Hi guys. I have an interesting issue.

Antifreeze is disappearing, but only in certain conditions.

In the wintertime, I drive my FD a lot less often. It gets cold here, and the salt on the roads for the snow isn't exactly something I want on my paint. However when I start it up in the wintertime on days that I feel comfortable driving it, the add coolant alarm goes off.

Here is the weird part. It is always the same amount of fluid gone. About 6-8 oz of fluid. Its only in the wintertime. This doesn't happen in the summertime, spring, or even fall. I've owned this car for 2 winters now, and it has done the same thing both winters, but only in the winters. I've never had to add fluid any other time of the year. I've tried placing rags, towels, blankets, whatever under the car to see if it is dripping, but I've never been able to find a trace of fluid loss. I've also tried starting the car up on different days (2 days from previous start up, as apposed to letting it set for a month and starting it again) but it doesn't matter how many days the car sits, it is always the same amount of fluid gone.

Here's some car specific info
- 1993 Touring
- Car had been in North Dakota for several years, previous owner doesn't know anything about this happening to this car
- Car is parked in the same spot under my carport at night, never anywhere else. It is very rare I take it out of town or over 45mph.
- It is bone stock other than aluminum AST and Koyo radiator. Neither of these two show any signs of leaks, and are less than 5 years old.
- I've watched the fluid level after I have poured it in, watching for the infamous bubbles to see if a seal has gone out, but I have not seen any bubbles. Once again, fluid loss is exclusive to the winter.

It really isn't that big of a deal, I just have to add a little bit of fluid before taking it anywhere when it is cold, but I was hoping one of you guys might be able to shed some light on this so I don't have to keep buying antifreeze haha

 

you can pressure test the system if you go to a part store and rent one of their testers.

 

Pressure test. And I'd closely monitor the level in your overflow and see what that's doing during these times.

 

I have a similar issue. I loose 1-2 oz of fluid after each use.

The car runs and cools fine. No issues in the Phoenix desert. But I'm always topping off my overflow 1-2 oz.

I noticed the belly pan is wet and my foam insulation is soaked. I can see accumulated fluid on the corners of my Koyo radiator. The leak is more of a weep. I can only assume the radiator seals when hot and weeps as it cools down.

Maybe the colder winter temperature doesn't allow the radiator to expand and seal the pesky leak/weep.

I had the radiator epoxied on the lower header but it did not fix it.

My research told me that aluminum radiators last about 8-10 years, so I'm planning on a new Koyo seeing that this is year 9.



On the other hand, make sure your overflow is larger enough for fluid expansion.

You may be dumping your 6-8oz out the overflow as the fluid expands

 

Pressure test the system. Find the leak. Either you are leaking coolant externally, the motor is burning it, or you have a pinhole leak and air is getting into the system and preventing the coolant from being recovered from the overflow tank as the car cools. I use a tester like this:

 

Check the top of the overflow tank to make sure that it is sealed correctly. Once upon a time I had a similar issue where I would drive the car and park it. As the coolant cools off and shrinks, it is supposed to pull additional coolant in from the reservoir. With mine, the top of the reservoir was loose and its hose ended up sucking air. Resulted in mysterious low coolant levels but no leak.

 

All good points. Could also just be a bad pressure cap that is either sealing badly, allowing some coolant to weep past it, OR not holding pressure. Get the cap tester with you coolant pressure testing kit and check the cap. If it doesn't hold the correct pressure for at least an hour I'd get a new cap. Also, test your new one to ensure that it's holding proper pressure. Just because a cap is NEW, do not assume that it's good.

 

Thanks everyone for the advice. Its gotten warm enough here where it won't be a problem until fall, I'll test the pressure out then, and pick up a new pressure cap sometime before then.

 

I use the same one too!!!

I winter drive my fd and ran into this issue as well. Turned out to be the thermowax hose had a pin hole leak that occurred only after 5k rpm and would spray downwards making it seem like the heater hose leaking

 

In Calgary I've had issues with mine where the cold temps of the morning will cause the coolant to drop low enough to set off the buzzer

if i leave the car let it warm up the buzzer turns off

if i add coolant when the car warms up it dumps out of the over flow, its a no win.

 

This makes sense, sometimes when I take the RPMs over 5k or so I get a weird unidentifiable smell. Maybe the coolant leaking onto something hot and burning?

 

Is it just me or does this sound like classic symptom of water seal failure? Starts out leaking (into the engine so you won't find any on the ground) a little when cold, fine when warmed up. Will slowly get worse, most notably when starting cold. That smell is likely the smell of antifreeze burning (sort of a sweet smell). Anyway, I hope it is something else, but I've seen and experienced many of these "mystery" water disappearing cases. . .Look for a little bit of white exhaust when starting cold--and that smell.