Overheated

cantdecide

Having done some research on the net about my poor idle in my '98 A6 2.8, I found that the water temp. sensors can go a bit awry. I've always had a 100% bang on needle reading ie, it never moves once it heats up. It has never burned a drop of water either. However, someone suggested unplugging the sensor sticking into the bottle to see if it had an effect.

I tried it today and straight away, the red temp. symbol flashed up on the screen and it started beeping. I plugged it back in and decided to never do that again.

Lately, my running has been in general very good but not perfect but after re-plugging the sensor, after maybe 10 mins in traffic, I noticed it starting to idle roughly again. I hit a tailback from an accident and was in traffic in total for maybe 40 mins. I was almost at my destination having watched, to my surprise, the needle creep slowly over 90. Eventually the temp got higher (maybe half way between 90 and the 120 mark(max) ) and the temp. symbol came on again. I stopped immediately. I got out and there was coolant pouring onto the ground from under the engine, the coolant bottle was empty and there was no pressure in the system.

HHHHEEEELLLLLPPPP!!!!!

crosstownk

cantdecide wrote: »

Having done some research on the net about my poor idle in my '98 A6 2.8, I found that the water temp. sensors can go a bit awry. I've always had a 100% bang on needle reading ie, it never moves once it heats up. It has never burned a drop of water either. However, someone suggested unplugging the sensor sticking into the bottle to see if it had an effect.

I tried it today and straight away, the red temp. symbol flashed up on the screen and it started beeping. I plugged it back in and decided to never do that again.

If you unplugged the sensor in the cooolant expansion tank (small football shaped container) then you have simply disconnected the coolant level sensor which has nothing whatsoever to do with the temperature sensor. Low coolant triggers the red temp symbol.

cantdecide wrote:

Lately, my running has been in general very good but not perfect but after re-plugging the sensor, after maybe 10 mins in traffic, I noticed it starting to idle roughly again. I hit a tailback from an accident and was in traffic in total for maybe 40 mins. I was almost at my destination having watched, to my surprise, the needle creep slowly over 90. Eventually the temp got higher (maybe half way between 90 and the 120 mark(max) ) and the temp. symbol came on again. I stopped immediately. I got out and there was coolant pouring onto the ground from under the engine, the coolant bottle was empty and there was no pressure in the system.

HHHHEEEELLLLLPPPP!!!!!

You have a coolant leak and you need to identify where the coolant is escaping from. Don't drive the car - you run the risk of causing further serious damage to the engine. Get it seen to ASAP.

LegacyUser

are you sure theres no leak from the rad?? Putting coolant into the rad can act as a type of cleaner and remove rust,dirt that may have been sealing a hole in the rad.

cantdecide

But it's hardly a co-incidence, cooling was always flawless?

LegacyUser

but all it would take would be a stone chip or some other debris to put a hole in your rad.

cantdecide

Oh, oh- One other thing is that it has a viscous fan and it also has an electrc fan (I don't know if this is normal) and I heard the electric fan kick in just about when you would expect it to. The traffic moved off at one stage for maybe 150m and the fan clicked off. When I stopped again, the fan never kicked in again and it was then that it started overheating.

crosstownk

cantdecide wrote: »

But it's hardly a co-incidence, cooling was always flawless?

But by no means impossible. You're engine was running rough, possibly due to overheating. You tried something that had no bearing on the temperature sensor - the problem may have simply developed further.

cantdecide

Joachim101 wrote: »

are you sure theres no leak from the rad?? Putting coolant into the rad can act as a type of cleaner and remove rust,dirt that may have been sealing a hole in the rad.

I have actually never interfeered with the cooling until about an hour before it overheated.

I never had to top it up, but it got changed about 5k miles ago with the t/b and water pump etc.

cantdecide

Went back and looked at the car. Bottom hose on the rad has blown off.

There is a temp sensor in the pipe just after the rad, If the hose blew off on it's own would this explain why the fan never came on?