Climbing temp gauge
 

Both fans are blowing full blast, and my coolant level is between the min and max lines. I'm also using a low temp thermostat.

Any idea why my temp gauge is past the 0 in the 180?

You did look to see for debris clogging the radiators?

I guess that's next!

How about checking it against the diagnostic display on climate control?
How old's the WP? Could be failing (broken impeller)? Thermostat not opening all the way?

Water pump failure

I've seen a few boxsters that had a lot of junk in between the condenser and radiator also. In fact, cars from Houston and eastward seem to have that problem more often. Boxsters from climates where it snow tend to have more dirt and very small pebbles crammed up inside the fins.

first thing I would do is check to make sure your coolant fans are working properly. PedrosBoard as a good diy. basically you remove the 4 fan relays above the fuse block and make a jumper using wire and a couple of spade connectors. Put 1 connector in the bottom middle slot and one in the top middle slot (before doing check pedros board I am writing this from memory). When I did this I found my right fan was not working at all the the left side only on high speed. the right fan was binding and causing my fuses and fuse block to fry. I replaced both fans and while I was at it cleaned the radiators. they weren't that dirty but while I was in there I cleaned them. Car ran much cooler but still had issues. replaced the thermostat, water pump, and front engine mount. I used a low temp thermostat. I found the thermostat was not working properly so that was another issue. the water pump was fine but while I was in there I replaced it. Lasted 2 years and just replaced it again, fortunately it just started to go so impeller hadn't self destructed. I also added an S center radiator from Woody. I have an 99 base. the center radiator was probably overkill but I can be stuck in traffic on the highway in 95 degrees and the car stays cool. I recommend checking fans first quick and easy. Contact me if I can be of any help. Just saw your initial post, oops fans are ok. I saw on Wheeler dealer big Edd used some kind of special coolant when they were restoring a TR6.

RandallNeighbour:
What's the driving situation?
Will the temp drop when you drive steady in the 45-50 mph?
I find I need steady driving in this range to get the temp to drop once I see it go into the 200s (At the right side of the 8 on the gauge).
How about hwy driving?

Last year I flushed the coolant system installed a new WP, low temp thermostat, and a center radiator. I have found that below 75° F the coolant temperature never exceeds 180° C (82° C), however over 75° F it will start to get into the 100-110° C range (the zero in 180 or past it), mostly in traffic or around town.

I have found turning off the AC helps it cool down. And I drive with the AC diagnostic menu up to keep any eye on the coolant temp, you can find that here: CB-Racing, 986 AC Diagnostics I am currently looking into wiring a switch to manually trigger the engine compartment fan and the high speed radiator fans. My next step will be adjusting the mix in my coolant from 50/50, to 60/40 coolant/water.

I have the same problem. After replacing the waterpump and after vacuum purging the coolant, once the temp reaches operating temp, if I let the car idle, it never cools down, the fans wont shut off and the temp creeps up past the second white line, past the 0 on 180 at which point I shut the motor off.

I guess I'll try cleaning the rads.

Would a bad thermo cause this? I would think that if it sticks closed, the motor will just overheat.

As long as I am driving or as long as I bump the idle up while not moving, the temp will go down.

For comparison, I recently replaced my water pump and all the rear hoses.

This past weekend I had to drive a 280 mile road trip (one way) to visit my dad. The outside air temperature went from low 90's at the start of my trip up to 102 degress. It bounced from 100-102 for over 100 miles on my outbound leg.

In heavy stop and go traffic (right where I expect the boxster to start hemorrhaging coolant) the needle would climb to the edge of the "0" in 180. Once moving however it would go down a needle width or two.

On the open road I tested out the theory of spinning the engine faster for improved coolant flow. Quite repeatedly, I was able to lower the temp to the right edge of the "8" by running 6th gear. If I down shifted and ran it that way the temp would increase (around the middle of the "0"). Rinse, repeat, I did it several times.

That was not the expected outcome - for me anyway. I faced similar temperatures on the way home and the car behaved perfectly for the entire road trip (another thing I'm not used to).

More surprisingly, I've found that I can run the A/C and it will run cooler even stuck in traffic (right between the "8" and "0"). Again, not expected by me since the condensers for the A/C are in front of the radiators and therefore add to the heat problem - not to mention requiring more effort from the engine to run the compressor.

Also, (and you'll want to verify this on your own) the way I learned it was that increasing the ratio of coolant/water is the wrong direction. Coolant is good at not freezing, but it's not awesome at carrying heat away. That's done by the water.

Are we taking into account the fact that the oil cooler is dumping BTUs into the water system?
I ask this because Last year I installed new WP, LT stat new hoses AND the larger S oil cooler on my 2.5 base. At the same time I removed both radiators and had boiled out and flushed. Now I have been watching the temp display on the AC panel religiously.
As Rick3000 says below 75 deg ambient the temp gauge at cruise speeds is at the 180 hash mark. Once temps move up the temp also increases. When I get into the hilly twisties the temps rapidly climb and will get to the right 0 edge, approx. 213 deg.
I think the additional BTUs (and ESPECIALLY the larger S cooler) due to work load rapidly heat the water the radiators are trying to get rid of. The LT stat is wide open with full flow to the rads. At this point if the radiators are not 100% you are fighting a losing battle.
My theory is this, it is only a theory. Increasing RPM on say the freeway only increases the BTUs from the coolant and the engine oil. I found that running in 6th with the resultant decrease lowers BTU output and the engine cools.
I also think that part of what stop and go does is lessens the air flow across the sump. If you think about the 100 deg differential between the 200 deg oil in the sump and 100 deg air, a considerable amount of BTUs are being swept away. I think a finned sump cover would be awesome.
I also have concerns about an engine with a LT stat, and S cooler in the winter. This may be due to my old school thinking but If oil in sump never gets above 180 how does it boil off the contaminates? Water boils off at 212 deg. Now at 6"WC vac (sump pressure) water boils at approx 195 deg. Is this why our cars have a 195 deg stat stock?

edit: Randall could your increasing temps be due to the increased humidity you guys have this time of year? Humid air has less effective heat adsorption?

911monty, I ran the LT thermostat and an S cooler last winter (temps down to 0° F) with no issues, my oil analysis also came back with no issues. :cheers:

Yeah I followed your threads and you also installed the center rad, which I did not, but it sounds like our cars are behaving very similarly. And you as I both live on the West Coast where we rarely see less than 20 deg. I suspect your 0 must have been at Mammoth Mtn.... :). I don't know what your all in was to install the center rad, but I have been considering the CSF radiators which will increase the capacity above the center rad without the added complexity. This is why I have been thinking about the main oil volume in the sump never getting above 180 (My oil and water temp are typically about 3 deg difference.) This would be akin to short drive cycles in the winter. So if I go to the CSF rads with the increased capacity, I may also go back to the 195 deg stat to ensure the oil gets hot enough. Again these are my thoughts on this since installing the S oil cooler.
The only reason I brought up in this thread is I'm not sure most consider the oil cooler as being a significant portion of the cooling system.

You are overlooking the fact that your oil is always hotter than your coolant, otherwise an oil to coolant cooler would not work. Even in the dead of winter, your oil is hotter than 200F, even with a low temp stat and the larger oil cooler. We have customers running low temp stats and using the cars in zero and sub zero F environs; UOA's show no adverse levels of water our fuel contamination whatsoever.

This is good to hear! I upgraded the cooler on your statements that it's the best upgrade to do for your car! I agree with it's a must do upgrade since it can transfer much more heat than the smaller cooler which certainly helps the engine internals. I do believe that it is really an exchanger and can exchange heat in both directions. I would think the coolant heats faster and can help warm the oil on startup. The one piece of this puzzle that I'm unsure of is, does oil temp on the Durametric actually indicate oil temp. I know the level transmitter has an oil temp sensor, but there is conflicting info on if it is actually measured or it is only used to backup oil level.
What I have observed is my oil temp on the Durametric is usually 3-5 deg higher than the oil temp on the AC panel which is extrapolated from water temp. So I have been basing my observations on that. So what I see is water 180 then oil is 183 durametric and so on. i know you have a lot better data since the 996 engines actually read oil temp.

Running the AC forces the fan on at high speed, that's why the temperature goes down. All points to a broken load resistor preventing the fan to run at low speed.

Durametric is reading the oil temperature using the sensor in the oil level unit, and it is accurate. The AC display, on the other hand, is not as accurate.

Thanks for the clarification! :cheers: