Parts Catalog Accessories Catalog Tech Info Tech Forums
 
Follow Pelican Parts on Facebook Follow Pelican Parts on Twitter Follow Pelican Parts on Instagram Follow Pelican Parts on YouTube Follow Pelican Parts on Pinterest Follow Pelican Parts on Tumblr
  Search our site:    
View Recent Cars  |   Cart  | Project List | Order Status | Help    
 >  >
Coolant Expansion Tank Replacement
 
Bookmark and Share

Pelican Technical Article:

Coolant Expansion Tank Replacement

Nick Czerula

Time:

2 hours2 hrs

Tab:

$100

Talent:

***

Tools:

Set of sockets, wrenches, screwdrivers

Applicable Models:

BMW Z3 (1996-02)

Parts Required:

Expansion tank, engine coolant

Hot Tip:

Work with a cool engine.

Performance Gain:

Car will cool down again, coolant leak repaired

Complementary Modification:

Change radiator hoses, Expansion tank mounting bracket, flush cooling system.

BMW Z3 cooling system components include:

  • Radiator and coolant overflow (expansion) tank.
  • Belt driven coolant pump bolted to the front of the engine block.
  • Electric cooling fan attached to rear of radiator. The cooling fan is controlled by the engine control module (ECM) via an output final stage.
  • Automatic transmission models: Belt driven fan attached to front of coolant pump. Viscous clutch controls fan speed based on engine compartment temperature and rpms.
  • Electrically heated ECM-controlled thermostat.
  • Automatic transmission cooler (heat exchanger).
  • Heater valve and heater core (for climate control).
  • Coolant level sensor inside expansion tank.
  • Coolant temperature sensor at cylinder head.
  • Radiator outlet temperature sensor.
  • Coolant hoses and lines.

When a coolant expansion tank ages it becomes brittle and develops hairline cracks. Inspect your expansion tank every time you change your oil. Look for cracks or any signs of leaks. Ignoring a small crack is a bad idea, as they can grow rapidly and create a major coolant leak before you know it. The coolant level sensor is located in the bottom of the tank. If you have a low coolant level message, but your coolant level is OK, you may have a faulty sensor. 

When a coolant expansion tank begins to fail a leak may develop at a plastic seam or connection point. On 4-cylinder models the expansion tank is attached directly to the radiator. You can replace it and the O-rings, usually done while the radiator is installed in the vehicle. However, they tend to get stuck and sometimes removing the radiator is a big help. On 6-cylinder models the tank usually cracks at the top, below the breather hose connection, causing a leak. This tank is much easier to replace than the 4-cylinder one.

In this tech article I will show you how to replace the expansion tank and test and replace the coolant level sensor.

Do not remove the expansion tank cap while the engine is hot. Coolant or hot steam may escape and will scald you. To do any work on the cooling system, wait until the engine has cooled off.

Keep in mind that when your car was serviced before, parts may have been replaced with different size fasteners used in the replacement. The sizes of the nuts and bolts we give may be different from what you have, so be prepared with different size sockets and wrenches. 

Protect your eyes, hands and body from fluids, dust and debris while working on your vehicle. If you're working with the electrical system, disconnect the battery before beginning. Always catch fluids in appropriate containers and properly dispose of any fluid waste. Recycle parts, packaging and fluids when possible. Do not work on your vehicle if you feel the task is beyond your ability. 

Vehicle models change and evolve, as they grow older, so the vehicle shown in our illustrations may vary slightly from yours. If something seems different, let us know and share your info to help other users. Do you have questions or want to add to the article? Leave a comment below. When leaving a comment, please leave your vehicle information.

Models with 4-cylinder engine

I am going to show you how to remove the expansion tank with the radiator removed. The expansion tank was stuck pretty well in the vehicle I used for the article and I wanted to share what it took to get it out without damaging the radiator.

Drain cooling system. See our tech article on cooling system draining and filling.

Remove cooling fan shroud. See our tech article on radiator cooling fan replacing.

Working at expansion tank, remove cap.
Figure 1

Working at expansion tank, remove cap. Then remove two 5mm Allen fasteners (green arrows).

Remove the radiator. See our tech article on radiator removing. You can try to replace the tank without removing the radiator. If you would like to, skip this step.

Once the radiator has been removed, lift the black plastic cover off the expansion tank. This is the cover that you removed two 5mm Allen fasteners from earlier.

After removing the cover, the expansion tank should slide up and out of the radiator. However, this is rarely the case. It has to be worked out slowly, as to not damage the radiator.

The first thing I do is spray soapy water into the joint where the expansion tank joins the radiator.
Figure 2

The first thing I do is spray soapy water into the joint where the expansion tank joins the radiator.

Then I use a plastic prying tool to slowly lever the tank up.
Figure 3

Then I use a plastic prying tool to slowly lever the tank up. I work my way around the perimeter of the joint, being careful not to damage the radiator.

Once the tank begins to move and there is small gap at the joint, I use a plastic hammer and a flathead screwdriver to drive the tank out a little more.
Figure 4

Once the tank begins to move and there is small gap at the joint, I use a plastic hammer and a flathead screwdriver to drive the tank out a little more.

Take turns levering the bottom and lever at the top.
Figure 5

Take turns levering the bottom and lever at the top. Keep in mind everything you are prying against is made of plastic and can break. Worst case scenario being you damage the radiator and need to replace it. When I use a flathead screwdriver as shown in the photo, I apply even and steady pressure, you will notice the tank will start to slide up as the O-ring releases. Add more soapy water to joint as needed.

Once the O-ring (green arrow) has cleared the joint, you can remove the tank from the radiator.
Figure 6

Once the O-ring (green arrow) has cleared the joint, you can remove the tank from the radiator.

Inspect the bleeder hole in the top of the radiator and be sure it is clear.
Figure 7

Inspect the bleeder hole in the top of the radiator and be sure it is clear. (green arrow)

Inspect the sealing joint and confirm it was not damaged during the removal process.
Figure 8

Inspect the sealing joint and confirm it was not damaged during the removal process. (green arrow) Clean the joint thoroughly before installing new tank.

When installing the new expansion tank, lubricate O-rings with clean coolant. Then slide tank into radiator until top is flush with radiator. Then install cover and fasteners, then install radiator.

Fill and bleed cooling system. Once complete, double check all hose connections and check engine for coolant leaks.

Models with 6-cylinder engine

The coolant expansion tank on 6-cylinder models is located at the left front strut near the brake master cylinder. When replacing, you only have to partially drain the cooling system to remove the coolant from the reservoir and the associated hoses.

Drain cooling system. See our tech article on cooling system draining and filling.
Working at the side of the expansion tank, use a small flathead screwdriver and lever the hose retaining clip (green arrow) up until it reaches the top.
Figure 9

Working at the side of the expansion tank, use a small flathead screwdriver and lever the hose retaining clip (green arrow) up until it reaches the top. Once released, remove the hose from the tank by pulling it straight off.

Then, use a small flathead screwdriver and lever the hose retaining clip(green arrow) up until it reaches the top.
Figure 10

Then, use a small flathead screwdriver and lever the hose retaining clip(green arrow) up until it reaches the top. Once released, remove the hose from the tank by pulling it straight off. Unclip the hose from the front of the tank and set it aside. Then remove the two 10mm tank fasteners (yellow arrows).

Disconnect coolant level sensor electrical connector at bottom of expansion tank then remove expansion tank from vehicle. If equipped.

When installing expansion tank, connect coolant level sensor electrical connector, then press hose into mounting bracket and engage retaining clip. Next connect lower hose to expansion tank, retaining clip is properly seated when an audible click is heard. Connect upper hose and engage retaining clips until an audible click is heard.

Fill and bleed cooling system. Once complete, double check all hose connections and check engine for coolant leaks.










Bookmark and Share
Comments and Suggestions:
Vee Comments: No need this car does not indicate level only temp electronically.
May 7, 2016
  Followup from the Pelican Staff: If you have a wiring harness that needs to be identified, as you mentioned in you first post, that is the best way to find it. - Nick at Pelican Parts  
Vee Comments: Verified coolant temp is only monitored there is no indicator for coolant level. Sensor is not used on this vehicle. No mention in repair or owners manuals of it. 2001 BMW Z3.
May 6, 2016
  Followup from the Pelican Staff: In that case, I would grab a wiring diagram, locate the harness using the wire colors. Then you will be able to identify it. - Nick at Pelican Parts  
Vee Comments: I have removed a leaky expanion tank on a 2001 Z3 3.0 and fond there wasnt a sensor or wire attachment to the original tank? I cnat find any trace of a wire with connect or sensor attached. Did some BMWs have the sensor elsewhere?
May 5, 2016
  Followup from the Pelican Staff: No, there should be a sensor int he bottom of the tank, on late model vehicles. - Nick at Pelican Parts  

  Search our site:    

View Cart & CheckOut | Project List | Order Status |  Help    

 

[Home] [Customer Service] [Shopping Cart] [Privacy Statement]
 [Contact Us] [About Us] [Shipping] [Map to our Location] [Careers]

Copyright © Pelican Parts Inc.

Page last updated: Fri 12/9/2016 03:05:31 AM