308 coolant vacuum fill

Hi all

Following changing the radiator in my 1979 308 GTB, it has taken me a long time to get all of the air out of the coolant system (and I still don’t think it’s all out).

In the meantime, I now think it needs a new water pump. The thought of draining the coolant again, and repeating the bleed process is something I am not enthused about…

I may have been watching too much Matt Armstrong on YouTube, but I was pondering attempting to vacuum fill the system. I appreciate I would need to clamp off the overflow pipe on the header tank, but I would appreciate any other thoughts on whether or not this was a good or bad idea, and any other steps necessary if you think it is a good idea.

Picture of the car post wash attached to make this post a bit more interesting.

Thanks all.




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Just go for a few drives get it hot ( fans on ) around under 90 *c .Park up hill and open the rad bleed screw .
Takes about 5-6 trips to get all the air out . Run for 10 mins with the heater on max to circulate,as well during the runs.

If you over fill it it will blow it off through the overflow pipe . This assuming your tank cap is to spec ?Level should settle 6 cm below the filler hole on the tank .

Try a fresh tank cap if you are still having issues ?
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Just done my GT4 today BTW .After an Alps jaunt .

Was 34 *C in the Italian valleys .
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Get an Airlift, simple, done. I now don't dread refilling the coolant.

Use my Airlift, take it for drive, open the bleeder on the thermostat, and the bleeder on the radiator... done.

 

I use an airlift because I have a shop and use it 5 times a week.
Filling the cooling system could not be easier. You cannot and do not want to eliminate all the air. The system has to have air in it.

Do it like they did at the factory. I have done it that way hundreds of times.
Open the radiator bleeder screw and take out the thermostat bleeder plug. Open the heater valve. Pour in coolant mix until it comes out the radiator bleeder. Ignore bubbles. Close the radiator bleeder. Continue to pour in coolant until it comes out the thermostat bleeder then reinstall plug. Continue to fill with coolant until tank is about 1/2 full. Install cap and ignore it until coolant needs to be changed again.

It really is that simple. No repeated bleeding, no continual fiddling with radiator bleeder, no jacking it up or parking on a hill. All that is total bull ****.

 

I knew that would get you going!

 

@ Brian I did exactly that except without the t stat house bleeder on the GT4 bcz there isn’t one , just poured it in until it came out of the rad bleeder .
Hmm , I still think it worth a home DIY er ( even for curiosity sake ) running it up and opening the rad bleeder once or few times more …..might as well park it nose high while you are at it too .

Agree it’s simple .
Appreciate in a shop you might steer away from taking them out especially in winter and test , run them up to full temperature……just eats time that could be used more productively. But a DIY er at home , retired with all the time in the world ?

 

And you are why there is so many wives tales and confusion.

Your GT4 had no bleeder plug, most did. You are in a tiny minority and not the car in question. Might as well include Daytonas too. Stick to car in question and facts at hand. Quit making it harder than it is.

 

In reality I have an airlift because of 360's. If all I ever worked on was 308 and 328 Id never have spent the money. They are just brain dead simple yet in typical internet fashion it has been turned into some complex operation. Mass stupidity.

 

No one ever accused me of being smart that's for sure

When I got mine it was for a couple of reasons. I had to replace every hose in the system and the radiator, so I wanted to make sure there weren't any leaks.

And there was a leak (forgot to tighten the rad sensor) so for me it was worth it because it saved me wasting coolant.

 

You can still bleed out air at the thermostat housing by loosening a hose clamp and carefully inserting a very small screwdriver under the hose to distort it and create a temporary "leak".

 

The tank is significantly higher in the GT4 compared to a 308. There’s a small vent pipe back to the tank from the T stat housing .
After a coolant refresh / fill up you can see air burping back into the tank ….bubbles when you initially run it without the cap .
That’s probably why they deleted the bleeder screw in the T stat house bcz air can escape upwards into the tank .
Mines a mk2 single dizzy motor FWIW ?

 

I think that you have that backwards -- they added the thermostat bleeder screw to both 308B/S and 308GT4 circa 1978 as shown here in the 1979 308GT4 SPC:

https://www.ferrariparts.co.uk/Diagram/Ferrari/308-GT4-Dino-1979/016-Water-Pump-And-Piping

If your "1979" doesn't have one, either they were using up the old part, or it was made before the change-over, or someone swapped in the older part. Of course, "model year" is rather iffy for the euro versions of that period so date of manufacture would better characterize your 308GT4's "year".

 

It a late 76 . Italian first reg .

Generic parts diagrams , I wouldn’t hang my hat on them . Helpful as they are there are discrepancies from time to time .

 

Yes, then yours would naturally not have a thermostat housing bleed screw. You made a claim: "That’s probably why they deleted the bleeder screw in the T stat house bcz air can escape upwards into the tank" -- if you have some evidence for that, please post it. The 1976 308GT4 SPC shows no thermostat housing bleed screw. The 1979 308GT4 SPC shows that they ADDED a thermostat bleed screw. Claiming that the SPCs often have errors is not evidence of your (false) claim.

 

Airlift, air compressor, done.

 

The man is right as usual. I could bleed air out of my 328 radiator every time after I've run the car. Absolutely no idea where it comes from, but its always there.

I have pressure tested the system umpteen times & it doesn't leak.

So I gave up bleeding it years ago & the coolant level in the tank is always the same.

In my experience the settled level in the tank (cold) is a bit below half way, if I put any more in it just spits it out the next time I use it.

 

Same.

I had always been under the impression that NO air should be in there. I would frequently bleed the system at the radiator (because it was simple and easy and I have a QV in the deep south) I never saw it without a tiny bit of air - and I had no leaks either. I quit doing this regularly years ago when I finally found out that's normal up on the top of that radiator.

 

Exactly the same here.

Just a theory... I believe air might be entering through the radiator bleed valve when the coolant cools off and a vacuum is created in the system. Air is sucked in over time to equalize the pressure. I think it's impossible to get enough torque on the crush washer just from our finger tips with that small radiator bleed valve screw to make an air tight seal. I believe, again just a theory, the crush washer should not be copper or aluminum, but a synthetic rubber (nitrile or viton) o-ring.

I'm actually putting my theory to the test. After bleeding air out of radiator for umpteenth time, I've replaced the copper washer with a nitrile o-ring. Now, if it will just stop raining, I'll go test it. I'll report back my findings. (Yes. Yes. I know. Rain isn't going to melt the car )

 

I'm gonna say if the bleed screw is water tight under a given pressure, it will also be air tight under a similar vacuum. And FWIW I've been running an O ring at the rad and thermostat housing for the last couple of years. They stay sealed. And the header tank always ends up with some air in it.

 

When did "THE SEARCH FOR AIR" become a thing? Buyers of new 3x8's back in the day didn't have to return to the dealer every few weeks/months to have air bled from the system. So why is regular re-bleeding, specialized equipment, and/or odd parking angles now seen as necessary?

 

It isn’t .

It’s just after refilling it after draining out old .
I mean are you saying after an oil drain + refill …you simply pour in the book vol ( circa 8 L ) and never ever check the dipstick level ?
Even maybe ok on that day a few times and hence forth never look at the stick until the next lub change a whole 50 weeks in between? ( assuming annual lub )

As I said curiosity gets the better in the first few runs out after a coolant change. The rad bleeder is very easy to access and a harmless procedure. Why NOT check it ??After a coolant change ? Or turned around why is it there ? …..before answering think if there’s a bleeder tap on the rads of your other cars first !

I have a cig lighter charger ( phone ) which shows Voltage. There’s no voltmeter on a GT4 ( or on a few cars others in my fleet ) so out of curiosity I occasionally plug it in to see the volts . Volts parked , and V running to check the alternator charge output .
Not every time sure maybe 2-3 times per yr for each car .

If you are going to open the rad bleeder on a 3#8 you may as well do it nose up on a hill especially after playing all the heater controls .

Nobody’s saying it’s compulsory it in the same group as checking tyre pressures , checking battery terminal tightness / cleanliness. Checking brake lights , brake fluid reservoir level etc etc .

It’s sat there a foot away from the battery asking to be opened , like the batt terminals asking to be wiggled .

 

It just defies a bit of logic that air continually finds its way in there.

The only thing I can think of is that there is a constant flow of fluid in & out of the expansion tank and it gets fired in there at quite a rate before getting pulled back down towards the rad & it's possible it's taking bubbles with it from all the splashing around that goes on in there.

 

"I mean are you saying after an oil drain + refill …you simply pour in the book vol ( circa 8 L ) and never ever check the dipstick level ?"

No, I check the dipstick BUT I don't open an oil fitting to see if oil is flowing. To check the level of coolant I open the filler cap and look into the expansion tank. I don't bleed the system to check for the proper amount of coolant, just as I don't open an oil fitting after changing the oil to see if oil is flowing out of it.

Using my 328 as an example, I have never checked for air after changing coolant/bleeding (on level driveway, no special tools). The car has no problem sitting in bumper to bumper traffic at 100+F outside air temps. (It did so for nearly two hours in Las Vegas at 108F). Is there some air in the system? I have no idea and don't care; the cooling system functions as designed. Why go looking for a problem that is no problem?

To paraphrase Pete "Maverick" Mitchell: "I see no need to re-bleed!"

 

You are a classic example of someone who has no understanding of how it works or the physics involved. Yet you cannot help but constantly intervene with a perfect functioning system in the belief you are doing some good, (you are not ) and share your lack of knowledge in the form of bad advice.
Leave the advice to those who do know and stop creating all the inaccurate tribal knowledge.

 

The system needs X amount of air to allow water expansion. Since the radiator top tank is a high point and it is hard for air to be pushed down by water it stays there. To top tank does not do the cooling it is not detrimental for the air to be there. It stays in a constant volume. If the system is filled correctly and working properly and you open the bleeder to let it out all you have done is reduce the amount of required air, lowered the overall fill of the system and probably replaced it with water which will get pushed out the overflow next time it goes through a heat cycle. The locations of the bleeders are cleverly located so CORRECT filling is easily done on a level floor via the force of gravity. I can assure you, the workers at the factory went through no gymnastics or special procedures filling the systems when the cars were new. Gravity is no different now than it was then so no need to do it any differently now.