fhp911

My new '11 Boxster S repeatedly overheated at a recent track day. It was VERY hot -- more than 103 degrees.

It had behaved just fine a week earlier at a 90+ degree track day.

One weird element is that the temp needle was fine for the first 10 minutes of the sessions and then it would shoot up into the red zone at the 11th minute. (As soon as I drove off the track the needle fell to the normal level.)

The dealer later replaced the thermostat, which doesn't seem to me to be a likely cause.

any ideas?

Macster

Are the radiator fans working properly?

Are the radiator ducts clear of trash/debris?

Some cars have coolant temp sensors/senders or dash gages that react more to coolant temp swings. Or it could be the t-stat.

I had the water pump on my 02 Boxster go out and along with the water pump the T-stat was replaced. A Porsche dealer did the work.

Afterwards, this new t-stat seems a bit lethargic compared to the other one, the original one.

What this means is the new t-stat seems to be slower to react to temps and opens slower/later perhaps then the original one.

As a result, the in-dash temp gage needle moves about a bit more than it did before. When the engine is hot the in-dash gage needle rises higher swings further to the right than it did before the T-stat change.

I've had my car in some pretty hot conditions and after one I consulted with the dealer's service department manager and the SM consulted with the factory and the word from the factory the SM passed along to me is as long as the warning light is not flashing or there is no other signs of distress the cooling system is fine.

Be sure you keep an eye on the coolant level and if it starts to drop there's a leak. The cap comes in for suspicion in many cases and rightly so but there can be other sources: water pump, coolant tank, a radiator has a pin hole in it, and so on.

Sincerely,

Macster.

stevecolletti

Is it a manual or a pdk? Pdk-equipped cars get the third radiator (in the middle). It is supposed to be relatively easy to retrofit the 3rd radiator.

fhp911

It's a manual, not pdk.

I've heard about the 3rd radiator, but I shouldn't need it, right? These cars ought to be able to take track use even on a hot day, yes?

So I assume there is something wrong -- not that I should have to add an extra radiator (at my own expense.)

stevecolletti

One would think not, though you are not alone. There are a couple of people on the Cayman Register (thread on overheating and another on adding the 3rd radiator) that have the same issue. To me, it's odd that the 986 Ss had the 3rd radiator and less horsepower.

This is something I'm watching closely since I have 6-speed Cayman R coming.

Macster

Your car may not have a problem. 103C is only 217F and I've seen in my 02 Boxster coolant temps up to 226F for for several hours or more when driving in amibient temps of over 110F one blazing hot summer day in AZ.

As long as the oil is proper (I had fresh (around 1K miles on it) Mobil 1 0w-40 oil in my Boxster's engine) and cooling system was in good shape and the car worked just fine and came out of the experience with no harm done. I've covered over way over 100K miles in the car since then sometimes in near the same hot conditions with no problems.

Your car may not have a problem.

Sincerely,

Macster.

cvazquez

I agree with Macster... below is just a recommendation:

1- Change your oil to 5-40W
2-Low temp thermostat instead of factory thermostat starts to open at about 187° F (86° C) and only fully opens at almost 210° F (99° C). The low temp opens at 160° F (71° C)
3- Add wet-wetter to your coolant system

I hope this helps.