Low Coolant warning today!
 

Haven't used the S8 for a couple of weeks and starting it today got a low coolant warning.
Indeed it was low, and as an emergency measure I topped up with softened water. It took about 750ml to get up to the correct level. :-(

Now I have to confess I haven't checked this in ages, so it could have been low for a while, though I think I would have noticed. So I'll monitor it regularly.

But what do I get to put in it now, assuming it will be OK for a while as is? The label says G12, but looking online it appears that G12+, G12++ or G13 supersede that.

Where would you recommend going and for what, to top up? I have a VW dealer not far away who ought to have coolant in the parts department.
Looking on ECP they recommend TRIPLE QX Antifreeze (Red (Concentrate) Antifreeze/Coolant 1Ltr) Product Code: 523770482, which is only £5/litre.

And would you syphon some out of the tank and top up with concentrate?

The usual culprits for coolant escaping are the radiator, oil cooler pipe and heater core bleed screws.

750ml of water isn't a lot in terms of diluting whats in there (10 litres). I'd grab a couple of litres of concentrate from wherever and put that in neat for the next top-up then use the old container to make a 50/50 mix. Any modern red / pink coolant will be compatible.

Thanks MJ, useful advice. +++
I'll pop along to my nearest ECP sometime and get a couple of litres of that red stuff then.

I'm old enough to remember topping up radiators on almost every journey so losing a pint or so over an unknown period doesn't worry me much!

Edit: Can't be bothered to drive to ECP so ordered online using whatever the current discount is; should be here Tuesday and just over £10 for 2 litres delivered isn't bad.

ECP seem to be on a go-slow; shipped today and due tomorrow now. At least they've said I'll get a refund on the next-day delivery charges so it's even cheaper now.
I was expecting to need the S8 this evening, but don't now, so fortunately not a problem. :cool:

Cracked coolant expansion pipe where the small hose connects also leads to slow coolant loss and is a common problem, mine has been replaced twice and is cracked once again. Another thing could be valves sticking open in the expansion tank cap so water is slowly evaporating or can be pushed out if car gets too warm (also happened to mine, failed electric fan meant it was getting a bit warm and stuck valves in cap meant coolant was disappearing.)

Mmm good point on the coolant bottle. I forgot about that one.

There's no reason to not drive it as long as the level is correct. That 750ml of water will make no measurable difference to anything since its diluted the coolant by only a few percent. It might freeze at -29 now instead of -30 ;) Since you have no idea of the concentration that was in there, just add 750ml of neat coolant next time it needs some and you know you've averaged out what you added to be 50:50 ish.

Yup, that's exactly what I plan to do MJ. +++
I don't use it much at this time of year, so it's just a case of monitoring for now then investigating once I see some change or detect a leak.

Edit: Pink stuff arrived so I topped up a bit more from just below Min to around Max (tricky as car isn't totally level) - half a litre of neat coolant.
Not exactly the weather for checking for leaks but there's nothing obvious around the header tank, it all looks good.
The cap wasn't "that" tight when I opened it to top up the other day; it's on firmly now.

Finally been for a short drive today, enough to warm up thoroughly then drive back home a few miles.
All seems well and on popping the bonnet on return coolant levels were fine, risen a bit due to heat expansion.

The only thing I noticed, and I think I've heard this before, was a gentle fading soft hiss from near the ECU bay. It faded away in less than 30 seconds.
It was definitely NOT coming from the area around the Auxiliary Coolant Pump, more behind/below and outboard (adjacent to the wing), I think the only pressurised stuff there is aircon piping?

I'll check again when the engine has cooled; I wasn't brave enough (this time) to loosen the coolant cap to see if it was holding pressure. :tuttut:

That hiss is normal. Its the aircon bleeding off pressure from the pump side through the choke which is just next to the ECU box, exactly where you describe.

Thanks MJ, I thought that was it, good to get confirmation. +++

Just checked this morning and cold levels are back to where I topped up to. No signs anywhere of leaks. :Confused:
Dare I risk a 200-mile round trip on Thursday...….

Mine had a leak like that for a couple of years at one time. It would seemingly lose coolant randomly, or whenever I wasn't watching it. When I remembered to check it, it never seemed to go down. Then I'd forget to check it for a week or two, only to find that expansion tank was down below minimum again. I drove it for thousands of miles like that, with a small (concentrated) bottle of coolant inside the spare wheel for emergency top-ups.

In my case it turned out to be the radiator. When it went in for a major service the garage spotted a small hole in it that was slowly weeping coolant. They fitted a new radiator and I've had no loss of coolant since.

The warning reappeared this morning, though I haven't checked in ages so don't know whether it's been slowly dropping or only when driven.
That's 5 months of low use, probably less than 500 miles. On 101773 now.

Again, took about 750ml to top up, this time the correct 50:50 mix.

So, I definitely need to call in an MJs after the annual meet to get it checked, assuming it gets there OK. ;)

I'd hazard a guess that it's the classic oil cooler plastic union/part that cracks, as the symptoms mirror my experience of coolant loss. Mine was replaced with the revised aluminium part when DS Autowerks changed the cam belt last year.

Could be that I guess, no obvious signs of any leaks but I'm no expert!
If it is that what are the chances of a catastrophic failure?

I thought it was an engine out job to replace, or did DS know a clever method?

The plastic pipe won't fail catastrophically because it is constrained by the oil cooler housing.

It is possible to change it with the engine in if you are determined enough. Its just not a pleasant job because of limited access, although its much easier with the front end off. I'll change it as a matter of course on an engine-out service, but I wouldn't take the engine out if that was the only job.

That's good news, thanks. +++

I do actually have a version of that pipe as a spare, bought some time ago from Poland and made of brass I think. I carry it as an emergency backup.
But if that's the problem, and you end up fixing it, do use your own preferred version. ;)

I have a brass one in mine +++

I had a number of slow leaks on S8 over the time. The one that keeps coming back is the small pipe on the expansion tank breaking, I think I have already replaced tank 3 times and it's broken again.

New Meyle tank arrived this morning and this time i put some epoxy putty around it to reinforce and relive some of the stress. Also used primer/activator/adhesion promoter from loctite palstic super glue kit as epoxy does not normally stick too well to plastic on it's own and I have used this primer with epoxy before and achieved good resuls. http://www.loctite-consumer.co.uk/en...-plastics.html

http://forum.a8parts.co.uk/attachmen...1&d=1558182784

Honestly, using chewing gum..

:p:p:p

Coolant, what coolant.
 

I don't think I've ever checked this :o , so got a bit of a shock yesterday on picking Herman up from his biennial gearbox service at Mackies last night to see a Big Red Warning Light in the display.

Popped the bonnet (or rather John @ Mackies did...) to find the coolant level was way below minimum. Very weird - no issues on the last two long distance drives (back from MJs and then up here to Mackies), so I read this thread with interest and will be keeping an eye on it on the drive south later this morning...

Hmm that's a tad worrying :(

A bit less now, maybe - back home after another 200 mile drive, with zero loss of coolant. So less worrying, just a bit strange, really :Confused:

Its not uncommon for the V8s to 'burp' themselves after having the coolant filled, and I had just refilled it before you picked him up. It may well be that it was just that and it only showed the light after a couple of journeys.

Keep an eye on it I guess and keep me posted :)

I've been away and the S8 has been just sitting there for the last 2 weeks, but checked this morning it's dropped a few mm below minimum!
Could that just be temperatures/expansion stabilising? No signs of any drips on the ground below. :Confused:

Edit: I was going to go for a short drive and see what that did, but the battery just didn't have quite enough "oomph" to start it. :(

That was my thought too - and I vaguely remember the same thing happening post-service a few years back. Still full and stable, but I'll keep an eye on it - well, more than before, at least!

All very strange, I've recharged the battery and done a couple of short journeys since the last post and it had dropped noticeably when checked at the weekend. No signs anywhere of any leaks or drips.

So I topped it up and went to buy some petrol today pre-meet, then did a precautionary country drive of about 40 miles or so, most at 60-70mph or so.
Temperature gauge was locked on 90 throughout, and on checking back home the level seems unchanged. :Confused:

I'll have a big container of water with me and when we arrive at MJs on Thursday afternoon for "Triage" it will be the first thing I'll ask her to look at. ;)

I can show you the lumbar support shenanigans too +++ I shredded a seat the other day while Bert was here since he has the same issue.

Ah good, if I remember I'll bring the spare motor/pump unit I bought from the USA. If nothing else, to just check it looks right.

Well MJ found the evidence (and showed it to me) of a definite coolant leak from the dreaded plastic oil cooler pipe.

Funny thing is, after getting home from the meet the level doesn't seem to have dropped. On the other hand what with driving sedately in Cornish convoys and terrible weather on the longer journeys there have been very few "overtaking opportunities".
So the revs have been consistently low. Indeed my gearbox had drifted off into "Cornwall mode" and was selecting top gear at anything over 30mph! :tuttut:

As for the valve unit I have for the seat (the pump motor is in fact separate) I now know where it goes and it may be inaccessible to a "mere mortal".
The one I have seems to be a different design, but has the same electrical and air connections so I'll see if I can at least get at those and try it - nothing to lose.

Here's a couple of photos that DS Autowerks took when they replaced the oil cooler plastic pipe/union with the modified aluminium one - this was done at the same time as the timing/cam belt. You can clearly see the tell-tale signs of pink spots of coolant in various places.

Pink sump bolts is a good indication +++

I haven't actually checked my coolant level since the meet, but did so today.
Down to minimum and I added half a litre of water.
But we know the cause and it should be fixed (by MJ) in October.