# Mixed coolant in jetta 2.5L



## vwgrl90 (Dec 23, 2009)

So I understand that my jetta requires g12 coolant .. 
while my father was poking around under the hood he "topped off" the coolant.
My coolant light has came on a few times in the past week .. but it was under 0 .. so It would turn off once my car warmed up
Sooo, do I need to do a coolant flush now? I've heard this can cause a sludge from the mixture of g12 and regular
Would a small amount cause harm, or do I only need to flush it if it was a lot?
thanks for the help ...


----------



## kungfoojesus (Jan 10, 2005)

g12 shrinks more than other coolant in extreme cold. this causes the light to come on. top it off with some distilled water and be done with it.
if you have mixed coolant, it may be ok. what type of coolant did your father add? these days, some coolants can be mixed with any other coolant. 
if you did mix the wrong type of coolant in, the expansion bottle will become sludged with gunk. this same gunk coats the pump, radiator, and heater core. this can cause a lot of issues down the road.
if you are not certain what went in, go ahead and flush it to be safe. otherwise you may be stuck with a very expensive bill.
on a side note, these alloy engines require silicate and phosphate free coolant. this preserves the head gasket and seals in the alloy engine that would otherwise corrode thanks to disimilar metals. i've even seen extensive damage to the cylinder head itself from the wrong coolant in a couple vr6 heads.


----------



## spitpilot (Feb 14, 2000)

*Re: (kungfoojesus)*

[QUOTEif you did mix the wrong type of coolant in, the expansion bottle will become sludged with gunk. this same gunk coats the pump, radiator, and heater core. this can cause a lot of issues down the road.
if you are not certain what went in, go ahead and flush it to be safe. otherwise you may be stuck with a very expensive bill.
on a side note, these alloy engines require silicate and phosphate free coolant. this preserves the head gasket and seals in the alloy engine that would otherwise corrode thanks to disimilar metals. i've even seen extensive damage to the cylinder head itself from the wrong coolant in a couple vr6 heads.[/QUOTE]
VW has long reccomended the "silicate/phosphate free coolant"....and those are not the "garden variety" you see on sale @ Walmart etc....It's bad to mix coolants with G12..you may well get gellin and gunk..too high a concentration of any coolant can also cause precipitation..both conditions can clog cooling system passages and lead to engine overheating..next summer anyway...LOL....If more than a few Oz were added, I'd flush and refill with 50/50 mix of a known "silicate phosphate free" coolant (G12, or compatible....or Prestone Long Life)...then only top up with 50/50 mixed coolant...distilled water mix, so you don't increase concentration as you top up! http://****************.com/smile/emthup.gif I've run both G12 and the Long Life for years in VW's with no cooling problems..just don't mix types in a given car.


----------

