Glad this thread seems to still be active.
I'm in more or less the same boat but with a small twist.
Last sunday I was doing a mountain run with two 993s. The hill climb is hard and the car normally runs at about 190-200. It's mostly a 2nd gear 6k climb witht he occasional quick grab of 3rd. The boxster has done it a few times before in the heat and even chasing 993s has had no problems. 2/3 of the way up the mountain the temp needle pegs and the red light comes on. I pull her over and shut the engine off but leave the key in pos. 1 to keep the fans running. Jump out and have a look around back. Coolant is POURING our of the corner by the pass rear tire. I pop the trunk. All kinds of steam coming out of the cap. However the carpet is dry. Key is still in so the gauge is still active and the sucker is red hot. Got to cool it down fast!!! Jump in the car and crank the HVAC heat to max with the fans at max. Start it up and turn it around. Put it in neutral and start coasting down the mountain to get some air flow over that sucker. Instantly the temp starts to drop. Within a couple minutes it's at normal temp. Ride it on down to the bottom of the hill and shut er off. Temp is cool enough to open the fill port. The level has dropped about 2.5" below min. Top it up with water. Start it up. Seems ok. Decide to go up the mountain at 3/4 speed and see how it does. It's fine. Get on it through the top sections. Still fine. Pull over at the top with the 993s. Leave the key in pos. 1. Fans don't seem to be on. Temp spikes! more coolant comes out (not nearly as much). Check the fuses on the radiator fans. They're ok. Fans come on after a minute or so. Temp is still high. Jump in and head down the back side of the mountain with the 993s. Temp drops instantly. It runs fine all the way down the backside. At the bottom of the hill I don't want to shut it off. Idling at the side of the road it doesn't overheat. Coolant level is holding. Drive it all the way home (40miles). No problems. Shut it off. No problems. Drive it on an errand. No problems. Coolant level is a little low. Top it up.
So the car has sat since sunday while I've been reading up on my little problem. I'm thinking the classic split tank. Pull all the carpet and board out of the trunk today. Little to no residue anywhere and the carpet is totally dry. Tank appears to be fine. What gives? Might be a faulty cap, but that wouldn't explain the coolant pouring out the bottom. Car ran and cooled fine after the loss but haven't driven it since sunday.
The only other thing that happened before the run was the day prior when I changed the oil and pressure washed and degreased the underside of the engine bay. I mean I layed into it with a pressure washer (with the engine running of course). I suppose I could have screwed something up with the pressure washer but I imagine if I did I would have had problems long before the 50 hard miles or so I drove on Sunday before the overheat.
Any thoughts?
How did i lose so much coolant so dramatically with out getting it in the trunk? Where am I losing if from? What detective work can I do?
Any help would be much appreciated.
thanks.
UPDATE: When I pulled the plastic cover off of the fill port cluster, there was lots of coolant residue in there. Of course I wasn't suprised the way the sucker was steaming over on sunday, but then I looked at what appears to be a drain tube in the middle of the cluster. Is it possible that my cap is bad (I have the old style) and all that coolant boiled over thru the cap and came out the drain tube??? Would that account for it overheating in the first place?