Coolant spray on header tank

A

andrewparkeruk

A2OC Donor
49354

Have recently been having problems with the engine coolant system overheating.

26-Sep-2018: dashboard warning; added 300ml to header tank (ironically the day before ...)

27-Sep-2018: camshaft drive belt / coolant pump replaced (scheduled service item)

27-Sep-2018: thermostat replaced as dashboard temperature display had become slow to reach 90°C with aircon working

11-Feb-2019: dashboard warning, along with braking system dashboard warning (after short, local trip). Can’t recall header tank level; didn’t top up as car recovered by truck due to braking system failure

12-Feb-2019: header tank and cap replaced

26-Feb-2019: dashboard warning; header tank had lost 500ml (after an hour on motorway with aircon off and OpenSky open, 22°C outside temp; waiting in traffic queue close to home). Due to new header tank, easy to see sprayed pink coolant apparently from safety valve

27-Feb-2019: sensor (at bottom of radiator) replaced. Service garage reports radiator fan is now working with aircon off, but only at lower speed. Service garage not clear communicating whether they higher speed isn’t working; or they were unable to recreate situation where higher speed would operate. I can check with them tomorrow

03-Mar-2019: routine check; some pink coolant spray visible in header tank. Cleaned header tank. One hour fifteen minute trip on motorway, then returning journey later (aircon on, set at 21°C; 10°C outside temperature). Checked header tank, more pink coolant spray visible, please see photo

I wonder if anyone has any ideas?

Thank you, Andrew
Edit: deleted misleading second photo following @audifan's note in post #2
 
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Replace the expansion tank cap, or just its seals if you can get them, firstly. Second carefully check the seam on the expansion tank as they can fail there. You could of coarse just replace the expansion tank and cap. The second picture looks more like the normal condensation that grows on the a/c refrigerant pipes - unless it is coolant, but can not see any colour to it. Run the car after replacing the cap or cap seals. If it is leaking out of the small square slot in the tank then you could have further problems. As I think I can see a trace just below the cap my money is on the cap.
 
What sort of miles has engine done
Why was header tank replaced

Blocked radiator ? Can u feel heat in hoses to and from radiator
Check radiator with infra red thermometer if available

Or if pressurising immediatly when cold head gasket
 
Thank you both.

Header tank and cap replaced 12–Feb-2019. If I recall correctly, the garage said the coolant system was losing pressure but no leaks were evident. They suggested replacing the header tank and cap to see if this may be the cause.

Engine/car has 157,000 miles.

I will try to check the hoses tomorrow (I don’t use the car every day)
 
Even though it is a new tank and cap there is still a chance they are faulty. Do you have the old parts? You could fit the old cap and see if things improve.
 
@audifan I agree: the first photo does show a drop directly beneath the cap of the header tank. I hadn’t spotted that on the car, only in the photo.
I will suspect the seal and try to speak with the service garage tomorrow. I expect the old header tank and cap are long gone.

Thanks again, Andrew
 
Oh dear.. I suspect the headgasket has failed! had exactly the same symptoms on mine last year. Get the garage to perform a test for exhaust gasses in the coolant. I bought a testing kit online, which confirmed this. Unfortunately expect around £1000 for a garage to replace the headgasket.
I too went through other possibilities first, like the expansion tank failing, cap not sealing etc..
 
My garage is convinced the fault is with the radiator fan control unit. They have tested it and it does run at the lower speed, but they weren’t able to get it to run at the higher speed. I don’t know how they tested this: it may simply have been by getting the engine to hot and switching off the aircon.

TPS have quoted £183.19 + VAT for 8Z0 959 501 Radiator Fan Control Unit.

I have then found this item
https://www.a2oc.net/community/index.php?threads/radiator-fan-not-running.25315/#post-199930
To recap then, going to the fan controller 6 pin plug on pin 1 is 12v when the engine is running, pin 3 is then grounded by either the aircon control or engine thermostat, this sets the fan to run at stage 1. Then pin 5 is grounded as per pin 3 / stage 1 but at a higher aircon demand or higher engine temperature this sets the fan speed to stage 2. Thus if you put 12v to pin 1 and ground pin 3/5 the fan should run, proving the controller.
There is is a constant 12 v supply to the fan controller which is fed from a large fuse above the normal fuse box (requires lower dash removed to access)

The fan controller then takes the 12 v feed and sets the output to the fan at either none, stage 1 or stage 2 dependant on the input

Using vcds you can test the fan output but if your aircon pressure is low this will not work, thus the test fire is done through the hvac system and not the engine or instruments which I thought strange.
Click to expand...

Does anyone near Manchester M20 have VCDS, and the time to try the procedure described in that last paragraph?

Thank you, Andrew
 
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Have you tried running the car until fully warmed up. With air con the fan always runs at low speed, it is only when the temp sensor detects about 97 does it switch to high speed. So gauge on 90 fan still low speed as the airflow over the radiator keeps it below the cut in point. If in slow traffic and hot that is when high speed kicks in. Why not fit a second hand fan controller unit and see if it clears the issue. The radiator is also a possibility if it is partially blocked, is there an even temperature over the whole of the radiator when running at 90? If possible use an infra red thermometer to check to avoid burns to yourself.
 
Thank you @audifan, your post is very clear and informative. Unfortunately I don't do my own repairs.
For what is worth, the radiator was replaced in 2011. The garage I have used since buying the A2 in 2009 is happy to fit a second hand radiator fan control unit if I source one. I would simply like to try the VCDS test first if I can find someone with the time to assist.
Cheers, Andrew
 
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