Mike lakes

I just bought gl 450 with 100k miles. The heater is not hot, sort of Luke warm. The code for engine temp sensor pops up. Is it possible this is causing the heater to not get hot? Thanks!

Mike lakes

It’s a 2014 gl 450

mikeolive

With that code, I would suspect the engine thermostat.

Mike lakes

Thanks. That’s what my mechanic thought at first but then He saw that the engine Temp sensor was the code. Temp stays right at 90. Coolant light was on briefly at cold start up so I added just a little bit of coolant then the light went off. Still only lukewarm heat

Mike lakes

Ordered in the wrong sensor and I left for vacation so we still don’t know what the problem is. Hopefully new sensor put in will fix the problem I don’t know

chassis

Poor heater performance, engine temp sensor error and low coolant means you have low coolant.

Correct the low coolant and monitor. You may have a leak or consumption of coolant. It might take several driving cycles to fully fill the system.

Mike lakes

I have tried many driving cycles still no change. Fluids stay full and no warning lights on dash. Heat still luke warm. If I set climate control on auto, the fan just stays on high. Engine temperature stays right at 90. Getting colder here in ohio, not sure i can make it to summer!

Jim Ma

Has the heat not worked properly since you have had the truck? You could possibly have an air pocket stuck in the heater core. If you turn the fan on low does it seem to get warmer?

Mike lakes

I bought it at the end of November and it was never really cold and i didnt really check out the heater before buying. I should’ve but I didn’t and the car was in really nice condition. I have noticed that if I park it and turn it off for a short bit, the heat seems hotter when i restart. But never hot. My local mechanic wants to install a new ‘engine temp sensor’ next week sometime but not sure if thats gonna fix it. Mecedes dealer is an hour away and i’d rather not go. Low coolant light was on briefly but added about a cup of coolant and it went off.

Mike lakes

And yes, it does seem to be hotter air coming out when fan is on low.

Jim Ma

I wonder if you need to bleed the air out of your coolant system. With the air being warmer with fan on low you may not be getting enough coolant in to the heater core to get is fully hot and when the fan is on high it is actually cooling down the heater core thus the cooler air on high. The level sensor in the expansion tank tend to fail when they get some age on them and the fix is to replace the whole tank that includes the sensor. That is why you get the low coolant light and only have to add a cup. I had the same problem.

I believe there is a whole pressure bleeding procedure to get all the air out of the cooling system. Maybe someone with access to the info could look it up for you.

Mike lakes

Thanks I appreciate it. I did a little bit of research, is that the procedure that involves squeezing the radiator hose and cold start with the cap off?

I’m curious about the humming noise after the car is turned off. Is there a fan somewhere that runs after the car is turned off? even in the cold months. It’s almost unnoticeable. Thanks again!

arsupisemnet

There are couple electric recirculating pumps in cooling circuit which making that noise

Mike lakes

Thanks!!

Jim Ma

File Type: pdf

X166 M278 replace coolant.pdf (407.1 KB, 25 views)
File Type: pdf

X166 M278 fill coolant.pdf (868.5 KB, 26 views)

Chassis had shared these with me. Hopefully they will help.

Mike lakes

Thank you so much! but man, that sounds very complicated to just refill coolant.

Mike lakes

So I stopped by the mb dealer and paid the 150 to have them diagnose my lukewarm heat output. They claim it’s a bag of silicone beads that broke loose inside of the coolant expansion tank and thus traveled throughout the cooling system. I’d like to know who at the Mercedes factory had the great idea to put a bag of tiny beads in there! anyways, there’s a chance Mercedes might pay for it. I’m hopeful but...