Cooling System Bleeding - Symptom?

[Pat Buckley]

After an intake manifold change I have been experiencing what appears to be a bleeding problem.

The car will idle for an hour - the fans will cycle normally - everything seems fine. If I drive it slowly there won't be an issue, but if I get on it at all - as in a blast to 5K - coolant will blow out the overflow at the filler cap and pretty soon the temp guage will shoot up.

I refilled and bled it using a special tool that creates a vacuum in the cooling system. Then I started it up and noticed that with the radiator cap off the coolant will ebb and flow out the filler hole, dumping about 10 -12 ounces of coolant each time.

I am not running the heater - a decision I made to make bleeding the cooling system easier and because I don't need one where I live... Right.

The question is: Aside from the temp guage shooting up, what are some other symptoms of an air pocket?

Thanks.

 

[BruceA]

As water heats up, it expands, which could prove why its coming out of the filler cap, and hence the need for an expansion tank.
How about the manifold gasket? Did you re-use the old one or put a new one on? Im kinda thinking there could be an issue with the gasket(s) if they are new ones you put on. You may have one or more of the water holes partially blocked or similar. I recall one day I had one set for a 'cough, Chevy, cough' that had a 3/8 hole in the gasket where the water entered from the head to manifold. Similar thing, ran cool when unloaded but boiled when pushed. Cured by taking the manifold off and out with the trimming knife .......

 

[Russ Noble]

Pat,

It seems more to me than just a bleed problem.

What sort of bypass is there for the thermostat on the new manifold? Are you running a thermostat? Have you tried temporarily removing it? Try fitting an old one and take the guts out of it so that it is effectively only a flow restrictor to maintain pressure in the block/heads/manifold.

Just a few random thoughts that may or may not help.

Cheers

 

[Pat Buckley]

I have tried it with no thermostat - just a blanking plate with a 5/8 hole in it.

I did put on a new intake gasket.

While the car is idling the coolant surges and dumps about 20 ounces and then the level recedes and then it surges and dumps again...etc.

With the radiator cap on the coolant gets blown into the expansion tank.

I checked compression - 155 - 165 across the board.

Thanks for the suggestions.

 

[Pat]

Pat,

Given the symptoms occured after the manifold change, that would be a logical place to start. I think as the other suggestions indicate, it may be that there is an internal leak to the gasket. I hope not.
One other thought:
I used to have bleed problems on my CAV until I installed a recovery tank below the expansion tank. The recovery bleeds the air and I haven't had any problems since.

Good luck

 

[John Fitzpatrick]

As water heats up, it expands, which could prove why its coming out of the filler cap, and hence the need for an expansion tank.
<snip>.......

Not to be a quibbler Bruce, but the thermal coefficient of expansion of water is only 0.00021 per 1° Celsius at 20° Celsius. It’s not the water that’s expanding, it’s steam within the water, which is probably what you meant to say, right?
I have no personal experience with this, so take it with a grain of salt, but the “ebb and flow” belching of water sounds like there’s a steam or gas pocket periodically being released.