Audi a3 overheating

[Ben d williams]

Hi guys

I have a audi a3 8p 2.0tdi and its overheating and blowing cold air from the fans. I've had the waterpump replaced and still no different. I have noticed on the twin fans that my smaller fan never works so could this be a cause of the problem?? Any help would be appreciated

 

[e9_mustii]

Hi guys

I have a audi a3 8p 2.0tdi and its overheating and blowing cold air from the fans. I've had the waterpump replaced and still no different. I have noticed on the twin fans that my smaller fan never works so could this be a cause of the problem?? Any help would be appreciated

Yea you need to replace your fan stitch its probably faulted, removing it and and cleaning terminal and refiting may help if there corrosion on there otherwise just change it next step would be to test your fans work

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[samisnake]

the smaller fan id assume is for the aircon condensor, so i wouldnt expect it to come on.

if its blowing cold air out the vents, but the cars overheating, that sounds like the thermostat.

 

[e9_mustii]

@samisnake is absolutely right now that ive re-read it, i had just woken up at the time of my comment lol you t-stat may be stuck closed

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[e9_mustii]

General rule of thumb if you change the waterpump change the stat aswell

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[Ben d williams]

Sorry forgot to say I have also changed the thermostat but this has made no difference. Any other ideas?

 

[samisnake]

was the system bled correctly?
was the thermostat a decent brand?

the heaters blowing cold is the thing that makes me think either the thermostat is a dud or there is air in the system.
do the hoses going to the radiator feel hot to the touch when the car is overheating?

 

[Ben d williams]

What's the correct way to bleed the system? I did have a coolent leak coming from a loose hose but tightened that up and the leak stopped and just topped it back up with coolant so there could earlier be air in there. Also thermostat was just the cheapest one on euro car parts I think. Im sure the hoses were hot but I will double check

 

[samisnake]

the official method by audi is to use a vacuum pump to pressurise the cooling system and fill it that way.

on the last car i had to refill the coolant from empty, a mk2 focus, i filled the coolant to max, left the cap off, ran the engine for about 15mins, and squeezed as many of the coolant pipes as i could to try and burp the air out. worked fine. you gotta get the engine hot enough for the thermostat to open so that the coolant is fully circulating to get all the air out.
on the mk2 focus, the heater matrix was contanstly in the cooling system loop, so it made no difference is the heater was set to max heat with the heaters blowing, but might be different on the a3. in that case, while the engine is running, turn on the heaters (ac off), max temp and leave that on while bleeding.

however a few years ago on a friends rover 25, we couldnt do that, and had to go to a garage to properly bleed it. symptoms were no hot air out of the vents, and the engine was running slightly hot. supposedly those k series engines were harder to bleed.

 

[Ben d williams]

No problem I will give it ago with the engine on with max temp on and see if that works of not I will get a vacuum pump and have a go with that. Also I have just heated my car up and checked the hoses and the hose going into th radiator is hot but the hose at the bottom left is cold. Is that normal or should all hoses be hot?

 

[samisnake]

one should be hot, one should be cold/cool, as that means the rad is doing its job. also means that the thermostat is doing its job, or at worst case scenario is stuck open (which would give you the opposite of an overheating engine).

so it looks like its a bleeding issue

 

[Ben d williams]

Ok thanks I ended up emptying the coolant and started from scratch and bled the system took it for a drive afterwards and it overheated slightly but only for about a minute. Also when my car was up to 90 degrees I left it ticking over and when I turned my fans on it was blowing cold air out but if I revved the car hot air started coming through. Is there a reason why it isn't putting hot air through when it's just ticking over?? Also I am stumped about my twin fan under the bonnet as I've never noticed the small fan come on at all and I am abit concerned why

 

[samisnake]

It's improving which is a good sign.

When you rev it, or are driving it, the waterpump is spinning faster, pumping the hot water at a faster rate into the heater matrix. the problem still remains, but the faster rate of hot water hides the issue.
the cause of it being cold when idle but hot when driving/revved is most likely one of 2 things; air trapped in the matrix, or a blockage in the matrix.

that you know of, has the car had a stop leak fluid added to the coolant, something like kseal? thatll block a matrix.


dont drain the coolant again, just rebleed it, this time with the front of the car jacked up as high as you can get it. thatll help shift any pockets of air in the matrix.

if that doesnt work, you can look into flushing the matrix, as at that point id assume its blocked.


only thing id add to the vid is to also run the hose from the outlet side as well, to flush it backwards


with the smaller fan, thatll be the aircon rad fan. as long as the bigger fan works, the smaller fan is a separate issue. on a hot day, run the aircon and the fan should kick on and off. for now check if it spins by hand, but atm the coolant issue is a priority.

 

[Ben d williams]

Funny you should say that. A while back I had a coolant leak and I had a guy look at the car and he said he would put k seal in it and that should fix the problem. Later on I realised I had a cracked cylinder head so ended up getting a new one put on it. So would kseal block the matrix and the also the silver pipes connected to the matrix? Ok I will try that with the fan. The fan does move by hand but like you say the coolant is the main issue

 

[Ben d williams]

I've followed that video and also flushed it backwards as advised but still having cold air while ticking over. Yet again only hot when revving or driving. What made you mention kseal?

 

[samisnake]

just a hunch really. weve narrowed down your issue specifically to heater matrix, so that left 2 possible causes (techincally 3 but youd notice coolant leaking into the car). kseal is a common cause of heater issues and a terrible thing that gets used too often.
that friend with the rover 25 used it and ended up having to bash globs of it out of the waterpassages in the block with a screwdriver a few months later when he changed the head gasket.

did you have any oil in the coolant when the cylinder head was cracked, or just water in the oil?

i wouldnt be suprised if your matrix is blocked pretty bad.

 

[samisnake]

could still be air trapped in the matrix, but if youve tried multiple times to bleed it, and jacked the front of the car up while bleeding it, and its still behaving the same, i cant see it being that hard to bleed an a3.

 

[alwaysconfusedaf]

100% it’s the fan. I had the same issue and replaced it, very common issue on these where the small fan won’t turn and the big one won’t cool the car. I found a fan assembly for £40 which isn’t bad at all and it fixed my issue.

 

[Ben d williams]

100% it’s the fan. I had the same issue and replaced it, very common issue on these where the small fan won’t turn and the big one won’t cool the car. I found a fan assembly for £40 which isn’t bad at all and it fixed my issue.

A fan assembly??

 

[alwaysconfusedaf]

A fan assembly??

Not sure about your second issue as I never tested to see if cold air would turn warm when revving. The fans issue is 100% something wrong with the controller I think so I replaced the whole fan assembly on mine (the two fans and the plastic shroud).