Club 80-90 Forums

Hey guys,

I’ve marked a line where my coolant level sits (cold engine) but everything I’ve read says it must be brim full.

Slight hiss sound of pressure escaping when I unscrew Daley cap to fill her up as well.

Early warning signs of something?

Cheers




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the header tqnk shouod be full to the brim when cold
the top up tank should be full to the max line when cold

It should hiss once its opened - cooling system runs under pressure.

What happens if you fill it up to the brim like it should be?

[quote="T25Convert"]It should hiss once its opened - cooling system runs under pressure.

What happens if you fill it up to the brim like it should be?[/

To the brim, so no air in it at all?

If I fill it up all the way and go for a good drive, the next morning when it’s cool it will be where is is in the pic.


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The system is very simple....
The headertank ( the one in the engine bay ) should always be full to the brim, and the top up tank ( behind the number plate flap) should be full to the max mark when cold. When the engine is up to normal running temp the coolant expands and is pushed into the top up tank, when the engine cools down the coolant is sucked back into the header tank

So you have a either a doggy cap on the header tank, or a porous or damaged pipe from it to the top up tank , or your top up tank is damaged

Mocki wrote:The system is very simple....
The headertank ( the one in the engine bay ) should always be full to the brim, and the top up tank ( behind the number plate flap) should be full to the max mark when cold. When the engine is up to normal running temp the coolant expands and is pushed into the top up tank, when the engine cools down the coolant is sucked back into the header tank

So you have a either a doggy cap on the header tank, or a porous or damaged pipe from it to the top up tank , or your top up tank is damaged

Hi Mocki, good clear advice as always.

She’s my first van and the coolant system is mind boggling but I think I’m finally getting the hang of it.

On closer inspection I saw the pipe that connects both tanks is a little frayed so I’ll replace it. The cap is 3 months old from brickworks so I’m sure it’s good.




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Spotted a new symptom.

On a short journey once she got to temp, the red light came on but needle was looking normal.

Overflow tank was full and header tank was at MIN mark.

I slowly unscrewed the blue cap to top it up and as I did the the coolant level rose to the brim which meant I couldn’t top it up.

Same thing has happened twice since and I’ve even changed header tank cap. I have 2, both from vwheritage.


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LewisMac wrote:Spotted a new symptom.

On a short journey once she got to temp, the red light came on but needle was looking normal.

Overflow tank was full and header tank was at MIN mark.

I slowly unscrewed the blue cap to top it up and as I did the the coolant level rose to the brim which meant I couldn’t top it up.

Same thing has happened twice since and I’ve even changed header tank cap. I have 2, both from vwheritage.


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That is correct and normal , as you Slowly undo the Darlek cap the pressure is released and the coolant level rises taking back the space the pressure has vacated . It should do that , that is why the top up tank works.

You still have air in the system which compresses more than coolant when under pressure , letting the coolant level drop below the sensor prongs and therefore setting off the low coolant warning .

Mocki wrote:

LewisMac wrote:Spotted a new symptom.

On a short journey once she got to temp, the red light came on but needle was looking normal.

Overflow tank was full and header tank was at MIN mark.

I slowly unscrewed the blue cap to top it up and as I did the the coolant level rose to the brim which meant I couldn’t top it up.

Same thing has happened twice since and I’ve even changed header tank cap. I have 2, both from vwheritage.


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That is correct and normal , as you Slowly undo the Darlek cap the pressure is released and the coolant level rises taking back the space the pressure has vacated . It should do that , that is why the top up tank works.

You still have air in the system which compresses more than coolant when under pressure , letting the coolant level drop below the sensor prongs and therefore setting off the low coolant warning .

Thanks Mocki



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Mocki wrote:

LewisMac wrote:Spotted a new symptom.

On a short journey once she got to temp, the red light came on but needle was looking normal.

Overflow tank was full and header tank was at MIN mark.

I slowly unscrewed the blue cap to top it up and as I did the the coolant level rose to the brim which meant I couldn’t top it up.

Same thing has happened twice since and I’ve even changed header tank cap. I have 2, both from vwheritage.


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That is correct and normal , as you Slowly undo the Darlek cap the pressure is released and the coolant level rises taking back the space the pressure has vacated . It should do that , that is why the top up tank works.

You still have air in the system which compresses more than coolant when under pressure , letting the coolant level drop below the sensor prongs and therefore setting off the low coolant warning .

Tried bleeding the system again then went for s good drive. On return the header tank coolant level was back to almost min.

When I slowly unscrew header tank cap to let air out I see bubbles entering through return pipe.

Is this exhaust gas do you think?

I also spotted a tiny leak from the metal coolant pipe which comes from the water pump and goes to the thermostat. Am I loosing coolant system pressure? Is this related to the bubbles entering the header tank?




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As I think I said about three weeks ago, if you have a leak , the system will not suck back the expanded coolant from the top up tank.
It will just suck air into the system.
Fix the leak ! Then start the process of fault finding all over again ...

Wouldn’t you know it, both header tank caps I bought from vwheritage we’re unable to suck coolant back in. Ordered 2 more from brickworks and they work perfect.

Waiting on coolant pipe coming back in stock then we should be good to go.

Will only buy from brickworks from now on


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