Coolant Bleed
Thread Starter
Racer
Joined: Jul 2003
Posts: 332
Likes: 24
From: Denton, TX My goal in life is to be as good of a person that my dog already thinks I am.
Coolant Bleed
I finished some work on my coolant system and bled the system three times as recommended. My temps seem a few degrees higher now than before the work. I let the car sit over night and thought I'd open the bleed screw before starting the engine. Nothing came out not even air. Is this normal after sitting over night? 1995 LT1 stock engine.
Safety Car
Joined: Sep 2004
Posts: 3,953
Likes: 550
From: Mission Viejo CA
The engine needs to be warm when you open the bleed screws. A warm engine has pressure in the cooling system, which is required to force the air out. If the engine is cool, air will go into the system when you open the screws.
Safety Car
Joined: Aug 2002
Posts: 3,842
Likes: 230
From: SANTA CRUZ CA
The LT1 engine is self-bleeding (yes, I'm aware of the bleed screws, and all the horror stories of gigantic bubbles in the system).
Just fill the coolant tank, and the overflow bottle to the 'cold' level. After driving, check the level of the overflow bottle when 'hot'.... it should be above the 'cold' mark.
After the engine has cooled, check the overflow level again..... it should be lower than the 'hot' level.
If the level in the overflow bottle has not lowered after cool-down,
then a siphon has not occurred, and there is a breach in the 'closed system' allowing air to enter and negating the siphon. Check the rad cap gasket for any deformity, check all hose clamps for tightness, and hose ends for splits.
If the overflow bottle lowers the level during cool-down, remove the rad cap and check the tank level..... add coolant, if necessary.
Your are good to go.....
Just fill the coolant tank, and the overflow bottle to the 'cold' level. After driving, check the level of the overflow bottle when 'hot'.... it should be above the 'cold' mark.
After the engine has cooled, check the overflow level again..... it should be lower than the 'hot' level.
If the level in the overflow bottle has not lowered after cool-down,
then a siphon has not occurred, and there is a breach in the 'closed system' allowing air to enter and negating the siphon. Check the rad cap gasket for any deformity, check all hose clamps for tightness, and hose ends for splits.
If the overflow bottle lowers the level during cool-down, remove the rad cap and check the tank level..... add coolant, if necessary.
Your are good to go.....
Pro
Joined: Oct 2004
Posts: 551
Likes: 23
From: Wills Point Texas
The LT1 engine is self-bleeding (yes, I'm aware of the bleed screws, and all the horror stories of gigantic bubbles in the system).
Just fill the coolant tank, and the overflow bottle to the 'cold' level. After driving, check the level of the overflow bottle when 'hot'.... it should be above the 'cold' mark.
After the engine has cooled, check the overflow level again..... it should be lower than the 'hot' level.
If the level in the overflow bottle has not lowered after cool-down,
then a siphon has not occurred, and there is a breach in the 'closed system' allowing air to enter and negating the siphon. Check the rad cap gasket for any deformity, check all hose clamps for tightness, and hose ends for splits.
If the overflow bottle lowers the level during cool-down, remove the rad cap and check the tank level..... add coolant, if necessary.
Your are good to go.....
Just fill the coolant tank, and the overflow bottle to the 'cold' level. After driving, check the level of the overflow bottle when 'hot'.... it should be above the 'cold' mark.
After the engine has cooled, check the overflow level again..... it should be lower than the 'hot' level.
If the level in the overflow bottle has not lowered after cool-down,
then a siphon has not occurred, and there is a breach in the 'closed system' allowing air to enter and negating the siphon. Check the rad cap gasket for any deformity, check all hose clamps for tightness, and hose ends for splits.
If the overflow bottle lowers the level during cool-down, remove the rad cap and check the tank level..... add coolant, if necessary.
Your are good to go.....
I was going through the same thing but found a cracked or slow leaking coolant tank at radiator neck.
What always confused me is where the bleeder valve is not the highest point. I would think they would have put the bleeder at the highest point or am I missing one somewhere. the only one I know of is the area by the throttle body.
I talked to a friend of mine that works at a dealer and they have a machine that bleeds the closed system's such as these and just wonder how that works.
Last edited by Smokeysvette; Mar 17, 2014 at 11:31 PM.
Safety Car
Joined: Aug 2002
Posts: 3,842
Likes: 230
From: SANTA CRUZ CA
seabright, Just a question here, if the siphoning is working correct after the car has cooled down completely, should you not check the upper coolant tank? Shouldn't it be full as this is the highest point and any trapped air would eventually end up there?
Yes, in my response I suggested to remove the rad cap (coolant reservoir) and check the coolant level when cold, and add coolant, if necessary.
I was going through the same thing but found a cracked or slow leaking coolant tank at radiator neck.
Good find..... since the cap requires considerable torque to remove and install, small fractures can occur. Unless you fixed the neck to prevent any air leak, you will need a new tank. New rad caps are easy on-off.
What always confused me is where the bleeder valve is not the highest point. I would think they would have put the bleeder at the highest point or am I missing one somewhere. the only one I know of is the area by the throttle body.
I talked to a friend of mine that works at a dealer and they have a machine that bleeds the closed system's such as these and just wonder how that works.
Yes, in my response I suggested to remove the rad cap (coolant reservoir) and check the coolant level when cold, and add coolant, if necessary.
I was going through the same thing but found a cracked or slow leaking coolant tank at radiator neck.
Good find..... since the cap requires considerable torque to remove and install, small fractures can occur. Unless you fixed the neck to prevent any air leak, you will need a new tank. New rad caps are easy on-off.
What always confused me is where the bleeder valve is not the highest point. I would think they would have put the bleeder at the highest point or am I missing one somewhere. the only one I know of is the area by the throttle body.
I talked to a friend of mine that works at a dealer and they have a machine that bleeds the closed system's such as these and just wonder how that works.
for the LT1. Air is forced out of the system at the overflow bottle.
Melting Slicks
Joined: Aug 2008
Posts: 2,082
Likes: 50
From: Palmdale CA
Let me tell you guys a little un-known piece of info on the 95 LT's, there is an 3/8 coolant hose Tee on the R/H side of the Radiator. Between the Tee it-self and the Aluminum pipe that runs up the frame rail to the surge tank is a rubber hose swedge clamped to the aluminum pipe.. under this connection is a small Brass fitting that is pressed into the aluminum pipe, this restrictor fitting was completely plugged on mine, and it serves as a means to allow air bubbles to escape the highest point in the radiator up to the surge tank. The Swedge clamp is easily cut with either a small radiac wheel or even a hack saw blade. The rubber hose is available at NAPA for about a buck a foot..
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