How do I bleed the radiator to get all of the air out?

[nycdude]

Hi everyone, I'm new here.

I have a 1986 astro (V6 engine) with about 80k original miles that recently formed a leak from the side of the radiator. I just replaced the radiator, and I thought it was a pretty easy DIY.

There is one problem however. I don't think I've been able to get all of the air out of the system. What are the correct steps? I can't find any bleeder screw.

I turned the car on after I removed the radiator cap and turned the heat to max. Then I filled up the radiator to the very top of the filler neck and saw some air bubbles but I currently do not see anymore. I squeezed the upper hose a few times and I got some more bubbles out, but I still think there is air in the system because the temp gauge would not move past 100 degrees as the car was idling.

If anyone could please tell me what I'm missing here, I'd really appreciate it. Is there a bleeder screw somewhere?

Thanks!

[Leeann_93]

No bleeder screw that I know of. My '92 Lumina had one, but these vans don't seem to.

You'll have to jack the front end of the van up, with the passenger side higher than the driver's side, and run through several cycles to get all the air out. The heater core and the upper rad hose are too close to being the highest points in the cooling system, so you have to alter the balance a bit.

[nycdude]

No bleeder screw that I know of. My '92 Lumina had one, but these vans don't seem to.

You'll have to jack the front end of the van up, with the passenger side higher than the driver's side, and run through several cycles to get all the air out. The heater core and the upper rad hose are too close to being the highest points in the cooling system, so you have to alter the balance a bit.

Thanks for the advice. I suspected a car this old wouldn't have a bleeder screw as well, and that's what the guys at the auto parts store thought too. So, I should take the radiator cap off, raise the car, put the heat on full blast, and then let it run for about 10 minutes? Also, should I have the heater set to the defroster or to the vents?

Also, would you happen to know the jacking point in the front? I couldn't find anything last time I checked. And where should the jack stands go? When I raised the rear up, I put the stand right under the eye of the leaf spring in front of the rear wheel.

[astro355]

Just loosen the radiator cap half way. You will know the air is gone once the coolant starts overflowing.

[nycdude]

Just loosen the radiator cap half way. You will know the air is gone once the coolant starts overflowing.

Thank you. Is lifting the car up still necessary or should I just loosen the cap and let the thing idle?

[Matrixx]

Hi nycdude

You can do either way that's suggested if you like. I just let the water pump do it for me, I cycle the heater control from hot to cold a couple of times then leave it on hot for a day or so, never had a problem. Just a thought.

[nycdude]

Thanks guys. Quick question: At first, I hadn't filled up the radiator all the way (only put in about 3/4 of a gallon of coolant) and let the car idle. It heated up quickly. After I had turned it off and filled up the radiator all the way, it didn't heat up at all when it was idling the next time. Does that sound normal? I haven't driven it yet, but I'm going to give it a shot tomorrow.

[nycdude]

Also, would anyone happen to know how to get the front end off the ground so I can put some jack stands under each side? I can't find a good jacking point in the center.

[astro355]

To jack up the van evenly, you would have to put the jack under the K-member. That is the part of the frame that supports the engine. If you don't have a jack long enough to reach the k-member, you will have to jack up one side at a time and use jack stands.

But as long as the radiator cap is the highest point of the cooling system, I would not worry about jacking up the front of the van. But like Matrixx said, cycling the heater normally will expel any air into the overflow container. So it should not be a concern.

It sounds like you have some air trapped in the system, somewhere. Just drive it and as long as it heats up and more importantly, it cools down the first time the thermostat opens, you'll be good.

[Matrixx]

Hi nycdude

Might I suggest you not do that nycdude (If you do), is to turn the motor off and then add water to it when it's hot? You didn't say how long you let it sit before adding water, but I just wanted to give you a heads up on this. Their is no faster way in cracking blocks than adding cold water to hot engine.

Is their a reason why you only added 3/4 gallon? The usual process, is to put as much in as you can (usually 6-8 liters or 1 1/2 gallons) when the engine is cold and off with the initial fill after replacing the anti-freeze (add anti-freeze first, then water)

Then fire the engine up, and allow the motor to warm up to running temperature on it's own so the thermostat opens. Leave the radiator cap off for this process and make sure your temperature selector is on hot while you do this. Once the thermostat has opened, then you will be able to add a bit more water to it (while the engine is running).

Once you have done that and topped the radiator off, then put the radiator cap on and top up the over flow tank to the appropriate mark. It will take a day or two to get all the air out on it's own, so maybe just keep an eye on the water level in the mean time. Hope this helps.

[nycdude]

I really appreciate the help from you guys.

Matrixx, the reason I had only put in 3/4 of a gallon was because that was all that I could find in the garage . Luckily, I had to go out and buy some coolant, so the car had cooled down by the time I came back and poured in the rest. I keep forgetting that this is an open system with an overflow tank unlike some other cars. I'll give it a drive tomorrow and cycle the heater and try to get out all of the air that way. I just hope this works okay because the radiator cap is definitely lower than the bend in the upper hose. This would definitely be easier than jacking up the car.

[astro355]

You'll have to forgive me. On my van, the radiator cap is the highest part of the cooling system. But my van is stock either...

[Matrixx]

Hi nycdude

3/4 of a gallon is all you could find? Of what nycdude? Anti-freeze or water? I was referring to water after you put the correct amount of anti-freeze in the system.

To clarify:
I use a 50/50 mix (apporx.) with my engine. When the system has been drained and ready to fill, I put 4-liters/1-gallon of anti-freeze in first, then the rest water (approx. 5 liters or 1 1/4 gallons more) . This gives me a -35 rating and is plenty good for the area I drive in (I don't have rear heat or rear A/C). I use the Prestone Long Life (5-year) Anti-freeze because that's what's called for for my year of vehicle (Long Life).

A 50/50 mix seems to be the industry standard and what I do all the time at the shop when I work on other vehicles that has had the anti-freeze drained from radiator for one reason or another "unless" the manufacturer or customer states otherwise.

Never mix Name Brand, Standard, Long Life or Pre-Mixed anti-freeze together. Keep it one name brand and one type only that's required for your system.

To Much Anti-Freeze will gel the system and over heat
Not Enough Anti-Freeze will overheat the system quicker (lower boiling point) and corrode it faster.

As Astro355 has brought up, the radiator cap is the highest point in the cooling system with these vans that don't have rear heat or rear AC).

I hope this helps.

[nycdude]

Thanks for clarifying. The 3/4 gallon of fluid was 50/50 premixed prestone that claimed it could be mixed with any type of antifreeze..i later went out and bought a gallon of pure texaco anti-freeze, mixed it 50/50 with water and topped off with that. Am I screwed?

I'm going to try bleeding the thing in a few hours in my driveway, which has a steep slope. Hopefully it works out.

[nycdude]

I just tried bleeding the system by bringing it up my sloped driveway and having the passenger side climb up the belgian block to make it higher than the driver's side. The radiator cap was off and I saw some air bubbles and then eventually the coolant itself started climbing to the top. I squeezed the upper hose a few times and I saw some more bubbles but eventually that stopped working. I put the cap on and took the car for a drive with the heater on high. I'm not sure if everything is good to be honest.

When I squeeze the upper hose, there is no pressure and it squeezes really easily. Is there still air in the system? Such a simple problem is becoming really complicated

[nycdude]

Also, the upper hose was hot but not too hot to touch after this drive. Don't know if that info is important.

[astro355]

If you had air in the circuit, you would not have been able to squeeze the upper radiator hose. When air becomes hot, it expands and creates pressure. If you had any pressure, your upper radiator hose would have been solid as a rock.

[nycdude]

Oh wow, so I guess that means I'm good!? I was thinking the exact opposite...i.e. air is easier to squeeze and if there is coolant in there, I won't be able to squeeze it at all because fluid is obviously more solid.

One thing i noticed is that my temp gauge is busted........it doesn't even move past 100 anymore. I swore I saw it move yesterday however. I'm a bit scared to drive now because I have no clear way of seeing if the car is overheating, but I think it must be good I guess.

[Matrixx]

Hi nycdude

Hmm, You didn't mention that before about your temp gauge not working. Maybe it is working and your thermostat is stuck open. Did you ever get hot air before the radiator change? Just curious.

[nycdude]

Yeah, the heat has always worked. Is it possible that I damaged the thermostat by squeezing on the hoses?

The fact that the coolant was warm/hot after I took it for a drive is a good thing, right? I feel that the temp gauge would move a TINY bit at the very least even if the thermostat was stuck open and not just stick to 100. The engine was definitely warmer than 100 degrees after that drive.