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Pelican Technical Article:

Coolant Flush and Replacement

Steve Vernon

Time:

2 hours2 hrs

Tab:

$15 to $50

Talent:

**

Tools:

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

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 coolant, thermostat gasket, engine drain plug washer, distilled water

Hot Tip:

Get a really big bucket

Performance Gain:

Fresh coolant

Complementary Modification:

New hoses

If you are changing your coolant this is also the perfect time to give your cooling system a good flush. While it is next to impossible to get all of the coolant and contaminants out of the system without removing the heater core lines and blowing out the heating system, this method will get the system as clean as possible and more than good enough for the next three years.

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

Allow the cooling system to cool down to a coolant temperature of less than 90 degrees C. Open the cap of the cooling system slowly. Place a rag over the cap. Turn a conventional coolant cap as far as the first detent. Turn a screwed coolant cap approximately 1/2 turn and release the pressure. Wear protective gloves, protective clothing and eye protection. NEVER pour coolant into beverage bottles, cups, etc... Someone might accidentally pick that cup up and start to drink. Coolant is hazardous and must be collected and disposed of according to your local regulations. NEVER pour coolant down a sewer.

Begin by safely jacking up and supporting your car. Please review our article on safely jacking up and securing your car on jack stands. With the car safely off the ground you will need to remove the engine tray. A great many of these cars have had the engine tray removed over the years and not replaced. If you happen to have a car that still has the under tray and original hardware, please see our article on under tray removal.

With the car safely in the air remove the cover on the lower right bumper.
Figure 1

With the car safely in the air remove the cover on the lower right bumper. The plastic cover (red arrow) just pulls down from a slot in the bumper (yellow arrow).

There is a drain knob (yellow arrow) and spigot (red arrow).
Figure 2

There is a drain knob (yellow arrow) and spigot (red arrow). Attach a drain hose and turn the knob counter clockwise to begin draining.

Open the cap on the reservoir (red arrow) to break the vacuum seal and help the system drain.
Figure 3

Open the cap on the reservoir (red arrow) to break the vacuum seal and help the system drain.

Our project car had suffered a catastrophic oil coolant contamination to the point that when I turned the drain knob nothing came out.
Figure 4

Our project car had suffered a catastrophic oil coolant contamination to the point that when I turned the drain knob nothing came out. If your drain knob and spigot is not working you can drain the coolant from the lower hose on the right hand side of the radiator. Use a screwdriver and remove the hose clamp and pull the hose from the radiator (red arrow). Be prepared as the coolant will come out of both the hose and the radiator at the same time.

This is what coolant looks like when it has been mixed with oil in a motor (red arrow).
Figure 5

This is what coolant looks like when it has been mixed with oil in a motor (red arrow).

If your coolant comes out looking like this do not just flush the radiator and refill it.
Figure 6

If your coolant comes out looking like this do not just flush the radiator and refill it. You have a serious problem that needs to be solved.

There is an engine block drain plug on the right side of the motor (red arrow) just behind the motor mount.
Figure 7

There is an engine block drain plug on the right side of the motor (red arrow) just behind the motor mount. Attach a hose to the nipple and using an 18mm wrench open the valve.

Use a garden hose and run water through the reservoir until water comes out of the engine and hoses clear (red arrow).
Figure 8

Use a garden hose and run water through the reservoir until water comes out of the engine and hoses clear (red arrow).

Working on the left side of the motor disconnect the upper radiator hose from the thermostat housing by removing the hose clamp (red arrow).
Figure 9

Working on the left side of the motor disconnect the upper radiator hose from the thermostat housing by removing the hose clamp (red arrow). Then pull the hose off the thermostat housing.

Place the garden hose into the upper radiator hose and run water through the hose until it comes out the bottom of the radiator clear.
Figure 10

Place the garden hose into the upper radiator hose and run water through the hose until it comes out the bottom of the radiator clear.

To flush out the engine block remove the three bolts (red arrows) on the thermostat housing.
Figure 11

To flush out the engine block remove the three bolts (red arrows) on the thermostat housing.

Pull the lid (red arrow) off the thermostat housing (yellow arrow).
Figure 12

Pull the lid (red arrow) off the thermostat housing (yellow arrow). There may be a bit of corrosion so use care when removing. Be careful that you do not damage the temperature switches next to the lid.

Pull the thermostat (red arrow) up and out of the housing (yellow arrow).
Figure 13

Pull the thermostat (red arrow) up and out of the housing (yellow arrow).

Reinstall the lid with the thermostat removed and place the hose in the opening (red arrow).
Figure 14

Reinstall the lid with the thermostat removed and place the hose in the opening (red arrow). Run the water until clear water runs out. This is a good flush. If you really want to get more of the old coolant from the system, retighten the engine drain plug, reattach the radiator hose, close the drain on the bottom of the radiator and fill the car with water through the reservoir. Place the cap on the reservoir and run the motor, top up fluid as needed, get in the car and turn the heat and fan up to MAX. Shut the car off after 5 minutes and re-drain and follow the procedure for flushing the system again. This will help get some of the residual contaminants out of the water pump and heater core.

When you are ready to re-fill the vehicle with coolant install the thermostat.
Figure 15

When you are ready to re-fill the vehicle with coolant install the thermostat. Note: Even if you are reusing the old thermostat, you will need to replace the thermostat gasket (red arrow). Retighten the engine drain plug while installing a new washer. Reattach the radiator hose. Close the drain on the bottom of the radiator. Fill the car with the proper coolant and distilled water ratio through the reservoir. Start the car. Run it for a few minutes. Stop the car and top up coolant as needed. Check for leaks.

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Comments and Suggestions:
Phil Comments: Is there a Pelican SOP for replacing the seal?
April 16, 2016
  Followup from the Pelican Staff: Our parts Specialists can get you one. Give our parts specialists a call at 1-888-280-7799. They can figure out what part or repair kit you need.
- Nick at Pelican Parts
 
Phil Comments: The threads on the drain knob look fine can't see the threads on the radiator and it screws all the way in but won't go tight. If it is all the way in why won't the valve close? Do the prongs on the knob have to hit a particular seat?
April 15, 2016
  Followup from the Pelican Staff: The radiator could be stripped, or the seal is faulty. - Nick at Pelican Parts  
Phil Comments: 1990 300te.I loosened the drain knob and I took it all the way out. Now trying to screw the new one back in I can't get it to a final tight position and the spigot continues to run at a dribble. Any suggestions.
April 15, 2016
  Followup from the Pelican Staff: I would assume something is stripped. Remove the plug and inspect the threads. - Nick at Pelican Parts  
R Comments: 16. To get air out & coolant in - pour what you can get into reservoir, Take large hose loose from top of radiator, pour half gallon or so into radiator hose to fill engine. While hose is off pour another gallon into reservoir it can flow into radiator now that it is vented. Put hose back on and run it a bit, check reservoir should be near full.
February 23, 2016
  Followup from the Pelican Staff: Thanks for the follow up. Glad to hear there wasn't an engine problem. - Nick at Pelican Parts  
R Comments: 16?. How do you get the coolant topped up? Mine catches an air bubble in the head. I run engine til engine gets hot and that flashes over to steam blasting out bubbles of air & steam & antifreeze, refill and go again about 1 more time or so. Would tilting up a steep hill & high at the reservoir make it easy?
February 19, 2016
  Followup from the Pelican Staff: You didn't mention what vehicle you have. Your vehicle may have an overheating problem. If you can't get it to stop getting hot and creating pressure, check the thermostat and head gasket. - Nick at Pelican Parts  
quest1966 Comments: Can you comment on using Zerex G05 rather than MB coolant. Any issues? Thank you.
June 11, 2015
  Followup from the Pelican Staff: If Mercedes-Benz has approved the coolant, then yes. I have not used or seen the Zerex to comment on it.

Give our parts specialists a call at 1-888-280-7799. They can figure out what part or repair kit you need.
- Nick at Pelican Parts
 

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Page last updated: Wed 12/7/2016 02:59:18 AM