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996 C4S vs C4 / C2 cooling advantage


Sao Paulo
13 Dec 2012
Just a thought but worthy of discussion maybe...

Does any one have any stats about the failure rate on C4S engines vs C4 / C2 engines? The reason I ask is the C4S has bigger rads so in theory better cooling. Does it make any real world difference to engine performance and longevity?

I'm gonna take a stab in the dark and say that it would be more prone to damage
Thought the general consensus was LTT etc to keep engines cooler, oil viscosity higher, protect engine :dont know:
The LTT just opens earlier but once open the flow rate is the same as a standard thermostat seriously I would have thought the bigger rads would be better especially if driving hard
My unscientific assertion is that scoring has more to do with manufacturing tolerances in individual engines and coatings, plus driving style, ie ragging when cold and/or labouring in too high a gear at low rpm. The American forums often say it afflicts 'cold climate' cars more...

Tiptronics do seem more prone, perhaps due to 2nd gear pull away or just being easier to drive harder from cold.

If anything I've seen as many or perhaps more 4Ss having had rebuilds, possibly functions of there being lots built, the 2 yr/20k mile service regimen beginning in 04 when they were selling very well relative to other models, and there being more tips than manuals.

Hopefully Baz will be along to give an informed view!
My understanding is that the problem is the distance of the rads from the engine and hence a lower temp thermostat is recommended to open the cooling system earlier.
Once the system is flowing I don't think the size of the rads have much influence, as the addition of a third radiator was disproved as being helpful during normal driving.
I think there could be benefits.

If I understand correctly....?
The thermostat is on the inlet to the engine at the bottom of the block, The hot water in the block opens the thermostat, cold water rushes in past the thermostat, closing it!

The issue is then cyclic with repeated opening and shock closing the thermostat until everything is warm.

If you over-cool the water in the rads, you continue the cyclic action which means water in the top - furthest most part (Cylinder 6) never gets a chance to get the cooler water as the thermostat keeps closing.

I'm sure Grant has all the stats but, if you either live in a cold climate or keep your air con on all the time, (running the rad fans constantly) or both, it'd be sense that the problem may be exasperated and may contribute to bore score?

Certainly, as mentioned above, the idea of a low temp thermostat is that it reduces the amount that the thermostat is closing and hopefully balances the system better. ie not over cooling or over heating.

BUT - when i'm driving in warmer weather, or giving the car a good spirited drive, the temp wants to sit at 95 deg C, unless I put the air con on and bring it back down again by using the rad fans on a constant low speed.

I wondered if my rads are on their way out and not cooling enough?
Or are they as intended and did Porsche do a better design job on the air ducts on the C4S and Turbo?

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