'15 VW GTI - no heat output for first 30 minutes of driving
Good Afternoon Diag.net I am looking for some better direction on this 2015 VW GTI - VIN 3VW4T7AUXFM051091. This vehicle was brought in with no heat output. The dealer had recommended a new heater core because it was restricted. We installed the heater core without verifying (first mistake) and still no heat. It is now sent to me to figure out what is actually wrong. After the engine runs for approx. 30 minutes it will eventually put hot air out the vents, but it is cold air up until that point.
There were some faults stored (PreScan attached) but nothing that I can tie to the heat issue. There was a compressor fault in the HVAC module, but that has not returned after being cleared. I am unsure about the trans. codes. The client has no driveability concerns with the vehicle/transmission. I did check for coolant wicking but have not found signs of coolant in any of the connectors.
This has the N493 Engine Temperature Control Actuator (thermostat) & belt driven water pump under the intake manifold. It also has the N82 Coolant Shut-Off Valve and V488 Heater Support Pump. The heater hoses stay at 60 - 70 degrees F. long after the engine temperature gets up to 200 F. The outlet temp sensor of the radiator (in lower hose) stays much lower than the engine temperature for 20 - 30 minutes of the engine running, but eventually it will get up to where it matches the other temperatures (see screen shot). The lower hose stays cold for the same 20 - 30 minutes also.
I have run the basic settings for the mode doors/temp. flaps. The basic setting completes with no faults. When the vents are blowing hot I can switch between Hot/Cold/AC just fine. I am pretty confident this not a blend door issue.
I have used output control to run the heater support pump and coolant shut valve. I also ran the Basic Setting for the Temp. Control Actuator.
Any info on system operation or experience with this heater set up would be appreciated!
I believe you need to verify the water pump is capable of circulating coolant. What you describe sounds exactly like VW ALH diesels with broken water pump impellers. The engine convection cools but cannot supply coolant to the heater core. Driving at reasonable loads in cool ambient temps will not overheat the engine as it circulates by convection.
How was the cooling system refilled? Did you vacuum it down to refill?
Yes, the tech who replaced the heater core did vacuum fill it. I pulled in into a vacuum again and was able to add a small amount of coolant. Pretty confident it is bled.
Hi Jordan, I believe there is a basic setting that needs to be run whilst filling the cooling system to open all of the coolant valves and set the temperature control actuator N493 to a predefined position. Seeing that you have VCDS you can do that while vacuum filling the system....Also, have you verified the coolant shut off valve N82 is 8n fact operating correctly allowing adequate coolant…
There is a basic setting for the N493, which I ran and it passed. It only runs for 10 - 15 seconds though. I will try and verify if the scan tool needs to be involved with the bled procedure.
The OE service info says to use the scan tool and select the Coolant Fill/Bleed function.
I saw that in All Data, but I do not have ODIS and the only option in VCDS is the basic setting for N493.
Jordan check if this vehicle has the electronically controlled water pump. A gentelman called Dave Sterl has a vid on YouTube about VW cooling systems that is worth a look. Sorry I don’t know how to attach a link , but if you google Dave Sterl Vw cooling system YouTube it’s there . Hope this helps ! Dave T...
What I refer to as VAPOR LOCK, I would disconnect or loosen all connections along the way in an attempt to bleed out any trapped air and verify coolant flow up to that point, worse case is to drill a small hole in the heater code pipe very near the end of the outlet pipe, need to know which is inlet and outlet, so when you pull the hose back the hole is uncovered to allow coolant and air to…
Duane for god sake buy a vacuum filler tool and save your self from this madness....
Bill, when I move back to America, I will pick one up, thanks.
The older Audis had the bleed hole in the heater hose. You could pull the heater hose back just far enough to expose the hole. So, I see where you are coming from on this, but I think I will leave my drill bits in the bottom drawer for now. ;)
Jordan looking at your screen shot of data values it seems there is a coolant flow issue as i would expect the radiator outlet temp to be higher at this point. Possible t-stat not opening correctly causing a lack of flow in the system or possible water pump impeller issue. Could you remove the return or bleed hose from the coolant reservoir and run the engine about 2000 rpm and verify good flow…
I am heading into the shop now, so I will check that and report my findings.
I have removed the small hose at the expansion tank and there is no flow at idle or higher RPMs. The engine is cold right now though. Should it have flow when it is cold?
No, I believe that test should be done with a fully warmed up engine and the rpms raised. If there is no air in the system, then I agree with Mike Michalak that you need to verify the N82 heater control valve is working properly. It's over by the vacuum pump. Might need to remove a turbo air duct to better access it.
Well Steven M. has me questioning myself now but i would say yes there should be some flow with 2000 rpm even when engine is cold. i have done this test on many VW/Audi over the years it is possible with modern technology that the flow is limited or none during cold start to speed up warm up time for emissions although. Wish i had a CXCA engine her today to verify for you Jordan
I am marking this one resolved. Thank you for the input! I ended up installing a plastic T fitting in place of the N82 Coolant Shut-Off Valve and there was heat from the vents in 5 minutes from a cold start. The output control test would make the valve click, but it was not actually opening mechanically. I am giving the bounty to Mike since he mentioned the Shut-Off valve first. Thanks again!
Thanks for your input Mike...you'r obviously a very experienced and knowledgeabl tech when it comes to VAG. I'm also in you're neck of the woods and hope to some day say hello. Can you explain (away) the lack of flow described with this 'sticky' valve? There was some question as to this point and would love to know your take on this.
Have you got a new gig, Queensway Audi? Jaguar-Land Rover Brampton? Have a great weekend all!
Hi Frank, I've been around a bit lol over the years. Forgot to update my profile. Spent most of my time with VW/Audi but also a few years with JLR. Actually just started at the new JLR Store in Brampton at the 410/Mayfield Auto Mall that opened last month. Have a great weekend!
When you have a moment...you're thoughts about the lack of flow cold? I don't think Jordan reported back on flow when hot - had it solved by then I guess.
Hi Frank, N493 regulates coolant flow through various components of the cooling system. This achieved by a DC motor controlled by the PCM which operates a rotary slide valve. When the engine is cold the N493 in conjuntion with shut off valves essentially stagnates cooling system flow and I haven't looked at the exact cooling system layout but I would expect to not see any flow to the expansion…
There was flow at the expansion tank hose once the engine was warmed up.
** Update ** The new valve arrived this morning from VW. The new valve has a rest position of open, while the old valve is shut all the time. Installed the new coolant shut-off valve and there was great heat in about 5 minutes.
I know i am chiming in late , does this vehicle have a thermostat for the transmission. We have experienced open thermostat for the transmission not allowing the cooling system to get hot