Coolant loss mystery

P

Pilchard

Member
My 1.4 diesel is losing coolant somehow.

It was serviced and topped up 11 days and 110 miles ago. Following the warning alarm today it took 0.85 litres to bring it to the max line.
The same happened 2000 before the service, and again just before the service, so I asked the garage to check. He had it on a pressure test while he did the service and he reported no pressure loss.
A bit of a mystery.

The temp-gauge is very lazy and never moves from its 60 degree start point unless on a long run... and then never hits the middle point where you'd expect it to be. There could be a connection... but maybe not. Either way... the lazy gauge is another mystery I've had in mind to look into.

There is no engine-bay staining visible from just casual inspection and, fortunately, there is no sign of oil contamination.

I did notice a little windscreen misting the other day, but assumed it was condensation from the water ingress I've been getting in the rear battery/underfloor area from the (I presume) vents behind the bumper.
Water-pump was done along with the cam-belt early last year.

So... can anyone advise on classic or well-known coolant loss locations?
 
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audifan said:
Think of the Webasto as a mini boiler. It is diesel powered and when running sounds like a jet engine. It lives in the engine bay against the right wing and if you have it you can not miss it. Curious what the switch on the dash is as the Webasto works automatically but can be turned off by pressing the ECON button. Webastos output directly feeds hot water into the coolant system allowing rapid engine and cabin heat up. If there is an airlock in the cooling pipes around the Webasto that could be part of your problem there is a bleed point on one of the pipes on the Webasto and the other bleed is on the radiator top hose, so worth opening these bleeds on an unpressurised system to see if any trapped air is released before running the car with the cap off at say 2000 rpm for 10 minutes to hopefully release trapped air. If coolant is being blown out while doing this then stop immediately.

View attachment 79198

Webasto heater.



Now the water pump...

Even when the thermostat is closed there is still the need for coolant to flow otherwise the system would burst. So this flow i believe returns to the expansion tank through that little upper hose that comes from the rear of the block. So in theory with the engine running there should be a flow of coolant coming back to the tank. Not saying it should be a torrent but a steady flow.
Water pumps have been known to fail and the plastic impeller fall off the shaft.


BTW if it makes you feel better then go ahead and hit it with a hammer, but I doubt you will fix anything. I await the results of the hammer!!
Click to expand...
Am glad you appreciate my hammer joke Audifan. Will try... TRY... to absorb and assess your instructions tomorrow, when the effects of the rather good bottle of Lidl Veneto Rosso Da Uve Leggermente Appasssite has worn off. All good fun on this car. It hasn't got me down... yet.
 
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audifan said:
Think of the Webasto as a mini boiler. It is diesel powered and when running sounds like a jet engine. It lives in the engine bay against the right wing and if you have it you can not miss it. Curious what the switch on the dash is as the Webasto works automatically but can be turned off by pressing the ECON button. Webastos output directly feeds hot water into the coolant system allowing rapid engine and cabin heat up. If there is an airlock in the cooling pipes around the Webasto that could be part of your problem there is a bleed point on one of the pipes on the Webasto and the other bleed is on the radiator top hose, so worth opening these bleeds on an unpressurised system to see if any trapped air is released before running the car with the cap off at say 2000 rpm for 10 minutes to hopefully release trapped air. If coolant is being blown out while doing this then stop immediately.

View attachment 79198

Webasto heater.



Now the water pump...

Even when the thermostat is closed there is still the need for coolant to flow otherwise the system would burst. So this flow i believe returns to the expansion tank through that little upper hose that comes from the rear of the block. So in theory with the engine running there should be a flow of coolant coming back to the tank. Not saying it should be a torrent but a steady flow.
Water pumps have been known to fail and the plastic impeller fall off the shaft.


BTW if it makes you feel better then go ahead and hit it with a hammer, but I doubt you will fix anything. I await the results of the hammer!!
Click to expand...
I really don't know why the name Webasto didn't ring any bells with me, but as soon as I read your reply... Webasto like Eberspacher make diesel-fueled heaters... Of course!
It also shows also how little time and effort I've spent getting to know this car "under-the-bonnet" because, there it is, tucked-in against the offside wing with its corrugated aluminium exhaust tube. Thing is though... I've never heard a peep out of this thing, regardless of whether the ECON button (what I referred to as switch on dash) is on or off. Both this winter and last winter I gave the ECON button several pokes both before and shortly after starting, to see what difference it made, and it never did a thing, so.... it's possibly goosed or in need of an overhaul.
But, just because it has never fired up in my ownership, could that kind of non-functionality be the cause of an air lock? And if so, why has it only started causing this problem recently.
It's all a bit worrying, because what had been showing as a low level of coolant in the expansion tank is now showing well over max, and that has not dropped either after cooling-off or after a couple of minutes running at 1500rpm. When I unscrewed the cap today between 50 & 100ml flooded out of the overflow vent and the inner part of that tank is now brimming. This means that part of the system is dry. There are only two possible causes of that in my view. One is that the head gasket is leaking exhaust gases into the coolant, but only when hot, and the resultant pressurisation or displacement remains after the system cools. The other is that steam was produced and the expansion caused the tank level to rise... BUT, on cooling that steam condensing should have sucked the level back down again... unless, possibly, that slim hose that connects to the top of the expansion tank has sucked air into the system instead, drawn in via the overflow vent.
Puzzling.
Either way, I'm not happy about driving this car... not even the 4 or 5 miles into town for shopping... until I've got my head around what is going on and what are the potential dangers.

Anyway... I went looking for a "bleed point on one of the pipes of the Webasto" without success. But I did spot something where the 40mm top hose connects to the offside top of the radiator. There's an approx 15mm button sized cap with deep slots in it forming a cross facing directly upwards. I'm reluctant to shove a large flat-bladed screwdriver into it and give it a twist in case it turns out not to be what I thought and it just snaps off.
See photo.

I think it's about time I got myself a workshop manual. Can anyone recommend one?
 

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Put yourself out of your misery about the the head gasket. Consider doing a sniff test. Cheap testing kits on eBay or a garage will presumably have a professional kit. Watch a few YouTube videos.

I doubt the test is 100% reliable but the late respected Tony of A2 Cars ran a sniff test on my FSI for 15 minutes when there was some doubt about the integrity of the head gasket after previous overheating.

Just a thought.

Andy
 
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Andrew said:
Put yourself out of your misery about the the head gasket. Consider doing a sniff test. Cheap testing kits on eBay or a garage will presumably have a professional kit. Watch a few YouTube videos.

I doubt the test is 100% reliable but the late respected Tony of A2 Cars ran a sniff test on my FSI for 15 minutes when there was some doubt about the integrity of the head gasket after previous overheating.

Just a thought.

Andy
Click to expand...
Yes Andy... I think I'll give it a go... they don't cost a fortune.
 
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Pilchard said:
..The other is that steam was produced ..

If steam is being produced, the coolant is achieving boiling point. Stupid question - could your coolant be somewhere under the correct concentration of concentrate - so the boiling point is closer to 100'C than it should be? I don't doubt that it is more likely to be something physical relating to a minor leak in pipework / coolant system itself, but that throwaway clue sounds like a piece of low-hanging fruit (that has probably already been answered earlier in the thread) - any thoughts?

In the one car we have that had a coolant leak issue when purchased, it was the expansion tank lid (I've replaced all three). Yours sounds a bit more involved than this - hope you can resolve the issue soon!
Click to expand...
 
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Pilchard said:
Thanks RAB. Will download that now.
Click to expand...
Christ RAB! That was a mistake. The file size is huge and, it seems, has every single VAG model... which I don't need... and is so complex to download onto my Mac that I don't think I'll live long enough to unravel this Gordian Knot. The vendor/provider seems to have a pretty random set of protocols and processes that only someone with a masters degree in computing... or a 15-year-old kid... will be able to fight their way through. Hit-and-miss guessing how to fix this A2 will be quicker than accessing this file. I've given up. Can't even find out how to get a refund.
 
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Robin... my mention of steam was just a hypothetical scenario.
Concentration is good... a very bright lurid day-glow pink.
I replaced cap last week.
Coolant not leaking, but being forced out of expansion tank overflow... despite level previously noted as low. Weird, but am sure all will be revealed... eventually.
 
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Pilchard said:
Christ RAB! That was a mistake. The file size is huge and, it seems, has every single VAG model... which I don't need... and is so complex to download onto my Mac that I don't think I'll live long enough to unravel this Gordian Knot. The vendor/provider seems to have a pretty random set of protocols and processes that only someone with a masters degree in computing... or a 15-year-old kid... will be able to fight their way through. Hit-and-miss guessing how to fix this A2 will be quicker than accessing this file. I've given up. Can't even find out how to get a refund.
Click to expand...
That's a bit of an exaggeration! I'm no fifteen year-old (unfortunately) and I managed it. Send me some CDs and I'll copy a set for you.

RAB
 
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RAB said:
That's a bit of an exaggeration! I'm no fifteen year-old (unfortunately) and I managed it. Send me some CDs and I'll copy a set for you.

RAB
Click to expand...
That's a very kind offer RAB which, which if after another stab or two I'm still unsuccessful, I'll take you up on. Yes, it was a bit exaggerated... and was not intended as any kind of rebuke to you... more a reflection on my own inadequacies. Since I foolishly allowed my wife complete autocracy over our TV watching more than a decade back, I am no longer able to operate our latest PVR and TV remotes.
 
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audifan said:
Do you hear the radiator cooling fan kicking in?
Click to expand...
I haven't yet got to running it for more than 2 minutes, so... no.
I've been a bit preoccupied getting our motorhome sorted for the upcoming Scottish NC500 in May, but am hopeful to get stuck into the car over the next few days.
You've been very helpful and generous with your time... don't go away. I WILL get back.
 
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OK... so I did the 20 minute test at 2000rpm today... just completed it and am still in the dark. All that seemed to happen is that the dashboard temp gauge rose to slowly to 90 degrees and stayed there, whereas in my entire 14 month ownership... despite giving it a few motorway canings... it has never risen above 70 degrees and generally not even that.

Before I started it I undid the bleed-screw at the rad end of the top hose. Of course nothing happened until I allowed air into the upper system by slowly slackening off the expansion tank cap. I allowed the coolant level in the tank to drop bit by bit til eventually coolant (rather than air) flowed from the bleed point. I locked the bleed screw back in and saw that the level in the expansion tank had dropped significantly. Hard to tell by how much because of the pink staining of the plastic inside the tank, but it was certainly below or at Min... and may even been empty. Having said that, I know the coolant level warning light and alarm work, as they had told me coolant was low a few weeks back. Anyway....
With cap and bleed-screw tight, I cracked it up and set to 2000rpm and had it running for 20-25 minutes. No coolant leaked from anywhere... not even the overflow. The level in the expansion tank never rose above its sub-minimum/empty level. the main top hose started warming while the bottom one stayed cold. The two smaller hoses on the expansion tank began to warm and by the time the main bottom hose had got to the same hottish temp as the top hose the upper/thinner expansion tank hose had got surprisingly hot too, while the lower/larger expansion tank hose remained a detectable number of degrees lower than the others.
In all that time the fan never came on and coolant level never rose. I sat there after switching off for ten minutes and the fan had still not come on.
I left it to cool and gingerly released the expansion cap with no hiss of escaping air and no sudden change in level.

All this has taught me is that the dash gauge WILL go to 90 degrees when made to do so, and that the cooling fan... if it works... needs above 90 degrees before it'll kick in.
I can't understand where the air in the top of the rad came from though... unless it's been there ever since the water pump was replaced in early March 2020, approx 5000 miles ago.
 
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