Centre radiator kit... anyone fitted one?

I was wondering if anyone her has experience of fitting a central, 3rd, water radiator to their 996 :?: It is on my list of additions to make to my car this year and before I purchase a kit I was looking for any advice regarding problems to watch out for and a guide as to how much time to allow for the job. Thanks in advance :thumbs:

Fitting instructions, part numbers etc all here. He reckons c.4 hours. https://www.renntech.org/forums/tutorials/article/69-3rd-radiator-install-instructions/

Thank you, that is exactly what I was looking for. :worship: You see that is what is so good about this forum, perfect. thanks again :thumb:

You are welcome - good luck and let us know how you get on.

Personally I wouldn't fit one without a thermostat for it. I will be looking at doing this on my car at some point and inline thermostats are available. My reasoning for this is as follows. As I understand it the thermostat on the 996 is on the return side of the coolant flow from the radiators. As such this will do what it can to regulate the temperature to the thermostat temperature. If the temperature drops it will reduce the flow. The temperature drop across the radiators must be the same as the temperature rise across the engine in steady state, therefore if the temperature drop across the radiators is increased, the temperature rise across the engine will also increase. Therefore the engine will actually run hotter on the outlet due to the reduced flow. When the engine thermostat needs to be open all the time then the extra cooling would be good, but under more normal conditions I am not sure that it is. MC

I believe Hartech recommend against this, for those very reasons.

I've driven mine on track and not had a problem with overheating. Personally I wouldn't bother to fit one unless i had a real issue with heat that I needed to solve, and even then my first port of call would be to remove, inspect and flush the radiators already there. The OP may have already done all this though. Please take pics and walk us through your experience. I can't access Renntech.org, they're blacklisted with my ISP (or they've blacklisted my ISP). Either way, I can't access it, and I would be interested in the process.

Interesting comments indeed. My reasons for wanting to add this to my car are that although I have increased the performance of the car somewhat ( 200 cell big bore cats, free flow rear boxes, performance manifold, K&N cold air intake/ wider range MAF/ 82MM throttle body/ REVO remap) I haven"t addressed the cooling needs of the motor at all (yet) other than new water radiators 2 years ago, low temperature thermostat and alloy housing and a new water pump last year plus the addition of Water wetter to the coolant. The concern I have is that, not on the move, but in standing traffic (I live and work in town)the temperature does wander up from 80 to 90+ easily. It drops immediately once on the move and all the fans check out as operating normally.

Adding another rad won't really help in traffic. When you are stationary, there is no air flow and cooling air is provided by the fans so the temp is then controlled by the thermostats which control when the fans cut in. This temp is higher than the normal running temp so that they are not running all the time. You could look at reducing the temp at which they cut in, probably a good idea for all of us with low temp thermostats. Are your fans working ok? See other threads on the resistors.

I would think you've probably increased the power of the car by 20hp if things are working well. Given that's a 6.6% increase, I wouldn't think it warrants another rad. Also, you mention you're in traffic in town when it gets warm. You're not using 320 horses in town all at the same time are you?

They sort of do and offer an in line thermostat with housing. I fitted this with the 3rd rad following their instructions. Day to day temps about the same, higher loads (including traffic and "runs") have resulted in lower than previous temps - it doesn't move that much.

You could fit all aluminium rads from a company like CSF, their rads claim to be 10-15% more efficient than the OEM ones.

I have fitted one, its not difficult but not as straight forward as the Renntech instructions. Fitting the passenger side hose is a pain in the @rse I ended up almost taking the rad out to enable the required access to torque/tighten up the hose clips to a level I was happy with. Driver side access is easier. Dependent on your front PU you may need to cut out the centre section with a dremel as oppose to the instructions shown on Renntech, I did with my aero PU. As others have stated when the car is static it makes no difference to temps, I did mine as I track my car, I also installed a LTT and modified my a/c to improve cooling. I see the addition as preventative maintenance, the X51 ran a centre rad, my temps on track even with a high ambient only just breaks the 0 of the 80, I know some guys see circa 100 on track so from my perspective I think its worth while.

This is looking like a very likely option. Once I have had a good root about with the front off I will make a call based on the condition of the rads in situ. If they appear good then the 3rd rad and thermo are more likely but if they are showing signs of age or blockage I will go for a pair of super shiny CSF's. Watch this space :grin:

I've had one fitted for a round 6 years and know it helps with cooling when really getting on it or at altitude, I don't have an additional thermostat fitted. I fitted mine before Hartech did their long time research into this and what is supposedly happening is, the now cooler coolant reaches the main thermostat and it is closing slightly more due to the colder temp and can cause hot spots in the engine due to the slower coolant flow. This is what Hartech found from their research. As I said mine had been fitted years, I have monitored it for all this time and I have never had a scored bore due to hot spots, if it had caused any issues I would have removed it. The third rad mod has probably helped keep my bores in good condition, it still has no scoring after 118k miles (around 65k miles with the third rad fitted) I do think it is saving the engine rather than causing it any harm. And yes it is fairly easy to fit.