On 11/11/2024 at 19:06, T07 said:

If your heater matrix is blocked the engine won’t overheat. There are three separate coolant circuits on the engine, engine, egr cooler and charge cooler. If the matrix is blocked when doing a regen the egr cooler gets substantially hotter and it can’t then pass through the full circuit to be cooled as the matrix is blocked so bypasses it back to the tank where it can boil the coolant out of the thank. The engine temperature sensor is on the block so will still read a steady 90

That's very interesting. Boiling coolant out - how does it get out, if the system is sealed?

 

Couple of other observations recently - the coolant tank cap is getting increasingly hard to turn and remove by hand, it is really stiff, especially when cold.

 

I did take the car on a long run last week - around 400km and it only used about 1/4" of coolant - bit odd when most days it needs topped up after less than 100km....

?

Are you filling to MAX,  that is not needed, the system can set it's own level, between MIN & MAX.  There is no FILL TO THIS LEVEL.

If it drops from Max then mark that, this is after it puts some out via the overflow.  Sealed system but with an overflow / pressure / liquid release.

It is the Coolant / & pressureished system that changes the boiling point. 

On 18/11/2024 at 16:21, Ootohere said:

?

Are you filling to MAX,  that is not needed, the system can set it's own level, between MIN & MAX.  There is no FILL TO THIS LEVEL.

If it drops from Max then mark that, this is after it puts some out via the overflow.  Sealed system but with an overflow / pressure / liquid release.

It is the Coolant / & pressureished system that changes the boiling point. 

Yes I'm filling almost all the way to the top, a mechanic mate said there's no harm in doing this but I can fill it less if needed.

18 minutes ago, chelon said:

Yes I'm filling almost all the way to the top, a mechanic mate said there's no harm in doing this but I can fill it less if needed.

You say are filling 'almost all the way to the top' is this correct? if so there will be insufficient air space in the EV - fluids are effectively incompressible, so coolant will be ejected via the relief valve as it heats up and expands. 

Edited 19 November, 20241 yr by Warrior193
added information

On 19/11/2024 at 21:52, Warrior193 said:

You say are filling 'almost all the way to the top' is this correct? if so there will be insufficient air space in the EV - fluids are effectively incompressible, so coolant will be ejected via the relief valve as it heats up and expands. 

Yes I was doing that initially but not any more, thanks for the tip.

 

@chelon Is your coolant level relatively steady now that you are not filling above max. line? NB. there will be some changes in level, depending on whether checked hot or cold, but should remain in vicinity of markers if no losses from system. 

NB. don't remove EV cap when checking coolant level. 

Edited 25 November, 20241 yr by Warrior193
added information

On 25/11/2024 at 12:23, Warrior193 said:

@chelon Is your coolant level relatively steady now that you are not filling above max. line? NB. there will be some changes in level, depending on whether checked hot or cold, but should remain in vicinity of markers if no losses from system. 

NB. don't remove EV cap when checking coolant level. 

 

I've only been doing it a few days so I'll monitor going forward - presume the EV cap is the filler cap? Can that cause probs?

1 hour ago, chelon said:

 

I've only been doing it a few days so I'll monitor going forward - presume the EV cap is the filler cap? Can that cause probs?

Yes filler cap. Loosening the cap, particularly when hot, releases the normal pressure build up in the coolant system - which can cause the coolant to rise, giving a misleading level. 

Even when cold, loosening the cap almost always results in a little hiss and release of pressure - my mechanic mate says this means the head gasket is on the way out as with a cold engine there should be no escape of pressure. I'm hoping this isn't the case and he's wrong - anyone know?

It is true that faulty head gasket can let combustion gases enter the coolant circulation from the cylinders, causing the system to be pressurised even when cold.

 

However, are you sure the hissing is not air flowing into the tank because of vacuum in the system? In closed system there shud be vacuum if closed warm and opened cold. Or if you have a leak and coolant leaks out from the system ie. when it is warm and pressurised.

 

Theoretically, if it is vacuum, the coolant level shud drop a little when opened and if it is pressurised the coolant level shud rise when opened. However, the change in coolant level is probably undetectable to naked eye.

 

Edited 28 November, 20241 yr by RattleWagon

Fwiw, I have a blocked heater matrix. I've lived with it for a while now (3 years😆) but my garage is replacing it next week for ~£600 including two coolant flushes. They will vacuum fill and use their  diagnostics to operate the coolant circuits. (They have Odis VW main dealer system). 

 

I have a slight level loss in the expansion tank over many months. Removal of the expansion tank cap when it's cold  it makes a slight hiss. It's under a little vacuum as mentioned which is normal. 

1 hour ago, paulski said:

Fwiw, I have a blocked heater matrix. I've lived with it for a while now (3 years😆) but my garage is replacing it next week for ~£600 including two coolant flushes. They will vacuum fill and use their  diagnostics to operate the coolant circuits. (They have Odis VW main dealer system). 

 

I have a slight level loss in the expansion tank over many months. Removal of the expansion tank cap when it's cold  it makes a slight hiss. It's under a little vacuum as mentioned which is normal. 

This sounds very similar to mine although mine is using a lot more coolant. I spoke to a mechanic he says he's very experienced in Skoda and will resolve it but he's not available for a while.

 

Anyone know if it'll do any harm just driving the car around like this and topping up coolant level every few days with anti freeze?

Well it really depends where the coolant goes. I bet it is not good for the emission equipment (DPF) if it leaks into the engine or exhaust (charge cooler, egr cooler..)

 

Edit:

Btw, just to make sure since I didn't see this mentioned, does the engine oil look like oil and not coffee with milk?

Edited 29 November, 20241 yr by RattleWagon

At least in older cars it was possible to open radiator cap or expansion tank cap when engine is running and see gas introduced into the system if head gasket was faulty, check youtube.

 

Not sure if this works on these cars. Only try when coolant is cold or get boiled hands.

4 hours ago, RattleWagon said:

Well it really depends where the coolant goes. I bet it is not good for the emission equipment (DPF) if it leaks into the engine or exhaust (charge cooler, egr cooler..)

 

Edit:

Btw, just to make sure since I didn't see this mentioned, does the engine oil look like oil and not coffee with milk?

Checked it once and it looks like oil - but the coolant sometimes has little brown flecks in it

If head gasket problems are suspected, best advice as a first check is to test coolant with a combustion products test kit.