How to bleed cooling system on 95 LT1?

[Fatsky]

Hello all, I just got a 95 LT1 and am doing as much as I can on her myself. Want to flush the cooling system and replace the thermostat. Can anyone tell me the best coolant to use and the best stat, to use. And what's the best way to bleed the system. Thanx alot.

 

[air1jpg]

I think the stock thermostat on a LT1 is a 180 degree thermostat.

 

[Curious George]

I use the private label anti-freeze from your local auto parts store. Prestone and the other brands are good, but the generic stuff is made by them too and is cheaper.

If your '95 has the "orange" high mileage stuff (Dex-Cool), be sure to flush it all out before refilling with the "green" anti-freeze. As far as a t-stat, just get a factory replacement - same type and temp (190~195).

To bleed, I usually start the vehicle up and let it idle until it comes up to temperature. As the engine begins to get warm, you will see a bunch of air being burbed out of the system. You probably will have to add more water as it warms up, but watch the resevoir opening carefully as the temp. gets close to 212, because the water will begin to boil out of the resevoir if you just leave it open. If done properly, when the temp. reaches 212 and the water just starts to boil out of the resevoir, put the cap on very quickly and you should be good.

If you need to bleed more air out you can always use the small brass screw on top of the t-stat housing, but using this usually gets water on the Opti-Spark, not a good idea. One way to tell if you have a lot of air in the system is by looking at your temp gauge. If it seems to be bouncing around and giving you erratic readings, then there is still some air in the system causing hot spots.

CG

 

[2VettesMike]

It has been a while since I did this last but with 3-4 changes and no air bubbles, etc let me offer a few garage tips I used:

Use GM thermostat if at all possible. LT1 has unique two way thermostat due to reverse cooling flow, most aftermarket thermostats get this wrong

While cool and filling up the coolant reservoir wrap a couple of shop towels around the thermostat brass air bleed screw and crack it open until you get coolant weeping out, the shop towels will keep it out of the Optispark.

After you get coolant out there go to the rubber hose that connects the aluminum steam vent line between the cylinder heads. This hose is near the back of the intake where the fuel lines come up. Take it loose, it's a squeeze clamp.

Keep filling the coolant reservoir until get coolant out of this line. At this point all the air should be forced near the highest point which is the reservoir tank.

Reconnect the hose and fill the reservoir tank up.

Start the car and let it idle until the thermostat fully opens, watch the temp gauge.

Top off the coolant reservoir and add coolant to the overflow tank, down low near the radiator to the hot line.

Enjoy and drive.

This seems to work for me with no air bubbles or overheating. May not be exact shop manual method but works well and seems easy.

Good luck, Thanks,

Mike

 

[JAKE]

I think the stock thermostat on a LT1 is a 180 degree thermostat.

Yep, 180. My 96 Owner's Manual (not the Factory Service Manual) has the bleeding procedure in it.

I stayed with Dex-Cool (orange) in spite of what others have written in both my 96 and my son's 96 - no problem.
Jake

 

[Fatsky]

Thanx boys will do tomorrow. Got the correct thrmstat. from GM dealer. Lookin forward to spendin the day w. my C4 in my nice , quiet (cept for the music) dry garage. I Love this car. You folks are wonderful here. I know whatever questions I have on my car you're always here to help. That's good peace of mind for a newby Vette owner . Thanx again.

 

[air1jpg]

I use the private label anti-freeze from your local auto parts store. Prestone and the other brands are good, but the generic stuff is made by them too and is cheaper.

If your '95 has the "orange" high mileage stuff (Dex-Cool), be sure to flush it all out before refilling with the "green" anti-freeze. As far as a t-stat, just get a factory replacement - same type and temp (190~195).

To bleed, I usually start the vehicle up and let it idle until it comes up to temperature. As the engine begins to get warm, you will see a bunch of air being burbed out of the system. You probably will have to add more water as it warms up, but watch the resevoir opening carefully as the temp. gets close to 212, because the water will begin to boil out of the resevoir if you just leave it open. If done properly, when the temp. reaches 212 and the water just starts to boil out of the resevoir, put the cap on very quickly and you should be good.

If you need to bleed more air out you can always use the small brass screw on top of the t-stat housing, but using this usually gets water on the Opti-Spark, not a good idea. One way to tell if you have a lot of air in the system is by looking at your temp gauge. If it seems to be bouncing around and giving you erratic readings, then there is still some air in the system causing hot spots.

CG

More than likely your '95 has the green coolant in it. GM didn't use the dex-cool in the vette until the '96 model year.

 

[WillC4]

It has been a while since I did this last but with 3-4 changes and no air bubbles, etc let me offer a few garage tips I used:

Use GM thermostat if at all possible. LT1 has unique two way thermostat due to reverse cooling flow, most aftermarket thermostats get this wrong

While cool and filling up the coolant reservoir wrap a couple of shop towels around the thermostat brass air bleed screw and crack it open until you get coolant weeping out, the shop towels will keep it out of the Optispark.

After you get coolant out there go to the rubber hose that connects the aluminum steam vent line between the cylinder heads. This hose is near the back of the intake where the fuel lines come up. Take it loose, it's a squeeze clamp.

Keep filling the coolant reservoir until get coolant out of this line. At this point all the air should be forced near the highest point which is the reservoir tank.

Reconnect the hose and fill the reservoir tank up.

Start the car and let it idle until the thermostat fully opens, watch the temp gauge.

Top off the coolant reservoir and add coolant to the overflow tank, down low near the radiator to the hot line.

Enjoy and drive.

This seems to work for me with no air bubbles or overheating. May not be exact shop manual method but works well and seems easy.

Good luck, Thanks,

Mike

Thanks, i will be replacing the distributor soon and still for the life of me couldn't figure out the LT1 vettes cooling system (I used to have a '96 Camaro LT1 and bleeding it was more straight forward). Very helpful.