graba

87 5k cs tq:

I'm going to replace my radiator and exansion tank this weekend. Recent cooling system maintenance/repair history

September: I had the water pump replaced (w/ t belt) and the cooling system flushed when I bought the car. Mechanic used green prestone.

November: I replaced the leaking heater core and stuck-open t-stat and a few hoses. I filled the system w/ orange extended life (dexcool compatible, silicate and phoshpate-free) prestone per advice read here. I added about a gallon of the new antifreeze. I only drained from the lower radiator hose. (I corked the heater hoses during heater core replacement)

On new year's eve, the radiator side tanks started leaking...I filled the cooling system (over a gallon!) with green antifreeze from the ski resort's maintenance shop and made it the 30 miles home. I've commuted a few times in it and now the leak seems bad!!

So I've got a mix of new antifreezes (green prestone, orange prestone, green ???) in the system.

My Basic Plan:

remove lower radiator hose and heater return hose (is this the one w/out heater control valve?) and let system drain.

replace radiator and expansion tank

re-fill with the orange prestone stuff described above

Any recommendations here? Do I need to flush the system since it was flushed in September? Flush before or after replacing radiator and expansion tank? Or does my general plan sound ok?

Thanks, graba

Will Ng

I don't know what advice you had gotten, but the prestone 'green' and the 'orange' (aka dexcool) is NOT compatible. You now have a witch's brew in your system. And a proper flush is defined as running clean water through your system several times until it comes out clear.

Prestone 'green' is not good for our type-44s. Although it's an ethylene glycol based coolant, it contains phosphates.

The 'orange' stuff is based on organic acid technology as its corrosion inhibitor. It's also marketed as Dexcool.
Unless a car is designed to use this stuff, you shouldn't use it. Dexcool does nasty things to brass and certain polymers. A fellow Audi enthusiast who transplanted a MC-2 turbo into his 4kq, discovered the Dexcool started to disolve the plastic impeller of his brand-new after-run pump!

You must use a phosphate-free ethylene glycol coolant. The Audi stuff is usually 'blue'. Although phoshate-free coolant does come in 'green'. I know that Honda also requires phosphate-free coolant and their OEM stuff is green. Also, Xerex makes a phosphate-free coolant, but it isn't readily available at your standard auto parts store. I believe it's marketed towards trucks, so try checking trucking supply companies.

BTW, back to flushing the system...flush and fill with clean water several times. This means you fill with water, run the car for 10 minutes, let it cool, drain and repeat. Once it flushes clear, fill you system with 50% coolant and 50% DISTILLED water.

And to answer the other question...the heater return hose is the one without the heater valve.

HTH,
Will

comp_jas

when you talk about types of coolant to use. From my limited understanding (Car and Driver article) the orange and green should not be mixed. Cars of older vintage should stay with older vintage coolant. That would be green. The whole phospate free argument ... who really knows. I used green.

I'd flush again regardless of which way you go.

graba

thanks much! I'll flush the system, then replace the radiator, return the prestone dexcool stuff, and order some coolant from the dealer. Interesting note: I checked the Prestone website and they say phosphate-free antifreeze is a non-issue in North America due to better water quality here than Europe. They also say that their orange extended life stuff is ok for every car under the sun...regardless, I'll listen to all of you and go with the dealer stuff.

thanks, as always
-graba