it fails.

How To Do It

1. Remove Intake Snorkel

The plastic snorkel that routes cold air from in front of the radiator to the filter box on top of the engine must be removed.  This is held in place by two plastic rivets close to the middle of the snorkel.  These rivets are simple to remove by grasping the center pin with pliers and pulling up.  For me, the whole rivet comes out with the pin.  Once the rivets are removed, you can lift up the forward end of the snorkel and pull it out of the air filter box.

2. Remove Front Upper Body Brace

The front brace for the body is held in place by 4 13mm bolts, two on each side.  Before removing the brace, you will have to pop the plastic line off of the brace that runs the length of the brace.  This line is held in place in 3 places along the engine side of the brace.  The bolts are secured underneath two hard air conditioner lines on the left and under the radiator ventilation hose on the right.  Once the 4 bolts are removed, the brace can be lifted up slightly on the right hand side.  Then slide the brace to the right until it clears the hard air conditioner lines.  After the brace clears the air conditioner lines, it can easily slide out from under the radiator hoses.

3. Remove Radiator Fan (Optional)

You do not need to remove the radiator fan, but it gives you a lot more room to work on the radiator hose quick connectors.  There is a single electrical harness on the left-hand side of the radiator fan that needs to be disconnected.  The fan is held in place by 2 plastic pins, one on either side.  To release these pins, simply press in on the plastic retainer spring above the pin with one finger while lifting up on the fan.

The pin on the left side is fixed, but the pin on the right side can rotate around once it is free of the retainer.  The right side pin needs to rotate 180 degrees around in order to clear the upper radiator hose fitting.  Once the right hand pin is flattened against the fan shroud, the fan can be lifted up and out of the engine compartment.  The radiator ventilation hose is in the way, but there is enough flex in it to get the fan out.

4. Remove Splash Guard From Underneath The Engine

In order to collect the fluid that will drain out, you will need to remove the plastic splash guard from underneath the engine.  This is held in place by several Phillips head screws that only require a quarter turn to remove.  The 4 screws along the front will actually fall out of the holes, while the other screws will stay with the splash guard once released. With the splash guard out of the way, you can place your catch pan to collect the coolant.

5. Disconnect Small Upper Radiator Hose Fitting

You can find this hose by following it from the large radiator-side connector.  It is secured to the frame by a retainer clip and should easily lift out of the retainer.  A metal clip holds the male and female connectors together.  This clip can slide half way down to an unlocked position.  In this position you can disconnect the hose, but I find it easiest to remove the clip entirely.  With this clip removed, the only thing holding the connectors together is friction of an o-ring.  I have found that the best way to disconnect these is to hold one end in each hand and pull while wiggling the male end.  Be patient and persistent and the connector will come free.

6. Let The Coolant Drain Out

Most of the fluid will drain out of the female end down into your catch pan.  I collected about a gallon and a half out of this hose.  It may take a few minutes for the fluid to stop flowing.  You will likely need to hold the female end out from the frame to help the fluid to drain without getting all over the frame.  Spilled coolant isn’t a big deal as long as it doesn’t pool anywhere.  Coolant evaporates readily, but is poisonous so you don’t want it to pool anywhere animals could drink it.

7. Cut The Ear Clamps On The Y-Connector

There are 3 ear clamps on the Y-connector that comes out of the coolant reservoir.  All three of these clamps should be removed.  You can cut the top of the ear with side cutters, bull nose cutters, or a dremel tool.  This may take a little work as these are steel clamps.  Alternatively you can pry the end up with a flathead screwdriver.  Of course, after you remove the clamps, they cannot be reused.  Don’t worry if you break the Y-connector like I did in the above picture.    This connector will be replaced by a simple coupling as the new part doesn’t have the hose to the reservoir from the engine.

8. Remove Radiator Side Connector

The BMW upper radiator hose can now be removed from the radiator.  This is done similarly to how the first connector was removed to let the coolant drain.  Simply remove the retainer clip from the “quick” connect fitting and wiggle the female end until it comes off.  You shouldn’t have any fluid drain out of this connection, since most of the fluid is already drained out.  You may see a black line on the male end from the o-ring.  It is worth taking some time to clean this up.  This will help prevent the fitting from leaking.

9. Remove The Engine-Side Connector

Third verse same as the other two.  Remove the retainer clip from the “quick” connect fitting.  Then wiggle and pull on the fitting until it comes loose.  These fittings tend to stick as the o-ring becomes bonded in place.  Cleaning the male end of the connection will help the new o-ring to seat well and not leak.  This is the last connection for the upper radiator hose assembly, so it can be removed.

10. Prepare The New Radiator Hose Connectors

I have found that applying a small amount of petroleum jelly to these connections aids in attachment.  You don’t need a lot of jelly on these surfaces, a thin film will do.  I suggest applying a thin film to both the male and female connectors.  This is done in order to lubricate the o-rings and make sure the fittings seat well without a lot of force.

11. Install The New Upper Radiator Hose

I suggest connecting the small fitting first, paying attention to how the hose was routed before.  You will need to use the retainer clip that was removed earlier.  Connect the engine-side and radiator-side fittings.  You can push these on with the retainer clip in place.  With the retainer clip in place, it should snap into its slot as you push the connector on.

12. Connect The Radiator To The Reservoir

Since the new part does not have a fitting for the small hose, you will need to use the 3/8 inch coupler to join the reservoir hose to the radiator ventilation hose.  This will require the coupler and the 2 small hose clamps.  You can see how this is configured in the picture from step 7.  The third connection from the engine-side fitting to the reservoir is not needed.

13. Reinstall the Radiator Fan

Looking down at the bottom of the radiator, there are two eyelets for the shroud to key into.  The right-side pin needs to stay folded in until it is passed the upper radiator hose.  Make sure that both pins are lined up before seating them.  If you snap the left-side pin in place first, you won’t be able to properly seat the right-side pin.  After the fan shroud is snapped into place, you can reconnect the fan’s electrical harness.

14. Mix Coolant And Fill Reservoir

Now that all of the connections are made, you are ready to fill the cooling system with fresh coolant.  You may be tempted to reuse the old coolant, but I don’t recommend this after it has splashed over the frame and catch pan.  Mix the concentrated coolant and distilled water in the clean bucket then use the clean funnel to pour it into the reservoir.  I find it useful to pour the mixed coolant back into one of the jugs for ease in filling the reservoir.  Go ahead and fill the reservoir to the maximum level as it will drop a little during the next step.

15. Burp The Cooling System Of Air

This step has to be one of my favorite parts of having an electric water pump.  The electric water pump can be run without turning on the engine in order to circulate the coolant and drive air bubbles out of the system.

Insert the key fob into the ignition
Press start button without brake pedal (don’t start the engine)
Turn Passenger and Driver climate controls all the way up
Turn the climate control fan all the way down without turning it off
Press the gas pedal to the floor and hold it for 10 seconds

You should hear the water pump cycle on after holding the gas pedal down.  While the water pump is running you can peer into the reservoir and see fluid pumping in from the ventilator hose.  The water pump will cycle on and off several times during the bleeding process, which takes about 10 minutes to complete.  I like to leave the reservoir open during the bleeding cycle to let air out.  Newer models may have a special bleeder valve to open on the reservoir.  If the bleeder valve is present, you should close the reservoir until the bleeding procedure completes.

16. Assembly Is The Reverse Of Disassembly

Waiting for the bleeding process to complete, about 10 minutes, is a good time to put everything back together.  This includes putting the body brace back, securing the hood release line to the body brace, and replacing the intake snorkel.  Once you are satisfied that there are no leaks, go ahead and replace the splash guard underneath the engine compartment.  Once the bleeding procedure completes, check the coolant level in the reservoir and top it off if necessary.