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2014 GL 550 with no heat. Just got cold in Chicago this week and turned on the heat for the first time this season and only blows ambient-temp air when control is set to heat. AC works fine. Engine coolant temps come up normally and stay in normal range so to me this suggests t-stat and cooling system is functioning properly. The temp controls seem to work fine and blower motor works. I'm mechanically inclined but haven't had the change to get to know this motor yet. Seems to me like hot coolant isn't making it to the heater core. Is there a heater control valve on these vehicles? If so, where is it, how hard to access, cost, etc?
I had same problem on 2013 GL 450. There is no heater control valve on this model. I replaced water pump, thermostat and auxiliary pump- still no heat. At the end I flushed heater core with radiator cleaner - heat came on.
Disconnect supply hose at plastic elbow which goes through metal divider behind engine and return hose at plastic T connector near expansion tank. Pour cleaner into return hose and let it seat for 15 minutes. Then flush core with water few times and compressed air. Reconnect hoses, add coolant.
It worked for me, getting 162F in cabin.
Good luck.
update
after 2 days I lost heat again. Flushed heater core again and flushed whole cooling system. Found expanded silica gels in expansion tank.
I believe adding non-dealer coolant cause this.
heat back on after flush.
Last edited by Davidgl450; 12-16-2019 at 11:47 AM.
Have had my 2013 for about 9 months and 18k miles and it has been rock solid. We have taken it on several long trips and it has been flawless. It is now at 85k miles. Until our return home this weekend from a 900 mile trip. Literally the last 25 miles and we had a near complete loss of heat. Sounds like the above, heater core partial blockage. Blower works fine. I can get some heat, but if you open all the vents and turn it on full, it quickly runs out of heat. Interestingly, the rear heat seems to have nearly full temp heat? Does the rear heat have a separate heat exchanger it uses??
Ironically, I did get a low coolant light the day before. The overflow tank was a little low so I found some of the blue coolant and put maybe 6 ounces in. To high engine temps based on the gauge.
Just checking my carfax history it shows it had a "heater housing" replaced and coolant flush & change under CPO Warranty at the local dealer on 9/23/19 or 68,754 miles. This is now over a year, but it is worth going back the the MB dealer to find out exactly what was done?
I am guessing my first attempt is to try and flush and replace the coolant? Perhaps it is only partially blocked and this may produce some results. I am not so excited to change a heater core on this!!!!!
John P. Kelly
Last edited by JPK_13_GL450; 10-27-2020 at 03:13 PM.
Have had my 2013 for about 9 months and 18k miles and it has been rock solid. We have taken it on several long trips and it has been flawless. It is now at 85k miles. Until our return home this weekend from a 900 mile trip. Literally the last 25 miles and we had a near complete loss of heat. Sounds like the above, heater core partial blockage. Blower works fine. I can get some heat, but if you open all the vents and turn it on full, it quickly runs out of heat. Interestingly, the rear heat seems to have nearly full temp heat? Does the rear heat have a separate heat exchanger it uses??
Ironically, I did get a low coolant light the day before. The overflow tank was a little low so I found some of the blue coolant and put maybe 6 ounces in. To high engine temps based on the gauge.
Just checking my carfax history it shows it had a "heater housing" replaced and coolant flush & change under CPO Warranty at the local dealer on 9/23/19 or 68,754 miles. This is now over a year, but it is worth going back the the MB dealer to find out exactly what was done?
I am guessing my first attempt is to try and flush and replace the coolant? Perhaps it is only partially blocked and this may produce some results. I am not so excited to change a heater core on this!!!!!
John P. Kelly
that’s exactly what happened to me. Coolant you add cause this problem. Make sure you thoroughly flash heather core, radiator and engine. Regular flash will get heat working only for couple of days. I did it 4 times.
Disconnect heater core hoses and flash it in opposite direction to coolant circulation. Disconnect radiator bottom hose and flash from tank. Only after this steps problem was fixed.
good luck
Its weird. I just checked and the previous owner did a coolant flush at the local MB dealer at about 69k miles. I only added water prior to the problem happening and only about 6 oz into the expansion tank. I did find some MB blue coolant and added another 6oz into the expansion tank yesterday.
I just made an appt at my indy repair shop. He said it would be unusual for a clogged heater core. I will be anxious to see what they find. I will follow up with the prognosis.
Hello Jacob, thanks for your sharing. I had same problem with you, I back flush the entire system 2-3 times and it helped me at the begining!
Later on, I had coolant drain issue and I realized that all cooland drained into the car. Now, I'm busy with cleaning of interior inc. floor carpet all electrical lines. It could be removing of all "Stop-Leak" materials from system
I would like to ask you that is it neccessary to remove all upper dashboard to change heater core? I removed right & left floor coverings, center console and as I see water dripping from heater core lower connection also there was coolant water inside ventilation ducts. I cannot diagnose heater core is broken or not at this stage. I attached dripping point below.
Is there any sealing at below connection such as O-Ring? How did you remove and install heater core? Is it neccessary to open hvac unit or it's like a cartridge?
I discconnected battery ground line when I'm removing front seats, center console and associated parts. Did you need XENTRY diagnostic system before and after this DIY if yes for what? Because, I scare to need re-programming of something. I have very basic delphi diagnostic system and I can remove some error code if there is.
Based on this thread, I took it to the Indy shop to reverse flush the heater core and change the coolant. No change after that, no codes. He said that flow was ok anyway. I still have no heat at all or very little, barely noticeable. Given the guy at the shop is right and heater core is ok, what could be the issue? Can anyone throw some ideas?
What should I do next? Dealer?
Based on this thread, I took it to the Indy shop to reverse flush the heater core and change the coolant. No change after that, no codes. He said that flow was ok anyway. I still have no heat at all or very little, barely noticeable. Given the guy at the shop is right and heater core is ok, what could be the issue? Can anyone throw some ideas?
What should I do next? Dealer?
I'm in the same damned boat with my 2013 GL450, except I haven't tried flushing the heater core yet.
Hallo!
I have Gl 450 from California, the same problem whit heater- no heat, probably is full and need flush . There is a smell from coolant inside. Is it possible this smell comes from heater? Is it possible heater leak?
Thank you!
Hallo!
I have Gl 450 from California, the same problem whit heater- no heat, probably is full and need flush . There is a smell from coolant inside. Is it possible this smell comes from heater?
Is it possible heater leak?
Thank you!
Hallo!
I have Gl 450 from California, the same problem whit heater- no heat, probably is full and need flush . There is a smell from coolant inside. Is it possible this smell comes from heater?
Is it possible heater leak?
Thank you!
You probably have a coolant leak somewhere. I think with the smell it could be anywhere. I had a BMW that was leaking oil over the exhaust headers and smell was inside as well. Does the dash say "low coolant"?
Our 2014 ML350 Bluetec just experienced this exploding-bag-o'-death. We bought the vehicle in 2016 as CPO and have done all of the servicing through the dealer.
So far the MB dealer has done a power backflush, plus replaced the expansion tank and coolant. There's still no heat and they want to replace everything attached to the cooling system to the tune of $10K. I'll go back today and see what they'll charge just to do the heater core replacement job.
From the looks of it, the heater core is the only component requiring tearing out the dash. Is this correct?
We're in the process of retiring and moving - selling house, buying a new house. Really did not need this. We also have a 2014 GL350 for which I just ordered a replacement expansion tank. I'll replace that myself.
If you are interested in buying these hoses and fittings from me let me know soon, otherwise I will toss them. Hard to believe, but this is about $60 worth of hose and fittings from HomeDepot. $10+shipping and it's yours if you want it. One hose for the heater inlet, another for the heater outlet (at firewall), various size adapter fittings, clamps, and valve to regulate flow and pressure with a garden-hose fitting adapter.
I know it's been a while, but can you snap a picture or explain where the heater core lines are located? I know it's supposed to be on the passenger side. I just want to be sure I'm looking at the right thing.
Its weird. I just checked and the previous owner did a coolant flush at the local MB dealer at about 69k miles. I only added water prior to the problem happening and only about 6 oz into the expansion tank. I did find some MB blue coolant and added another 6oz into the expansion tank yesterday.
I just made an appt at my indy repair shop. He said it would be unusual for a clogged heater core. I will be anxious to see what they find. I will follow up with the prognosis.
Can you advise what they determined, and any action taken/results?
that’s exactly what happened to me. Coolant you add cause this problem. Make sure you thoroughly flash heather core, radiator and engine. Regular flash will get heat working only for couple of days. I did it 4 times.
Disconnect heater core hoses and flash it in opposite direction to coolant circulation. Disconnect radiator bottom hose and flash from tank. Only after this steps problem was fixed.
good luck
I am about to attempt a flush on my w166. Your diagram looks like the same setup I have. Which line is the inlet and which line is the outlet? I was thinking the outlet was the hose closest to the center of the vehicle and I need to be attaching a regulated water hose to that line. Is this correct?
I am about to attempt a flush on my w166. Your diagram looks like the same setup I have. Which line is the inlet and which line is the outlet? I was thinking the outlet was the hose closest to the center of the vehicle and I need to be attaching a regulated water hose to that line. Is this correct?
Sorry for late response. No. Inlet is at firewall, outlet at expansion tank. Attach water hose to outlet line at expansion tank
Last edited by Davidgl450; 05-24-2024 at 12:59 AM.
12-14-2019, 11:56 AM
