SL55/63/65/R230 AMG: Intermittent Coolant - Visit Workshop msg & Red temp symbol?
Thread Starter
Junior Member
Joined: Jul 2025
Posts: 44
Likes: 4
From: 27587
03 SL55 AMG
Intermittent Coolant - Visit Workshop msg & Red temp symbol?
So I've read through several threads on this topic but have not seen one that matches my issue...
(2003 SL55 AMG, recently purchased, 114K miles)
The Coolant - Visit Workshop message will appear at startup as does the red light behind the temp symbol in the gauge pod.
Once running/driving, the message will turn off for a moment, then re-appear. Same with the red light behind the temp symbol in the gauge pod.
After about 30 mins of driving, the message clears and the red light is no longer in the background of the temp symbol in the gauge pod, and neither returns until the next cold start .
Temp gauge reading stays at 80-85 degrees once warm (C) and the coolant is at the top of the white section of the reservoir.
I've not seen anyone report the intermittent message situation.
Does the level sensor in the reservoir monitor the level for being too high (as well as low)?
Possibly related is that the windshield washer fluid reservoir has a leak and does not hold fluid and it drains out immediately.
Not sure where the washer fluid leak is in the reservoir yet but I'm assuming it is towards the bottom of that tank as it takes about a half gallon of liquid to fill it.
I understand the coolant and washer fluid sensors share a circuit but not sure if this configuration impacts the intermittent message.
Thoughts?
(2003 SL55 AMG, recently purchased, 114K miles)
The Coolant - Visit Workshop message will appear at startup as does the red light behind the temp symbol in the gauge pod.
Once running/driving, the message will turn off for a moment, then re-appear. Same with the red light behind the temp symbol in the gauge pod.
After about 30 mins of driving, the message clears and the red light is no longer in the background of the temp symbol in the gauge pod, and neither returns until the next cold start .
Temp gauge reading stays at 80-85 degrees once warm (C) and the coolant is at the top of the white section of the reservoir.
I've not seen anyone report the intermittent message situation.
Does the level sensor in the reservoir monitor the level for being too high (as well as low)?
Possibly related is that the windshield washer fluid reservoir has a leak and does not hold fluid and it drains out immediately.
Not sure where the washer fluid leak is in the reservoir yet but I'm assuming it is towards the bottom of that tank as it takes about a half gallon of liquid to fill it.
I understand the coolant and washer fluid sensors share a circuit but not sure if this configuration impacts the intermittent message.
Thoughts?
Super Member
Joined: Sep 2021
Posts: 537
Likes: 115
From: Ann Arbor, MI
2004 SL600
I found the coolant reservoir to require coolant to the very top or else I got the coolant message. As it warms up the level goes up a bit.
Or perhaps the level sensor is stuck when cold.
Or perhaps the level sensor is stuck when cold.
Thread Starter
Junior Member
Joined: Jul 2025
Posts: 44
Likes: 4
From: 27587
03 SL55 AMG
Super. Thank you!
Yesterday, I pulled some fluid out to just below the while/black tank separation to see if it made a difference. No difference.
This evening I'll add it to completely full and see what I get.
Yesterday, I pulled some fluid out to just below the while/black tank separation to see if it made a difference. No difference.
This evening I'll add it to completely full and see what I get.
Super Member
Joined: Sep 2021
Posts: 537
Likes: 115
From: Ann Arbor, MI
2004 SL600
Yes it is variously documented to fill to the line between the black and clear portions. But I had to fill well above that.
Just a guess, perhaps the float seeps in a bit of liquid over 20 years and becomes heavier.
Keep us posted.
Just a guess, perhaps the float seeps in a bit of liquid over 20 years and becomes heavier.
Keep us posted.
Thread Starter
Junior Member
Joined: Jul 2025
Posts: 44
Likes: 4
From: 27587
03 SL55 AMG
Filled it to the top. Same thing.
I'll need to pull the tank I guess. Looks like the float assembly/sensor is integral to the tank.
I'll see if I can measure resistance at the connector on a bench when the tank is full of water.
I'll need to pull the tank I guess. Looks like the float assembly/sensor is integral to the tank.
I'll see if I can measure resistance at the connector on a bench when the tank is full of water.
