MK4 GTi Cooling System Corrosion Issues.. Help!!

[tendyfish]

Hello. My 2002 1.8T AUM is having issues with rust in the cooling system. Bought it two years ago, seemed like it had been sitting for a while, with rust deposits in the coolant bottle. I had the system flushed of the old coolant and replaced. Two years down the line, i'm getting the same deposits in the coolant bottle, this time the quantities are higher, recently it started leaking from a metal coolant supply pipe 06A 121 065 AK which had suffered severely corrosion. The pipe was replaced and some flushing was done with water, but still seeing rust deposits. Need help with identifying the source of this rust and thoroughly clean the system before putting some brand new coolant. Was also wondering if products like Shield radiator Flush are any good to try. Thanks

[Howie-WP]

What coolant was used when refilling after the flush?

[PoloB]

Are you using regular tap water or distilled water with coolant?

Distilled water is meant to address the rust issue and therefore a requirement by all manufacturers when dealing with coolant systems

[tendyfish]

What coolant was used when refilling after the flush?

Thank you for quick replies, I used one called Eurol Antifreeze GLX G12+ from Goldwagen mixed with water from those Reverse-Osmosis tanks, they claim its pure water with no minerals nor salts.

[tendyfish]

Are you using regular tap water or distilled water with coolant?

Distilled water is meant to address the rust issue and therefore a requirement by all manufacturers when dealing with coolant systems

Right now i've used Tap water temporarily while i try to clean out the system, will then use distilled when i'm certain all the dirt is out

[MarshallGTi]

Are you using regular tap water or distilled water with coolant?

Distilled water is meant to address the rust issue and therefore a requirement by all manufacturers when dealing with coolant systems

some places the tap water is far from great, and i've seen some places use borehole water. Also, no matter what water you use, if you run plain water for any period of time the inside of the motor will continue to rust, coolant not only stops freezing but also has rust inhibitors and a bunch of other good things.

Easiest option would be a premix 50% coolant, and fill with just that, dont let the workshop dilute it at all. Also use a proper flush not one of the cheapies like Shield, i think LiquiMoly has one. Best would be to flush 2 or 3 times with that, obviously with heater open and thermostat out, and then a flush with distilled water, then fill with the premix coolant.

[VAG Fan]

Reverse osmosis water should be more than good enough.

In my experience and humble opinion, the addition of sufficient coolant (which contains antifreeze, raises the boiling point, lubricates the pump and inhibits rust) is more important than the exact quality of the water. I've used tap water with 30-50% coolant in 5 cars for 30 years now and have not picked up rust problems.

[tendyfish]

Thank you very much guys for all your contributions. I had overlooked the thermostat, so i took it out and ran some STP Radiator Flush a couple of times during the course of the past week , i then ran the flush with tap water until there were no deposits in the coolant bottle and finally drained everything, put back the thermostat and filled her up with some G12 coolant, 50/50 dilution with Reverse osmosis water. Will be monitor the situation hopefully i got everything out. Again, thank you for the tips, they were indeed useful and much appreciated.

PS:**coudnt find Liquimolly flush anywhere near me**

[Rascal69]

Did you drain the block when you flush the cooling system?

[tendyfish]

Did you drain the block when you flush the cooling system?

Not 100% sure how that's done but there was little to no water on the thermostat housing flange when i took it out.

[Rascal69]

There's usually a bolt on the engine block somewhere that you open and the coolant running inside the block will drain out of there... I replaced the thermostat and cooling system on a customers Z4 last week... even after draining and removing the coolant tank, pipes, thermostat.ect , i still had to drain about 1.5-2 litres of water from the engine block before i could fill up with coolant/distilled water mix.

[tendyfish]

There's usually a bolt on the engine block somewhere that you open and the coolant running inside the block will drain out of there... I replaced the thermostat and cooling system on a customers Z4 last week... even after draining and removing the coolant tank, pipes, thermostat.ect , i still had to drain about 1.5-2 litres of water from the engine block before i could fill up with coolant/distilled water mix.

The Haynes must be referencing the older, 058 block 1.8Ts (AEB and ATW) with the external water pump.

On the 06A, I think you just pull the t-stat housing and t-stat to drain the block. It's what I did on my AWP (transverse)

**Got this from one of the VW forums**

Relief!!!!