Anyone had this problem of coolant pressurising and dumping out of the coolant cap every few hundred miles?

 

Changed water pump and cap also

Dumping out of the coolant cap? Can you clarify what you mean here? If the cap is correctly screwed on it shouldn't be able to escape from there.

The cap acts as a pressure relief valve

Doesn't sound good. I would be doing a block test and checking for exhaust gases entering coolant

Any other symptoms? It could be as simple as a problem with the cap or header tank.

Pressurising coolant used to be a classic symptom of head gasket failure, needs checking ASAP

No other symptoms, car doesnt overheat etc

 

Cap has been replaced but doesnt seem to happen as often after replacing it tho

Have you found out what's wrong?

 

Have you found out what's wrong?

Mines also doing the same after I've had a new genuine water pump n timing belt fitted! Never did it before I had the work done! 

 

On 14/05/2019 at 18:46, TaxiB said:

Have you found out what's wrong?

Mines also doing the same after I've had a new genuine water pump n timing belt fitted! Never did it before I had the work done! 

 

 

No still trying to find out what's going on. It only happens after a good few hundred miles so surely if it was something serious it would happin far more regular??

 

 

Water pump issue? Just wondering as they stay closed until warmed up

Water pump was changed couple of months ago

Just wondering if they got something wrong on it, or was the problem there before that?

Problem was there before that. At a loss now

 

Been told heater matrix slightly blocked to cause the issue too

Sorry - so what actually is happening, read the thread a few times but don't understand

On 26/05/2019 at 07:48, ScoutCJB said:

Sorry - so what actually is happening, read the thread a few times but don't understand

 

The problem only happens every few hundred miles.

 

Drive the car

 

Park up

 

Come back to the car, start up and low coolant light is on.

 

Lift bonnet and you can see that coolant has come out of the pressure relief cap.

 

Refill and as I say wont happin for another good few hundred miles.

 

Temperture gauge never goes above 90°

 

Pressure test and new pump has been fitted.

 

 

Edited 27 May, 20197 yr by Steveyboy

I have this issue and have just had EGR cooler replaced (£990!) but not solved it...

 

Once discovering this  expensive repair didn’t work, I tried some controlled conditions to test when the pressurisation of coolant system happens... I suspect it is a head gasket issue leaking combustion gas into coolant system, but I’m no mechanic!!

 

Control test - drive under minimum engine load:

I drove 400 miles (4x 100mile) on motor way not exceeding 2,000 rpm and the symptoms did not show...

 

Control test - drive under heavier engine load:

I then drove 50 miles putting engine under more load - accelerating up to 4,000 rpm through gears when needed and cruising in 4th to keep engine load a bit higher.

 

This then replicated the symptom of pressurised coolant expansion tank. I allowed to cool overnight and there was still pressure in the system and the expansion tank completely empty.

 

no signs of external leak and no signs of coolant contamination in engine oil.

 

only done 87,500 miles, mostly motorway cruising.

 

Absolutely gutted at the moment...

 

Anyone with ideas or knowledge of a good VAG mechanic in Hampshire would be greatly appreciated as I need the car to live for another 18mths!

Just now, bigbluevRS said:

I have this issue and have just had EGR cooler replaced (£990!) but not solved it...

 

Once discovering this  expensive repair didn’t work, I tried some controlled conditions to test when the pressurisation of coolant system happens... I suspect it is a head gasket issue leaking combustion gas into coolant system, but I’m no mechanic!!

 

Control test - drive under minimum engine load:

I drove 400 miles (4x 100mile) on motor way not exceeding 2,000 rpm and the symptoms did not show...

 

Control test - drive under heavier engine load:

I then drove 50 miles putting engine under more load - accelerating up to 4,000 rpm through gears when needed and cruising in 4th to keep engine load a bit higher.

 

This then replicated the symptom of pressurised coolant expansion tank. I allowed to cool overnight and there was still pressure in the system and the expansion tank completely empty.

 

no signs of external leak and no signs of coolant contamination in engine oil.

 

only done 87,500 miles, mostly motorway cruising.

 

Absolutely gutted at the moment...

 

Anyone with ideas or knowledge of a good VAG mechanic in Hampshire would be greatly appreciated as I need the car to live for another 18mths!

(She’s a ‘63 Derv VRS)

Just a thought have your heaters been working when on warm ? When you guys filled it will coolant did you leave the cap off to allow any air trapped in the system to escape, I have only ever know this happen on two applications. One was a blow head gasket, but that had oil in the coolant also and the other was air expanding in the expansion from unbled coolant system.

On 31/05/2019 at 23:24, Ash007ks said:

Just a thought have your heaters been working when on warm ? When you guys filled it will coolant did you leave the cap off to allow any air trapped in the system to escape, I have only ever know this happen on two applications. One was a blow head gasket, but that had oil in the coolant also and the other was air expanding in the expansion from unbled coolant system.

 

Yea the heater is warm when at hi setting but not hot! 

Is there a procedure to follow now when the system is filled to remove any trapped air?

I start with the engine off, fill to the required height and then have someone turn the engine on with the heater on fully hot and the fan off. It should then purge any air out of the system. It does sound like that's your issue.

 

You will notice the coolant level dropping and see air coming out. Just keep it topped up.

Edited 3 June, 20197 yr by Ash007ks

JKM in Portsmouth have a good reputation when it comes to VAG Servicing and Maintenance, I've used them on previous cars and always been happy with the work carried out. http://www.jkm.org.uk/

4 hours ago, Gti Jazz Blue said:

JKM in Portsmouth have a good reputation when it comes to VAG Servicing and Maintenance, I've used them on previous cars and always been happy with the work carried out. http://www.jkm.org.uk/

Driving from Yorkshire to Portsmouth should get rid of any air trapped in the system🙂

2 minutes ago, ords said:

Driving from Yorkshire to Portsmouth should get rid of any air trapped in the system🙂

LOL - sorry that was aimed at bigblueVRS who is in Hampshire 🤣

On 04/06/2019 at 15:21, Gti Jazz Blue said:

LOL - sorry that was aimed at bigblueVRS who is in Hampshire 🤣

Cheers - JKM were an option - its being taken in this morning for Cylinder head rebuild.

 

I’ll let you know how I get on!

 

🚙💷💨💷💨