Running Hot? - 986 Forum - The Community for Porsche Boxster & Cayman Owners

I noticed temp went up after driving home and sitting in driveway idling: Then after driving it came back down. Should I be concerned?

I would be. Those things never get better on their own. Your fan probably kicked in to drop it that little bit. Do you know when the water pump was last changed? Can you hear the fans running?

I had a similar situation with my 996 - check the fan operation - common for fan ballast resistors to fail.

I get similar behavior, if I idle for a bit the temp starts to creep up. As soon as I start driving I goes right back down. Or if I turn on the AC which kicks the fans on high. It never (at least I do not recall) gets hot enough for the fans to come on by itself. Even when I was at Sebring last weekend in 90+ highest it ever got was as high as the first picture though. I figured it was normal. I am not sure what the turn on parameters for the fans are though.

Could be a number of things... Fan, ballast resistors, water pump, low coolant, t-stat, cracked coolant tank, lots of debris in between condenser and rad, etc. Definitely inspect further ASAP. Good luck

I was reading about fans, water pump and cleaning radiator behind condenser. Just bought this couple of weeks ago. I will listen for fans. May be good idea to put new water pump in proactively.

Do yourself a favour and remove the front bumper and split the condensers / cooling radiators. You will be shocked how much debris you will find trapped between them - and it costs nothing. Putting a new coolant pump with blocked rads will achieve very little - but of course if the pump is original or old its an added bonus to change it out too.....

Thanks I will start with bumper removal and radiator clean. Watched video doesn't seem too hard.

Fast way to check to see if your radiator fans are working correctly is to: a) bring the motor up to temp b) turn on the AC full blast (lowest temp) c) get out of the car and see if both fans are blowing hot air toward the ground ahead of each tire. My left fan and/or ballast resistor was shorting out the system and blowing fuses about once every six months, so I bought a new resistor and now it's good. Even when all is working properly, remember you have a real heat reading, not a glorified idiot gauge with a needle on it. There will be swings based on what you're doing with the motor. Interestingly, my buddy's 07S has a temp needle that moves to a preset spot shortly after the motor has been run for x seconds and it stays there no matter what you do with the motor.

This is normal operation for the pre 2001 (non-buffered temp guage) cars like yours, if the following is also true : While idling (or sitting in stop and go traffic) after the car is fully heated up, both radiator fans cycle on (low speed) and off (really off) as the needle hits the right side of the '0' and to the left of it. The actual position on the gauge may differ from car to car, but mine is similar to yours. If the fans are not cycling, than the temp resistors may be bad as others point out. Note that with the A/C running, the fans will always be running at at least low speed and so the temp should only creep up like that under heavy load and then the fans would kick on high at some point.

Mine runs about the same on the temp gauge on a hot day here in Florida. It is a 1997. If I kick on the A/C the fans come on and drop the temp to what was the first temp picture. I have a new water pump and my radiators are clean. My Indy mechanic says that is a normal operating range for an early car with only two radiators.

When the AC is on and the ballast resistors are OK, the fans run at low speed even if the coolant is cold. IIRC correctly, when the AC is off, the fans will run at high speed when the coolant reaches a certain temperature Because your coolant temperature goes up to a certain level and stops when your car isn't moving and goes down when you move forward, my bet is your ballast resistor have failed and the fans won't operated in low speed mode. As another poster suggested, try turning on the AC first thing in the morning when the coolant isn't hot and see if the fans run in low speed. If they don't the ballast resistors have failed.

+1 This is how I diagnosed mine. It was a really easy fix, spliced in a new one part in a bit over an hour. Keep in mind this includes pulling and replacing the bumper cover. The actual repair was only 15 minutes or so.

You don't have to remove the bumper to access the 2 x ballast resistors -you can get to them from under the bumper behind the air scoops.

when i was having this problem I found a DIY on the internet to make a "jumper". I removed the 4 relay's in the fuse box for the coolant fans and using the "jumper" I determined my right fan wasnt working at all, binding and causing frying in the fuse box for the row of fuses for the fans are. My left fan was only working on High indicating the resister was shot. I chose to replace both fans, and cleaned the radiators.

Quotes source post: 450317

True, but I did a rad & condenser cleaning at the same time... forgot to mention it.

Wow thanks everyone! Glad I found this forum

after my low temp t-stat was installed it took much longer for the needle to hit the 12 o'clock position. Sometimes I'll drive for 30 minutes and it's still barely past 180 Lately when its warm out I run the AC even with the top down and just close the vents, not full blast but enough so I can hear the fans. To the OP, if you're still on the original water pump. Get a a new one. That should be changed out every 5 years or so regardless of mileage according to our resident engine experts. get in the habit of checking the coolant level until you get the new WP and make sure to install the latest version of the coolant cap. If your cap is a decade old its probably not holding enough pressure. And if you have a leaf blower or see one of those hose type blow dryers at the coin-operated car washes try blowing out any leaves from the intakes in the bumper vents.

Is there any way we can "evaluate" the age of the water pump? The whole coolant has to be drained when water pump is swapped or it is possible to keep the current coolant?

My 1999 base has always done exactly what yours is doing. I've cleaned the radiators, changed the coolant tank, fluid and cap all with no change. In the summer months the gauge is always slightly to the right of the zero when idling. It will move to the middle of the zero on the 180 once I get moving again. I always thought that was normal?