Thread: Thermostat & Radiator Questions

Recently, my engine has been running a little warmer than usual. Still staying outside the red area, but it bounces between mid-point on the radiator fluid temp gauge and just below the red area. I'm thinking about draining the radiator and replacing the fluid cause I just recently had work done on it but I'm not sure if they used Dex-Cool or not, i still have to ask them. How do you bleed out all the fluid from the radiator though? I know where the reserve tank and pressure caps are, but since those are the high points of the radiator setup, is there a plug/cap on the bottom of the radiator to drain it?

Also, I was thinking of maybe replacing the Thermostat since it seems to be a pretty simple thing to replace. What temp Thermostat should I get for my engine though? I have the supercharged 3.8L (hence being in this thread), only modifications to the engine so far have been K&N Air Intake, MSD Spark Plug Wires & Pulstar Iridium Pulse Plugs. All in all I'm probably not going to do very much, if any more work into the engine so it's probably gonna stay with this setup for a long time.

Any help would be appreciated, thanks!!

GM obviously says Dex-Cool to use, but is there something else that could be used instead that lasts just as long?

I use Peak Global. It's gold in color and is a 5 year or 150k coolant. Go with a stock 195 stat.

Any idea how much coolant the radiator needs?

Something like 1.25 gallons.

I'd bleed the system after doing a thermostat. If the wrong coolants are mixed it turns to brown. If your coloration is right, then assume they used the right stuff or an anycolor coolant. I don't bother buying dex or green anymore. You never know what is going to be in a customers car. Makes life easy and costs the same.

AnyColor.. the best color.

My first attempt is going to be just to bleed the air out, i think there is a bubble in there causing the temp gauge to move alot.

If that works out and everything works normally, then the next step will be to do the thermostat at a later date along with bleed/refilling the entire system.

If there was no air, or that didn't help, then I'm gonna replace the thermostat very soon and bleed/refill the entire system.

Honestly, this is the first time for me doing something like this. I'm not worried as it doesn't seem very difficult. But where is the drain for the radiator? I know I could disconnect the bottom hose, but I'd rather use the drain that I'm supposed to use. Also, is is best to take off the bottom air dam to get to the bottom of the radiator for the drain/hose? After bleeding out the system, is it ok to flush it out with water or should i just bleed/refill it? Thanks for the help.

If the drain comes loose and drains, I'll be impressed. Us vets go after the hose because it's never a problem/fight.

If you want a problem/fight.. have at the POS, MF'ing, Gunnabreak, Craptastic drain. Yeah, that's my real feelings about the drain.

Well, if the drain is that much of a problem i'll just go for the hose(which seems to be on bottom passenger side). Doesn't seem like there is alot of room though, is it easier to access if the air dam is removed?

My drain still works fine.

Since you're worried about minimal MPG changes don't get a 180*, you will theoretically get worse MPG.

wouldn't I only get worse MPG if i used the increase HP from keeping the engine cooler?

when bleeding the air out with the screw, are you supposed to leave the radiator cap off so the system doesn't gain pressure, or are you supposed to leave it on to help push that air out?

So I filled up the radiator (took nearly a 2 liter bottle of 50/50 Dex-Cool/Water mix), started the car, made sure the radiator was filled to the neck while running and bleed out the air with the screw till the coolant came out of it. Tightened down the screw, checked the neck for coolant, capped it and rinsed the engine down so coolant wasn't sitting anywhere.

We shall see how this works, seems it was just low on coolant. Which is kinda strange cause it was just recently flushed & filled at my repair shop while they had to fix the 90* rubber hoses on the left side of the engine anyways. I guess I'll see if it gets low again, and see if there are any leaks at all. thanks for the help guys and hopefully this will fix the issue for now.

Next will be to replace the thermostat with a 195* or 180* since it's probably the original thermostat and I want to keep this car for as long as possible.

Ran well today, stayed just under the middle point of the temp gauge. I decided to buy a 195*F thermostat cause as some of you said, along with the guy at the shop, unless I have a scanner to change the settings of the engine/fans and such, a 180*F won't help me much/if any. I figured even if the Thermostat is working fine, I can replace it now that I'm over 100K and it will be good for well over another 100K and I won't have to worry about it at all. Plus who knows how dirty it is with the old radiator fluid and all, so I may as well take it apart to clean around there anyways, and replace the thermostat while doing that.

I bought the RTV sealant since i guess I'm supposed to use that to seal around the bolts and such. It says it's 24hr. cure time, so I guess I'll do this and have to now drive the car for a day. Should i use the RTV sealant just around the two bolt holes? or should i make a bead all the way around the housing as well to create a full seal?

I didn't use any on mine and it's fine.

replaceing the mixture with 70% water and 30% coolent should lower the temps, did on mine and since your in FL should work for you to