Mercedes-Benz Radiator Replacement Guide

Plan on 3 to 4 gallons of Mercedes approved coolant mixed 50/50 with distilled water, and keep a quart of transmission fluid to hand. The step people forget is the transmission cooler lines, which run through the radiator on most of these cars. Disturb them and you will lose fluid, and a radiator that fails internally can push coolant into the transmission, which is a far more expensive problem than the radiator.

The majority of the pictures in this guide are from an E-Class. These instructions should help you replace the radiator on Mercedes-Benz models such as C, S, ML, GL, GLK, GLE, GLS, etc. Replacing the radiator on a Mercedes-Benz is easy and takes about two hours.

What you will need

Below is a list of parts and tools to change the radiator on most Mercedes-Benz vehicles.

• Mercedes Radiator
• Mercedes Engine Coolant
  • Between 3 and 4 gallons. Check capacity in your owner’s manual.
  • Mix Anti-freeze coolant and distilled water in a 50-50 ratio.
• May also need Mercedes Transmission Fluid: 1qt

Tools:

• Screwdriver
• Work gloves
• T25 Torx
• 10mm wrench
• Needle nose pliers
• Oil pan

Before you start

• Allow the engine to cool down. Do not work on a warm or hot engine.
• Disconnect the negative battery terminal.
• Secure the vehicle with jack stands.
• Ensure parking brakes are engaged, the shifter is in the park position, and the rear wheels are blocked.

Procedure

1. Park the vehicle and allow it to cool down.

2. Raise the front wheels and secure the vehicle with jack stands.

3. Remove the bottom engine cover. It is held in place by 8mm screws.

4. Open the drain plug on the driver’s side of the radiator and allow the engine to cool down. Make sure to have a drain pan under the radiator. In some models, the drain plug is red.

5. Pry out the two plastic pins at each end of the top radiator bracket

6. Remove the upper radiator support

It is held in place with three T25 bolts on each side. On some models, such as CLS and CLK, you may also need to remove the front grill.

7. Disconnect the wires from the horn

8. Remove the top radiator support bracket.

9. Carefully release the hood release cable from the top bracket. It is clipped to the bottom of the top radiator bracket.

10. Locate the electrical connector on the back of the cooling fan.

Press the connector and pull it to disconnect it.

11. Remove two U clips at each top corner of the radiator.

These clips can be removed by prying them up with a screwdriver.

12. Slide the radiator cooling fan up

Look at the back of the cooling fan for hoses that may prevent it from coming up. If any of the hoses prevent the fan from moving up, move the hoses out of the way. At the bottom, the cooling fan slides into two channels.

13. Open the C clips on all of the coolant hoses. The C clips need to be pulled out slightly. It doesn’t need to be removed.

14. Disconnect all the coolant hoses

Once the C clips are in the unlock position, the hoses can be removed by pulling out on the hose.

If the hose refuses to come off, use a flathead screwdriver to pry out the hose. Be careful not to puncture the radiator hoses.

15. Use a screwdriver to loosen the clamp for the expansion tank hose

Pull out the hose to disconnect it.

16. Move the C clips for the transmission cooling lines to unlock position. Pull out the transmission cooling line.

Oil may drip from the lines. Have an oil pan ready to collect oil.

17. Squeeze the plastic retainers with needle-nose pliers to unclip the condenser from the radiator.

The retainers are on both sides of the condenser.

18. Pull the condenser up slightly to unlock it from the radiator brackets located at the condenser/radiator’s bottom.

19. Carefully lift the radiator

Make sure to close the drain valve before you remove the radiator. If the radiator drain valve is left open, the coolant left in the radiator will spill as you lift the damaged radiator.

Install in reverse order. Make sure to reinstall the rubber grommets. The rubber grommets sit on the frame and fit on the bottom of the radiator.

Add 50/50 engine coolant from the expansion tank.

Check transmission fluid level. On Mercedes-Benz with 722.6 (5-speed) transmissions, you will need dipstick part number 140589152. On Mercedes-Benz, with 7-speed transmissions, you will need a 722.9 transmission fill adapter.

Most Mercedes have the transmission cooler integrated into the radiator. When you disconnect the transmission line, you may lose up to 1 quart of transmission fluid.

Notes

• Discharging the air conditioner system may be required on some models.
• Removing the engine cover and engine air ducting will make replacing the radiator easier.
• Run the vehicle until it reaches operating temperature. Allow the engine to cool down and recheck the engine coolant level.

Do not forget the transmission cooler lines

On most Mercedes the automatic transmission cooler is built into the radiator, which is why this job involves transmission lines as well as coolant hoses. Two things follow from that. Check the transmission fluid level afterwards, because some will be lost when the lines are disconnected, and remember that these gearboxes have no dipstick, so the level has to be set at a specific fluid temperature with the engine running. The second is the reason many people have this job done rather than doing all of it themselves.

A radiator that fails internally can ruin the gearbox

When the internal barrier between the coolant and the transmission cooler splits, coolant and transmission fluid mix. The classic sign is a pink milkshake in the expansion tank or on the transmission dipstick where one exists. If that has happened, fitting a new radiator alone is not enough, because the contaminated fluid is already through the gearbox and will destroy the clutch packs. The transmission needs flushing and the cooler lines cleaning as part of the same job.

Bleed the air out properly or it will overheat again

These cooling systems trap air, and an air pocket will make the car overheat even with a brand new radiator and a full expansion tank. Fill slowly, run the engine with the heater on maximum until the thermostat opens and the top hose goes hot, and top up as the level drops. Watch the temperature gauge throughout the first few drives and check the level again once the engine has cooled completely.

Use the right coolant, mixed correctly

Mercedes specifies a particular coolant type and mixing it with a generic green coolant forms a sludge that blocks the radiator and heater matrix. Concentrate must be mixed with distilled water, not tap water, because the minerals in tap water scale up inside the system. If the old coolant was brown, gritty or oily, that tells you something about why the radiator failed and is worth investigating before the new one goes the same way.

Safety

• Work only on a cold engine. Opening a hot cooling system can spray scalding coolant.
• Drain coolant into a container and dispose of it properly; it is toxic to people and pets.
• Support the car on jack stands if you remove the lower splash shield from underneath.
• Disconnect the battery before unplugging the fan or any sensors at the radiator.

Frequently Asked Questions

How do I know my Mercedes radiator is failing?

Common signs are coolant drips at the front of the car, a sweet smell, crusty residue at the plastic end tanks, or the temperature climbing in traffic. Cracks often start where the plastic tank meets the aluminum core.

Do I need to bleed the cooling system after replacing the radiator?

Yes. Trapped air causes overheating and a cold heater. Fill slowly, run the engine with the heater on, and top up as the air works out, or use the bleed procedure for your model.

Which coolant should I use?

Use coolant that meets the Mercedes specification for your car, listed on the reservoir or in the owner’s manual, mixed 50/50 with distilled water unless it is premixed.

More guides: browse all of our Mercedes-Benz repair and troubleshooting guides.

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