Peter 642

Fantastic help; a few thoughts:

Thanks; it went about 100 miles or so, but still. Upgraded cap is the -04, or more recent?

Not yet; I'm going to play the noob and admit that the car is new to me, and that any minor work even makes me slightly nervous, although I did minor repairs to the 944 (window motor, etc). With a diagram and some help I'm sure I can search for how to remove successfully.

I assume this is with the bumper cover removed, and AC condensers out of the way? I don't have a lift, so I'll have to do the best that I can.

I haven't seen dripping liquid or puddles in the garage, but I will check again and update.
Thanks again.

redridge

my bet is that you are loosing coolant from the overflow... the tube drains down the sides and doesnt touch anything (like your ac drain). While you drive it overflows (expands) and when stopped, the coolant resettles below where you last filled it. Im thinking that this level is the coolants normal level.... The min/max window is very small on the tank.... The 996 has cooling issues and this is where your coolant level wants to sit.... its not that big of a deal if it sits at this level all the time. I suggest you drive it more and see if the level continues to drop. If you dont... then this level is normal for your car. But, If you continue to loose even more fluid, then for sure you have a problem. Also, when filling makes sure you burp the line by driving the car for a day or so with the pressure valve open.... after the drive, just close the valve to seal the line. This will purge most of the air out of the line.

Peter 642

Thanks. I did not "burp" the line when last filled, but with this filling today, I will open the valve x 1 day and do so. I should mention that the car is new to me (800 miles ago) and was PPI'd on purchase last month; completely "clean." Unsure whether this would have been seen, if it was a major leak, if they did not drive it.

Stephen Tinker

Peter,
The "burping" mentioned above will require a few heating cycles - up to normal engine running temps and then cooling down to ambient with the pressure bleed valve open. Some people (me included) drive for a few days with the valve open to rid the system of any trapped air. Top up the coolant every day untill the system stabilises.
When I replaced my coolant the first time, I couldn't understand why I was having to top up every other day - I then found out that the pressure bleed valve HAS to be open to expel all the trapped air....

Peter 642

Thanks.
So if I'm understanding right, there's no harm in keeping the valve open for a few days, when the car is either in use or not, in garage? Drive car, let car cool, refill, repeat x few days until stable, all the while with the valve open, correct?

It sounds like the options are (1) this isn't a disaster, it's normal and it may take a few days; or (2) I'm hosed and there's a leak somewhere yet undiagnosed. Either way, a few daily drives with valve open and refilled as needed should do the trick and clue me in.

Stephen Tinker

That is correct. If you do have air in the system, it will take ages to clear without the valve being open and it looks just like you are losing coolant but you are actually only topping up. Of course, if you do have a leak, then you will continue to have to add coolant and it's imperative for you to see where it's disapearing to.....
As a matter of interest, I keep my coolant level approx one inch below the bottle "max" mark, and indicate it with a pencil or crayon. Then I can see immediately if the level changes.
Make sure you fill to the mark with a cold engine and check it with a cold engine, as when it heats up the coolant is above the bottle's "max" line....

redridge

driving with the valve open will not harm the engine at all.... from what I understand, the cup cars run like this during races without issues.

Tarek307

I just had the front drivers side radiator replaced because i cracked it hitting road debree, it took 3 days to get the air pockets out, i had to keep going back to the place to have them top it off..maybe as simple as that! and finally now the coolant smell is going away ..they had dumped some and it burned off and smelled nasty ..these cars are notorious for the time it takes for the air pockets to go away

Peter 642

Took a look today cool and was still right above Min, where I left it. Did exactly what Macster recommended; ran until warm, then 2K x 30 secs, then idle x 30 secs, repeat. Fans went on/off. Shut car off and looked for leak. Not a drop.

Checked the reservoir (by sight only!) when hot; was just under Max. Left alone for a few hours, cooled down and it's back to where I left it cool, right above Min.

Will open air valve tomorrow and this week while driving (keep it open for 2-3 days), then repeat process and see how I do. Let's hope that it's a non-issue, and I can't thank ya'll enough, since it was on its way to the shop before I posted.

Might still end up there, but heck, at least I'm more informed.

Macster

I'm a little uncomfortable running the car with the bleeder valve open. The only thing that keeps the coolant from boiling is pressure. If the valve is open and if this open valve allows pressure to escape the engine could see localized overheating as the hotter spots in the engine flash the coolant to steam and this steam blocks further coolant flow. This is a sneaky kind of problem cause the coolant temp may not, almost certainly will not, go up any big amount since the coolant is flowing by the hottest spots and removing heat.

I've never had to bleed my cars' coolant systems. In all cases the cooling system was refilled using a vacuum/refill system that ensured no pockets of air. And no driving around with the valve on the coolant tank open.

Sincerely,

Macster.

Peter 642

Macster, what makes you nervous? I'm interested in learning, and multiple opinions are the only way to do so. Do others concur?

I'm down again today, meanwhile....

fpb111

When the engine is at operating temp the bleeder is up hard against the top of the bleeder housing.

When the engine cools the bleeder is down unless the bail is in the upright position holding it up (open?).
So driving with the bail up it seems that the engine would not see anything different. It looks like the bail causes a vacuum break that lets the hot air pockets pull water into the maze displacing the air as the system cools??
That is why multiple heat cycles seem to purge the system better then one long drive.

grdtii

Wierd....I am having the same problem! Just bought a 2002 C4S with 30K miles...was having an issue with mildly fluctuating oil pressure gauge, and while playing with the connections, noticed that the coolant level was below Min....filled it up two days ago...looked yesterday and it's back down about a pint or so...after driving only around 50 or so miles...did you ever figure out what caused your issue?

logray

You should never drive it below min mark. If it is low enough you risk introducing air pockets which can cause engine cracks (and much larger problems).

It is possible there is air in your system and since you've added more coolant now it is able to purge this air out, thus requiring more coolant. Or it is possible you have a leak.

When the car gets hot enough the bleeder valve opens by itself thus allowing the system to bleed itself to a certain degree.

Or on a cold car you can manually pull up the bleeder valve to ensure it gets bled (although there are more exact procedures on doing this properly - you should search/read up on the subject).


If you have a vacuum system (such as uview airlift) you can test for leaks and or use it to refill the system properly without any air.

Or take it to a shop that has a vacuum system.