Third Coolant Reservoir Cracked and Leaking

[ChevMali99]

Hi friends,

Just as the title states, this is what I'm facing. I've already sent for a fourth reservoir... my question: Is there anything I could do to avoid this from happening a fourth time? I don't fill the reservoir full but is it odd that there is no way for "excess vapor" to escape and thus relieving "pressure" and avoiding further cracking. Though I'm seriously thinking of changing cars, I'm very curious as to why the reservoir in this car continuous to fails. Could the fact that the radiator and the entire cooling mechanism is closed?

The malibu, minus its three flaws - Intake manifold leak, unreliable gas gauge, and cracking coolant reservoir, is a decent car.

[FISH96]

the system is not closed. as the coolant expands and moves to the 'bottle' ( actually an expansion tank) the air pocket above the coolant in the bottle is compressed. if the air reaches the limit of the cap the excess pressure is vented to the atomsphere. as the coolant cools and decreases in volume it is drawn back into the engine. the pressue cap allows outside air into the bottle preventing a low pressure ( partial vacuum) area to exist. i suspect the pressure cap is your culprit. if you look at the part of the bottle that faces the fire wall you will see a small diameter rubber hose( 3/8") with the outlet facing down this is the point where the excess pressure; above cap rating; is vented and air is drawn in as the engine cools.

[FISH96]

clarification needed the air pocket above the coolant is compressed by two actions: the movement of coolant into the bottle as it is heated and expands, and the heat transfer from this coolant to the air thus expanding the air volume,

[johnaschmitt]

I've been through a few of these as well.

I agree on the cap not releasing pressure. Often you will find a good deal of brownish sludge on and in the cap. I'm not a doctor, but that can't be helping. Could be the reason I had one tank split right on the seam.

Another weak point is where the two smaller lines clamp on to the surge tank. Be sure they're not transferring any strain to the little tubes sticking out of the tank. I had one crack at that location.