Heater issues

[drw8]

Just had both radiators replaced today as one was leaking and the other was heavily corroded along the bottom. Before them being replaced I was barely getting any hot air through any of the vents and just put this down to the leak. Now the leak has been sorted I'm only getting hot air from the windscreen vent and barely warm from the side/central and foot vents. I've done the CC flap reset and there is no difference. 

 

Can anyone suggest what the next port of call would be? I don't have VCDS, TIA. 

[Guest]

Both radiators?

[KenONeill]

1 hour ago, drw8 said:

Just had both radiators replaced today as one was leaking and the other was heavily corroded along the bottom. Before them being replaced I was barely getting any hot air through any of the vents and just put this down to the leak. Now the leak has been sorted I'm only getting hot air from the windscreen vent and barely warm from the side/central and foot vents. I've done the CC flap reset and there is no difference. 

 

Can anyone suggest what the next port of call would be? I don't have VCDS, TIA. 

Which heating do you have?

[drw8]

1 hour ago, MicMac said:

Both radiators?

On the invoice its written up as primary and secondary radiator and was shown 2 rads of similar size. Explained that everything up front bar the a/c condenser was replaced. 

1 hour ago, KenONeill said:

Which heating do you have?

How do you mean?

[Guest]

The cooling pack from front to rear consists of the A/C condenser, turbo intercooler and coolant radiator.

 

Sounds like they did the latter two.

 

If the windscreen vent is good and hot with the engine up to temperature but the others aren't, keep resetting the distribution flaps for a few minutes, they can become stuck and with repeated operation should free off although it is possible an electrical connection is bad preventing the relevant flap(s) from working properly.

 

If you don't have access to diagnostic tools to check the flap positions and vent temperatures all I can suggest is checking the heater matrix in/outlet pipes on the engine compartment firewall for heat, it may be that the heater matrix is partially obstructed with debris and isn't getting fully hot to supply the vents properly although it's hard to say via a forum.

 

There are instructions on here as well as videos online showing how to access and remove the matrix, maybe a coolant system flush additive would help if it is blocked, followed by removal and manually flushing it clear or replacement.

Edited 24 December, 2021 by MicMac

[drw8]

Have managed to get out a few times now on decent length drives and reset the flaps a few times each journey. Air coming from the centre/side and footwell vents have progressively gotten hotter. Might have been a small air bubble(s) causing the problem. But for now it's behaving. 

[drw8]

So now I'm having issues with overheating. First time it's been on a 20 mile run since the rad has been replaced and it slowly crept up a 1/16th past 90 degrees and then dropped back to 90. Then it crept up 2/16ths past 90 degrees and dropped. Before it hit red and a warning came on I pulled over and checked for any leaks (coolant tank was still well above empty line) and there was no debris blocking air flow, both fans were running. Cracked the cap on the coolant tank in case of any air locks and carried on a few more miles to my destination where it stayed at 90 degrees. 

 

On the return journey, around the 20 mile mark the temp crept up and got into the red and a warning light came up, pulled over immediately (engine off) and checked everything again. Temp dropped back to 90 and carried on with the last few miles of the journey home with heaters on full hot and full blast (have now lost any heat from heaters) 

 

Hooked up carista and the only coolant relevant fault code I've got is P0480, but I suspect my overheating is either a blockage, faulty thermostat or (worse case) a water pump. 

 

Any suggestions on how to diagnose or get a definitive component at fault? TIA

[PipH]

If you remove the small coolant pipe near the top of the coolant reservoir then poke it in the reservoir top.

Start the engine, coolant should circulate through the pipe & into the reservoir.

That will prove the pump is working.

 

If no coolant comes out, either the pump is defective or the small pipe has a blockage. 

[Guest]

Is there any debris in the coolant reservoir?

 

You may be able to feel the coolant hoses as the engine gets up to temp, any suspiciously cool may indicate what you suspect.

 

Removing the thermostat temporarily would be an idea to test for restriction, you could also test it by placing it in a mug and pouring boiling water in to see if it opens.

 

Running the engine with a coolant hose disconnected, although messy should show if the pump is working.  Study the coolant circuit so you don't disconnect a hose downstream of a potentially closed thermostat which would give a no flow situation and lead to a false diagnosis of the pump.

 

In fact if the pump is working you should be able to observe coolant returning to the reservoir, you may need to open the cap to see and engine temperature may have an influence on the flow.

[drw8]

Thanks both for the suggestions. I'll do some testing tomorrow when I have some daylight.

[drw8]

OK, so there is no debris in the expansion tank. I took off the small hose and I'm getting a steady flow back to the expansion tank. I can get an 83 degree C thermostat from ECP for £10, so I'm going to change it as it's so cheap (pretty sure it'll be the original, 11 year old) and then I'll take it for a 20 mile drive and see how it goes. 

[drw8]

Changed out the thermostat and hasn't overheated since. Plastic and spring part of the thermostat were covered in a film/sludge and I found random bits of red crap (congealed coolant?) around the part that opens. 

 

Still having problems with getting hot air at windscreen vents but warmish at the side vents. Tried the flap reset a few times, but doesn't seem to be working this time. 

Edited 15 February, 2022 by drw8

[pikpilot]

Perhaps try flushing the cooling system and replace with new coolant. Surprised the debris is that colour.

Perhaps someone put in the wrong coolant at sometime. VAG cars are fussy about only using VAG coolant.

[drw8]

It could have had incorrect coolant added when it went in for a pressure test to find out it was leaking from the rad and again when the rad was replaced. G12/13 is the correct stuff to use? 

[Guest]

It looks like a fine rust coating and possibly some sort of sealant.

 

Could be indicative of a prior issue where the coolant was partially diluted with water and a leak or other work on the system was addressed.

[drw8]

Prior to the rad being changed, rad weld was put in the cooling as a temp fix to avoid a big bill just before Christmas. The coating on the spring and plastic part is like a skin and does peel off. 

[drw8]

So I took it on a decent journey out to ECP to collect antifreeze ready to flush the heater matrix and cooling system this weekend. During the journey there I did the flap reset every few mins and the air did slowly get warmer from the side/centre vents. When I pressed the recirculation button, the air got much warmer. When I got home I checked the feed/return from the matrix and they are all pretty warm. 

 

Now I'm confused, is this pointing more towards an electrical/flap motor problem rather than a restriction in the cooling circuit?

[Guest]

The matrix inlet should be engine coolant hot so untouchable, the outlet slightly less so depending on heat/fan settings.

 

Out of curiosity, with the engine up to temp and the heating to auto/22C/50% fan, what happens when you place a hot cigarette lighter in front of the cabin temperature sensor (centre of fan control)?

 

You can also try placing bagged ice or similar on the sensor to see how that affects things.

 

Without diagnostics to monitor the various temperature sensors it's difficult to say what is going on but this test can at least give you an indication of what the car thinks the cabin temperature is.

 

I used this method to address aircon not functioning properly and later resoldered the sensor for an improvement despite diagnostics showing approximately the correct temperature values beforehand but the aircon solenoid valve is suspect... that's another story.

[drw8]

So I've tried what you suggested (heating to auto, 22 degrees) and that puts it to 2 leds lit for the blower 'strength' but if I try to increase the power of the blower it takes it off auto. 

 

So I put a lighter in front of the little black dot sensor and didn't notice any difference in temp, but it's very difficult to detect as there's barely anything to feel from any of the vents. 

 

I did out of interest and looking at other topics, remove the centre dash storage and found the r/h temp sensor not fully seated. 

 

Will get a chance to test again tomorrow and if there's no difference, will crack on with a matrix/coolant flush. 

 

Thanks for the continued help/suggestions. 

[drw8]

So I haven't managed to get a matrix/coolant flush done yet due to work and the weather. I bought an air temp thermometer and did a few checks. What I found was with the coolant temp at 90 after doing 20/30mins of driving (blower and temp at full) side vents only the temp is 44 degrees. If I change to windscreen and side vents, temp at the side vents steadily drops to 32 degrees but the windscreen gets really hot. With car stationary but engine running (side vent only) temp at the vent drops to 23 degrees. If I increase revs above 1200 temp starts to climb.