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Coolant Level Sensor Replacement
 
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Pelican Technical Article:

Coolant Level Sensor Replacement

Steve Vernon

Time:

1 hour1 hr

Tab:

$10

Talent:

*

Tools:

10mm socket

Applicable Models:

Mercedes-Benz 260E (1987-89)
Mercedes-Benz 300CE (1988-93)
Mercedes-Benz 300E (1986-93)
Mercedes-Benz 300TE (1988-92)
Mercedes-Benz E320 (1994-95)

Parts Required:

New coolant level sensor

Hot Tip:

Replace the sensor with the engine cold

Performance Gain:

Knowing the level of your coolant

Complementary Modification:

Flush cooling system

If you need to replace your coolant level sensor you can change it out in under an hour. It may actually take longer to let the car cool down than perform the work. The coolant tank is located in the engine bay on the right side. I would recommend letting the car cool for a little bit before beginning work as it is a tight fit in there. You're going to have to drain some of the coolant. You don't want to work around a hot tank, coolant and hoses. You will need to drain the coolant level to below the bottom of the sensor opening. If you are going to be replacing the sensor, now may be a good time to give the cooling system a good flush and refill. Please see our article on coolant flush and replace for either draining or flushing.

Begin by opening the hood and having a look at the engine.
Figure 1

Begin by opening the hood and having a look at the engine. The coolant reservoir (yellow arrow) is located on the right side of the engine bay (red arrow). Don't forget all directions are given as if you are sitting in the car. You will need to remove all or part of the air filter box to get access (red arrow).

There are two clips that hold the air box lid to the intake and MAF (red arrow, one shown, one below) and four clips that hold the lid to the air box (yellow arrows).
Figure 2

There are two clips that hold the air box lid to the intake and MAF (red arrow, one shown, one below) and four clips that hold the lid to the air box (yellow arrows).

Release the two clips on the intake tube by pulling them back towards the lid (red arrows).
Figure 3

Release the two clips on the intake tube by pulling them back towards the lid (red arrows).

The four clips holding the lid to the box release by lifting up on the plastic tabs (red arrows).
Figure 4

The four clips holding the lid to the box release by lifting up on the plastic tabs (red arrows).

Lift the lid up and away from the intake tube (red arrow).
Figure 5

Lift the lid up and away from the intake tube (red arrow).

Pull the filter back and out of the air box (red arrow).
Figure 6

Pull the filter back and out of the air box (red arrow). Depending on how long it has been since your last air filter change the air box may have substantial debris in it (yellow arrow). I recommend removing the air box and giving it a good cleaning; this will also allow you to check for windshield and coolant reservoir leaks.

To remove the air box remove the 10mm nut and bracket by the windshield washer reservoir (red arrow).
Figure 7

To remove the air box remove the 10mm nut and bracket by the windshield washer reservoir (red arrow). You can see the coolant level sensor at this point (yellow arrow). If you have small enough hands you may be able to remove it without removing the lower section of the air box.

At the front of the box remove the circlip (red arrow) and the overflow hose from the lid (yellow arrow).
Figure 8

At the front of the box remove the circlip (red arrow) and the overflow hose from the lid (yellow arrow).

Pull the lid up and out (red arrow).
Figure 9

Pull the lid up and out (red arrow). This will free up the snorkel on the air box so you can remove it (yellow arrow).

Pull the box straight up and off the two rubber mounts in the chassis (red arrows).
Figure 10

Pull the box straight up and off the two rubber mounts in the chassis (red arrows).

With the air filter box removed you can get access to the level sensor (red arrow).
Figure 11

With the air filter box removed you can get access to the level sensor (red arrow). You will now need to drain the coolant below the level of the sensor opening (green arrow).

Squeeze in the tabs on the electrical connector (red arrow) and pull it off the sensor (green arrow).
Figure 12

Squeeze in the tabs on the electrical connector (red arrow) and pull it off the sensor (green arrow).

If you have had leaks or overflow from the sensor there is a very good chance there is corrosion in the connecter (red arrows).
Figure 13

If you have had leaks or overflow from the sensor there is a very good chance there is corrosion in the connecter (red arrows). Make sure to clean this up with some Emery paper before reinstalling.

Remove the circlip (red arrow) that holds the sensor in the reservoir.
Figure 14

Remove the circlip (red arrow) that holds the sensor in the reservoir. You may need to use a circlip tool but ours came off and went on easily with finger pressure.

Make sure you don't lose the circlip (red arrow) and give it a good cleaning before reinstalling.
Figure 15

Make sure you don't lose the circlip (red arrow) and give it a good cleaning before reinstalling.

Remove the old sensor (red arrow).
Figure 16

Remove the old sensor (red arrow). Clean the opening to the reservoir and the mounting area before installing the new sensor. Make sure the float on the sensor angles downward (red arrow) when installing. Installation is the reverse of removal.






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Comments and Suggestions:
Tom P. Comments: The fit on the sensor is very tight on the new tank.I do not want to break it. Any advice on installing it.
April 27, 2017
  Followup from the Pelican Staff: Be sure to clean the sensor bore thoroughly. Then lubricate the new sensor with clean coolant to help with installation. - Nick at Pelican Parts  
Edgar Comments: very good and accurate description - thanks! Edgar
November 8, 2016
  Followup from the Pelican Staff: Thanks for the feedback. Glad we could help.
- Nick at Pelican Parts
 
Ken Comments: I am having to maintain my in-laws 1993 300E since they know nothing about cars. I find your technical notes to be the best that I have found online so far. I sure wish you had such good notes on my Kia and Ford ranger.
March 16, 2015
  Followup from the Pelican Staff: Thanks for the feedback. Glad we could help.
- Nick at Pelican Parts
 

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Page last updated: Mon 8/21/2017 03:05:40 AM