I was thinking of changing my coolant in my LT4 until I opened the radiator cap. Now I have
too. Yuck!! I'm embarrassed. The previous owner ran the red stuff which is now harboring
visible "junk". I want to switch over to the green stuff probably prestone 50/50 but I read that if I
mix the new with the old I'll get a build up do to a reaction? Anyway the manual states to take
the car in to get the old flushed.

If I pull the knock sensors out and completely drain, fill with water let run and drain again as the
manual states, will that be good enough? or should I take it to the mechanic?


SVX

 

you should be fine, just make sure that the water is clean before you put the new stuff in.

 

Just keep repeating the process till the water runs clear--it took me a few refills-restarts and circulating to get it clear/clean.

 

Just make sure the water comes out clear before you start pouring the new stuff in. IIRC, your year car did not come originally with the orange Dex-Cool. The orange/red DexCool (which used organic acids instead of silicates) and both the yellow Prestone and the amber Peak do not use silicates or nitrites. I don't think it was used in new GM vehicles until 1996 and many people, including GM, IIRC, warn not to mix Dex-Cool with other coolants.

I believe the 'North American' green coolant used silicates and phosphates as the corrosion inhibitors. I found this out by reading the back of the labels of all four and seeing the chemicals they are comprised of differ.

If your car did originally come with the old green ethylene glycol with silicates, the only place I was able to find it was NAPA. I went to Wal-Mart, AdvanceAuto and Autozone before I called NAPA. I believe someone also said Carquest may have it.

Jonathan

 

Use a name brand premix that works with both types and you're golden.

 

I refuse to get into the green/oraange debate--But, the red/orange stuff came in your and my LT4.


I run it in all my cars with no problems.


Now over to the green crowd.

 

Dex-cool was used in your LT4. I saw LT4, but processed '94 - go figure. And yes, the debate is endless - it always seems to end saying to use what came in your car. Green for green, Dex-cool for Dex-cool.

 

I run DEXCOOL in my 95. Yes, the 95 came with the green coolant but, I flushed it 4 times and I've been running DEXCOOL for 3+ years.

In my CE LT4 once all surgery is done, DEXCOOL will go in the rad.

I mix it 60/40. Two Gals of DEXCOOL and the rest with distiled water.

 

DO NOT use a pre-mix unless you remove the knock sensors AND blow-out the block to assure no water/coolant remains.

Reason: using a pre-mix is adding a 50/50 ratio to less than a 50/50 ratio -- result -- (much?) less than the desired 50/50 ratio (and paying a premium for 'water' too).

BTW, almost every brand/model anti-freeze has a slightly different chemical composition in addition to its color (trust me, between our 94 vette, our 2000 Vette and TA, our 96 Camry, and my diesel engine in the sailboat -- I have had to become very familiar with the differences and incompatibilites) and mixing them can have all sorts of issues from junk to jelling to eating incompatible rubber components (yes, this happed with my diesel engine).

So, especially if your owners manual recommends Dex-Cool, to avoid any chance of chemical incompatabilities, consider just buying the anti-freeze from the dealer (not that much more expensive, and worth preventing issues). If by change your owners manual does suggest using the old green type anti-freeze (ethelyene glycol with silicates), one brand that is still 'old style' is from Texaco (found it at a local parts place).

Also, if you would like to avoid removing the knock sensors, a good alternate approach is to just drain/refill/run to temp/drain/refill/run to temp -- until the drained water is clear.

If you choose this approach, suggest using steam-distilled water to do each refill -- assures no minerals are deposited inside, and further, after the last drain, leaves nearly pure steam-distilled water in the block -- the preferred water to use when 'mixing' anti-freeze.

Then, after the last drain -- CHANGE the thermostat (remember they dies slowly -- opening less and less -- until they just up and fail completely, sometimes during the Sunday drive -- why have this happen after you have put all that nice water & anti-freeze and work into the cooling system -- better to do it when it is nothing but water to drain out to change the thermostat.

Lastly, remember to put the cap quickly after topping-off the coolant system -- this allows pressure to build and move air-bubbles around -- and keeps them from expanding into large flow-restricting air pockets.

 

When I flushed mine, I left a water hose feeding in water through the radiator cap and I left a draining point open -- can't remember if it was the radiator drain or a hose on loosely. Anyway, it was easy to replace the amount draining and it took a really long time to completely clear. (I had removed and flushed the radiator by itself before replacing.)

Anyway, that was going on for several minutes with the radiator cap off, the coolant circulating, new water coming in, some mix draining, and all of a sudden all h*ll broke loose. It seems that I had managed to flush the coolant and when it hit 212 F it was like the entire system turned to steam at once. No harm, but lots of excitement for a few seconds.

 

Also, remove the filler tank and clean it out. Mine came with the green coolant, but still sludged up because of those stupid tablets that GM used to recommend.

 

Thanks for all the responses. Well after a long day she is done. I first drained all the coolant out
of the radiator, pulled the knock sensors (yes you have to pull both) and watched in amazement
of how much coolant came out!! Put it all back together and filled it with house water. I really
wanted to use distilled for this but the hose was just more convenient and used on all my other
cars in the past. Then I let the car warm up to operating temp and took it all apart and did it
again. The last drain was basically water.

I chose to go with Prestone minus any phosphates though it is ethylene glycol. Mixed it with
distilled water and filled her up.

One thing I would like to mention just in case someone comes across this thread looking for
advice, I had a heck of a time getting the wires off of the knock sensor. After I buggered it all up
I realized that all you have to do is take a pair of pliers and squeeze the "ears" of the clip and it
pops off. For some reason every single electrical plug on this and my other car are taken off
differently.....finding this out only after I break it

Thanks for the help guys, the people on this forum are great. SVX

 

I'm thinking about doing this myself, but I have a really stupid question: What did you do with the old coolant?

Dave
'94 Coupe 6spd

 

I went down to the store and bought a 6+ gallon jug for water (right next to the gas jugs) and
poured it in there.

I called the city and they have a place down by the dump where they recycle it. In the past the
local radiator shop let me dump it in theirs but I have too much this time I think.