I have just flushed my coolant system on my car. The person who had it prior had installed a flush connection on the upper heater hose. I flushed thru the radiator and then thru the heater hose connection to the lower drain port on the radiator and flushed till almost 100% clear water. I never saw anything that resembled antifreeze. All of the flush just looked like rusted water. Tomorrow I will get some preston 50/50 and fill the sytem. I thought I would fill thru the heater hose connection then thru the radiator. Does anyone have a suggestion on the type antifreeze to use and how to approach the filling of the system? Will I create air pockets doing the fill this way? I only have a Haynes Manual and it is not chocked full of info. I appreciate any good insight.

 

Do not use anything made by Prestone! There are better choices for antifreeze. Do a search, there was a good thread a while back on antifreeze choices as well as how to flush and refill your coolant system.

I suggest GO-5 ethlene glycol coolant. It is a HOAT modern type long lasting coolant that has non of the downside of Dex-Cool or Dex-Cool clones (Read Prestone). You can get it dyed red from Ford, blue from Mercedes, light yellow-green from Zerex, and my favorite, dyed bight orange from Mopar.

 

I've been using Prestone green (ethlyene glycol) coolant for years and I currently have it in my 87. I have never had any problems with it nor has anyone I know that uses Prestone had any sort of issue.

The early C4's came with green-type coolant and if you follow the recommended intervals for flushing, you will have no problem with any good ethlyene glycol coolant. There is no real need to use long-life or multi-application coolants.

Going with the pre-mix stuff is expensive. Get the regular concentrated coolant and an equal amount of distilled water. The concentrate will be about the same price as the pre-mix and distilled water runs about a buck a gallon at any grocery store.

You should drain as much of the coolant as possible from the system. Drain the radiator and remove the knock sensors at the bottom of the block. If the radiator hoses are more than 6-8 years old, now is the time to replace them both.

Close everything up and add two gallons of coolant concentrate followed by the distilled water. Once the coolant level in the radiator is at the filler neck, start the engine and let it idle. Watch the coolant level and when the thermostat opens, the level will drop quickly. Keep adding the distilled water until the coolant level is just below the neck. Increase engine RPM to about 1100-1300 and fill to the base of the neck. Put the radiator cap on.

You should be keeping an eye on the temp gauge during this procedure. If the temps hit 220 or so, shut the engine off until it cools down some and start again.

It will also help if you jack the front of the car up. That helps with removing any air bubbles or pockets from the cooling system. You may have to keep adding coolant for a couple days until any air pockets work their way out. You can use a 50-50 mix here or just make some up from the concentrate and distilled water.

 

cruiser, since i flushed thru the heater hose do I need to remove knock sensors? I got clean water while flushing. Is this adequate?

 

Great advise on flushing and refilling the cooling system with coolant.

But.....................

Some things you should know about that "green Prestone" that you have been using for years. The hi-silicate "green prestone" that was originally spec'd for your C4 hasn't been made by Prestone in well over a decade. You can still get it made by Peak and possibly Zerex, Thats It!!
Prestone only makes Dex-Cool and Dex-Cool clones (Modern OAT type) Read the labels. Do not use Prestone any/make model. This is not the best choice for Cooling your C4! Do a search for the nightmares Dex-Cool can give you in a C4!!!!!!!

The advantages of modern long life coolants are not to be dismissed. Modern HOAT tpye coolants will not clog your cooling system with silicates that drop out of solution (green snot ~ everybody old enough to remember original Prestone will understand) They provide engine cooling and better corrosion protection and last up to three times as long as "original" or "old green" hi-silicate ethyene glycol coolants.

 

Using a jack and jackstands

 

It won't clean out the rust down in the block. I know this from flushing mine several times then getting around to draining the block, there was a lot left down there.

 

Don't they have some sort of coolant flush where you dump it in and drive a bit and drain it all out?

What is the best coolant then?

 

I don't know if there is a "best coolant" but I'm sure Dex-Cool and Dex-Cool clones (Anything made by Prestone) would be near the "worst coolant" choice you could make for your C4.

If you want to use what was orginally spec'd by GM and don't mind doing annual coolant flushes you can still buy an "old green" type silicate phosphate ethyene gylcol coolant made by Peak. If you want to use a long life, modern technology coolant without any of the associated problems of OAT or Dex-Cool type coolants, you could use a HOAT or Hybrid Organic Acid Technology ethylene gylcol coolant. These coolants are rated to last up to 5 years or 100K miles but I would change them every two ~ three years.

 

I did that as well, doesn't flush out the debris down on the bottom of the block.

 

Where do you put the jack and stands at?

And does that thing work on an L98? I found the knock sensor on the passenger side, but couldn't find a block drain on the driver side.

 

What is the name of this coolant and where do you get them?

 

I believe L98 only have one KS.

 

It's called GO5 and was first used by Mecedes with excellent results over 20 years ago. GO5 is a Hybrid Organic Acid Technology ethylene gylcol coolant.

Best place to get it; any national auto retailer that stocks GO5 made by Zerex dyed light green-yellow, (a little hard to see in your overflow bottle). You can also get GO5 from any Ford dealer dyed red or any Chrysler/Dodge/Jeep dealer dyed bright orange. Mecedes dealers also sell it but it will be more expensive, just like everything else there!

 

I did not know that Zerex is better than any other coolant. My DD uses Zerex, I flushed it for the first time at 125,000 miles and it was not rusty, brown or nasty. I just did.

 

 

?? Who said Zerex is better than any other coolant??