Hi All,

I've been thinking about various cooling upgrades for a while as I have a hot running issues whilst on track (circuit). I've seen temps a little over 120C whilst on track and on a cool down lap they dont come down by more than 2-3C unless I turn the heater on. Oil and trans temps in similar ranges as I would expect as they are are cooled by the same coolant circuit. I dont have any temp issues around town, it runs "hot" in traffic which is fairly normal for a benz (95-100C, really hot day 105C), drops to 87-92 at cruise and aux fans pretty much always on at least low speed in summer with A/C on when stationary.

I was seriously considering a custom radiator to help with this issue but I managed to get a NOS genuine radiator with box damage for the right price. Just looking the radiator fin design on the "new" radiator I was starting to think I'd found the cause of the problem. The "old" radiator design looked like it was blocking air flow at high speed and hence the limited capacity under high spped and loads.

My original radiator was the one fitted since new, I've had it out before to get it flushed and confirm there are no blockages. It uses round tubes and very closely space fins, it very much resembles a heater core design rather than what I'd expect to see being used as a radiator. The new design cross refernces to also fit a CLK55 (W208) and SLK32 (R170), both are based on W202 chassis design so not surprises there, it's an identical shape but it has the transmission oil cooler in the radiator end tank. I've just lef tthe cooler blocked off and retained the std C43 trans cooler, for those who are concerned about transmission temps then maybe ultalising the facotry cooler AND the cooler in the radiator might be a cheap option. The tubes in the new radiator are thin and flat for the full thickness of the radiator with a fairly traditional fin design.

Anyway, I swapped the radiators. If you're ever doing a radiator on your C43 then I would suggest checking the harmonic balance whilst the radiator is out, always change the top idler pulley as the radiator needs to be out to get the bolt out and hose out the condensor from the back to make sure it's clean. I would also suggest replacing the fan shroud (very cheap) as they bow and shift the top radiator hose closer to the drivebelt. The shroud is cheaper than the hose!

End result, Immediately I notice the aux fans wouldn't come on, I had to block the radiator to make sure they were working! 2-3C lower tems in traffic, but if it got hot they came down really quickly once moving. Did a track day yesterday so finally got to see if i was right........Big difference!
The car was on circuit for nearly 4 hours, 20mins per session, 2 drivers back to back for 11 sessions and only turned off once for fuel in pit lane. My dad couldn't get temps over 95C (He's still a beginner) and the Highest I could get as 104C but on a cool down lap ot would drop very quickly to 95C. To me 104C is absolutely fine considering the coolant is also used as the trans cooler and oil cooler. Especially seeing C63s are seeming to have trouble running on the circuit at all due to overheating!

Anyway, have a look at the pics and you'll see the problem is pretty obvious!

 

Thanks for the interesting info and pointing the way to improve the cooling

 

Very good input,, Thankss for sharing.....

ZAYED,,