I'm having a problem with losing antifreeze on my '91 Firebird (3.1 V6) and I can't figure out where it's going. I'm losing I would guess around a 3/4 to 1 gallon every 100-150 miles. About 2 months ago I noticed that the heater control valve was leaking so I replaced it. Only the loss of antifreeze didn't get any better. There are no "visible" spots of leakage when I look at the engine and there's never any spots of fluid on the ground under the car. The heater core isn't leaking fluid into the passenger compartment (like it did on my '86 when the heater core cracked). There is no sign of antifreeze mixing with the oil to suggest a blown head gaset. And the exhaust is not billowing smoke (steam) anymore than it should be in 35-40 degree weather so I'm thinking it's not a blown head gasket leaking fluid through an exhaust port and out the exhaust. Although earlier tonight when I was topping off the radiator and I got done, I noticed small spots of water underneath the exhaust tips but I assume that's just normal condensation from the outside temp being so cold and the exhaust pipes being so hot??

I'm stumped on this problem and I'm not sure what it is. On top of that, the fluid in the overflow tank isn't getting sucked in to the radiator when it's low which is also causing a problem and confusing me as to the purpose of the overflow tank (see my other post in this forum).

If anyone has any thoughts, suggestions, advice, or otherwise PLEASE let me know. I'm desperate here.

TIA!

 

In your other post on the overflow tank I stated the radiator cap could be faulty.Have you had the system pressure tested?You might start with a new radiator cap and go from there.

 

whats your oil look like?

 

Brand new radiator cap (could still be faulty). Oil looks like oil.... no sign of antifreeze in the oil.

 

did you recently do ANY engine work? anything at all, even changing the oil. you know what i mean...you did something like changed the oil and then the next day you noticed the problem.

my engine leaks fluid at the thermostat, you can notice gasket leaks when your gasket is soaked in fluid, regardless of engine status. it could be something stupid like a water hose that only leaks when its hot, then when it cools down the crack seals up before it can leak any more. the thing that i do to find oil and coolant leaks is to take it to like a self car-wash and give the engine a gentle shot of water with a pressure washer. just wash the rad, engine block and water pump, and perhaps some other places you think it could be comming from. wash and dry thorougly and then drive around, take perodic checks mayb once a day. try it and see what happens.

 

The only thing I did prior to noticing this going on was change the heater control valve that sits next to the alternator. From the day that I got the car, I noticed anti-freeze leaking on to the ground under the car. Then one day my friend noticed that the heater control valve was leaking. It looked like the diaphragm inside the valve had busted and it was leaking. I replaced the heater control valve and the leak stopped. From that day I have never seen any antifreeze leaking onto the ground. I didn't notice this new problem until a month or so later.

My friend and I have also come to the conclusion that's it's possibly something that's only leaking when I drive the car. Sounds odd if you ask me that it would only be leaking when I'm driving. You would think there would be something, even if it's just the tiniest drop, on the ground when I park the car but there's nothing. But I have no other conclusion as to why I'm losing antifreeze. I suppose I'll just start replacing all of the hoses and the radiator when the weather gets warmer again and go from there. There's only so many things that can be replaced and I figure if I just start eliminating them 1 by 1 eventually I'll find the problem. 98% of everything under the hood is the original 15 year old parts anyway so it probably wouldn't hurt to change some things anyhow.