Rickker

Fergus, does your engine compartment fan come on?

fbgh2o

No, the car never gets hotter than 95C at speed, and even idling it takes a while to get to 100C.

What I have noticed is that if I accelerate hard I can bring the temperature down from 95C to 92C within a few seconds.... I am starting to think that it may well be the water pump or the tension on the belt.

smshirk

My 996 acted exactly as you describe in the summer months but never actually got hot. It bothered me as well watching the needle inch up in traffic on hot days. I went to the cooler thermostat from L&N when upgrading my Boxster engine to a 3.6 and it runs below the 180 mark and thus far has not moved once up to running temps.

BruceP

I'm curious about the LN thermostat, but skeptical for the same reason: I see how it can delay the engine getting hot, but I don't see how it can ultimately prevent it. Like the fan mod, it brings intervention to the table sooner, but it doesn't change the cooling capacity or the cooling process at all.

Especially with the new rads I put in last year, I find my car's cooling system works a treat... unless it's sitting still on a hot day for a long time. Then, even with all the fans whirring away, it gets hot and stays that way until the car is moving again.

To me, a helpful mod would be an aftermarket fan blade that moved more air. That would actually make a difference.

fbgh2o

Have continued to monitor this issue. My indie mechanic has looked at it and cannot find a pressure leak and on the scan tool shows it operating 3C lower than the climate control display and generally within spec.

This said, since my original posting I have observed the following

• 230 km trip to Montreal - temperature consistent at 90C or 91C ; return trip from Montreal - temperature consistent at 94C or 95C - External temperatures within 2C or 3C and dry
• Trip to Montreal in pouring rain and some snow - temperature consistent at 84C to 86C
• Trip to work - temperature climbs to 90C on highway and immediately drops to 84C upon exiting highway. This behaviour is quite common. It will drop 2C or 3C at least upon slowing from 110 kph to 70 kph or less.
• I also find that driving in clean air (i.e. no traffic) results in the car taking much longer to get from cold to 90C+, when compared to driving in traffic where the air flows are presumably more turbulent.

My only thought is that perhaps I have a wonky thermostat, but until the temperatures go well beyond the normal operating range, I am not going to worry about it any more (but will monitor, given my paranoid tendencies )

fbgh2o

Finally found a small leak in the expansion tank and replaced it. Replaced the expansion tank cap with a an OEM one and installed the LN Engineering 160F thermostat. Can runs measurably cooler.

Stephen Tinker

Fergus - good result...pleased to hear you've won after such a long time
I've followed your cooling issues and believe that your original thermostat may not have been opening to its full open position. The only other suspect would have been the water pump not operating 100% efficiently.
I had quite a similar problems as you had and elected to replace the T'stat (160 deg), water pump and coolant together. Temp gauge now sits @ 80 deg unless in heavy traffic.