HVAC111

Any tricks to draining the old antifreeze and refilling on a 1991 l-98 i take it i us the green antifreeze

PLRX

Flush, rinse and drain using by removing your knock sensors out. I believe the L98 has one KS, do the best you can.

Use distilled or ozonated water, do not use tap water.

HVAC111

Is soft water , from a water softner ok ?

Tulsa Vette Guy

Is there only one KS on the L98 ??, Where is it located ??, do I need to jack the car up to get to It ??, Will this drain the block ?? and how do you get all the air pockets out when refilling with new coolant ??

c4cruiser

Most all grocery stores have bottled 1 gallon jugs of distilled water. Usually about a buck each.

GM went to Dex-Cool in the 95 model year, so anything prior to that uses the green ethylene glycol coolant.

In the long run, it's cheaper to use a concentrated coolant and water to mix in a 50-50 ratio. A gallon of pre-mixed coolant costs about the same as a gallon of concentrate. So mixing your own gives you nearly twice the amount of coolant for the same price as a jug or pre-mix. The 50-50 mix will protect to -37 degrees F.

As shown in the pic the knock sensor is located at the bottom of the block (the pic looks like an LT1 block but the location will be the same). So you do have to get under the car to access the KS.

To drain, loosen the radiator petcock and remove the pressure cap. You should get a good 1.5 gallons out from there. Removing the KS will drain the block and that's at least another 1/2 gallon or more. If the system has not been flushed in some time, put a garden hose in the filler neck, close the radiator petcock and let water flow thru the system and out the KS hole. When the water comes out clear, replace the KS (don't forget to add some anti-seize to the threads), open the radiator petcock and drain the radiator.

Close everything up and you're ready to add fresh coolant. I like to pre-mix the concentrate and distilled water first so I have a supply of it. If you make 4 gallons (2 gal concentrate and 2 gal distilled water) you will have more than you need to fill the system and have extra if it's ever needed. At this point, raise the front of the car as high as you can with a floor jack and jack stands or at least until the filler neck is higher than the engine.

Fill the system until the coolant comes up to the base of the filler neck. Start the engine and let it idle. When the thermostat opens, the coolant level will drop quickly so be ready to add more coolant. Keep an eye on the coolant temp and fill until the coolant is at the base of the filler neck. It helps to run the engine at 1200-1500 RPM to insure that coolant is being pushed thru the engine and pulling out any air pockets. If the coolant temp hits 230 or so, shut the engine off and let it cool down, then start again. When the level stays full, replace the pressure cap.

It's probably a good idea to replace the upper and lower radiator hoses if they are more than 6-8 years old. A new pressure cap doesn't cost that much so get a new one. Remove the overflow tank and clean it. Reinstall and fill with the coolant mix to the Cold line.

Let the engine cool down (under 150 degrees) and check the coolant level. Add coolant as necessary to bring it up to the top of the filler neck and replace the cap.

HVAC111

Thanks for taking the time to give me such detailed information ! This is just one more reason i like this forum.

Tulsa Vette Guy

Many thanks for your reply C4Cruiser

Sweet 90

Read the thread below. Very interesting
http://forums.corvetteforum.com/c4-g...n-dexcool.html

Jim

mako41

Yes there is only one knock sensor on an L98. It is located on the right or pass. side of the engine block. On the exact opposite (drivers side)you will find an engine block drain plug. Remove both of these to completely drain the coolant from your engine.

josephf31

see where anyone mentioned the trick about drilling one or two small (1/8") holes in the thermostat...