My short list of possible culprits:

Yesterday, the coolant light was blinking while the engine was newly started from cold. Upon return from my trip, I checked the coolant level. It was right on the bottom of the expansion tank.
I added some coolant - perhaps 2 cups - and so far things look fine.

I changed the expansion tank a couple years back. I do not smell coolant after long trips or in the trunk.
But I understand the system is a closed loop.

So the 10,000 question is where did the coolant go?

The fear is a head gasket. But I have no evidence of that. Although I will obviously look for it now.
Other ideas? I would hope for horses, not zebras.

2000, 2.7L

BTW - my commute is exactly 8:02 - at least this AM. I know this because the opening strings of Stairway to Heaven began as I rolled out of the driveway and the end occurred just as I hit the bump stop of the parking space. As a result, my car does not always get close to operating temperature. I typically have several longish trips per month though. No idea if this is significant. Just noted.



Edited 1 time(s). Last edit at 10/01/2019 10:24AM by JMstamford,ct. (view changes)

I had the same issue.
It was going on for quite some time. It was a very very small leak at the water pump gasket.
My Indy called it "sweating". The heat and cold will contract the metal and if your gasket is not perfect it can sweat.
In my case it when on for 3 years until I changed the water pump.

Maybe the cap, maybe a pinhole someplace.

I have a 2 hour trip each way tomorrow. We will see if there is a result. I might have to get out the ramps and start looking around.

It might give me an excuse to deal with the known oil leak.

The joy of 20 year old cars.

What are the last two digits of your coolant cap?

Why didn't you check the coolant level and top it up *before* you drove away?

Boxsterra I think asks the right question, is on the right track.

Most likely a bad cap. Both the cap on my Boxster's tank and the one on the Turbo developed a leak and I replaced both of them. (At different times.) The cap can't hold when the pressure gets too high and vents vapor which of course is water and the coolant level drops.

Do a "hot" pressure test. Make sure the coolant tank is topped up. Not too full but not too low either. Be sure the cap threads are clean and ditto the tank threads.

Then put the cap on and be sure you tighten it all the way. It takes more effort than you might think. But do not over tighten -- probably not possible by hand unless you are the Hulk -- or you can break the cap or worse the tank.

Prepare a piece of alum. foil to "tent" over the fluid access bay in the rear trunk.

With the A/C off drive the car around in town until the coolant is hot enough to cause the radiator fans to come on. Back on your driveway raise RPMs to just over 1K and hold until the radiator fans come on. Shut off the engine. Open the rear trunk lid and "tent" the fluid service bay with the foil.

Wait.

When I did this after not many minutes there was condensation under the foil. While it could have come from any leak I saw no signs of any leaks anywhere and I smelt no odor of antifreeze. I diagnosed cap and replaced it and the disappearing coolant stopped.

Another time I did this and the coolant tank gushed hot coolant.

I stopped the car and restarted. The light was off.

Upon my return home, the light was still off. but I checked the level - and it was borderline low. So I topped off.

I will check the cap this weekend. I hope that is it. But I changed it with the coolant tank just a few years ago. So it is not original. New, of course, is not a guarantee of continuous non-defective performance.

The fact that the tank has been replaced makes that a suspect. You can check that the three hoses protruding from the front of the tank (in the engine compartment) are all straight and have hose clamps near the firewall. Also take the coolant cap off and check the threads on the tank to make sure they're not stripped.

Years ago I needed to replace my tank and I was super busy at work and didn't have time to do it before BRBS. I took it to the Porsche dealer and they replaced it for a fair price. About 100 miles into the trip, one of the coolant hoses came off and coolant vapor started billowing out the back. On inspection it turned out that one of the hose clamps had never been put back in place (it was on the hose, but not in the right place).



Edited 1 time(s). Last edit at 10/04/2019 11:41AM by Boxsterra. (view changes)

Quote
JMstamford,ct
I stopped the car and restarted. The light was off.

Upon my return home, the light was still off. but I checked the level - and it was borderline low. So I topped off.

I will check the cap this weekend. I hope that is it. But I changed it with the coolant tank just a few years ago. So it is not original. New, of course, is not a guarantee of continuous non-defective performance.

Well, I would have erred on the side of caution I think and still checked the coolant level. Having the right coolant level and a good oil level and properly inflated tires are pretty important before one sets off any drive of any length.

Not sure if any of the older caps are still in circulation. When I went in for a cap the dealer parts department had the newer part number cap in stock. This was years ago.

A new cap could be suspect. Rare -- at least I haven't come across any reports -- of a new cap failing but there's a first time for everything.

The new coolant tank could be suspect, but like a new cap new tank failure is rare.

Once again I think Boxsterra is on the right track. The tech when he did the coolant tank on my Boxster told me the job was "fiddly", referring to the work to get the hoses connected to the coolant tank and the clamps properly located and tight.

It would be a easily made mistake to not get one of these properly secure with the result the hose leaks fluid when hot and under pressure.

If it was longer than that, I would have made another choice.
But I know that even the entire drive from home to work, the coolant does not get up to temperature in the winter.
So the likelihood of overheating was almost 0.

Not aware the drive was that short. But I just am not comfortable heading out with any vital fluid low regardless of how brief the trip might be.

1. The darned overflow tank. but you replaced that.
2. Water pump. First they leak, then they gush.
3. Loose hose clamp or failing hose. Sadly, there are miles of them under there.
4. An ageing radiator. Ask me how I know.

I think you would know about a head gasket - that's a LOT of water. So consider that possible good news.

I'd bet on the H2O pump

Grant

Grant

gee-lenahan-at-gee-mail-dot-com