QuestionQUESTION: yea i have a 93 s10 2.8 v6 and im leaking antifreeze from the overflow reservoir when i drive the thermostat was replaced not to long ago and it started doing this again so i figured it was the thermostat and took a screw driver and pushed it in for constant flow but didn't help
ANSWER: Hey Craig,
The rad cap is designed to vent cooling system pressure and fluid when the specified pressure is exceeded. Usually 14-16psi. Have the cap checked or replace it wiht known good cap.
If problem still exists there might be combustion gases entering the cooling system from a small head gasket leak. These pressure can get quite high and force the coolant out into the reservoir.
The cooling system is designed to transfer coolant to and from the reservoir and thats why there is a min/max level on it. If the reservoir is too full it will overfill it and put coolant on the ground.
Wayne Howie
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QUESTION: i have replaced the resivior cap bc that is where i saw it leaking from but the problem does still persist comes out from the resivor cap so i probably have a blown head gasket?.. if my engine is totally cool the resivor coolant is at proper level, but when i get through driving it, it is flowing out the top of the resivor
ANSWER: Not the reservoir cap, the radiator cap. The radiator cap has the spring loaded seal inside it to maintain radiator pressure.
Wayne
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QUESTION: ok ill check that but one more question if i have the radiator cap off and the reservoir cap off and the radiator cap off shouldn't the level of the reservoir (currently all the way full) drop down some and the level of the radiator come up some? sry for all the questions but im stupid when it comes to vehicles
AnswerNo. If you have the rad cap off and the reservoir cap off you will have no transfer between the two. The coolant level might drop a bit for a while but as soon as it gets warm it will start to spill out the rad fill hole.
Essentially the system is designed to work like this:
When the vehicle is cold and the cooling system is full the reservoir should be between the min and max level. As the vehicle warms up the coolant expands and creates system pressure. That system pressure combined with the glycol will raise the boiling point of the liquid to a maximum threshold. Should the system pressure exceed volume and cap pressure the coolant will work against spring pressure and force its way out of the rad into the reservoir until the pressure lowers. As the vehicle cools down the rad creates a low pressure area (close to a vacuum) and draws coolant back out of the reservoir to ensure the cooling system is full again when started cold. This process transfers back and forth during different driving conditions.
Things like overflowing reservoirs and collapsed rad hoses indicate defective caps. When a head gaskets fail they create a bubble front that forces excessive coolant out into the bottle and onto the ground. A product called IRONTITE can be addedto the coolant to help condition and seal these small leaks.
Wayne Howie
