Re: '87 5KCSTQW Coolant Question

[Lowell Lamb <lamb@macs.oandm.uiuc.edu>]

> 
> I was just reviewing some records I got with my '87 5KCSTQW a few months 
> ago. Apparently, a dealer had recently flushed and replaced the coolant 
> with the phosphate-free coolant as per Audi.
> 
> In some work done since I've owned it, I realized that one mechanic 
> topped it up with regular Prestone and and his ok so did I when I changed 
> the radiator thermoswitch.
> 
> Is there any grave danger to the cooling system in having the mix. I know 
> it is not recommended but I was wondering if anyone out there has any 
> first-hand experience or at least knows the science of it all.
> 
> Paul Levine
> '87 5KCSTQW
> Ft. Collins CO


You took the question right off my fingertips.

>From the tone of your post I presume the 'regular' antifreezes 
don't qualify.  Can other followers confirm?

I was reading a www or faq somewhere yesterday something about
the phosphates reacting with existing alum oxides (alum rust)
already present in radiator.  The gist seemed to be that this
exposed more alum to oxidation (rusting), to which the phosphates
would react with, exposing more alum to oxid, and so on.  The 
point seemed to be you would eventually run out of alum.

Enough from me, let's hear from someone who knows what they
are talking about.  I'm only 5 days into my Audi audiction.


Lowell