Coolant Boilover

Coming home last night the temperature began creeping up to 190. When I got home and parked, coolant was boiling out of the engine compartment. This morning I filled the empty coolant tank only to hear a gurgling sound. The coolant level quickly disappeared. I filled it twice more only to see the same result. There is no coolant on my garage floor. Questions: Where is the coolant going? Is it a water pump failure? Can I drive the car the 30 minutes it will take to get to the shop?

Look at the dip stick for the oil. If it is milky you have a problem. Check under the drivers side tail pipe. Do you see stains from coolant possibly leaking from the expansion tank? Check the cap? Was the coolant leaking from the cap? Look everywhere you can under the car. Give more detail about your statement, "coolant was boiling out of the engine compartment". What does that mean?

Dipstick clean, nothing but fresh oil on the stick. My understanding, the tank in the engine compartment is a coolant expansion tank. This is the tank that is empty and the tank into which water/coolant disappears. This would implies since the coolant is not on the garage floor, that the coolant I am adding is filling the radiator. So maybe the thermostat is stuck resulting in the coolant boiling out ? Should I just fill the expansion tank until ultimately the furling ceases and the the tank stays full?

When i say coolant was boiling out of the engine compartment , I mean that is the source of the steam . Since the tank is empty I can only infer that the contents in the tank boiled out. Still have no demonstrative leak and can only conclude that either the thermonstat isn't working and/or the water pump. But If no coolant is circulating at all wouldn't that result in the temperature going far above 190?

I'd start with the simple fix of replacing your expansion tank cap. The tank/cap need to be able to withstand the pressure of the system in order to avoiding boiling of the coolant. Because the system is at higher pressure it can withstand temperatures much higher than 190 without boiling. If your cap is not pressure tight, the coolant boils at a lower temperature generating steam, which then escapes out of your cap (which isn't sealing).

well, the boiling is happening due to suddon loss of pressure in the system. Unlike an american v8 the water cooled 996-7 engines are very critical to coolant loss. Even if the temp gauge is not showing a over heat condition, a hot spot and be made in the engine and you can crack a head really fast. I suggest if you do not have the skills to find the issue fast, you take it to someone who can. Have it towed, and make sure it is someone that knows the 996-7.. becasue if you choose some motor head that may be fantastic with the american cars, he can ruin a p-car in a hurry simply from his lack of p-car knowledge.

Need to knowmore about the car, age-miles, and the weather when driving. It may be as simple as clean the front radiators.

But to answer your question about where the water is going that you are pouring in, it is replacing the water that boiled out. So, yes, keep pouring it in until either: A) It fills up and seems to hold without leaking, or B) It starts to pour out from somewhere else. The ONLY inlet/outlet point for water should be the filler hole. If it leaks out while filling, then do not attempt to drive the car for the 30 minutes. Suck it up and have it (properly) towed to a knowlegable certified Porsche mechanic. Could be many things: Bad cap (just old) is not uncommon and it needs to be really cranked down hard after you top off. Easy to replace with BRAND NEW Porsche part. Crack in the expansion tank is not uncommon. more expensive to replace. Water pump would make noise and water would be on the ground. Front radiators need cleaning (remove front bumper, separate each side from the A/C condensor, and CAREFULLY but COMPLETELY clean out the stuff BETWEEN them). Cracked coolant hose. Less likely but possible. And yes, folks do need to know details about the car such as year, model, mileage, and any recent relative services in order to help you efficiently here.

Thanks for the feedback. 1999 C2. 66000 miles. Hot Florida evening. Stop and go driving . Had the car for two months. Great service record and very clean. I had added coolant , maybe 8 ounces, to weeks ago. Driven several times since then. The cap appears tight, but will order a new one.

Make sure you get the updated cap. Part# ends in -04.

Pressure test is the first thing to do. It will quickly show you where coolant is leaking. Don't drive it.

Hopefully you added a compatible coolant type. If not it can gel up and cause additional issues to your cooling system. If you added the wrong type it will need to be flushed

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+1...

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I would also add a deteriorating AOS to the list. There have been several recent posts about the condition of the coolant attachment points on replaced AOSs indicating that coolant had been leaking out at that one or both places. Those AOS coolant hose nipples are pretty fragile and can easily crack through age or damage.

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There's a coolant leak. My WAG would be the coolant tank has split. But a failed AOS that is letting coolant spew out is another good guess, though of course not mine but someone else's. If the tank is split the split can close up when the tank cools down and adding coolant/water to the tank may not have any fluid leaking. The gurgling is the coolant running into the engine's cooling system passages. Regardless, you can *not* drive the car 30 minutes in this condition. Arrange to have the car flat bedded to a qualified shop. You need to get the car to a qualified shop for proper diagnosis and repair, which must include a proper refill of the cooling system with the right anti-freeze/distilled water mixture and with no air pockets in the cooling system. Sincerely, Macster.

Seems the tank is not leaking and/or in need of replacement. Bought a gallon of coolant this morning and added nearly a gallon to the coolant tank. This time the gurling did not occur and the level stayed constant. Ordered a new cap. Will wait until the cap is replaced before taking a short drive. Hoping the cap is the culprit. Else, i would guess the thermostat and/or water pump. If the car begins to overheat again, I will immediately stop and call a flatbed . Thanks.

Flip the bail up on your bleeder, black thing behind the filler in the pic, and run the car in the driveway until the fans come on. Then run the rpm up and down to help burp the cooling sys. Make sure that both fans run at low and high speeds.