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I've got a no-spill funnel but can't get to the point where I get no further air bubbles. I rev the engine to various RPM levels, squeeze the hoses, the air bubbles slow down a lot but don't stop completely. Is the slanted radiator more problematic to air bleed for some reason?
Insights appreciated.
Last edited by brassplyer; Apr 25, 2024 at 10:49 PM.
From: I tend to be leery of any guy who doesn't own a chainsaw or a handgun.
The radiator has never been a problem in my experience. I don't recall what year your car is, but many/most C3s have a burp hose that goes from the top right of the radiator, up to the overflow/fill tank by the right front tire. The tank is supposed to be the highest point in the system, so the air ought to naturally rise up to there over time.
The radiator has never been a problem in my experience. I don't recall what year your car is, but many/most C3s have a burp hose that goes from the top right of the radiator, up to the overflow/fill tank by the right front tire. The tank is supposed to be the highest point in the system, so the air ought to naturally rise up to there over time.
Thanks - mine's an '80. I just clicked on the signature option.
Photo of a Milodon high flow thermostat. That's what I run. See the little high spot at almost 3 o'clock in the photo. There's a little hole there at that stamping. That's the air bleed. Points to the front of the engine. I purchased a Stant brand one not to long ago, maybe 3 years ago. Same type of vent/air bleed built in.
The worst thing you can do now is to install the Rad Cap.
I don't know why people do that all the time after filling the system. They must think somebody is going to steal their coolant?
Once you install the cap, you can't see what's going on with the coolant level. But worse yet, you are trapping any air that needs to escape.
Like others said, front end up on ramps, Rad Cap off, vary RPMs and wait it out.
If you fill the rad well below the neck, two inches or more, it helps burp the system easier. Then top-off later.
Lots of air pockets in the block, heads, hoses, etc. Have patience.
Brassplyer,
The worst thing you can do now is to install the Rad Cap.
I don't know why people do that all the time after filling the system. They must think somebody is going to steal their coolant?
Once you install the cap, you can't see what's going on with the coolant level. But worse yet, you are trapping any air that needs to escape.
Like others said, front end up on ramps, Rad Cap off, vary RPMs and wait it out.
If you fill the rad well below the neck, two inches or more, it helps burp the system easier. Then top-off later.
Lots of air pockets in the block, heads, hoses, etc. Have patience.
To clarify you're not saying you *never* put a radiator cap on are you?
Or if you're saying you just low-fill the radiator while burping the system it's not clear to me why this is better than using the no-spill funnel - i.e. a big cylindrical funnel that's purpose-designed for burping the cooling system. It sits on a fitting that's held in place with with a piece that's configured like a radiator cap with a hole in it. The fitting has a rubber gasket to make it air/water tight. You fill it about 1/3 then run the engine - it has enough volume to accommodate the expanding coolant as it heats up specifically so you can watch for air bubbles. Turn off the engine, let it cool to suck the expanded overflow back in. There's a stopper with a long handle so you can then seal off the funnel and remove it. I then dump whatever is left in the funnel into the overflow tank.
By low-filling and running the engine the way it sounds like you're suggesting when you finally top it off and put the cap on won't that trap some air at the very top of the upper tank? Also you won't have the visual reference of seeing the bubbles.
Last edited by brassplyer; Apr 26, 2024 at 11:47 AM.
To @4-vettes point, of course, put the rad cap back on once you know you are done.
A cracked head gasket may inject air bubbles into the coolant, and you'll be able to see that with the rad cap off, too. But be sure to elevate the front of the car on ramps.
I bought some sort of vacuum system especially for my LS motor.. I can't say more about it because I am ignorant of how it works and have to reread the directions every time. But it's magical!
Just to share with you, last week installed my new water pump, and drained coolant at the same time on my 78 L82. I was concerned from the beginning on having to burp my radiator at the completion of the installation. I also decided to add, heater core shut off valves, to the Upper/Lower hoses during the job. I asked my corvette mechanic his suggestion on burping my radiator. He recommended to take your upper heater core hose that connects to the intake manifold, before connecting to your new shutoff valve, raise the hose above the engine and start filling your radiator. When you begin to see coolant come from the hose - connect to your new shut off valve. Before you start your car, keep your radiator cap off and add coolant into your radiator plastic overflow tank, about 30% full. Started the car with burping and bubbling occurring for 10 minutes, once my car hit 220 degrees, dropped to 190 degrees and the coolant in my overflow tank emptied out and transferred to the radiator. Let the car run for another 10 minutes and shut off. Added more coolant to the overflow tank just up to the Cold line. Since than no issues or leaks and coolant levels staying full. I have talked to friends that their burping did not go as easy as mine did, stay persistent and patient, I am sure you will get it to burp.
Here is how I do it with my 496. I have a 78-79 over flow tank (works same as the older ones, just doesnt leak).
- Fill radiator. Leave cap off.
- Fill overflow tank to cold line.
- Start engine. Radiator level will drop a bit. Top off.
- Wait for thermostat to open (180 on my car). You will know when it does because radiator level will drop quite a bit. Top off again and install cap.
- Let car continue to warm up and make sure fans come on.
- Do a couple of hot/cold cycles driving car while keeping an eye on reservoir. It may drop a little as air is purged when car gets hot and then fluid sucked back whe cold.
From: I tend to be leery of any guy who doesn't own a chainsaw or a handgun.
Originally Posted by SteveG75
Here is how I do it with my 496. I have a 78-79 over flow tank (works same as the older ones, just doesnt leak).
- Fill radiator. Leave cap off.
- Fill overflow tank to cold line.
- Start engine. Radiator level will drop a bit. Top off.
- Wait for thermostat to open (180 on my car). You will know when it does because radiator level will drop quite a bit. Top off again and install cap.
- Let car continue to warm up and make sure fans come on.
- Do a couple of hot/cold cycles driving car while keeping an eye on reservoir. It may drop a little as air is purged when car gets hot and then fluid sucked back whe cold.
Thats it. Been working for 30+ years.
That's pretty much the same routine I do. Nothing special involved.
(On the rare occasion that I'm in a bit of a rush to get the system filled, I unhook one end of the upper radiator hose and rest it nearby while I fill the system. With the hose disconnected there are two additional paths for air to escape during the fill process.)
I typically drill three 1/8" holes in my LS thermostats.
Then a few years ago I bought the Harbor Freight radiator vacuum device. Works like a champ to get all air out of the cooling system. I think it cost $75?
I drill a couple small holes In the thermostat flange that helps too. But someone will say that's wrong.
I do that to all my thermostats and it's never caused any problems. The way I fill my Vette full of coolant is to fill the block through the thermostat housing then the radiator through the upper hose. This way I have the upper hose installed on the radiator and I can hold it up until my radiator is full. Doing it this way I've never had any issues burping the coolant.
It's hard to explain though.
Burping cooling system taking a long time
That's pretty much the same routine I do. Nothing special involved.
