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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?
Need to understand what you mean by "... turned on the heat for the first time this season ..."
The automatic climate control system should run both the heat and the air-conditioning together, modulating their outputs and the fan speed to maintain your temperature set point. What happened during the Summer when it was hot in Chicago ... did it keep you cool? How about last Winter in Chicago ... did it keep you warm?
In the 3+ years we have owned our 2015 GL550 we have never "turned on the heat" ... or the 'cold' ... the system maintains our 72º set point regardless of the season. For that matter, we've never turned the system off or on ... it starts when the car starts. How does yours work?
My 2014 operates the same way as your described your 2015. Your description of how the system operates was more elegant than my statement of "turned the heat on". I too keep the temp control set permanently, at about 72F. Now that it is cold in Chicago, the car should be blowing hot air once it warms up, but it does not. After driving the car 15 minutes and getting engine coolant temps up to normal operating range, it does not matter where I set to temperature control for cabin temp, at 72 or as high as it goes, the result is ambient temperature air coming out of the vents. What I mean by ambient, is whatever temperature the air in the cabin in already. So if I'm starting the car up from a cold environment, the air stays cold and the cabin never warms up.
I took the car to an indy mechanic that specializes in imports for diagnosis. He said there are no diagnostic trouble codes stored. The engine thermostat is functioning properly, as is the primary auxiliary coolant pump (feeds turbos) and secondary auxiliary coolant pump (feeds heater core). He said that on rare occasions, the silica gel bead packs that Mercedes puts in the coolant reservoirs can rupture and release the silica beads into the coolant system, and then they travel throughout and plug up either the heater core or radiator. He disconnected the lower radiator hose and drained down the radiator into a clean bucket and said that he did see a few silica gel beads which confirmed his hypothesis. He said he spoke with a friend who is a tech at a Mercedes dealership and confirmed that this is a known phenomenon, and the solution is to drain the whole system, flush the block, and replace both the radiator and heater core. I was quoted about $5k for parts/labor which is a deal killer for me. I will trade-up before spending those dollars. I understand the mechanic's position on requiring replacement of the radiator and heater core as he is in the business of making repairs only once, and not risking a customer coming back mad that flushing the plugged parts didn't fully fix the issue. I would like to try back-flushing the heater core myself and see if I can get a good flow of water from a garden hose going through the core. If so, then I don't see why that wouldn't fix the issue. I would also drain/flush the radiator, and drain the engine block to replace all the existing coolant and maximize the likelihood of getting all the beads out. Then replace the coolant reservoir with a new one that has a non-ruptured silica-bead-pack. Fill it all up and fingers crossed hope for the best. I would think that this could be done in my garage on a Saturday and be drastically less labor than removing and replacing both the radiator and heater core, not to mention the parts-cost savings. I can't find any info online about back-flushing on a X166, I suppose they are too new for many DIYers to be doing this yet. I'll dig in under the hood and report back what I find. Hopefully it's as I expect and simply an inlet and outlet hose from the heater core, and that they are accessible without having to remove too much.
Oh, and the mechanic said that there is no such thing as a "heater-control valve" on these engines. No mono-valve or duo-valve. Just a secondary auxiliary coolant pump that circulates engine coolant through the heater core. He said the pump runs just fine; therefore heater core must be plugged/restricted.
If I were you I will take the car to new dealer and ask them to do coolant flush it cost 2-300$ thats it instead of playing with garden hose in 20F. Not sure where you live in Chicago I got 2 indy mechanic top notch you can give a shot to them PM me for more details.
I hear you about not playing with a garden hose when it's 20F outside, but I'm concerned that a standard coolant drain/refill wouldn't accomplish what is needed here. Flushing the entire system could work to get out the beads if I had flow through the whole system, but I don't. I need to unplug the restriction/plug, and best to do that by isolating the heater core inlet/outlet hoses, and flushing through the core only, ideally in the direction opposite of normal flow so that I can "back-out" the plug rather than trying to force it through the whole core.
I'll do the work in my attached garage which is typically about 50F so it's bearable, and I have a hot-water spigot for my garden hose in the garage so I can flush with 130F water.
You just going on 1 guy theory and touching sensitive systems. I have seen lot of people coming to workshop with half baked pie "Cars" to my friends garage. I would say take couple of more opinions before going on change spree. It could be simple fix.
I finally got around to resolving this issue. Had the wife driving around with no heat from November until February before we got a -30F cold-snap in Chicago that moved the issue up on the priority honey-do list. I took the vehicle to the local MB dealership for diagnostics and they came back with an absolutely shocking cost estimate of $20,000 to replace the heater core, radiator, water pump, thermostat, and all engine coolant hoses. Um, no, that's basically blue-book value on the vehicle. The mechanic said he found evidence of Stop-Leak in the cooling system and that the heater-core was plugged. I purchased the car used with 40k on the odo from CarMax 2 years ago. Shortly after purchase I had another cooling system failure, burst turbo coolant hose, and had the dealership perform that repair for $1,200 so why they didn't note the evidence of Stop-Leak in the coolant at that point I will never know. Clearly the previous owner dumped in a bottle of this poison and traded it in rather than fix a leak. A big sarcastic "thank-you" to the attorney from California, who shall remain nameless but was the original owner of the vehicle for dumping a bottle of liquid crap into the cooling system and then dumping the car.
Understanding the problem better now, I decided to start with trying to backflush the heater core. I spent about $100 on hoses and fittings at the hardware store, disconnected the heater-core hoses at the firewall, and back-flushed the core using a garden hose. This took about 4 hours and didn't really work. I went from having "zero" heat to "some heat" but it was still far from acceptable and not enough to keep the car warm. The core was 100% obstructed to start, and I got a trickle of coolant moving through it after flushing, enough for dashboard vent air temps of 65F after the engine was totally warmed up to 90C.
So I decided to bite the bullet and tear into the heater core replacement job myself. This is no small job. I consider myself a very capable DIY-er when it comes to automotive repair, I've built engines, swapped transmissions, clutches, rear-ends, so I know my way around a wrench. But still, the scope of this project and extent of interior tear-down required had me dreading the task. I ordered an "eBay special" version of WIS/ASRA and printed out all the step-by-step instructions for the interior tear-down. It took me a full 8-hour day to tear down the interior and get to the heater core, then another full 8-hour day to put it all back together. What a pain. I drained down and thoroughly back-flushed the entire cooling system to get all the Stop-Leak gunk out. It was clearly Stop-Leak, tons and tons of gold flakes. Once back together, I brought the engine up to temp at 90C and voila, dashboard heat just like it should be with 156F discharge air temps. Some pics:
65F dash temps after back-flushing the heater core... minor improvement.
The amount of interior tear-down required...
The end result, heat!
Lessons learned: (well, kinda already known, but just saying...)
1. DO NOT PUT STOP LEAK IN A CAR. EVER!
2. Be ethical people. It's not nice to trade in your problem cars and make it somebody else's problem.
3. Buying used vehicles is never without risk. See #2.
Awesome Job.....So you kinda pocketed $20K :-) for yourself.
Eitherway this seems to be a massive job, any good DIYer would be able to disassemble the Dash but the challenge is to put it back.. Hats off to you....
You should have put the actual Heater Core pic that would have been nice....
Again great job and slap the SA with this post say here your $20K goes in drain. Because 20K for 20Hr job seems to be steep high. I wouldnt mind 2-3K but 20K is rip off.
To be fair to the dealership, their $20k price included replacing a lot more than I did. They wanted to replace the entire cooling system. I figured why not start with replacing only the part with the blockage and flushing out everything else. Here is a video of me performing a hi-tech "blockage confirmation test" on the old core vs. the new core. It was like blowing through a drinking straw vs. blowing through a 1" diameter pipe.
I need to do this to my car too. But first I will try the backflush with garden hose. Then if not succesful my power hose.
Be careful with the pressure. Cooling systems see 10-12 psi typically for normal working pressures; City water pressure can be much higher. I pushed 25 psi through a pressure regulator on my garden hose and didn't want to risk going any higher than that. I wouldn't recommend a "power hose" (although I'm not sure what that is exactly). The construction on the heater core is crimped metal where the core mates with the end-caps; would make an awful mess behind your dash if it were to rupture due to over-pressure.
My thoughts were. If it's choked I had nothing to lose. But now you mention it, if it ruptures there will be a big big mess with water all over the electrics behind the dash.
I need to do this to my car too. But first I will try the backflush with garden hose. Then if not succesful my power hose.
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.
Jcob2. I would have bought it in a shot. But the postage would kill me. My location. Aberdeen Scotland.
Now I will add my location to the sidebar thingie under my name.
My GL550 is down in NYC and I am in Michigan. It happened just yesterday. I lost coolant on the highway due to a faulty plastic elbow near the firewall. I had the car towed to a local towing company and I took a rental back to Michigan and setup a shipment from NYC. Today they will pick it up so I want to get prepared with parts I will need, but I spent hours today searching for a clue what the broken part actually is (part number) and if I will have to take the dash out to replace it or not.
The elbow in question is located on firewall near the top on the driver side. It looks like a 90 degree elbow about 3/4" in diameter that goes into the firewall on one end and is hose clamped on the other. I am assuming it is going to the heater core. The mechanic at the towing place said it is part of the actual heater core, but I did not really trust that statement. The best assessment I could make was that it is outside of the part 9 on this drawing:
Sorry to hear of your misfortune. The part you need to replace is on the interior side of the firewall and runs through the firewall to connect some metal pipes to the heater core. It is not an integral piece to the heater core, it is a separate part. Unfortunately, the pathway to replacement is still the same, if not more, and will require a total dash tear-down to access. While you are there, I would recommend replacing the heater core, because why not, it's another 30-seconds of labor and $99 part. Part #7 in your diagram are the metal inlet/outlet tubes for the heater-core (outlined in yellow below), and it **looks like** those connect to Part #8 which may be the plastic piece you are talking about. Part #9 is I think just a piece of gasket material at the firewall. You may actually need to take out the entire HVAC-box assembly to get those hoses out to get to Part#8, I'm uncertain, but if so, then that means the AC evap core coming out as well and even more work for evacuating and recharging the AC system. Ugh. Good luck! Take lots of photos and mark/label everything. Lots of labelled baggies for all the screws, etc.
Inlet/outlet metal pipe routing to/from heater core to firewall:
That is what I was afraid of :/ Thanks for your response, I appreciate it.
Well, here is my plan. First I will get my local INDY shop quote tomorrow although the car is still in transit. I wanted to see how much they will want for the dash tear-down to these tubes. I am figuring it will be at least 16 hours job per your post x $90/hr, so nearly $1500 total in labor. I am already $1600 deep in one way rental and shipping from NYC, so spending another $1500 is not an option. If that is the case, I will attempt to do it myself.
I've never done more than brakes and suspension work on my GL. I am a lot less experienced than you jcob2, so it will be interesting. I will first attempt to glue a "ring" on the end of that broken tube as there is enough to make it work since only the last 3/4" or so that was inside the hose broke off. The I will re-clamp the hose if I have enough length. I know it's not ideal, but I am willing to take that chance, especially since I don't know yet what was the root cause for this. Maybe there was too much pressure in the system and will occur again. Last thing I want is to tear down the dash twice
Is there the same pressure on the heater core side as in a radiator?
I will send some pics of the damage once I get my Benz back here.
Here is the photo of the broken elbow. I actually don't think this is the one for the heater core as there are two lines for the heater core and this is a single line and located more to the passenger side. Does anyone know what this is for and how to go about replacing it? jcob2, what is your take on this?
I managed to remove the part from the engine side. I post a new thread, but I think it needs to be reviewed by admin. I will post a link here as soon as the post goes love. Thanks!
11-10-2018, 09:44 AM
Once back together, I brought the engine up to temp at 90C and voila, dashboard heat just like it should be with 156F discharge air temps. Some pics:
Especially since it has two hoses going into it
