When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
Hello, I just took delivery of a 2015 CLA 45 with the M133 4-cylinder. The first service preformed was the hi/low coolant flush and a/c freon, and differential service. Now, a week later, my thermostat is leaking coolant... When I had my car in service, three different techs, then myself, preformed a full underbody inspection on the car--looking for all the things that need to be sorted out to bring the car to perfect mechanical condition. There was no leak at the time of inspection. Before I shell out $900, is there anything that can correlate the leak to the hi/low service? To save you guys sometime, I know where the thermostat is positioned in correlation to the coolant reservoirs. I also know it could be unconnected events, but I figured someone might know more than me.
It’s definitely possible the coolant flush disturbed something. Sometimes old gaskets or O-rings get brittle and once fresh coolant starts flowing under pressure again, it exposes weak points especially around the thermostat housing. If the system was pressurized during the flush, that could’ve nudged something loose or exposed a crack that was sealed with buildup. I’d check the thermostat housing bolts for proper torque and inspect the gasket for signs of age or pinching.
So I had the tech go ahead with the thermostat replacement. Mercedes did a great job creating the highest horse power four cylinder from a production car with the M133. What I am learning about is the design that was needed to cram everything into the engine bay.
This is the thermostat housing for the M133 in the 2015 CLA 45 AMG. The thermostat itself, sits inside of the housing. The housing is connected externally to the engine block, beneath the intake, between the block and fire wall. Because the thermostat is entirely plastic, like much of the hosing for this particular car, experiencing heat shrink is common. The thermostat must be purchased with the entire housing from Mercedes. According to the tech, it is common to experience coolant leaks from the thermostat housing on these cars.
If you look at the photos I attached, the housing is a two piece unit, make from plastic sealed with some screws and a gasket. It makes sense that you would experience failure when you see the material and location for the housing. So if you get a M133 CLA 45 AMG, make sure the previous owner has already serviced the thermostat with Mercedes, or save up a little bit of change in anticipation..
Note: this car only has ~67,000 miles.
Hello, I just took delivery of a 2015 CLA 45 with the M133 4-cylinder. The first service preformed was the hi/low coolant flush and a/c freon, and differential service. Now, a week later, my thermostat is leaking coolant... When I had my car in service, three different techs, then myself, preformed a full underbody inspection on the car--looking for all the things that need to be sorted out to bring the car to perfect mechanical condition. There was no leak at the time of inspection. Before I shell out $900, is there anything that can correlate the leak to the hi/low service? To save you guys sometime, I know where the thermostat is positioned in correlation to the coolant reservoirs. I also know it could be unconnected events, but I figured someone might know more than me.
Originally Posted by Vic0n
It’s definitely possible the coolant flush disturbed something. Sometimes old gaskets or O-rings get brittle and once fresh coolant starts flowing under pressure again, it exposes weak points especially around the thermostat housing. If the system was pressurized during the flush, that could’ve nudged something loose or exposed a crack that was sealed with buildup. I’d check the thermostat housing bolts for proper torque and inspect the gasket for signs of age or pinching.
Originally Posted by AMGMoterWorks
So I had the tech go ahead with the thermostat replacement. Mercedes did a great job creating the highest horse power four cylinder from a production car with the M133. What I am learning about is the design that was needed to cram everything into the engine bay.
This is the thermostat housing for the M133 in the 2015 CLA 45 AMG. The thermostat itself, sits inside of the housing. The housing is connected externally to the engine block, beneath the intake, between the block and fire wall. Because the thermostat is entirely plastic, like much of the hosing for this particular car, experiencing heat shrink is common. The thermostat must be purchased with the entire housing from Mercedes. According to the tech, it is common to experience coolant leaks from the thermostat housing on these cars.
Thermostat Leak
