I have searched and read up what was contained in the forums, but still don't have a complete understanding of which coolant I should use. I don't have a user's manual, but do have a FSM and the FSM just said(or at least the part I read)was to use 50/50.

I have a 1989 with aluminum radiator and heads. What coolant should I use? dex-cool or what? The coolant that is in the system now has turned brownish and I think its from rust. I intend to flush it, but I do not know what type of antifreeze to put back in it.

I think the car runs a little on the hot side, doesn't overheat as the fans kick on in the respected temp range. I think it doesn't have the right coolant and quite possibly maybe it needs a higher performing water pump. Any comments about this would be welcome so I can make a good decision.

Thanks
Robin

 

Use the green stuff, or the universal stuff that will mix with anything. Green was specified in that car. If you mix dex cool with it you are just asking for trouble down the road as they don't play nice together.

 

If you're not using 50/50 mix, dilute the coolant with distilled water rather than tap water.

 

Your car uses the green ethlyne glycol coolant. Use a 50-50 mix of coolant and distilled water. A lot of the coolants you see on parts store shelves are pre-mixed and are more expensive that mixing it yourself.

C4 motors do run warmer as they are designed that way to help reduce emissions. It's common to see operating temps of anywhere from 185 to as high as 230. Is that the temps you see?

It can't hurt to do a flush and refill using the correct green coolant. How old are the hoses? If the upper and lower hoses look original or if they are more than 6-8 years old, replace them. Can't hurt to replace the pressure cap if the rubber seal looks worn or has torn areas.

If the motor is stock, a different water pump may not be worth the added cost. Water pumps will lose their ability to move water over time especially if the cooling system has lots of rust in it. The impeller can rust away or rust can clog water passages.

Also, it's common for dirt and debris to build up at the front of the A/C condenser and that can reduce the airflow through both the condenser and the radiator. You can easily see that by looking up under the license plate. You can force the gunk out by directing a stream of water through the fan shroud.

 

Great post c4cruiser, thank you and it makes alot of sense. I actually just had the blown head gasket replaced not more than 3 months ago. New radiator, new water pump, hoses and thermostat.

I finally found the coolant specs in my FSM - its an ebook and sometimes hard to find things. And yes my c4 averages in those temp ranges. At first it made me nervous but after reading here I came to realize it was how c4s run on the hot side. It has never overheated except on the day the head gasket blew. I shut it down immediately and had it towed - did no damage as a result. I do watch that temp gauge with an eagle eye.

Regarding a higher performing water pump, as I understand it - when the car is idle such as like a stop light, the temp climbs pretty quick - because the water pump isn't pushing through enough coolant. A higher performance water pump may take care this?

from the FSM
use 50/50 a good quality ethylene glycol base antifreeze GM part no. 1052753.

 

From what you stated regarding climbing/high coolant temps at idle, I would suspect the cooling fan is not coming on when it should. You mentioned installing a new WP and other components so you should have adequate coolant flow. Did you replace the pressure cap at the same time?

If all of this was done at a shop, I would expect that the cooling system was properly filled (i.e. burped) so that there are no air pockets. You can check this at home and add coolant as needed.

With the engine cold from sitting for overnight, raise the front of the car as high as you can and support the front with jackstands. Remove the radiator cap and start the engine.

Let the coolant warm up until the thermostat opens; you should see the coolant level in the radiator drop. Raise the engine RPM to about 1500-2000 RPM and add pre-mixed coolant so the level comes up to the rim at the filler neck. Return the engine RPM to the normal idle and watch the coolant temp to see if it's stable.

FWIW, my '87 will idle all day long and the coolant temp never exceeds 210 even on a hot day. Original radiator and WP too. Even during track days, coolant temps won't exceed 235 and the temps come back down after only one cool-down lap.

 

C4cruiser - Is there a way to adjust the cooling fans so that it would come on at a lower temp? They do fire religiously between 228 - 234. I used to hear it come on, but that was before I had the flowmasters installed. And it when it does come on, the temp is quick to drop. Wouldn't a new radiator cap come with a new radiator? It looks new. Yesterday when I drove her, she never exceeded 202, even at a stopped idle.

Another thing I noticed was the overflow tank at cold has enough coolant in it to mark the hot line on the stick. Also the coolant at this time is sorta green brownish which is what prompted this post. That piece I know I have to flush and refill and I'm ok with that.

I don't think I have a over heating problem, but I want to be proactive so that I never do.

Thanks so much for you posts, they make sense and are very helpful. - Robin

 

If you changed the radiator, water pump, hoses and thermostat just three months ago and your coolant mixture is now a thick brown liquid, SOMETHING IS SERIOUSLY WRONG with your Corvette.

I flushed my radiator and installed a new pump and hoses more than 2 1/2 years ago and my coolant is still a clear iridescent green. Are you sure that your head gaskets are in good shape? You need to track down your cooling system problem asap.

 

Turn on the AC.

Also, my advice, just come to grips with ther fact that these cars are designed to run hotter than you are used to.

 

No not thick and brown, normal coolant viscosity, but neon green tinged with light brown.

 

your radiator didnt get flushed , completely, or it has orange and green antifreeze mixed in it, need to flush it completely, there's a real easy way to do that. open the petcock, open the radiator cap , start the engine, start pouring antifreeze in till no more brown comes out . there are several ways to lower the fan turn on temp. hows your mechanic skills, they range from very simple to complex. Simple is a manual switch to one of them, after that it gets more fun. others will chime in, I'm sure btw, the issue with mixing the two colors is that they turn to jelly, sometimes.

 

thanks Alaska...I agree, it needs to be flushed. Hope you are doing well. : ) The vette is running better than ever. : )

 

Excellent Robin, I'm still on top of dirt...sofar. got rid of my C4 and got a C3 but if I can ever help, let me know, I'll keep an eye out, respectfully, Bob

 

Regarding vette running at high temps my 94 run at around 220. I know they are made to run at this temp but still make me little nervous has any one put a lower temp thermostat in there's and with what results