Why is my engine using so much coolant???

[twoqu]

the culprit on mine was the water after run pump, didnt show up on any pressure test's only came to light when i placed my finger under it, it felt all moist!
come to think of it, the pump only leaked when it reached a high temp or when the pump cut in, both obviously linked!
hope yours is an easy fix

Hi!
You could certaintly try and bypass the pump temporarily by getting some 19mm copper pipe. You will need to get a fitting with approximately the right angle (no pun intended!). Join the hoses together with some extra clips and see if that makes any difference.
If its the original then its likely that either the stubs are brittle and have cracked or that they have gone soft. Either way the connection might seem ok but as the temp increases perhaps the seal is being broken. You should still have some evidence of coolant loss.
Oh and if you were worried about the cost of the MFS, don't ask about the pump!
In fact, if you are going to fiddle with the pump connections, go and find something to allow you to reconnect the hoses NOW! At least that way the car can still be driven if there is a problem with the pump.

[twoqu]

Hello!
Whilst i have my thinking head on!
Just wondering if there is a connection between the gauge not working and the coolant loss!
I have had the MFS fail before and leak water into the rubber boot that covers it. Might be worth removing the boot and checking the bottom of the MFS. Thats the larger of the two switches in the water rail beneath the inlet.

[S4 Miss]

ok, will go check. cheers!

[alg]

The afterrun pump has to be considered.
I had the afterrun pump replaced but there was clear evidence of dried coolant in the area as it sprayed out under load.
Do not trust a pressure test. I recently had the car back after it passed the pressure test to lose half the coolant tank level within 48 hours. The front lower aux rad hose had split the wrong side of the banjo clip and you could see it weeping coolant after running the car for 10mins or so.
My advice is to start from scratch. Run the car until its hot and check every pipe with care. You may feel the leak under the pipe before you see it !
Good luck its a boring job !

[S4 Miss]

Decided to drive with utmost beans everywhere i went in the hope of finding evidence of the leak...and you know what!?! Its not lost any!!!!

A good thing you might say...but the fact it was disappearing coolant and has now stopped for no reason also worries me...the car fear is immense...

Did check after run pump area though and no sign whatsoever...could it be something to do with the water cooled turbo!?! She's not as pokey as she was...

[andre]

Not sure if this applies here as I don't know how much coolant you have put in, but after doing some work on my car which required a rad pipe to be removed I had a bit of a scare. I filled up the rad and the header tank and off I went, only to check a bit later to find the header tank almost empty. Refilled and it emptied itself again twice over the next few weeks. Turns out there was a huge air lock in the cooling system that was slowling being worked out.

Apparently one should warm the car up after filling the cooling system and then loosen the little bolt on top of the main rad to let the air out. Not to sure if this is the way it should be done, but there was still quite a bit of air in mine when I did it and since no water has been needed.

[twoqu]

Hi!
Andre makes a good point! I know you mentioned having the fan replaced. So if they disturbed any component in the water system like the rad or a hose causing coolant to be spilled and only topped the level up without following the normal procedure to allow for air to be bled, then that could explain it. Basically the cooling system will draw the coolant from the expansion tank to replace the air dispelled! Obviously it would depend on how much was needed to refill it.
Just keep you eye on the level! Clearly if there is no evidence of a leak and you are confident it is not burning it then this is a plausable explanation. When a prob starts shortly after any work, there is usually a relationship!

[Fat Audi 80]

When refilling, I usually run the cooling system with the expansion tank cap off until the car is up to temperature, whilst going round and squeezing the pipes. You can then be relatively confident you have no air locks.

Back to the original poster. If you find you lose water again, I would do as someone else said and take off the undertray and run the car up to hot and look for leaks. If it is losing a lot you WILL spot it. More often than not it will be coming out when all the pipes are hot and expanded and the coolant is under the most pressure.

Cheers,

Steve

[iain1067]

To bleed the system on the S4/6 you need to set heater to max, then pop off the big plastic rain cover that goes over where the wiper motor is, on the passenger side of the car in this area you will see a couple of hoses going into the bulkhead one of them has a bleed screw on, undo it until you get a trickle of coolant coming out, you will see/hear any air being purged. When i changed the thermostat on mys6 it took ages for the heater and system to bleed.

Iain

[Azman]

I have a strange one along these lines too. Noticed though that on small runs where the thermostat doesn't open but the water gets plenty hot enough I lose water!!!! WHen the thermostat opens I don't!!!! Try to figure that one other than pressure build up. But where is it going? and it's not in the head!

[WabTheKing]

not the after run pump either cause you aint got one of them either!!

[S4 Miss]

Not sure if this applies here as I don't know how much coolant you have put in, but after doing some work on my car which required a rad pipe to be removed I had a bit of a scare. I filled up the rad and the header tank and off I went, only to check a bit later to find the header tank almost empty. Refilled and it emptied itself again twice over the next few weeks. Turns out there was a huge air lock in the cooling system that was slowling being worked out.

Apparently one should warm the car up after filling the cooling system and then loosen the little bolt on top of the main rad to let the air out. Not to sure if this is the way it should be done, but there was still quite a bit of air in mine when I did it and since no water has been needed.

Spot on Andre it was an airlock! Must have been a lot of air to get through that much coolant

But at least the S4 is a happy bunny again! I think the tank of V-power helped her get over her coolant truama, and she's purring like a kitten again.

She's driving across France tomorrow so at least I can do that without the car fear!

Back in a couple of weeks...will miss you guys!

[BRY]

We will miss you too, Miss.