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Pelican Technical Article:

Radiator Replacement

Steve Vernon

Time:

2 hours2 hrs

Tab:

$250 to $500

Talent:

**

Tools:

19mm wrench, 10mm socket, flathead screwdriver, large bucket

Applicable Models:

Mercedes-Benz W123 (1977-85)

Parts Required:

Radiator, coolant, transmission fluid

Hot Tip:

Get a really big bucket

Performance Gain:

Proper engine temperature

Complementary Modification:

New hoses

Radiators are an essential part of your car's cooling system. A failed and/or leaking radiator can cause serious damage to the engine. Fortunately, replacing the radiator on the W123 is a rather simple job as there are only three hoses attached to it and no other components need to be worked on to remove it. There is only one issue that requires special attention: the transmission cooler is attached to the lower section of the radiator and you will need to remove these lines and then top up the transmission fluid after you install the new radiator.

You will need to drain the coolant before you begin to remove the radiator. Modern coolants last a very long time and if you need to drain your coolant you really should consider draining it into a clean container so you can reuse it.

A couple of safety precautions/instructions you may want to observe before beginning:

Allow cooling system to cool down to a coolant temperature of less than 90°C. Open the cap of cooling system slowly; turn a conventional coolant cap as far as the first detent and turn a screwed coolant cap approx. 1/2 turn and release the pressure. Wear protective gloves, protective clothing and eye protection. Always dispose of used coolant in accordance with the regulations in your region; NEVER pour coolant down a drain, on the ground or into a sewer.

Begin by safely jacking up and supporting your car. Please see our article on these procedures for additional help.

Remember your car may have been serviced before and parts 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 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. Never work on your vehicle if you feel the task is beyond your ability.

Our vehicle may vary slightly from yours as models do change and evolve as they grow older. If something seems different, let us know and share your info to help other users. Questions or want to add to the article? Leave a comment below. When leaving a comment, please leave your vehicle information.

Working on the top of the motor first you will see the radiator (red arrow), the overflow reservoir (yellow arrow) and the top hose that connects the top of the radiator to the thermostat housing (blue arrow).
Figure 1

Working on the top of the motor first you will see the radiator (red arrow), the overflow reservoir (yellow arrow) and the top hose that connects the top of the radiator to the thermostat housing (blue arrow).

Begin by opening the cap on the overflow reservoir to break the vacuum in the system.
Figure 2

Begin by opening the cap on the overflow reservoir to break the vacuum in the system. Make sure the coolant is cool before releasing the pressure. If the coolant is still hot and under pressure you can seriously hurt yourself.

There are two mounts for the radiator under the front of the car, one is just a mount (yellow arrow) and the other is the mount and drain plug (red arrow).
Figure 3

There are two mounts for the radiator under the front of the car, one is just a mount (yellow arrow) and the other is the mount and drain plug (red arrow).

Place a large bucket under the drain [plug and use a flathead screwdriver to open the drain plug.
Figure 4

Place a large bucket under the drain [plug and use a flathead screwdriver to open the drain plug. If you are going to reuse the coolant make sure to drain it into a clean container.

The drain plug will unscrew and then pull out from the bottom.
Figure 5

The drain plug will unscrew and then pull out from the bottom. Make sure to check the condition of the plug for damage as this can lead to potential leaking.

Use a flathead screwdriver and remove the clamp from the upper hose and carefully pull it back off the radiator.
Figure 6

Use a flathead screwdriver and remove the clamp from the upper hose and carefully pull it back off the radiator. The top of the radiator is plastic and are known for breaking off. If you hose is stuck do not just pull on it, try running a small flathead screwdriver or pick around the hose to break the seal.

Next use a flathead screwdriver and remove the clamp and hose from the top hose to thermostat housing (red arrow).
Figure 7

Next use a flathead screwdriver and remove the clamp and hose from the top hose to thermostat housing (red arrow). Be prepared for coolant to escape when you remove this hose.

Working under the car remove the two lower hoses and be prepared for even more coolant to escape.
Figure 8

Working under the car remove the two lower hoses and be prepared for even more coolant to escape.

There is a power steering cooler attached to the left side of the radiator.
Figure 9

There is a power steering cooler attached to the left side of the radiator. Use a 10mm socket and remove the mounting bolt (red arrow).

Next use a 19mm wrench and remove the two transmission cooling lines (red arrows).
Figure 10

Next use a 19mm wrench and remove the two transmission cooling lines (red arrows). Fluid will escape so if you are planning on reusing your coolant make sure you drain these lines into a different bucket.

Remove the 10mm bolt from the top of the radiator to power steering cooler (red arrow).
Figure 11

Remove the 10mm bolt from the top of the radiator to power steering cooler (red arrow).

With the bolt removed pull the bracket up and off the radiator.
Figure 12

With the bolt removed pull the bracket up and off the radiator.

Use a flathead screwdriver and pry the two clips off that connect the radiator to the cross member.
Figure 13

Use a flathead screwdriver and pry the two clips off that connect the radiator to the cross member.

If the fan and shroud are still in the vehicle remove the shroud clips, lift it up and sit it back on the fan.
Figure 14

If the fan and shroud are still in the vehicle remove the shroud clips, lift it up and sit it back on the fan. You can lift the radiator up and out. Installation is the reverse of removal and do not forget to refill and bleed the coolant as well as top up the transmission fluid.

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