Changing to G12 plus, best way to flush system.

[rhencullen1989]

Hi, i am about to replace the thermostat on my 1996 A4 1.8T, the coolant in there at the moment is a blue colour and i recently topped it up with normal ethylene glycol antifreeze. Having looked into it a bit, it seems that mixing certain antifreezes together will create a gel like substance and ruin your engine! even heard of it turning gaskets to mush!! Anyway, i have bought some Audi G12 PLUS coolant additive which i intend to mix 50/50 with de-ionised water. It says on the bottle that it is miscibile with G11 and G12, in otherwords it will mix ok with them, but what about normal ethelyne glycol antifreeze. How do i flush my system to make sure ALL the old stuff is out without removing pipes and radiators etc. I thought this job would take 30 mins!!! Any flushing experts out there?.........

[Crasher]

Drain it out (there is a tap on the rad lower hose fitting), remove all the hoses you can and flush all the hoses, the block, rad etc through with clean water from a hose, paying particular attention to the heater matrix. Fill it up with clean water and run the engine, allow it to cool and drain again and it should be reasonably clean but it would not hurt to pull some hoses and run it through with clean water again. The blue coolant you have is incorrect and any remaining G11 would mix badly with G12 but G12+ is more tolerant to G11 types.

[rhencullen1989]

Done the job today, took a long time, but my 3 year old daughter liked the "test drives" every half hour or so, i flushed the system through with the garden hose then connected everything up without the thermostat and filled with tap water, drove the car for 5 miles or so, then dropped the bottom hose, repeated 4 times until water was clean. New thermostat fitted, filled with 50/50 G12 PLUS and de-ionised water, temp now a steady 90 degrees and the cabin is nice and warm now too!! one thing, the 2 bolts that hold the thermostat housing on are a pain in the a.. to get at, a crows foot 10mm ring spanner seemed the best alternative. I wonder what a main ******* would have charged for a relatively simple but time consuming (for me) job of replacing the thermostat?.................Oh i nearly forgot, cheers Crasher!!

[Crasher]

I didn't suggest you pulling the stat (it is the best way to do the job) as they are such a pain to get at, but well done for persevering with it. I was doing the same job on a Golf 2 16v between 10 and 11 this morning and it was very cold, especially when the pressure wash splashed back at me with freezing cold water.

[rhencullen1989]

Hi crasher, i had to pull the stat out as that was my reason for doing the job in the first place! the gauge in the car never went over 60 deg. unless cought in traffic. New stat in and running at 90 deg. most of time, job done. Yes it was cold yesterday, having cold water running down my arm every time i pulled the bottom hose was not funny! at least i was in the relative protection of my garage.

[wackyracer]

I have to change my themo too, for the same reason. having just found where it is i am seriously wondering whether or not to have it done by a garage! It looks a complete pig to get to. Also heard that the bolts can be trashed after removal!
Would welcome estimated cost of garage job!

[Crasher]

Would welcome estimated cost of garage job!

I would need to know the cars details to guesstimate what you would pay for that so PM me the chassis or reg number.