Allroad overheating problem

[AllroadIdaho]

So about 5000 miles ago I replaced the water pump, thermostat, thermostat housing, coolant temp sensor. Now that it has been getting really hot here in Colorado my 02 allroad has started overheating anytime I try to run the A/C. I got it into a Audi shop today and the mechanic warmed up the engine and let it idle for an hour with the A/C on without it overheating. This has to be a flow issue I'm thinking, the mechanic told me that if it only overheats while driving it maybe the radiator has build up or has a clog. By the way the A/C works really well and blows cold, no problem there. When it heats up the coolant temp goes way up and so does the engine temp. I forgot to add that it overheats a little even when im not running A/C at all. Does anyone have any ideas?

[LakeTahoeQuattr]

I vote water pump. Does the heater work?

[carmudgeon]

If the Allroad has an auxiliary A/C 'puller' fan behind the radiator like my S6, make sure its spinning. If its not spinning when the A/C is on it could be an issue with the temp sensor or the fan controller.

[G0to60]

If the Allroad has an auxiliary A/C 'puller' fan behind the radiator like my S6, make sure its spinning. If its not spinning when the A/C is on it could be an issue with the temp sensor or the fan controller.

The allroad (at least the 2.7T) has three fans. A mechanical clutch fan, an Aux puller fan that comes on when things get warmer or when the AC is on, and a smaller AC pusher fan that only comes on when the AC is on. I would check if any of these fans are not coming on. Also, you may need to clean out the radiator fins. That could help with cooling. My mechanic friend has a theory that with the 2.7T the mechanical fan, even on the freeway, moves air within the engine bay to help keep things cool even though it's not really pulling any additional air through the radiator.

Last summer after I did my timing belt job I removed the mechanical fan because it was starting to crack. On a road trip to SE California I had some overheating issues on the long grades in the mountains even with the AC off. Now I'm going to replace the mech fan with an electric and spray out the cooling fins on the radiator. I'm hoping that this helps things.

[PaperToast]

if it helps, yesterday in longmont it hit close to 105 (way too hot for middle of june)
was driving around town with the ac on, did ok for the morning
in the afternoon, while driving, it did get to 1 tick past middle for a while, but it kept its cool
when it was parked i popped the hood to let it cool (if there is such a thing in 105 heat)

i do have a cracked t-stat housing, i know that doesn't help.
all the fans work and even the after run system was working overtime
the oil temp didn't break 250, at least i had that going for me

but you could have a stuck thermostat, water pump, or like your tech said, an issue with the radiator

[AllroadIdaho]

I vote water pump. Does the heater work?

Took it back into my Audi Tech, he told me the water pump looks to be leaking. Not sure how I feel about that though, all they did was test drive it and pop the engine covers off to look. I have a long standing coolant leak from the seal on the cross over pipe on the back of the block. I'm thinking its possible the tech saw residuals and made an educated guess. I'm not saying he is wrong though either, I installed the pump myself and its possible I screwed up the seal (being its the first one ive ever attempted).

[AllroadIdaho]

I haven't tried running the heater yet its been hot as hell in Colorado. Ill try that today.

[AllroadIdaho]

Thanks everyone for your replies, I think I am going to get a second opinion from another Audi shop before I commit to spending a ton on a water pump replacement. Maybe Ill just have a coolant flush done before I do this and clean the fins on the radiator like G0to60 said.

[AllroadIdaho]

If the Allroad has an auxiliary A/C 'puller' fan behind the radiator like my S6, make sure its spinning. If its not spinning when the A/C is on it could be an issue with the temp sensor or the fan controller.

Ran it today and let it get hot, took the coolant res cap off while it was running and cranked the heat which blew hot. I didn't see any air bubbles so I guess there isn't air trapped in the system. Before this while it was really warm I blasted the A/C, it blew cold but when I looked under the hood the A/C puller fan wasn't on! The main mechanical clutch fan was on and so was the A/C pusher fan in front of the condenser, but the fan behind the radiator was not. I have already replaced the coolant temp sensor twice due to the old water pump burning it up, you think it could still be that?

[G0to60]

It's really easy to see if the problem is just a dead Aux fan or something wrong with the controller. On the driver side under the cover for the power steering fluid is where the fan connections are. Two have two wires that power the Aux fan and the AC fan. The other has many wires and is for the fan controller. Unplug each of the power plugs for the each fan and put 12v to them and see if the fan turns on. Check both just to be safe even though you saw the AC fan turn on. If you put power to the fan and it doesn't turn on then you have a dead fan (happened to me for both fans a few months apart). Replace that fan and you should be good. If both fans turn on with direct power then there is something wrong with the fan controller so you may want to look into sourcing a new (used) one. Good luck.

[AllroadIdaho]

It's really easy to see if the problem is just a dead Aux fan or something wrong with the controller. On the driver side under the cover for the power steering fluid is where the fan connections are. Two have two wires that power the Aux fan and the AC fan. The other has many wires and is for the fan controller. Unplug each of the power plugs for the each fan and put 12v to them and see if the fan turns on. Check both just to be safe even though you saw the AC fan turn on. If you put power to the fan and it doesn't turn on then you have a dead fan (happened to me for both fans a few months apart). Replace that fan and you should be good. If both fans turn on with direct power then there is something wrong with the fan controller so you may want to look into sourcing a new (used) one. Good luck.

At the other shop I tried, guy said it was the fan itself and controller was okay so ill replace that. They also said to replace coolant after-run pump(is this aka aux water pump?) so that it wont continue to heat up after I turn the engine off. Thanks for the advice.

[DCandDGK]

At the other shop I tried, guy said it was the fan itself and controller was okay so ill replace that. They also said to replace coolant after-run pump(is this aka aux water pump?) so that it wont continue to heat up after I turn the engine off. Thanks for the advice.

Aux water pump is another name for it. It is below the intake. You can also find relocation kits for it which aren't a bad idea since those love to go out. Good luck.

[PaperToast]

At the other shop I tried, guy said it was the fan itself and controller was okay so ill replace that. They also said to replace coolant after-run pump(is this aka aux water pump?) so that it wont continue to heat up after I turn the engine off. Thanks for the advice.

for it to work properly your gonna have to get the lower temp switch to actually turn the thing on. the oem from the factory one, the temp is too high and it never runs

[AllroadIdaho]

for it to work properly your gonna have to get the lower temp switch to actually turn the thing on. the oem from the factory one, the temp is too high and it never runs

Is the lower temp switch called the thermo-switch? Or is this the aux fan control switch? Also, I'm having a hard time figuring out where they are located. Looks like the fan switch is in a radiator hose?

[PaperToast]

Is the lower temp switch called the thermo-switch? Or is this the aux fan control switch? Also, I'm having a hard time figuring out where they are located. Looks like the fan switch is in a radiator hose?

they call it the after run switch


it lives in a coolant pipe near the expansion tank at the rear corner of the engine
here is the article that goes into more detail about it cool that coolant

[AllroadIdaho]

Thanks PaperToast, great find on that write up. Im gonna replace this switch but im reading there is cooling fan switch too. The problem im having is the after run pump doesn't come on after i kill the engine. Im thinking the thermo switch will fix this? And the aux cooling fan doesnt come on, im thinking cooling fan switch will take care of this? I think this is the one in the lower radiator hose, maybe should get coolant flush when doing this one. What do you think?

[PaperToast]

ehh, it never hurts to replace those silly things.
as cheap as they are, why not?

[glennda5id]

The afterrun pump will only turn on if the temp gets above 240 I believe. Either way, this thread seems to have gotten away from you initial issue of overheating while driving. Have you verified your fans? Have you verified your viscous fan coupler is working properly?

[AllroadIdaho]

The afterrun pump will only turn on if the temp gets above 240 I believe. Either way, this thread seems to have gotten away from you initial issue of overheating while driving. Have you verified your fans? Have you verified your viscous fan coupler is working properly?

Well, the issue with it overheating seems to be the aux fan not running. I wanted to exhaust all options(the switches) before I decided to replace the fan itself. It was hot as hell today, I drove further than I wanted to and the engine temp and coolant temp got up there. When I shut it down I saw that the a/c fan came on and was flyin! Aux fan wasn't working unfortunately. So what im thinking is the switch could be okay since the a/c fan came on after i killed the engine. I probably should replace the aux fan, the aux fan switch, and the thermo-switch with the lower temp. trigger if I can find the right one. Also im thinking of doing a coolant flush on top of this. Any thoughts?

[CAL4.2]

Well, the issue with it overheating seems to be the aux fan not running. I wanted to exhaust all options(the switches) before I decided to replace the fan itself. It was hot as hell today, I drove further than I wanted to and the engine temp and coolant temp got up there. When I shut it down I saw that the a/c fan came on and was flyin! Aux fan wasn't working unfortunately. So what im thinking is the switch could be okay since the a/c fan came on after i killed the engine. I probably should replace the aux fan, the aux fan switch, and the thermo-switch with the lower temp. trigger if I can find the right one. Also im thinking of doing a coolant flush on top of this. Any thoughts?

I had this issue last month. Turned out both fan clutch and electric fan were not operating properly and needed to be replaced. now my oil temp sits at 190ish all day long.