Engine temp question

2001 C4 Aero Coupe with no mods at 69.1k I've been driving the 996 all week and the temp has "felt" off to me. The ambient temp has been in the 70s to high 80s when I've been driving. What I've noticed is three things: 1) The water temp gets up to the 180 mark faster than I expect (within a mile or so). 2) the temp continues to climb to a bit over halfway between the two "normal" hash marks over the 10 mile/30 minute commute. 3) The cooling fans are screaming about halfway through the commute, but they immediately shutoff when I turn the engine off and I don't hear the engine bay fan. It got driven a fair amount over this cold winter which may be skewing my view, but my gut says this doesn't feel right I plugged up the Durametric when I got home and got the following temp readings while idling: Engine: 102.0c Engine Compartment: 69.0c Oil: 104.3c Cat: 50c Otherwise seems to be running fine and there are no codes. How does this sound to everyone else? Normal or something to get looked at?

Have you ever replaced the thermostat and the water pump? It may be time... Engine fans can't run when ignition is off (no power to them). If I hear my engine fans running after I park, I will just let the engine idle till the fans are off before turning off the engine.

Nope, both are original. The pump hasn't shown the classic signs of an impending failure (squeal, lateral movement, leaking), but I know that's not 100%. It's on my "while things are torn apart" later this summer when the transmission get rebuilt.

The reason I asked is you said "The water temp gets up to the 180 mark faster than I expect (within a mile or so)." If that's from a completely cold engine, that's indeed strange. Barring any sensor issue, one way for that to happen is the water pump is not moving the coolant. Normally it takes a few miles of driving to get the temp up to normal.

Yeah I would normally expect in the 3-5 range, though this winter with the really cold temps it was just getting up to temp by the time I got to the office which kinda takes the fun out of it The slow to warm this winter was in line with my Cayenne which was doing about the same so that doesn't have me concerned.

I know the feeling. As a temp obsessed driver I can give you my cars norms. All my other cars get to operating temp and stay there regardless of the season or type of driving. The Porsche temp depends on the ambient temp. All winter car runs at a lower temp. I was concerned this winter the car was not getting warm enough. With the temps in the 80's I see the thermostat got into the 0 on the 180. In city driving temp climbs to 99. In prolonged city driving I have seen as high as 104, but usually below 100. I don't have a durametric. I use the secret menu to see the actual temp. And yes, it warms up much,much quicker. But never in a mile or so. At 2.6 miles from a cold start and sitting at a stoplight with the ext temp at 76 degrees (really - this was today) I was still no up to operating temp. Almost at the 8 but not quite. It took another couple miles on the high way to get between the 8 and 0.

Exactly. Up to temp in 1 mile sounds quite extreme. Gnat, how's your coolant level?

Appears to be good and no sign of anything untoward there (e.g. Intermix).

Clean the debris from your bumper. This will create a situation where air cannot pass through the radiators fast enough. Do you have an OEM front bumper?

Its the full MkI Aerokit from the factory. I'll check for debris tomorrow, but it never seemed to collect stuff like the ones I see posted here.

Quotes source post: 12319909

Well, you know the car best and it feels abnormal to you so it probably is abnormal. I can tell you that even on an 80F day starting out with a cold engine neither of my cars' engines are up to temperature yet in just a mile's driving. With a coolant temp of 102C (215F) the radiator fans would be on at least low speed maybe even high speed. (With my Boxster the fans switch to high speed at 216F coolant temperature.) Assuming the temperature is real -- a coolant sensor could be acting up and misinforming you -- did you check the air from the radiators and is it really hot? -- it reads like a T-stat is not operating properly. However, as I mentioned above in just one mile's driving neither of my engines is very warm at all and I'm having a hard time understanding how your car's engine could get so hot in such a short time. Check the radiator ducts for any trash and clean them out if you find any but even if the radiator ducts were completely blocked based on my experience with my two cars I find it hard to believe the engine would be hot enough to trigger the radiator fans in just a mile's driving. (I can drive nearly 10 miles at say around 55mph and the engine coolant only reaches the "180" mark at the time mile point.) If you want to throw parts at the behavior a new water pump and T-stat would be the parts to throw. If you want to do some diagnostics if you can arrange to get the cold car on a lift. Start the cold engine and raise the car and check the coolant fittings at the water pump and block to see if there is a big difference in temperatures suggesting the water pump is not circulating coolant properly or perhaps the T-stat is not operating properly and instead of opening and routing ever hotter coolant to the radiators it is not opening at least not opening fully. Listen to the radiator fans. If the hottest spots of the cooling system you can reach are not yet that hot -- 212F is pretty hot -- but the fans come on that's a sign the coolant temperature sensor is acting up. Be careful under the car for you will be near hot exhaust and very close to a nasty serpentine belt. Get your fingers where they shouldn't be and you would regret it for the rest of your life.

Took it out for a 10 mile errand this evening (forgot to check the rads ). Been sitting in the sun all day with a 90ish temp. On the way out my RPMs were kept in the 2-3 range with a few 3-4 blips. Distance is listed from the trip start. 1.5m the needle was at the 1. 2.5m touching the 8. 4.7m back side of the 8. Parked for 10 minutes. 7.6m brought it to the middle of the 0. This leg had higher RPMs with a nice 5-6k sustained run. Parked for 5 minutes. 9.8m needle was at the back side of the 0. More spirited driving. There is more idling/crawling in my commute, but I usually still find a half mile or so to wind it up to 6+k at better than highway speeds after it is warm (at least in the morning, afternoon sucks ).

I think you may have an air pocket in the cooling system... That exactly the symptoms I had when I replaced the coolant for the first time and I thought I had bled the system properly. Except I hadn't. I have a Boxster S which has a bleed valve in the coolant tank - you simply flip the valve open for a couple of heat cycles to rid the system of air, but I don't know if the 996 differs in that respect. How is the level in the coolant tank with the engine cold?

Or the coolant tank cap or pressure relief has gone bad and made for less system pressure. I'd replace the cap first. It still sounds like a dirty bumper to me.

Quotes source post: 12322883

Agree the OP needs to check the rads. When dealing with a problem leaving no stone unturned is best. Between checking the rads and replacing the cap the effort is about a tie. 'course if the radiators are found to be trashed up cleaning them out takes more effort than replacing a bad coolant tank cap. But it takes what it takes to put the car right again.

At least looking in and feeling around the rads seem clear and very little came out. The bumper was off about 1.5 years ago for a respray. Not that it's even the same fruit, but when I took my P!g out today it's water temp jumped fast just like the 996 did. It was reporting 183 at 1.5m and was at 200 around 3.5-4m which its normal temp. The oil temp was much slower to rise (as expected) and didn't reach 200 until about 10 miles. It's diesel vs gas and front vs rear so it's not the best comparison, but I'm a bit less concerned seeing the Cayenne behave in a similar manner. I'll order a new cap though. It's cheap, easy, and a known problem point. Silly not to go ahead and replace it if there is any question.

Were you able to feel and look between the air conditioner rad and water rad? If so please tell us how, because taking the bumper cover off is a pain.

Quotes source post: 12324361

Nope, just what I could see/feel with the bumper on. I am planning to get back out there this week with my USB scope to get a better look though. Aren't the rads in that pic sandwiched together? If so how would that much stuff get between them?

There's a gap of about 20mm between the radiator and the condenser which allows the debris caught in the bumper ducts to be forced between them by the onrushing air. Its not a difficult job to remove / reinstall he bumper - especially considering the negative of having 5lb of crap reducing the cooling air flow....

Scope didn't really help as the head was too big to manipulate in there. I did bend up a coat hanger which allowed me to get up between the rads a bit and I did get a bit more junk out, but not much. I expect there is more up there, but what I got didn't feel packed in so I don't expect that it's too terrible. Checked the Cayenne while I was out there and found its a good crap magnet too, but the grill is tight enough that I can't get my arm in there at all. That bumper is a royal PITA to remove too