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antifreeze question

Backstory: '99 Cavalier 2.2. Coolant was low. Then, very low. Thinking it had a leak, and needing to drive it, I added straight water. I drove it like that for a couple of weeks like that, and the water level in the surge tank stayed the same. (So, there's still a question as to why the coolant was low in the first place.) But, for now, my question is ...

I drained the coolant (radiator & block), and got most of it out. I put in an appropriate mix of A/F and water. And, after driving it, the coolant level in the surge tank is down: I had it about 2/3 full; now, it's maybe 20% or less. I think I've seen this before. I've read that A/F expands when it gets hot. Is that true? And, if so, how high should the cold level be in the surge tank?

(Note: I don't see a fill line on the tank, and I don't see any spec in the Chevy service manual. Of course, sometimes I miss things that are right in front of me.)

Thanks, George

Reply to
George
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Coolant flow is restricted greatly until the thermostat opens up. Until this happens, trapped air in the cooling passages can't easily make its way to the top of the system, then out to atmosphere. It takes patience during the bleeding process --or-- multiple top-offs to stabilize the level of coolant in your overflow/pressure tank. Recommended cold level is about 1/3 full on many bottles. It wouldn't hurt to go nearer 1/2 full in anticipation of this slow bleeding process.

It would be wise to diligently keep your system topped off even if you are planning to find/repair your potential leak. Superheated air (voids) in the system can damage deck surfaces and gaskets, causing very expensive repairs.

Toyota MDT in MO

Reply to
Comboverfish

What most likely happened is you had an air pocket in the block, and when the thermostat opened the 'bubble' worked its way to the top of the system(as it should). The air will compress and go past the radiator cap, and bubble out into the overflow tank.

When things cool off a bit the cooling system will draw coolant back into the radiator from the overflow, and the level in the overflow will drop.

I don't think you have a problem right now, just top off the overflow tank to about halfway full and keep an eye on it. Check it every day for the next couple days and see if you are still losing any.

Generally speaking when you change the coolant you should fill the radiator, and while doing so squeeze the upper and lower hoses until you get all of the air out. Then you start the engine and let it run with the heater on for a few minutes until the temp gauge comes off the cold peg, and then you fill it up AGAIN if it has dropped any. The reason you have to turn on the heater is some vehicles do not circulate coolant through the heater core unless the heater is on, and the idea is to get ALL of the air out of the system at once. So you turn the heat on. ;)

Then after you do all of that you put the cap on and top off the overflow tank.

Good luck with it.

Chris

Reply to
Hal

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