Coolant Loss - Expansion Cap? Where can I get one?

[Petrolhead_Rich]

Evening,

My otherwise reliable Audi has decided it doesn't need coolant any more and is loosing it (somewhere)

I've been round it a few times and can't find a leak, but its loosing around 2-4 litres every 1000 miles

There is also a slight hissing sound after it's turned off from a drive, but its gone by the time I've opened the bonnet.

Could it be the radiator cap?
If so where (other than a main dealer) could I get a NEW replacement for a B5 Audi A4 2.8 V6 30v (1999)??

Also is there such a thing as "Leak Tracer" that would glow once it exits the pipework? I'm sure there is!

[andy-xr]

[Petrolhead_Rich]

andy-xr said:

where do i get those from then????

[BliarOut]

GSF

[andy-xr]

Petrolhead_Rich said:

where do i get those from then????

Sorry, still a bit early for typing

You might have a bigger problem than just a rad cap. Might not, but worth investigating anyway with that much coolant being lost. It's going somewhere...so if it's not obviously dripping onto the ground, it's evaporating either in the engine bay or going out the exhaust. The above are tests for headgasket leaks mainly, but the compression tester will give you a good idea on the health of the engine as well. You should be able to pick both up for under £20 at any motor factors.

[M1VT]

how about opening the bonnet whilst the engine is still on then getting someone else to turn it off, plum

I doubt it will be anything serious, it is VAG afterall

[maniac0796]

Grab a torch and look for water staining around the engine if you can. Might have to take off some of the many engine covers audi and VW insist on putting on their cars. Depending on how old it is, it'll either be red, or blue probably.

Aswell as the cylinder compression checker, and the block tester, you could buy or acquire the use of a a coolant pressure tester, and test for any dodgy connections/blown hoses/cracked expansion tank. It should also let you test the cap.

[cptsideways]

Leaky expansion bottle caps are very common, the VAG ones are rubbish.

[Gizmo!]

You could have a cracked expansion bottle: plastic does get old.

Alternatively GSF or Eurocarparts.

Just hope it isn't the heater matrix: does the blower still come on hot?

[bigdods]

pinhole in the rad ? I had this a while back , never showed any water marks but coolant was going somewhere. Eventually found it by running the engine on the drive on a freezing day and looking for the steam .

[Petrolhead_Rich]

Well Ive been looking at the engine while it's on and hot and there is no steam, with it being the 2.8 there is a nats whisker between the chassis rails and the engine.

Expansion bottle, radiator etc are all new (were replaced with the water pump at 82k/14 months ago

Fairly happy it isn't going down the exhaust, there is no steam or water vapour coming out, and the oil is fresh as a daisy.

I will try a rad cap and see if it fixes it.

[tubbystu]

bigdods said:

pinhole in the rad ? I had this a while back , never showed any water marks but coolant was going somewhere.

If there is no obvious water staining around the cap, and as you've checked the other obvious areas, I'd concur about a pinhole in your rad. Its fixable, probably.

Or £60 new from here http://www.radiatorshop.net/products/audi-a4-i-24-.... Which seems a bit of a bargain

[Petrolhead_Rich]

Right then, flushed the whole radiator through, put in fresh 50/50 mix of antifreeze and a new cap.

The hissing is just the air-con, if you leave it off it isn't there

I did notice a very small amount of crystals around a sensor on a steel pipe at the back of the engine, but it doesn't seem to be leaking.

Again, the radiator is new, although it was attacked by a pigeon the other week, but I checked again today and can't see any leaks, even with the coolant system under pressure

Will see how it goes and keep you updated.

[Petrolhead_Rich]

tubbystu said:

Or £60 new from here http://www.radiatorshop.net/products/audi-a4-i-24-.... Which seems a bit of a bargain

Mine is a 2.8:

http://www.radiatorshop.net/products/audi-a4-i-28-...

Oddly that makes it £5 cheaper!!

[Blakeatron]

My 2004 diesel touran is loosing coolant like a pro - searched and searched and cant see any leaks and the under the oil cap is still nice.


Given up and its in the garage next week

[Fleckers]

if your sure its a leak and not the head gasket put some fairy washing up liquid in qith the coolant and run it till hot with fan kicking on and off

then look for bubbles

[HellDiver]

M1VT said:

how about opening the bonnet whilst the engine is still on then getting someone else to turn it off, plum

I doubt it will be anything serious, it is VAG afterall

Yeah, because VAG is the ultra reliable, never ever breaks manufacturer, plum. VAG's cars are a crap as everyone else's.

[Petrolhead_Rich]

HellDiver said:

M1VT said:

how about opening the bonnet whilst the engine is still on then getting someone else to turn it off, plum

I doubt it will be anything serious, it is VAG afterall

Yeah, because VAG is the ultra reliable, never ever breaks manufacturer, plum. VAG's cars are a crap as everyone else's.

Generally though VAG suffer from lots of little faults rather than major faults compared with other manufacturers, because like most German cars they are mechanically over engineered.

[Chiswickboy]

When the radiator was changed were the hoses changed as well?

I have heard of pinholes in hoses only showing up when the coolant system is fully under pressure. No staining near the leak because there is a jet of water which immediately stops when the engine is turned off and any wetness dries out immediately.

[Petrolhead_Rich]

Well couple of days down (250miles), coolant level hasn't moved so looking good at the moment, If it's still not dropped by the end of the week, it's definitely fixed!