I am trying to figure out how frequently and with what type of fluid to flush and refill the cooling system. The manual says to use something conforming to “GM Specification 1825-M" for my 1994 LT1.

What is the best frequency and coolant? Thanks

 

NAPA, Peak, and Carquest manufacture the Green antifreeze meeting this spec.

 

Frequency is usually every 20-30k miles, or 2-3 years.

 

I had some guys at a AAA care car center tell me to use the Dex-Cool/Orange stuff because of the aluminum in the cooling system. Should I only use the glycol/green stuff?

 

Don't use Dexcool/orange, it will make mud with your green coolant. In my 94 I use the Prestone formula that is compatible with any brand/color coolant.

 

Oh god, don't let some moron convince you to use Dex-cool. Use the green stuff your car was designed for.

 

I had the entire system flushed and converted to the Dex-Cool, so there shouldn't have been any mixing.

When did the Corvette's get the Dex-Cool?

Will the Dex-Cool hurt the car?

 

No, not if it has been completely flushed.

 

Which is assuming a lot.

 

Dexcool recommends 5 year/100,000 mile changing frequencies.

 

Thanks for the answers. There was a ton of sludge in the overflow tank when I bought it. So, I had the flush done. The AAA guys said they use a pressurized system that matches the pressure of the coolant system. Supposedly, they flushed out whatever was in there and all of the sludge. (There is no sludge almost two years later). Then they refilled it with the Dex-cool. If I have converted to Dex-cool successfully:

Can I go 5 years in between flushing the system?

Will visible sludge return as a warning for problems with the coolant?

 

Prestone still makes Green Coolant.
I have 3 gallons in the garage I bought this past winter.
The old straight non watered down formulation.
I had to shop around for a long time to find it below $11 or $10 a gallon.
I found it for $7.00 a gallon here in Illinois at my local "Farm & Fleet" store.

There is only one major brand of "DEX-Cool" Orange anti freeze I would ever use in my own cars.
That is HAVOLINE LONG LIFE ANTI-FREEZE- DEX COOL COMPATIBLE.

I personally would pass on every other type or manufacture of the orange stuff.

Don't mix orange with green of course.

Any trace of green antifreeze or brown sludge needs to be thoroughly flushed out of the cooling system.
Even if it takes you all day to do so and 1,000 gallons of water.
Get all the old crap out.

Brian

 

When you say Prestone still makes "green" coolant. Are you just referring to what the coolant looks like?

The only Prestone I've seen is the Dexcool clones (OAT) "any make any model".

What I refer to as "green" coolant is the green coolant (non-OAT) used before Dexcool, not necessarily what it looks like.

 

many guys recommend the ZEREX coolant
they make the green stuff, dexcool clone and G -05 which is for Ford and Chrysler.
I think many use the G-05 stuff

 

Most auto repair shops have machines that do what is sometimes referred to as a "power flush". It works fine for flushing a cooling system and refilling with the same type of coolant in the correct proportions (50-50 mix). Even the drive-thru oil change places have them but are run by people with no real technical training and experience. Those places should be avoided like the plague (for any kind of work).

It really isn't that big of a deal to do a flush at home as long as you can get to the knock sensors on the bottom of the block and remove them to let all of the old coolant drain out so that you can flush the system with plain water. There is a procedure in the FSM for cooling system flushing. Once all of the old ethylene glycol (green) coolant is gone, you can refill the system with Dex or similar long-life coolant.

As long as your cooling system is in good condition, a 5 year cycle is fine. But even simply draining the radiator and refilling with a fresh mix every three years could be good insurance. Only takes something like two gallons to do.

As mentioned, the Havoline Dex-Cool stuff is available at most all parts stores, Wal-Mart, Costco, and even some grocery stores, is the same stuff that GM uses. IIRC, Havoline worked with GM to formulate Dex-Cool for use in GM cars.

 

There are some very intelligent and caring people working in those quick lube places.
Its a rare find.
Sometimes the Main manager working days is best guy to do the job.
That's if he is the type willing to get away from the front desk and get dirty under the hood and in the oil change pits.
Hanging out in different shops of the type, you can spot the best guy.

They dont pay those guys much $. Around minimum wage.
But a few are aspiring to be professional mechanics and have the right attitude to begin with.
And those few can be trusted to changed out fluids in any Corvette.

A friend was a manager of a quick lube place for 7 years.
He opened his own auto repair shop last year and is doing ok in this bad economy.
I helped him one on one for 5 years teaching him Basic and very advanced auto repair.
When I am not on C4 at night by 5pm central time,
I am at his shop helping him with very tough mechanical and driveabilty problems.
Vettes and porches too.
He pays me $$$ so why not help him.
Its good for him and me.

He is on 26 years old by the way.
I am 41.
Its a matter of trust and faith always.


Brian

 

I'm new to this forum and I don't own a Corvette. But I found this thread because I was searching about coolant specification 1825M which I needed for my wife's car (2004 Chevy). The manual explicitly states the coolant used should be safe for aluminum parts. That should clarify that issue. I finally went to Advance Auto Parts and they ran an application that looks up the compatible coolant by year/make/model. It turns out that Dexcool (a GM formula) is recommended for 1825M applications.

Color is very important, as in electronics, you don't connect a red wire to a black wire. Green is the oldest modern coolant. My 1997 VW takes red colored. The Dexcool, which looks pink, they always color-code with an orange cap. Then came OAT which is Organic-Acid-Technology for late model cars. Supposedly Dexcool is an OAT type coolant but it's still color-coded with an orange cap regardless of the brand.

 

I believe the '96s were the first with Dex-Cool, that's what was in mine and what the book calls for...now running 'Green', BTW.