Tips: Best way to purge air from coolant system after rebuild

[GN SBS]

I'm about to start a rebuilt motor and wanted to get some tips for getting all of the air out of the coolant system. So, I've filled the radiator with distilled water-- what are some good things to do to squeeze out all of the air once I start it?

thanks,
Scott

Note this thread has a few tips: www.turbobuick.com/forums/showthread.php?threadid=110956&referrerid=1129

 

[Buick Beginner]

2 cents

I've heard that by drilling a small hole in your thermostat it will do the trick. Maybe someone else can chime in. - BB

 

[Ormand]

Be sure to have the heater set wide open, so you can get the air out of the heater core. Then when you run the engine long enough to heat up, shut it down, let it cool, etc, all the air will go away in a couple of cycles. Most will go away in first cycle, but little pockets may linger, somewhere. When the system gets up to pressure, it will absorb most of those little "bubbles".

 

[tom h]

Re: 2 cents

Originally posted by Buick Beginner
I've heard that by drilling a small hole in your thermostat it will do the trick. Maybe someone else can chime in. - BB

BUT, there is already an S-shaped "bypass hose, from the intake manifold to the suction side of water pump. Don't see how a tiny hole in the thermostat will add much, compared to the approx 1/2" hose.

 

[scottyb]

Originally posted by Ormand
Be sure to have the heater set wide open, so you can get the air out of the heater core. Then when you run the engine long enough to heat up, shut it down, let it cool, etc, all the air will go away in a couple of cycles. Most will go away in first cycle, but little pockets may linger, somewhere. When the system gets up to pressure, it will absorb most of those little "bubbles".

What Ormand said.
I run the engine with the rad cap off and watch for the level to drop ,and add water as needed. If the temp reaches 200, I'll shut it down and cycle. Some times the cycle is not needed, and all the air will purge. When I see good flow in the rad and the level isn't dropping, I put the cap on and it's done.

 

[steve hughes]

Drill a small hole in the thermostat. It does make a difference. If you have a cooling system pressure tester pressurize the cooling system after you fill it up . Then start the car and run it a high idle for a few minutes. Shut it off top off the radiator. That usually takes car of the problem.

 

[2 SLOW]

GN SBS,

I will assume you have a new cam and lifters in this new motor. If not you can disregard this. Or if it is a roller cam.

When you start the motor you must immediately bring it up to 2000 - 2200 rpm and keep it there for 20 minutes to properly break in the cam. I have done this several times and have simply added water a couple of times while it is running and put the cap on. What little air is left won't hurt anything and will work itself out.

By the way, if you haven't done this before don't be alarmed when you see the headers glowing red. This is normal. They also glow every time you go WOT. Thats why they crack so much.

HTH

 

[gofstbuick]

Fill your radiator up, turn the heater on and leave the cap off and place a funnel in the radiator fill hole. Add coolant into the funnel until the funnel is filled 1/3 up. Start your engine and begin your cam break-in process. Best to have another person helping you. So you can watch your gauges and someone can watch what is happening under the hood. As the engine warms up and the thermostat opens a few times, the air bubbles will purge through the funnel and coolant will be drawn in. Add coolant if you need to. After a few times of the thermostat opening, remove the funnel and cap it.

 

[mgmshar]

Just wanted to add a note here, because I had a weird thing happen to me once...

After I got done with one of my many drain-and-fills on the coolant system last summer (trying some experiments to improve cooling), I filled the radiator and started the car. Then a weird thing happened. After about a minute or so, I noticed that the coolant temperature sensor reading was skyrocketing upwards, right past the thermostat opening temperature (160 degrees). It just kept climbing, and fast. But, when I turned the heater on, it blew cold air.

Fortunately, I figured it out pretty quickly. There was a large air bubble in the lower hose, and it was preventing the water pump from priming. So, I was running my engine with no coolant flowing through it! Yikes!

I fixed this very simply: After I shut the engine off, I simply grabbed the lower hose and jiggled it as much as I could. When the air bubble popped out, I could see the fluid in the radiator drop as the hose and water pump filled.

I've only had this happen once. Ever since then, I ALWAYS give the lower hose a good jiggle to knock any air bubbles out of it before I start the car. The last thing you want to do with a new engine is start it up, rev it to 2500rpm, and have no coolant going through it.

Hope this helps...

 

[Rickracer]

The hole in the t-Stat makes it easier to get all the air out without starting it

It only needs to be 1/16" to 1/8". There is a thing called a Spill-Free funnel that looks like a funnel with a radiator cap on the bottom of it, it will hold about a half gallon of coolant. I use mine all the time. Makes filling and bleeding an easy task, and you don't have to watch the coolant level in the radiator so closely. When the system gets full, there is a long plug that you stick in the funnel, then remove the funnel and hold it over the recovery tank, or the coolant jug, and drop the excess coolant out of the funnel (hence the name Spill-Free )