SL/R230: Red coolant light + check coolant level
Thread Starter
Junior Member
Joined: Jun 2019
Posts: 54
Likes: 9
From: London, UK
2010 E350 CGI S212 // 2004 SL500 R230
Red coolant light + check coolant level
Hello there
On my R230 SL500, I just got started it and received a "check coolant level" message, along with the red coolant light illuminated. I drove it up the drive enough to turn around and park again.. by the time I had gotten back the light had gone off, and I think the warning too.
It is worth nothing that in the past, I have noticed a leak (a number of times) from the car. One time I picked some with my finger from the ground and it didn't smell, so I assumed it was just water from rain... that said, it was coming from a drain hole in the underbody panel.
The car has 78k miles on the clock, and the weather has been dropping to about 5 degrees celsius the past couple weeks.
I'm wondering where to start diagnosing this. I know some big causes can be pipes and/or radiator, but what are the smaller items I can troubleshoot first?
Many thanks
On my R230 SL500, I just got started it and received a "check coolant level" message, along with the red coolant light illuminated. I drove it up the drive enough to turn around and park again.. by the time I had gotten back the light had gone off, and I think the warning too.
It is worth nothing that in the past, I have noticed a leak (a number of times) from the car. One time I picked some with my finger from the ground and it didn't smell, so I assumed it was just water from rain... that said, it was coming from a drain hole in the underbody panel.
The car has 78k miles on the clock, and the weather has been dropping to about 5 degrees celsius the past couple weeks.
I'm wondering where to start diagnosing this. I know some big causes can be pipes and/or radiator, but what are the smaller items I can troubleshoot first?
Many thanks
Super Member
Joined: Jul 2014
Posts: 992
Likes: 245
From: Tucson, AZ
'20 X5 M50i; '17 Ram 3500; Golf Cart; Bikes; Scooters
It is possible you are losing coolant, or just need to top it up to stop the warning. Here is what I would do...
I would start by filling coolant to the recommended level, then monitoring it.
Then, pull the trays off from underneath and put clean cardboard under for the night. See if there is coolant dripping in the morning. Location will tell you where to look for leaks.
Get a strong light and poke around. Look for traces of coolant and follow them.
In my case, I also have the supercharger intercooler and pump to deal with, which doubles the number of hoses and parts that can leak.
You may also be seeing a leak from the window washer reservoir, which is known to have issues.
I would start by filling coolant to the recommended level, then monitoring it.
Then, pull the trays off from underneath and put clean cardboard under for the night. See if there is coolant dripping in the morning. Location will tell you where to look for leaks.
Get a strong light and poke around. Look for traces of coolant and follow them.
In my case, I also have the supercharger intercooler and pump to deal with, which doubles the number of hoses and parts that can leak.
You may also be seeing a leak from the window washer reservoir, which is known to have issues.
Thread Starter
Junior Member
Joined: Jun 2019
Posts: 54
Likes: 9
From: London, UK
2010 E350 CGI S212 // 2004 SL500 R230
It is possible you are losing coolant, or just need to top it up to stop the warning. Here is what I would do...
I would start by filling coolant to the recommended level, then monitoring it.
Then, pull the trays off from underneath and put clean cardboard under for the night. See if there is coolant dripping in the morning. Location will tell you where to look for leaks.
Get a strong light and poke around. Look for traces of coolant and follow them.
In my case, I also have the supercharger intercooler and pump to deal with, which doubles the number of hoses and parts that can leak.
You may also be seeing a leak from the window washer reservoir, which is known to have issues.
I would start by filling coolant to the recommended level, then monitoring it.
Then, pull the trays off from underneath and put clean cardboard under for the night. See if there is coolant dripping in the morning. Location will tell you where to look for leaks.
Get a strong light and poke around. Look for traces of coolant and follow them.
In my case, I also have the supercharger intercooler and pump to deal with, which doubles the number of hoses and parts that can leak.
You may also be seeing a leak from the window washer reservoir, which is known to have issues.
Many thanks for your hints.. I had every plan to try these all out but I just hadn't time, hence my slow reply. That said...
I was losing coolant and I found the leak (by accident). After small trips there would be a little pool, but this evening I drove the car for a good hour, after leaving the car and coming back I noticed a good steady drip coming from the under tray on o/s front.
I was able to identify the auxiliary water pump (part A2308350264) was leaking - mystery solved.
Now, I don't have reason to believe the electrical pump is faulty (heat control works). Therefore I am curious about the feasibility of repairing (re-sealing the pump housing). It looks like it can be opened with screws, so I wonder can it be resealed?
Any idea? Thank you.
Super Member
Joined: Jul 2014
Posts: 992
Likes: 245
From: Tucson, AZ
'20 X5 M50i; '17 Ram 3500; Golf Cart; Bikes; Scooters
Glad you found the source of the issue.
Pretty sure the aux pump is only used when the car is not running to circulate warm coolant inside the car with the ‘Rest’ feature on.
No idea if they can be rebuilt. Might be a good DIY project to share.
Again, if it were me, here’s what I would do.
I would bypass this pump, as I believe it is not required unless you use the ‘Rest’ function, then tear it apart on the bench and see if I could fix it. Your car may throw a code because the pump is no longer fitted, but it would only be an annoyance.
Fix it and celebrate your skill and talent. if it can’t be fixed, find a replacement part, and fit it.
Keep is posted.
Pretty sure the aux pump is only used when the car is not running to circulate warm coolant inside the car with the ‘Rest’ feature on.
No idea if they can be rebuilt. Might be a good DIY project to share.
Again, if it were me, here’s what I would do.
I would bypass this pump, as I believe it is not required unless you use the ‘Rest’ function, then tear it apart on the bench and see if I could fix it. Your car may throw a code because the pump is no longer fitted, but it would only be an annoyance.
Fix it and celebrate your skill and talent. if it can’t be fixed, find a replacement part, and fit it.
Keep is posted.
Thread Starter
Junior Member
Joined: Jun 2019
Posts: 54
Likes: 9
From: London, UK
2010 E350 CGI S212 // 2004 SL500 R230
Thanks kbob999
I have put the car in storage for a few months, where there is an attached DIY self serve garage.
One of the items on my list is to take out this pump, strip it down and have a look at resealing. I have seen some guys do this online. If that fails, i'll just replace the pump.
I have read that the pump is used to circulate coolant around the engine when engine shuts down to ensure uniform cooling, I would regard that as important, no?
I have put the car in storage for a few months, where there is an attached DIY self serve garage.
One of the items on my list is to take out this pump, strip it down and have a look at resealing. I have seen some guys do this online. If that fails, i'll just replace the pump.
I have read that the pump is used to circulate coolant around the engine when engine shuts down to ensure uniform cooling, I would regard that as important, no?
Thread Starter
Junior Member
Joined: Jun 2019
Posts: 54
Likes: 9
From: London, UK
2010 E350 CGI S212 // 2004 SL500 R230
How would you go about bypassing the pump?
Thanks
