Running without radiator cap

[thunderkyss]

Just curious if anyone has ever ran their cars without the radiator cap?

With old SBC, it's not a big deal, you can watch the water flow in & out of the radiator. I've tried this with my LT1 & once the engine warms to operating temp, the water begins to explode out of the radiator.

Don't ask me why I was doing this, I just was. The car doesn't overheat, it runs fine. When filling the radiator, I generally bleed it, drive it for a while, bleed it again. Sometimes I bleed it as many as three times before all the air is out.

Anyway, just asking.

[96LT1355Z28]

Not sure why you would want to run W/O a cap but the short answer is the system uses psi to help circulate coolant. Without the cap the coolant pushes out of the fill hole instead of out to the heads because it is lower then the T stat housing. The old style SBC the coolant is puled fom the bottom and returned to the top of the radiator so it didn't rely on psi as much.

The long answer is: on the older SBC imagine the water pump pulling gravity fed coolant from the bottom of the radiator and then pushing it up through the block, heads, and intake and then droping it back into the top of the radiator. Our cars are reverse cooled, they pull from the radiator and push it to the heads, then the block and back to the radiator. You'll notice the hoses on the LT1 radiator are at almost the same height not at the top and bottom corners like a traditional system. The radiator fill height is lower than the T stat housing so with the engine running it will push all the collant out the fill hole rather than to the heads, which is why it needs a cap.;)

[1fstss]

lt1 cars have a self bleeding system too.. you just get most of the air out and the system wil take care of the rest

[Spartan7]

I run mine without the cap to bleed the system. Once the thermostat opens I shut it off, fill it back up, then put the cap back on.

[RamAir95TA]

Without the radiator cap the system cannot pressurize which results in a lower boiling point of the coolant, reducing its ability to remove heat.

And LT1s are NOT self-bleeding. Thats why there are two bleeder screws on every LT1 engine.

[firebird_1995]

I've run without a cap after sprouting a pinhole in a hose. It keeps the system from pressurizing. After the coolant expands and runs off, it won't continue to run out unless it boils over.

[Spartan7]

And LT1s are NOT self-bleeding. Thats why there are two bleeder screws on every LT1 engine.

I never use the bleeder screws, and have not ever had an issue with overheating.

[Puck]

I never use the bleeder screws, and have not ever had an issue with overheating.

That is far form the norm, LT1s are notorious for their difficulty to get fully bled and sometimes take multiple heat cycles and bleedings to get all the air out. They are not self bleeding.

The trick is to open the bleeders BEFORE you fill the system, let it run (with the rad cap on of course), then close the bleeders when coolant comes out of them.

[meissen]

Yeah bleeding the air out is a real pain in the arse.

[Spartan7]

I know the normal method for bleeding. But doing it my way is easier, it only takes a few minutes to bleed it. I don't even bother with the bleeder screws.

[RamAir95TA]

I don't see how opening and closing two screws could be hard. Half the battle is filling the system the right way.

[Spartan7]

I don't see why any of you are arguing with me at all. My method works great for me, and I'm going to continue to do it this way.

[RamAir95TA]

No one is arguing. Calm down.

[firebird_1995]

Don't feel bad, I do it the same way. Fill it up about 2" from full, start it up, let it run till the thermostat opens, top it off, shut it off. Make sure the overflow tank is full to the hot mark and it will push/pull out what it needs. Never a problem this way either.

[Badbird_96]

I filled mine up until the thermostat opened then continued to top it off as air bubbled out when air finally stopped bubbling out and the level stopped dropping I put the cap on and opened the top bleed screw. Had alot of air so I gave it a little gas until coolant came out then let it settle and when the coolant started coming out I tightened the screw up and topped off my coolant reservoir. But thats just me lol

[Tyler Wheat]

I don't see why any of you are arguing with me at all. My method works great for me, and I'm going to continue to do it this way.

I've done it this way before, but its been awhile. I always just get the car at a slight incline, which seems to make it easier. Either method is easy and they both will get the job done.

[1fstss]

the LT1 will self bleed... after its in open loop top off the radiator cam and any little air pockets will eventually come out and bleed out into the resevoir... ive only on rare occation ever had to use the bleed screw

[Spartan7]

No one is arguing. Calm down.

Oh hey, no panties in a wad over here lol. I'm just throwing info out there for others, and some seem to want to refute it. Their loss. Glad others have had the same success.

[firebird_1995]

My panties are always in a wad. Its the cost of living obese I guess...

[dzltek]

My panties are always in a wad. Its the cost of living obese I guess...

AMEN!!! Contrary to popular belief, being fat CAN be fun!!!!!!!!!