Coolant

[AlS3BE]

Hi guys
Got another weird one I’ve noticed.
when the engine is cold like overnight I can see the coolant is more or less at the max line in the reservoir. After a drive and the car is warm the coolant drops to min line but once cooled it goes back up.
move maybe topped up 100ml in the last few months possibly longer. Is this normal behaviour? Can’t remember having a car that’s did this.
coolant looks clean and no mayo in the oil cap.

 

[Wibbly]

Could there be air in the system that's being compressed when the water is hot/under pressure?

 

[AlS3BE]

Could there be air in the system that's being compressed when the water is hot/under pressure?

It’s the factory coolant and not been touched since it left the factory. only noticed the other day when the warning came up on dash. Parked car up and let it cool and it was half way between min and max.
Don’t think it was part of the services I’ve done on the car.
wouldn’t know where to start to get the air out the systems.

 

[JohnM100]

The level does drop when the engine has been used and still hot - it’s the pressurised system.

First thing - check silica bag in coolant reservoir for integrity or buy a new reservoir & cap as the replacements come without the silica bag. World of pain if the silica beads escape. They are there to make to coolant a ‘fill for life’ & not need changing (well, until the poorly designed thermostat fails but that’s another story).

The level has to drop a fair bit for the warning to come on and guidance is to fill up to about an inch above the max level when cold. This also covers the scenario for when the car is on up-ramps and down-ramps in car parks.

If it gets too low it sucks air into the cooling system and that’s a PITA. If it does, then put in more than an inch above the max line and keep an eye on it. After my thermostat & coolant were changed, I had about 500mL of air in the system (or dissolved in the replacement coolant/water mix) which had to work its way out: several trips with stop start traffic so the fan kicked in as well as a spirited blast, and when you know the coolant level is high, set the climate control on max temp while driving to push coolant through the cabin heater matrix. No guarantee it’s all out though.

Any crystals/crustiness around the coolant reservoir cap or wetness around centre-line of the reservoir? Difficult to properly check the thermostat housing for leaks without a ramp or boroscope type gadget.

I carry a 750mL (Evian) bottle with pre-diluted coolant just in case.

 

[AlS3BE]

The level does drop when the engine has been used and still hot - it’s the pressurised system.

First thing - check silica bag in coolant reservoir for integrity or buy a new reservoir & cap as the replacements come without the silica bag. World of pain if the silica beads escape. They are there to make to coolant a ‘fill for life’ & not need changing (well, until the poorly designed thermostat fails but that’s another story).

The level has to drop a fair bit for the warning to come on and guidance is to fill up to about an inch above the max level when cold. This also covers the scenario for when the car is on up-ramps and down-ramps in car parks.

If it gets too low it sucks air into the cooling system and that’s a PITA. If it does, then put in more than an inch above the max line and keep an eye on it. After my thermostat & coolant were changed, I had about 500mL of air in the system (or dissolved in the replacement coolant/water mix) which had to work its way out: several trips with stop start traffic so the fan kicked in as well as a spirited blast, and when you know the coolant level is high, set the climate control on max temp while driving to push coolant through the cabin heater matrix. No guarantee it’s all out though.

Any crystals/crustiness around the coolant reservoir cap or wetness around centre-line of the reservoir? Difficult to properly check the thermostat housing for leaks without a ramp or boroscope type gadget.

I carry a 750mL (Evian) bottle with pre-diluted coolant just in case.

silica bag is good and intact.
cap is dry
No crystallisation leaks anywhere that I can see but don’t have a clue where thermostat and water pump is.
just bought a ready mixed bottle of g13 coolant and keeping it in the car just in case. Will keep an eye on it.
cheers for the input.

 

[JohnM100]

Thermostat location: between engine and radiator - right of centre around where the air intake comes out towards the air box but lower on engine.

 

[AlS3BE]

Just had a nosey after a drive and don’t know if I’m imagining it but the water/expansion bottle is hissing. Can’t see anything coming out though. Could it be a faulty cap?

 

[JohnM100]

Possible, though it vents for excessive pressure - hence my Q about crustiness, also why when replacing the reservoir, also replace the cap.

 

[AlS3BE]

Well think I found the leak. It’s at the back of coolant bottle where the bracket to the car is. Only dribbles when I’m parked on a steep hill.
anyone got the part number for new bottle and cap?

 

[JohnM100]

I am planning to change the one in my SB this coming week. I must have ‘put it somewhere safe’ but when I find it I’ll let you know the part number.

Can’t remember - is yours SB or saloon?

 

[AlS3BE]

I am planning to change the one in my SB this coming week. I must have ‘put it somewhere safe’ but when I find it I’ll let you know the part number.

Can’t remember - is yours SB or saloon?

Sportback

 

[ahtcap]

Starting point
5Q0 121 407?

 

[JohnM100]

Ahtcap - good shout!

Found the receipt (but sadly not the reservoir itself).

A 5Q0 121 407 M - is the one without the silica bag. £28.50 inc VAT.

Got a turkey baster as well to extract coolant from the existing tank.

Don’t have the cap part number - sorry.

 

[AlS3BE]

Ahtcap - good shout!

Found the receipt (but sadly not the reservoir itself).

A 5Q0 121 407 M - is the one without the silica bag. £28.50 inc VAT.

Got a turkey baster as well to extract coolant from the existing tank.

Don’t have the cap part number - sorry.

so revision M is without the tea bag. That’s the bit I wasn’t sure about.
Will have a look at my cap tomorrow and post the number up.

 

[AlS3BE]

2Q0 121 321 cap part number

 

[AlS3BE]

Here’s another quick question.
the coolant cap/bottle says use g13 coolant or something like that.
what’s the difference between g13, g30,g40?
Can they be mixed without any detrimental effects?