coolant leak 2.0 non turbo

[mkc]

Hi, my A4 has started leaking a large amount of coolant. The coolant is dripping out of the gaps in the floor pan and only seems to drip when the engine is OFF. I top it up and it drives fine, gets to temp fine, I check the coolant level and no change in level. However, once parked up she starts to drip for a few hours and then stops.

looking from the top of the engine down with all plastic covers off I see no leak, no residue from burnt coolant, nothing is wet. It's coming from something under the engine. The water pump was replaced 20k a go and everything looks dry in that area. It's almost as if once the water pump stops, whatever is left in a pipe just leaks out until it's empty then stops. Then when running the pressure of the fluid moving about doesn't appear to reduce the volume of the coolant.

its going in Wednesday to be looked at but has anyone any idea what part of the car could be leaking. I have to drive it so just hope she holds up, as long as I keep an eye on coolant and temp I'm hoping she will be fine for two more commutes.

thanks

[markoA4]

this happened to me an turned out to be the (CTS) coolant temperature sensor on the top back end of the engine block. dont know whether yours is different being a petrol model. but where that sensor is and when taken out there an o ring on it. mines was wore an corroded. might not be that .but it wouldnt hurt to have a look for coolant round that area. hope you get to the bottom of it

[rhencullen1989]

Maybe a daft answer, but its not your aircon dripping condensation is it?????

Mine will do this especially on a hot day, i am only thinking this as you say there is no change in coolant level

[mkc]

Maybe a daft answer, but its not your aircon dripping condensation is it?????

Mine will do this especially on a hot day, i am only thinking this as you say there is no change in coolant level

No, valid question as I didnt explain myself very well. Whilst the car is running there is no drop in coolant, only when the car is off does it start to leak and then the coolant level drops. But it only drops like a few 100ml and then stops. Its almost as if whilst the coolant is circulating its fine, then when off, whatever is left in a particular hose or part of the piping drops out on the floor.

It doesnt appear to be the coolant sensor as suggested, I located that and its dry all around. Leak is defo from under the engine.

[Doc B]

The o-rings on the CTS at the back of the block are known to fail (so I was told by TPS man). Took me ages to work out that mine was leaking after being all around & under the engine. The coolant level only drops very slowly with this leak...... A new o-ring from TPS is is around £1.20 & we'll worth the effort. Oh & get yourself a spare clip for the CTS incase you drop it & lose it - I did & had to go back for a new one!!!

[mkc]

The o-rings on the CTS at the back of the block are known to fail (so I was told by TPS man). Took me ages to work out that mine was leaking after being all around & under the engine. The coolant level only drops very slowly with this leak...... A new o-ring from TPS is is around £1.20 & we'll worth the effort. Oh & get yourself a spare clip for the CTS incase you drop it & lose it - I did & had to go back for a new one!!!


Well, turns out its the Water Pump thats leaking. Not happy as it was only replaced about 30K ago when I had the timing belt done.

[rhencullen1989]

Was it a genuine Audi part? It will have a 2 year guarantee.

I thought my pump was goosed in March, i had no heat in the cabin unless i revved the engine over 3K and no flow back into the coolant reservoire.The timing belt was just about due anyway, so i stripped it down, the pump was fine, and was a genuine audi plastic impellored one, i was told by the previous owner that he had had it replaced with a metal impellored one!!

Anyway, i replaced the timing belt and associated components and the waterpump (again with genuine one) i then noticed a piece of broken plastic when i removed the pump, turns out there is a plastic plug that blanks a hole off at the rear of the pump in the engine block, this had broken up, the o ring had gone mushy and it was leaking from here, i can only assume it had caused an air lock in the system, hence no flow.

Replaced this plug and also put a new thermostat in (had to remove this to get to the plug) cost of the plug was a couple of quid, but it cost me 180 in parts (from TPS) for the belt kit, waterpump, hydraulic belt tensioner, aux belt, coolant, thermostat etc............