HELP NEEDED BIG TIME!!! Over Heating! **UPDATED**

[G60Dan 0]

I was driving along tonight, when my water light came on. Then I looked at the gauge & the temp was over 110 and slowly rising!!! :shock: I stopped the car, opened the bonnet, expecting to see water pi55ing out of a pipe................ and nothing???!?!! Header tank is still under pressure, no water on the road?? I spent a good 10 minutes looking round it trying to find out what was wrong, with no luck.

 

I got back in the car, started it up & it was find. Must have got half a mile away it does it again! So again I'm under the bonnet & can see nothing wrong??? But then I also spotted the spoiler has stayed up?? It works fine on the manual switch, and when driving raises as normal, but won't go down on it's own!

 

The car keeps chucking this warning light up, but the hoses don't feel any hotter than normal?

 

Anyone any idea's? I thought it could be a dodgy thermostat? But then why the spoiler? There doesn't seem to be any fuses blown??

 

Thanks

 

Dan

[chubbybrown 0]

Ive read through it Dan and all I can think of is Electrical,

I respect what you say about the thermostat,but just the flashy on the dash then the spoiler relay etc makes me think electrical

check the fusebox for water/water ingress

maybe thats possible after the snow thats been around.

 

Sorry If Im wrong..

 

Roy

[G60Dan 0]

I was thinking electrical. I always leave the car in the garage over night, also I have used it to go to work & back today, then went out this afternoon & then it's all started.

[quicksilver 0]

Don't know if its the same on the Corrado but my old Scirocco used to do exactly as you are describing when the water was a tad low in the header tank.

 

It made the warning light flash and the temperature rise even though it was running at a perfectly normal temperature.

 

I know it sounds obvious but check the coolant level when its cold and top up if necessary. It might not be the answer but at least its free and only takes a couple of minutes to check!!!

[G60Dan 0]

Just warmed the car up, it seems to be chucking loads of water into the header tank?? It looks as though there is 2 much in there now?? I topped it up the other day to the max & it's been fine all saturday, sunday & most of today

 

The plot thickens.................

[quicksilver 0]

air lock maybe ....... run it with the cap off until the fan comes on and give the bottom hose a few squeezes to help it along

[G60Dan 0]

Will give it a go tomorrow night when I can devote some time to it in the light. Thanks all, keep the suggestions coming!!

[Reggit 0]

A similar think happened to my VR, coolent showing sky high temps, warning light flashing. I also had fans coming on with a near cold engine. Turned out to be the blue temp sender. That wouldn't explain spoiler though.

[G60Dan 0]

I did think about that, but as you said, it wouldn't explain the spoiler.

 

I'm getting the both senders at lunch, if that doesn't work I'll do the thermostat at the weekend.

 

I'm putting the spoiler down to a coincidence at the moment and will see how it goes.

 

If the spoiler isn't related to the heat problem, can anyone explain why it would go up as normal, but not down unless I use the manual override switch???

 

Cheers

Dan

[olly elworthy 0]

i had the same temp light flashing issues as you and the gauge going up when everything else seemed to be fine and it was the black temp sender on the front of the head at fault,,

[Henny 0]

A dodgy earth or loose plug onto the clocks would expain all of your problems... ;)

[G60Dan 0]

A dodgy earth or loose plug onto the clocks would expain all of your problems... ;)

hail the great one :notworthy:

 

What colour is the earth wire on the back of the clocks?

[Henny 0]

all earths in VW cars are brown... 8)

[G60Dan 0]

top man 8)

[G60Dan 0]

**UPDATE**

 

I've added an earth to the clocks to the brown wire and it's still doing it. And there is no change.

 

The fan isn't cutting in, but is working when I bridge the connector with some wire.

 

The twist is, even when I make the fan come on, it isn't effecting the temps??

 

I have tried the air lock idea, also with no luck. What's next? Front water sensors?

 

Cheers

Dan

[potatonet 0]

if at idle check radiator, if at high revs then check thermo, if thermo is brand new like mine, check the funny hose that goes to the expansion tank from the radiator's top hose, I just posted a comment saying that it has a funny piece of plastic in it to release pressure, yes it really does have one henny. if it happens right after you turn the car on, its most definitely an air lock. running it with the cap off is the worst idea in the world. fill it up at the top of the radiator hose and just keep filling both radiator and hose. once full, run it and squeeze the top hose rapidly, it will make the air come out to the top by forcing water into the holes. then fill it up again. I would check all your senders as well, I have replace all of mine recently, I am hoping to finally fix my overheating issues but one never knows.

[G60Dan 0]

Cheers potatonet, I replaced all my sensors when I got the car about 18/19 months ago. I'm going to have to do them again for piece of mind though.

 

I have no record of the thermostat ever been changed.

[G60Dan 0]

I have bought both the water temp sensors from G&S, along with a thermostat. If the sensors don't sort it tonight, I'll do the thermostat at the weekend.

[quicksilver 0]

Which pipes are hot when this happens? Try to feel the pipes either side of the thermostat as they should be roughly the same temperature, if not and the light is flashing then the thermostat could be the culprit.

 

Turn the heater to the hot position - is the air as hot as you would expect or pretty cool when the light is flashing?

 

Also how long does it take before the car thinks its overheating as normally a failed thermostat will make it overheat within a few minutes.

 

Is the water in the header tank boiling?

[potatonet 0]

good questions

[G60Dan 0]

I think all the hoses are getting hot to a degree, it is hard to tell if something is a miss there. I'll get a better idea tomorrow when I can look at the car in the light.

 

I haven't tried the heaters, but I can see your way of thinking. I'll give that a try. Where are the heaters plumed in, in regards to everything else? Is it rad, head, heater matrix, back to the head then rad again? If it is, the heaters should be blowing out really hot, and any hoses the head side of the thermostat should be considerably hotter than the hoses pre-thermostat.

 

Yes I the water is getting hot in the header tank. Holding pressure 2.

 

I didn't get a chance to change the sensors in the end last night. They will ether get done tonight or tomorrow.

 

Thanks for your help lads, keep the suggestions & question coming.

[potatonet 0]

dude check your head flanges they can leak small amounts of water causing an air pocket and then an air lock, this is why it will overheat so quickly. drop water on them when you turn the car on to see if the escaping air bubble the water, it just allows the water to evap and mess up the system.

[Guest]

Lets think about the cooling system on the Corrado, it is used to keep the motor at a constant temperature but within a certain range. The cooling system can be designed in many ways but the easiest way is to make it both mechanical and electrical. VW could have designed the system so it relied only on an electric mulit-speed fan and this would work. The problem is it is not efficient and you would go through rad fans more quickly. You could also make it entirely mechanical by using a thermatic control like a thermostat by this would cause a wider range of temps before the system was able to control the temps. What VW did is combine both, the thermostat opens at about 80 degrees. The electric fan is used to fine tune this and give additional cooling when the car is driving slow, under load, or the AC is on. With this system both have to be working for the car to run at a proper temp. You need to check that both the rad fan and thermostat are working.

 

The electrical part is a little different but I will explain the VR6 cooling system because I have one. The VR6 uses a 3 speed radiator fan opposed to the 2 speed one used in the G60 and 16V. The VR6 also uses a temp gauge and a flashing light. The flashing light indicates low coolant in the system and overheating conditions. The cooling system uses two sensors that are located on the thermostat housing, a brown one and a yellow one in Pic 1, Item # 2 Underhood VR6 The yellow sensor sends the signal for the gauge and the overheat signal for the flashing light. The brown sensor is used on cars with AC and is the sensor for the thirdd speed on the rad fan, if the AC is on the fan will be on full speed anyways. The over-fill tank has a sensor in that is used for the flashing light because of low coolant.

 

The first and second speed are controlled by a thermoswitch that is mounted on the left side of the radiator end tank. No matter what, the low speed should turn on at about 92 - 97 degrees C, if this doesn't happen then there is a problem. The second speed turns on around 99 - 105 degrees C and the same as above applies, if it doesn't step up speeds then you have a problem.

 

If this were my car, using the basic information above this is what I would do to diagnose this problem. I would start the car and let it get warm, as the temps get around 75 - 80 degrees C start feeling the upper and lower rad hoses as close as you can to the thermostat and feel for them getting hot. No matter what by 90 degrees C the thermostat should be fully open, it is not or really takes it time opening then replace it. Next, as the car keeps warming up wait for the rad fans to come on, they should turn on around the temp ranges listed above.

 

If either of those things fails then you know you have work to do. If the thermostat doesn't seem to be opening then you can almost say that it is defective and needs to be replaced. There could be a blockage in the system or all of the rad fins are filled with junk and there isn't enough cooling provided. You would be suprised, I dropped 20 degrees C in engine temps by taking a hose and spraying the rad & AC condensor out from the back side when I did my timing chains & head gasket. If you do change the thermostat do yourself a favour and buy a thermostat housing and a cross-over pipe. Both of these parts usually need to be replaced and because they warp over the years and get really brittle. Replcace all of the o-rings, don't use any sealant, and make sure to carefully follow the torque specs- they seem like they are too low but they are not. If you over tighten the fasteners you can easily warp the thermostat housing.

 

Next, if the rad fan didn't come on you can easily check this device. You will see that there is a 3 wire connector on the thermoswitch, one is a power signal and the other two control the low and high speed. Depending what year your car is you jump the power to the different speeds and you make sure the fan comes on. If the fan does indeed come on then you know it is the thermoswitch and if it doesn't then it is the relay / control unit depending what fan system your car has. You can also test the third speed on AC powered VR6's by turning the AC on, you can test high speed on all other cars by doing the same. If the relay / control unit seems to be the problems then your first step should be to test for power at the thermoswitch on the rad. Check all of the fuses and use the manual and check for the powers to the control unit / relays.

 

If you have a VAG-COM or a mate with one you can also use the ECU temp signal to verify that the temp gauge is accurate, it is in one of the data blocks. I have also used this method to test the ECU temp sensor against the temp gauge. I can see one going but it is pretty doubtful that they will both go so they make a pretty comparison.

 

I the best way to diagnose any problem is to try to understand what is happening then you can test how the different parts interact. Start the car from cold and as it gets warm test the thermostat and then the cooling fans. By the car is up to running temps you will have a really good idea of what is wrong and where to look. You always want to try and avoid replacing things that aren't really need because it can be wasteful and expensive. Don't get me wrong, it isn't a bad thing to do but it is often not needed. Many problems can have the same symptoms but different causes so a systematical approach is usually the most efficiant and cost effective.

 

When you finish with the cooling system you need to make sure you flush out the cooling system and replace the coolant if it is over 2 years or 48,000 kms old. If you are running a VR6 you must use VW spec G12 (the pink stuff) or better. The older green coolant that was first used has phosphates in it and this caused corrosion on the cylinder head and this would damage the head gasket and corrode the head. The VR6 also commonly leaks out out the front of the block in front of cylinder # 2 but that is due to the design of the motor and would be very hard to correct. If you have green coolant and want to upgrade to G12 you must flush all of the old coolant out because green coolant + pink coolant = gel, it is not a nice site. G12 also has high freezing and boiling points as well, I pay the bit extra and buy the factory stuff because it is meant for that car.

 

I hope this helps out and make sure to by the cross-over pipe and all of the thermostat housing parts just in case because the chances are good that it will start leaking right after you put the old stuff back in. Whatever you don't have need for you can always return. I'm not sure what model you have so I kind of combined them all so I hope it isn't too confusing.

 

Cheers, Dennis

[Supercharged 2]

G12 has now been replaced with G12+ (which can be mixed with both G11 and G12)

[G60Dan 0]

Thank you for your reply Dennis! Very helpful.

 

I did the thermostat on Saturday Morning & it's cured the problem!! I'm well happy!