'14 GL450 no heat diagnosis
Thread Starter
Junior Member
Joined: Feb 2022
Posts: 23
Likes: 7
From: Philadelphia, PA
'14 MB GL450, '14 Audi Allroad
'14 GL450 no heat diagnosis
Of course as soon as it turns cold here in Philadelphia I go to turn the heat on and it blows cool at full speed fan setting. If I set the fan speed to 2, then it blows barely lukewarm, but you can at least tell there is a little heat. This leads me to a flowthrough problem with the heater core.
I'll document my no/barely heat troubleshooting and diagnosis here for anybody here who may be interested or need this information in the future as well as photos if I have to dig into the heart of the beast.
It's a '14 GL450 with 104,000 miles, full service history through the Mercedes dealer before I bought it. I am the third owner. I am an advanced DIYer. I don't pay mechanics unless I am too lazy to do something or don't have time. I have a heated/cooled garage, all the tools I need, and a lift in the garage. I do my own wrenching.
Start with the easy stuff first.
1) Coolant is 3 weeks old, topped off, and no air bubbles.
2) Air is blowing from the correct vents based on the control panel settings.
3) Once vehicle is warmed up, hoses going into and out of the heater core are warm/hot to the touch. The inlet hose is in very close proximity to the engine, so it is difficult to ascertain if it is "contact" heat, or actual coolant heat. Need to get out my temperature gun and take another look at that for major discrepancies between the two. ETA: No major variation in external surface temperatures of both hoses. Both at around 120F.
4) I have an Autel scanner, so I used that to manually turn on the auxiliary coolant pump that feeds the heater core. The pump is working, at least in that I can hear and feel the electric motor run. Haven't determined if there is potentially an issue with the impeller/mechanical side of things yet though.
5) I had the cooling system opened up a couple of weeks ago replacing a leaking hose that crosses over under the car, and no silica gel beads were observed in the drained coolant.
Next steps will be as follows once parts/additional tools arrive.
6) Replace the auxiliary coolant pump. It's inexpensive and easy enough to change to rule it out as a cause.
7) Disconnect hoses from the heater core and do a backflush to see if I get anything out of the heater core.
If the backflush ends up producing no or little improvement, then I'll start ripping the interior apart to replace the heater core and provide a documented thread on that since a detailed post does not seem to exist, other than a couple of high level posts with a few photos. If the backflush produces full heat, then I may chalk it up to luck, with the understanding that I may end up replacing the heater core sometime soon anyway.
If I do have to replace the heater core, I'll be replacing the evaporator core, actuators, anything else I find that might potentially fail in the future. I've pulled the dash out of cars before for this procedure, and I'm not interested in doing it more than once per car.
As they say, more to come.
I'll document my no/barely heat troubleshooting and diagnosis here for anybody here who may be interested or need this information in the future as well as photos if I have to dig into the heart of the beast.
It's a '14 GL450 with 104,000 miles, full service history through the Mercedes dealer before I bought it. I am the third owner. I am an advanced DIYer. I don't pay mechanics unless I am too lazy to do something or don't have time. I have a heated/cooled garage, all the tools I need, and a lift in the garage. I do my own wrenching.
Start with the easy stuff first.
1) Coolant is 3 weeks old, topped off, and no air bubbles.
2) Air is blowing from the correct vents based on the control panel settings.
3) Once vehicle is warmed up, hoses going into and out of the heater core are warm/hot to the touch. The inlet hose is in very close proximity to the engine, so it is difficult to ascertain if it is "contact" heat, or actual coolant heat. Need to get out my temperature gun and take another look at that for major discrepancies between the two. ETA: No major variation in external surface temperatures of both hoses. Both at around 120F.
4) I have an Autel scanner, so I used that to manually turn on the auxiliary coolant pump that feeds the heater core. The pump is working, at least in that I can hear and feel the electric motor run. Haven't determined if there is potentially an issue with the impeller/mechanical side of things yet though.
5) I had the cooling system opened up a couple of weeks ago replacing a leaking hose that crosses over under the car, and no silica gel beads were observed in the drained coolant.
Next steps will be as follows once parts/additional tools arrive.
6) Replace the auxiliary coolant pump. It's inexpensive and easy enough to change to rule it out as a cause.
7) Disconnect hoses from the heater core and do a backflush to see if I get anything out of the heater core.
If the backflush ends up producing no or little improvement, then I'll start ripping the interior apart to replace the heater core and provide a documented thread on that since a detailed post does not seem to exist, other than a couple of high level posts with a few photos. If the backflush produces full heat, then I may chalk it up to luck, with the understanding that I may end up replacing the heater core sometime soon anyway.
If I do have to replace the heater core, I'll be replacing the evaporator core, actuators, anything else I find that might potentially fail in the future. I've pulled the dash out of cars before for this procedure, and I'm not interested in doing it more than once per car.
As they say, more to come.
Last edited by g-rex; Dec 16, 2022 at 10:21 AM.
Banned
Joined: Nov 2021
Posts: 32
Likes: 5
Lift type/ brand
Of course as soon as it turns cold here in Philadelphia I go to turn the heat on and it blows cool at full speed fan setting. If I set the fan speed to 2, then it blows barely lukewarm, but you can at least tell there is a little heat. This leads me to a flowthrough problem with the heater core.
I'll document my no/barely heat troubleshooting and diagnosis here for anybody here who may be interested or need this information in the future as well as photos if I have to dig into the heart of the beast.
It's a '14 GL450 with 104,000 miles, full service history through the Mercedes dealer before I bought it. I am the third owner. I am an advanced DIYer. I don't pay mechanics unless I am too lazy to do something or don't have time. I have a heated/cooled garage, all the tools I need, and a lift in the garage. I do my own wrenching.
Start with the easy stuff first.
1) Coolant is 3 weeks old, topped off, and no air bubbles.
2) Air is blowing from the correct vents based on the control panel settings.
3) Once vehicle is warmed up, hoses going into and out of the heater core are warm/hot to the touch. The inlet hose is in very close proximity to the engine, so it is difficult to ascertain if it is "contact" heat, or actual coolant heat. Need to get out my temperature gun and take another look at that for major discrepancies between the two. ETA: No major variation in external surface temperatures of both hoses. Both at around 120F.
4) I have an Autel scanner, so I used that to manually turn on the auxiliary coolant pump that feeds the heater core. The pump is working, at least in that I can hear and feel the electric motor run. Haven't determined if there is potentially an issue with the impeller/mechanical side of things yet though.
5) I had the cooling system opened up a couple of weeks ago replacing a leaking hose that crosses over under the car, and no silica gel beads were observed in the drained coolant.
Next steps will be as follows once parts/additional tools arrive.
6) Replace the auxiliary coolant pump. It's inexpensive and easy enough to change to rule it out as a cause.
7) Disconnect hoses from the heater core and do a backflush to see if I get anything out of the heater core.
If the backflush ends up producing no or little improvement, then I'll start ripping the interior apart to replace the heater core and provide a documented thread on that since a detailed post does not seem to exist, other than a couple of high level posts with a few photos. If the backflush produces full heat, then I may chalk it up to luck, with the understanding that I may end up replacing the heater core sometime soon anyway.
If I do have to replace the heater core, I'll be replacing the evaporator core, actuators, anything else I find that might potentially fail in the future. I've pulled the dash out of cars before for this procedure, and I'm not interested in doing it more than once per car.
As they say, more to come.
I'll document my no/barely heat troubleshooting and diagnosis here for anybody here who may be interested or need this information in the future as well as photos if I have to dig into the heart of the beast.
It's a '14 GL450 with 104,000 miles, full service history through the Mercedes dealer before I bought it. I am the third owner. I am an advanced DIYer. I don't pay mechanics unless I am too lazy to do something or don't have time. I have a heated/cooled garage, all the tools I need, and a lift in the garage. I do my own wrenching.
Start with the easy stuff first.
1) Coolant is 3 weeks old, topped off, and no air bubbles.
2) Air is blowing from the correct vents based on the control panel settings.
3) Once vehicle is warmed up, hoses going into and out of the heater core are warm/hot to the touch. The inlet hose is in very close proximity to the engine, so it is difficult to ascertain if it is "contact" heat, or actual coolant heat. Need to get out my temperature gun and take another look at that for major discrepancies between the two. ETA: No major variation in external surface temperatures of both hoses. Both at around 120F.
4) I have an Autel scanner, so I used that to manually turn on the auxiliary coolant pump that feeds the heater core. The pump is working, at least in that I can hear and feel the electric motor run. Haven't determined if there is potentially an issue with the impeller/mechanical side of things yet though.
5) I had the cooling system opened up a couple of weeks ago replacing a leaking hose that crosses over under the car, and no silica gel beads were observed in the drained coolant.
Next steps will be as follows once parts/additional tools arrive.
6) Replace the auxiliary coolant pump. It's inexpensive and easy enough to change to rule it out as a cause.
7) Disconnect hoses from the heater core and do a backflush to see if I get anything out of the heater core.
If the backflush ends up producing no or little improvement, then I'll start ripping the interior apart to replace the heater core and provide a documented thread on that since a detailed post does not seem to exist, other than a couple of high level posts with a few photos. If the backflush produces full heat, then I may chalk it up to luck, with the understanding that I may end up replacing the heater core sometime soon anyway.
If I do have to replace the heater core, I'll be replacing the evaporator core, actuators, anything else I find that might potentially fail in the future. I've pulled the dash out of cars before for this procedure, and I'm not interested in doing it more than once per car.
As they say, more to come.
I have everything you have except for the lift which I have been weighing options. What did you have installed and would you pick the same one if you had to do it all over again.
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Joined: Sep 2018
Posts: 14,692
Likes: 4,584
From: unbegrenzt
2017 GLE350 4MATIC
Of course as soon as it turns cold here in Philadelphia I go to turn the heat on and it blows cool at full speed fan setting. If I set the fan speed to 2, then it blows barely lukewarm, but you can at least tell there is a little heat. This leads me to a flowthrough problem with the heater core.
I'll document my no/barely heat troubleshooting and diagnosis here for anybody here who may be interested or need this information in the future as well as photos if I have to dig into the heart of the beast.
It's a '14 GL450 with 104,000 miles, full service history through the Mercedes dealer before I bought it. I am the third owner. I am an advanced DIYer. I don't pay mechanics unless I am too lazy to do something or don't have time. I have a heated/cooled garage, all the tools I need, and a lift in the garage. I do my own wrenching.
Start with the easy stuff first.
1) Coolant is 3 weeks old, topped off, and no air bubbles.
2) Air is blowing from the correct vents based on the control panel settings.
3) Once vehicle is warmed up, hoses going into and out of the heater core are warm/hot to the touch. The inlet hose is in very close proximity to the engine, so it is difficult to ascertain if it is "contact" heat, or actual coolant heat. Need to get out my temperature gun and take another look at that for major discrepancies between the two. ETA: No major variation in external surface temperatures of both hoses. Both at around 120F.
4) I have an Autel scanner, so I used that to manually turn on the auxiliary coolant pump that feeds the heater core. The pump is working, at least in that I can hear and feel the electric motor run. Haven't determined if there is potentially an issue with the impeller/mechanical side of things yet though.
5) I had the cooling system opened up a couple of weeks ago replacing a leaking hose that crosses over under the car, and no silica gel beads were observed in the drained coolant.
Next steps will be as follows once parts/additional tools arrive.
6) Replace the auxiliary coolant pump. It's inexpensive and easy enough to change to rule it out as a cause.
7) Disconnect hoses from the heater core and do a backflush to see if I get anything out of the heater core.
If the backflush ends up producing no or little improvement, then I'll start ripping the interior apart to replace the heater core and provide a documented thread on that since a detailed post does not seem to exist, other than a couple of high level posts with a few photos. If the backflush produces full heat, then I may chalk it up to luck, with the understanding that I may end up replacing the heater core sometime soon anyway.
If I do have to replace the heater core, I'll be replacing the evaporator core, actuators, anything else I find that might potentially fail in the future. I've pulled the dash out of cars before for this procedure, and I'm not interested in doing it more than once per car.
As they say, more to come.
I'll document my no/barely heat troubleshooting and diagnosis here for anybody here who may be interested or need this information in the future as well as photos if I have to dig into the heart of the beast.
It's a '14 GL450 with 104,000 miles, full service history through the Mercedes dealer before I bought it. I am the third owner. I am an advanced DIYer. I don't pay mechanics unless I am too lazy to do something or don't have time. I have a heated/cooled garage, all the tools I need, and a lift in the garage. I do my own wrenching.
Start with the easy stuff first.
1) Coolant is 3 weeks old, topped off, and no air bubbles.
2) Air is blowing from the correct vents based on the control panel settings.
3) Once vehicle is warmed up, hoses going into and out of the heater core are warm/hot to the touch. The inlet hose is in very close proximity to the engine, so it is difficult to ascertain if it is "contact" heat, or actual coolant heat. Need to get out my temperature gun and take another look at that for major discrepancies between the two. ETA: No major variation in external surface temperatures of both hoses. Both at around 120F.
4) I have an Autel scanner, so I used that to manually turn on the auxiliary coolant pump that feeds the heater core. The pump is working, at least in that I can hear and feel the electric motor run. Haven't determined if there is potentially an issue with the impeller/mechanical side of things yet though.
5) I had the cooling system opened up a couple of weeks ago replacing a leaking hose that crosses over under the car, and no silica gel beads were observed in the drained coolant.
Next steps will be as follows once parts/additional tools arrive.
6) Replace the auxiliary coolant pump. It's inexpensive and easy enough to change to rule it out as a cause.
7) Disconnect hoses from the heater core and do a backflush to see if I get anything out of the heater core.
If the backflush ends up producing no or little improvement, then I'll start ripping the interior apart to replace the heater core and provide a documented thread on that since a detailed post does not seem to exist, other than a couple of high level posts with a few photos. If the backflush produces full heat, then I may chalk it up to luck, with the understanding that I may end up replacing the heater core sometime soon anyway.
If I do have to replace the heater core, I'll be replacing the evaporator core, actuators, anything else I find that might potentially fail in the future. I've pulled the dash out of cars before for this procedure, and I'm not interested in doing it more than once per car.
As they say, more to come.
1. double and triple check proper level and no bubbles
6. good idea
6.5 source a XENTRY system from @BenzNinja or elsewhere. It will save you tearing the dash apart unnecessarily. There is an HVAC diagnostic section in XENTRY that should pinpoint the issue. Third party OBD scanners are not sufficient for this. Or take it to an indy with XENTRY (must have XENTRY) and have them do the full HVAC diagnosis and have them tell you what needs replaced. Need to agree this before they start the diagnosis, that you want a diagnosis without parts replacement.
7. after 6.5
Thread Starter
Junior Member
Joined: Feb 2022
Posts: 23
Likes: 7
From: Philadelphia, PA
'14 MB GL450, '14 Audi Allroad
Great intro and qualifications.
1. double and triple check proper level and no bubbles
6. good idea
6.5 source a XENTRY system from @BenzNinja or elsewhere. It will save you tearing the dash apart unnecessarily. There is an HVAC diagnostic section in XENTRY that should pinpoint the issue. Third party OBD scanners are not sufficient for this. Or take it to an indy with XENTRY (must have XENTRY) and have them do the full HVAC diagnosis and have them tell you what needs replaced. Need to agree this before they start the diagnosis, that you want a diagnosis without parts replacement.
7. after 6.5
1. double and triple check proper level and no bubbles
6. good idea
6.5 source a XENTRY system from @BenzNinja or elsewhere. It will save you tearing the dash apart unnecessarily. There is an HVAC diagnostic section in XENTRY that should pinpoint the issue. Third party OBD scanners are not sufficient for this. Or take it to an indy with XENTRY (must have XENTRY) and have them do the full HVAC diagnosis and have them tell you what needs replaced. Need to agree this before they start the diagnosis, that you want a diagnosis without parts replacement.
7. after 6.5
After verifying proper level and no air bubbles (put it on ramps, with heat on full temp, low fan, and manually engaging auxiliary pump), no change in status. Just prior to this step I replaced the auxiliary pump to determine that the original was working correctly, so I put the old one back in and now I have a spare for when it eventually does die. All things electrical/mechanical will.
Since I had time this weekend, and no XENTRY availability until Monday at the earliest, I went ahead and did the heater core flush. I did get some junk out of the system, and sillica beads. Not real happy about that part. They must have all been jammed in against the heater core. I flushed the core out about 4 times, put it all back together, and I now have "burn your face off heat" as I should, so I'm happy with the results.
I intend to do a few more flushed over the next month or so to make sure there's no more junk in the system that collects, but it looks like I can call this one done, for now at least.
