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Coolant Expansion Tank Replacement
 
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Pelican Technical Article:

Coolant Expansion Tank Replacement

Steve Vernon

Time:

1 hour1 hr

Tab:

$40 to $100

Talent:

**

Tools:

10mm socket, flathead screwdriver

Applicable Models:

300E (1985-92)
260E (1987-90)
300CE (1988-89)
300TE (1988-91)
300E2.6 (1990-92)
300TE 24 (1989-92)
300CE 24 (1990-93)
300E 24 (1990-93)
300CE (1993-94)
280E (1993-94)
300E2.8 (1993-94)
E280 (1994-96)
320TE (1993-94)
E320 (1994-96)

Parts Required:

New expansion tank, coolant

Hot Tip:

Replace the tank with the engine cold

Performance Gain:

A major cooling system leak fixed

Complementary Modification:

Flush cooling system

Over time, the coolant expansion tank tends to turn yellow, become brittle and form micro fractures and sometimes leak. When the car warms up, both the heat and pressure of the coolant starts to attack the weakest point 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 around an hour.

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 weeping/staining the crack or seam. It's important to tackle this problem as soon as possible.

You do not need to drain all the coolant from the vehicle. Just drain enough so that it is below the coolant reservoir. If the coolant in the car is new there is no reason to replace it as long as you drain it into a clean container. Coolant is expensive and not too great for the environment. So if the coolant in your car is good, try and save it to reuse it. If your coolant is old this is also a good time to perform a flush and install new coolant. Please see our article on coolant flush for additional assistance.

You will also need to remove the air filter air box to get access to the reservoir sensor and hose. Please see our article on air filter replacement for additional assistance.

If you are just replacing the coolant expansion tank you can use a turkey baster or fluid pump to remove the coolant from the tank (red arrow).
Figure 1

If you are just replacing the coolant expansion tank you can use a turkey baster or fluid pump to remove the coolant from the tank (red arrow). There may still be a little spillage when you remove the lower hose so be prepared for it. If you are planning on draining and flushing the system while performing this work please see our article on radiator drain and flush.

With the air filter box removed you can see the three hoses and one sensor you will need to remove to replace the reservoir.
Figure 2

With the air filter box removed you can see the three hoses and one sensor you will need to remove to replace the reservoir. The radiator to reservoir hose (purple arrow), the reservoir-overflow hose (green arrow), the reservoir supply hose (yellow arrow) and the level sensor wiring connection (red arrow).

Begin by pulling the overflow hose off the neck of the reservoir (red arrow).
Figure 3

Begin by pulling the overflow hose off the neck of the reservoir (red arrow). If you are replacing the reservoir there is a very good chance the overflow hose is shot and you should plan on replacing it as well. The hose gets very old and brittle over the years.

Use a flathead screwdriver and remove the hose and clamp for the radiator to reservoir overflow hose (red arrow).
Figure 4

Use a flathead screwdriver and remove the hose and clamp for the radiator to reservoir overflow hose (red arrow).

Squeeze in the tabs for the electrical connection and remove the connection from the level sensor (red arrow).
Figure 5

Squeeze in the tabs for the electrical connection and remove the connection from the level sensor (red arrow).

Always check the condition of the electrical connection and clean it up with a little Emory cloth if needed (red arrows).
Figure 6

Always check the condition of the electrical connection and clean it up with a little Emory cloth if needed (red arrows).

Use a flathead screwdriver and remove the clamp and hose from the bottom of the reservoir (red arrow).
Figure 7

Use a flathead screwdriver and remove the clamp and hose from the bottom of the reservoir (red arrow). This hose supplies the coolant to the radiator.

Use a 10mm socket and remove the two 10mm nuts that hold the reservoir to the fender wall (red arrows).
Figure 8

Use a 10mm socket and remove the two 10mm nuts that hold the reservoir to the fender wall (red arrows).

The reservoir (red arrow) sits in a rubber grommet in the fender wall (yellow arrow).
Figure 9

The reservoir (red arrow) sits in a rubber grommet in the fender wall (yellow arrow). You will need to pull up sharply to get the rubber plug in the reservoir to let loose.

Before installing the new reservoir make sure to check and clean the fender wall of any spilled coolant or corrosion that may have started (red arrow).
Figure 10

Before installing the new reservoir make sure to check and clean the fender wall of any spilled coolant or corrosion that may have started (red arrow). Installation is the reverse of removal. Do not forget to top up or refill your coolant!




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Comments and Suggestions:
alan Comments: 124 under wing tin reservoir 3 pipes 1986 manual saloon lhd rusted out
October 25, 2014
  Followup from the Pelican Staff: Give our parts specialists a call at 1-888-280-7799 and they can help figure out which part or repair kit you need.
- Nick at Pelican Parts
 
alan Comments: hi i have a 124 manual box 230e 1986 looking for reservoir tucked in under wing with 3 pipes and filter its rusted out! LHD left wing under plastic shield!protecter?
October 25, 2014
  Followup from the Pelican Staff: Give our parts specialists a call at 1-888-280-7799 and they can help figure out which part or repair kit you need.
- Nick at Pelican Parts
 

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