Function of M13/5 (re)circulation pump with standard 2 zone THERMATIC

Sep 20, 2020 | 12:27 PM

chassis

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From: unbegrenzt

2017 GLE350 4MATIC

Function of M13/5 (re)circulation pump with standard 2 zone THERMATIC

As the title states. What is the function of this pump, in other words, why is it in the vehicle? It pumps coolant, got it. Why? I have standard two zone THERMATIC climate control, no REST function or stationary heater. I read the WIS function description and it isn't model or option code specific, but rather speaks to all of the possible combinations. Thanks!

p.s. I used Google and the search button on this site, no answer to the question.

Last edited by chassis; Sep 20, 2020 at 12:56 PM.

Sep 20, 2020 | 06:37 PM

whitewagon

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Aston Martin Vantage, GLE 43 AMG, Volvo XC60, BMW X1 35i, Ram 1500, BMW Z4 35i

Quote:

Originally Posted by chassis

it circulates coolant to heater core at low engine RPM's and also provides residual coolant flow for REST function, although you don't have that function. it's a DIY fix if needed.

Sep 20, 2020 | 08:26 PM

chassis

Thread Starter

Out Of Control!!

Joined: Sep 2018

Posts: 14,692

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From: unbegrenzt

2017 GLE350 4MATIC

Quote:

Originally Posted by whitewagon

it circulates coolant to heater core at low engine RPM's and also provides residual coolant flow for REST function, although you don't have that function. it's a DIY fix if needed.

@whitewagon Thanks. Since the vehicle had 10,000 miles on it, I have smelled coolant in the area of the circulation pump M13/5, in the front left (driver side) fender well adjacent to the wiper washer bottle. I have scoured the area repeatedly, and it appears that coolant is "misting" or "sweating" (aka leaking) from the hose connections at the circulation pump. It almost looks like the hoses are letting coolant out through the hose wall itself, as in the coolant is permeating the hose. I wouldn't put it past Mercedes to use biodegradeable hoses that have borderline levels of permeability. If/when it starts actually leaking and dripping, I have found the WIS procedure and it seems straightforward by removing the forward half of the wheel arch liner/fender liner.

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