Coolant "consumption"

[jimbof]

Since last having the water pump done (40,000 miles ago, non-genuine metal impeller unit) my coolant level (proper G12 fluid) has dropped from bang on in the middle of MIN-MAX to MIN.  Not sure what that represents in actual amount of coolant - but I guess not much.

 

Is this the kind of amount that should just be topped up and put down to "that's life" - or is it something to worry about and try and track down?

Also, for this kind of amount, could I just buy a bottle of G12 and put it in neat to refill to the middle of MIN-MAX - or does it always have to be diluted?

 

I've never done anything around the water on a car before, so please forgive my (possibly dumb) questions.

[dieselV6]

First of all, always check coolant level when engine is hot, the level is lower when it is cold as water shrinks faster than engine block.

 

This small amount can safely be topped up with neat G12/G12+/G12++. In fact, I prefer to use 50% G12 to 50% water overall solution (higher than factory 35% - 40% G12 fill) on my cars, as this gives headroom for an unexpected top-up on the road with water (even 2l water will still keep G12 above 35% if you start from 50% G12).

 

Also, if this little coolant is lost over a year or so, at least on a V6 TDI it might mean that it is time to replace coolant bottle. It is placed too close to exhaust on a V6 (note 1.9 placement might be different) and the plastic gets tired after a few years. Replacing coolant cap did not fix the very slow coolant loss on my Superb, so I replaced my coolant bottle ~2 years ago and glued aluminium tape underneath the bottle to reflect some heat from the exhaust. Never had coolant loss since. HTH

[Jigger72]

First of all, always check coolant level when engine is hot, the level is lower when it is cold as water shrinks faster than engine block.

 

This small amount can safely be topped up with neat G12/G12+/G12++. In fact, I prefer to use 50% G12 to 50% water overall solution (higher than factory 35% - 40% G12 fill) on my cars, as this gives headroom for an unexpected top-up on the road with water (even 2l water will still keep G12 above 35% if you start from 50% G12).

 

Also, if this little coolant is lost over a year or so, at least on a V6 TDI it might mean that it is time to replace coolant bottle. It is placed too close to exhaust on a V6 (note 1.9 placement might be different) and the plastic gets tired after a few years. Replacing coolant cap did not fix the very slow coolant loss on my Superb, so I replaced my coolant bottle ~2 years ago and glued aluminium tape underneath the bottle to reflect some heat from the exhaust. Never had coolant loss since. HTH

 

I always thought you were supposed to check/top up coolant when cold? You live and learn.

 

I've been having the same problem on my 1.9TDI PD. It had two separate pressure tests early this year, and the emissions test, and absolutely nothing wrong came back. The oil is fine and there's nothing else untoward. It's a mystery.

 

I replaced the cap recently but still getting slight loss. Maybe I should try a new tank?

[dieselV6]

Checking when hot makes sense as otherwise manufacturer cannot predict if you are e.g. checking the level at -20degC outside, but they do know coolant will be about 90degC when hot. The difference is not large, I'd say half the max-min distance over 10degC - 90degC. But nevertheless the "max" marking is for hot coolant.

 

Topping up coolant when hot is fine so long that you open the cap slowly, allowing for the system to de-pressurize. If your coolant looks very heavily pressurised after e.g. a motorway run (e.g. bottle level is well below min prior to opening cap, and shoots up to max after opening cap), the engine might be on it's way to a new head gasket. 

 

@Jigger72, I have just glanced at a 1.9TDI Passat engine bay photo and it looks that exhaust to coolant tank proximity is V6 engine specific. I'd inspect for hose leaks, or radiator leak or water pump leak, any leaks can be identified by telltale coolant residue.  If this does not show the problem, I'd get a new tank as it is relatively cheap and easy to fit. 

[jimbof]

I'm only a few mm over the minimum level when hot.  So definitely in need of a little top-up, will go to the dealership and get a bottle of G13 tomorrow.  Be interesting to see how long it takes to drop again after refill.

 

Out of interest, what is the mechanism for it leaving via the coolant bottle?  Vapour coming out of a leaking cap?  Hose connections?  Plastic seam?

 

I notice that both my cap and the side of my tank have some minor water marks:

[dieselV6]

Normally coolant goes through the cap to outer hole and under the tank, so any marks on the side of the tank would likely be a result of spills while topping up, unless the cap is faulty or the bottle is damaged (seam failure?), or some hose next to the bottle sprang a leak.

 

I'd clean all marks up, including the cap and bottle threads and outside, and see where new marks appear, if any.

 

To be honest, I'm not sure how exactly the coolant tank failed on mine, ie evaporation or leak, all I know is that replacing the cap did not fix it, but replacing the tank+cap fixed the leak. Hoses all round were fine. But as I had said, heat related fatigue might be specific to the V6 as the coolant tank sits much closer to the exhaust downpipe.

[jimbof]

That's what I plan to do.  I'm tempted to get the new tank anyhow as this one is a pig to read now due to yellowing of the plastic, but in the interest of not spending any more than I have to now I think I'll leave it pending result of the test.   Picked up the G13 so will be topping up a little later.

[jimbof]

Took around 250ml to bring it up to level.  Note to self - 136K miles...  Briskoda, you have just become my indelible notepad  

Be interesting to see how long it takes to go down.

 

Does anyone know if all G13 is purple, or is some still red?  The reason I ask is the new stuff I got is definitely purple.  The stuff in the car (which was supposedly G13 when the garage filled it after water pump change) definitely looks more red-ish than purple.  I guess at best I have some kind of generic G13 clone...

[iob]

Starting with G12+, the stuff is purple and backwards compatible with G12 as well as miscible with it. Maybe they had some G12 left over and they used that after the pump change...

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[jimbof]

I guess that even though it says "G13" on the invoice, it is actually something more like "Quantum Long Life Red Coolant" - VW "house brand".  Quantum don't do a purple one.

[iob]

I used only HEPU G12 for refill/change (red) - from spare parts dealers, but I know that from the main stealer you can get only the purple ones, OEM (>G12+). Other brands didn't try/wasn't interested...

[oh_superb]

I have only had to top up once in 5 years, that's when I had the whole system drained and filled with fresh G12, and it's been in there since, with only around 300ml distilled water added in about 18 months ago.

The plastic must develop a bit of porosity over time, and it seeps out.

[jimbof]

So I've lost about another 250ml over 4,000 miles or so. 

 

When I took the car to have the suspension done the mechanic had a look - he could see some evidence of it being released by the cap, and did a gas test which indicated no head gasket failure.  He suggested I change the expansion vessel cap and see how that goes.

 

I changed the cap, and noticed that since changing it some of the marks have come back. Today I drove mostly sedately and nothing appeared to go amiss; checked under the hood.  Gave it "some beans" and got a couple of drips which have definitely come out of the overflow (I can feel the overflow port is wet, and see the drips below).

 

So the questions are:

1) if the drips are coming out of the overflow, as opposed to some other place on the expansion vessel, that pretty much rules out the expansion vessel, unless it is the expansion vessel to cap seal which has somehow aged (but the major component of that - the sealing o-ring - is renewed by changing the cap)

2) Can the head gasket be gone yet still pass a gas test?

3) Or could I be looking at something even smellier, like a cracked head?

 

Thanks!

[dieselV6]

So the questions are:

1) if the drips are coming out of the overflow, as opposed to some other place on the expansion vessel, that pretty much rules out the expansion vessel, unless it is the expansion vessel to cap seal which has somehow aged (but the major component of that - the sealing o-ring - is renewed by changing the cap)

2) Can the head gasket be gone yet still pass a gas test?

3) Or could I be looking at something even smellier, like a cracked head?

 

 

1) could still be the vessel, it's cheap to replace and best point to start (replacement complete with cap). However, given that it is a 1.9TDI, my bet is on 2)

 

2) yes, an overheated head gasket will slowly deteriorate and leak exhaust under high engine load. Happened to me on 1.9TDI Octy, after TB job and coolant not refilled correctly with airlock in the engine head. Ended up replacing the gasket (and another TB job) a year later.

 

3) possibly, but more likely it is 2) as head gasket leaks are quite common on old 1.9 TDIs.

[jimbof]

In your case could you see the coolant leak from the overflow point, or was it the case that it was leaking and replacing it just fixed it? I am tempted to change it just to be able to see through it properly, but I hate doing jobs for the sake of it!

[dieselV6]

On the Octavia 1.9TDI (with the problem gasket), the leak was entirely through overflow.

On the Superb 2.5TDI (just expansion tank replaced, fixing the problem), both overflow and cap threads had coolant residue on them.

In any case, that tank is far cheaper than the gasket job, ~20 times?

[jimbof]

Yeah, I will probably do it anyway. Already bought a new Gates cap a couple of weeks ago. Debating whether to go genuine on the expansion tank or pick one up at GSF for £14.

[jimbof]

Also noticed on climatronic diagnostics mode that my coolant never goes above 83 - I guess this is an overly eager thermostat?

[iob]

I don't think that is cause to worry, what you get from the diagnostics mode of the climatronic is the accurate value sent to the ECU, compared to the more relaxed instrument cluster reading...

 

Although you always have a 90 degC reading onboard when engine is warm, that is not the exact temperature measured by the G62 sensor...

[Gaz]

Debating whether to go genuine on the expansion tank or pick one up at GSF for £14.

 

I wouldn't have a problem going with GSF.  Can't see an expansion tank being that OEM critical (awaits being shot down in flames for having the audacity to think it, let alone say it  ).

 

Fingers crossed it's not you head gasket Jim, but if it is, at least you've probably caught it nice and early.

 

Gaz

[jimbof]

My OCD wouldn't let me fit the pattern part tank picked up from GSF - it had a lot of loose-ish plastic swarf inside the various openings, and the glueing together of the two halves was all over the place. Interestingly it had a metal ferule in the output port - which the genuine one doesn't have - indicating perhaps a lower quality plastic.

I picked up genuine from TPS - the cap and tank came to £40 inc VAT.

Fitted this afternoon - sucked most of the coolant out of the old tank with a siphon, struggled with the hose clips a bit (particularly the top one) and then drained the last drops into a small container. Topped it back up and back running. Gave the old girl a wash too just so that she knows I still love her...

Be interesting to see how this goes. At least it will be much easier to watch my coolant level dropping, the old one was pretty opaque...!

[jimbof]

Well, took it out today and gave it a bit of welly. Not seen anything coming out of the overflow yet. Time will tell.

Glamour shot:

[jimbof]

No consumption so far it seems - nothing being dumped out of the overflow - 1000 miles covered so far.  Will give it a month more, but so far the new expansion tank + cap seems to be good.

[jimbof]

Well, the tank and cap didn't actually fix it, still losing a little between services.

Looks like I found where it is going.  There is a plug on the waterpump which has been leaking and making a right old mess (see the collection of crust at the bottom of the belt cover)

 

The eagle-eyed out there might also notice the state of my crank bolt.  Some @%^£@ left the dust cap off the damper pulley, and as a consequence the inside of the pulley is nice and rusty, too, had a little bit of fun getting the pulley bolts out.

 

Not got the car back together yet - thinking about whether I should be getting a new damper pulley or not.

[Rabarbaras]

Hey is it a problem if I mix G12 Coolant with G13?