Help... Overheating!

[benberry]

Hi Guys,

I was working on a separate problem on the Avant yesterday, had the engine running whilst I worked in the boot.

After about 30 mins I noticed smoke/steam coming out from under the bonnet.



When I opened it up I could see the coolant tank was bubbling over so I turned it off to investigate.



It turns out that the fans weren't running at all, hence the overheat where not moving.

I checked the temp gauge and never went over 90 but foes drop when it cools down.

The fan does work when I turn the aircon on?



What do you think is broken?

Ben

 

[AlexGSi2000]

Check the fan fuse / relay.
What engine is it?

 

[benberry]

Its a 3.0 v6


Which fuse do you have in mind?


Fan does work when Aircon is on but doesnt seem to detect its getting hot and kicking in on its own?

 

[AlexGSi2000]

Are there two fans on the 3.0 V6?
There is an independent fan on my 2.5 that operates regardless off the air-con (this is a viscous fan I know, but thought other engines had electric fans)

On my 1.8 there was a relay / control unit next to the main fan itself.

Check your instruction manual for fuse locations.etc

 

[benberry]

Just a single fan as far as I can see, works fine.

The problem I've got is it doesn't recognize its getting hot and isn't kicking in like it should, only when I turn Aircon on!

 

[mattyb6]

Just a single fan as far as I can see, works fine.

The problem I've got is it doesn't recognize its getting hot and isn't kicking in like it should, only when I turn Aircon on!

Put a new stat and temp sender in, and check fuses like above.

Does your vents in the cab blow hot air? Because if not it could be a sign the water pump is failing/ and head gaskets.

flush the water through aswell. Could have an airlock aswell.

 

[pauldazzle]

Coolant temp sensor failure is extremely common which resulted in VAG revising the part.
It has 2 outputs one to the gauge, & the other to the ECU. If the ECU feed is reading low engine temp the ECU won't turn the fans on.
If you have the old black type CTS it's worth changing to the revised green type ( fit genuine VAG part only) as it will fail at some point.

 

[benberry]

Ok thanks. I take its ok to drive still as I can still turn the fan on manually with the AC.

 

[Mike B]

There must be 2 fans

 

[benberry]

Really? I can only see one?

 

[Mike B]

The aircon needs its own fan cos the engine may not be hot but the interior is .

 

[benberry]

The aircon kicks the fan on when you turn the air con on, it' off otherwise - would indicate it uses the same fan?

 

[Mike B]

They are independent systems.No way can one fan cool the aircon rad and the engine coolant rad.On my 2.5tdi the aircon fan is smaller less obvious and mounted to the drivers side alongside the large engine fan.Could be that there is a temp sensor in the rad which has failed .Diagnostics should tell you

 

[hades-]

the aircon fan wont stop it overheating

when you drive does the temp gauge go up and down ?
does it sit at 90 all the time ?
id get it looked at if its the WP and it goes fully your looking at cooking the top end and turbo

 

[Mike B]

the aircon fan wont stop it overheating

when you drive does the temp gauge go up and down ?
does it sit at 90 all the time ?
id get it looked at if its the WP and it goes fully your looking at cooking the top end and turbo

The fan has failed.Must be a sensor.Hapend on wifes Bora last year when they let it idle for the MOT .The sensor in the rad had failed.It would soon boil if the w/pump u/s

 

[benberry]

I'm getting it booked in on Tues to get checked.

In the meantime I need to drive to Cumbria and back (600 odd miles)!


I've left it to run with a warm engine and fan on for 10 mins and seemed to stay cool. When I tried to do the same experiment but with no aircon it started to get hot.

The fan that blows is definitely the main coolant fan so surely as long as that's running full pelt it will work? Its a 3.0 v6 NASP so no turbo.

I'll get the sensor or whatever changed but manually for now will do.

 

[hades-]

depending on what has failed even with fan on it could still over heat

i wouldnt risk 6 miles let alone 600 with it the way it is
it it is the pump on its way out it could fail fully same as mine did
and i have to have a new head turbo etc

 

[Mike B]

depending on what has failed even with fan on it could still over heat

i wouldnt risk 6 miles let alone 600 with it the way it is
it it is the pump on its way out it could fail fully same as mine did
and i have to have a new head turbo etc

Dead right. In this weather more so.You know there is something wrong needs fixing

 

[AlexGSi2000]

+1

600 miles with a cooling issue could spell disaster.
If you absolutely need to drive to Cumbria, make sure you can cool the engine by whatever means possible.
(remove front grille, remove plastic engine covers, keep interior blowers on a high heat.etc)
Sounds extreme, but that's what I'd do!

 

[Mike B]

If its just a sensor it would take 20 mins to change