SARRAS

Intro and Caveat: Its been noticed that a lot of RX-8s are now experiencing main radiator fan failure. This can be chronic as in the fan seizes and blows the fuse, or vastly more subtle in that the fan gets stiff in the bearing but continues to rotate, albeit not fast enough to do anything useful.

I have a 2005 (2006 in US Speak) RX-8 with 60,000 klms on it and it has the MazSport (?) aftermarket fan mod which makes the fans cut in sooner, so its possible that it has worn its fans even more than other RX-8s of the same vintage. I also have the Racing Beat gauge set so I get something of an accurate reading on the water temperature...

Anyway - 'normal' behaviour in this car with the above setup is that she runs at about 95 celcius on the RB gauges (203 F), then the fans cut in to rapidly drop the temps down to the mid eighties (185 F), and then the cycle repeats and so on.

Mid January this year we were driving along and it was particularly hot (in Sydney, outside temp 39 Celcius ((102 F)), and I heard the VERY LOUD version of the marbles in a can thing happening above 4,000 rpm - its quite loud when it does happen! Scanning the gauges I realised that my water temp was over 105 celcius (221 F), which NEVER happens usually. So we turned the air con off and drove home slowly with the temperature hovering in the high nineties. It would hit past 100 and then the secondary fan would kick in, and bring it back to the nineties, but no lower.

I have since pulled the radiator and the fans and guess what - the main fan is stiff in the bearings and clearly would not be doing a very good job, though it was still running as such. As you can't see the fans in our cars, the only real way to test this is to pull the fans from the vehicle.

So - to recap and add some comment. No blown fuse occurred, and the main temp gauge was reading perfectly 'normal', but clearly the car was running hot. As it was not getting cooled as it should be, which means cavitation at the water pump could well have been happening (the loud MIAC noise)... and the only outward sign of this is the higher temp readout on the Racing Beat gauges and the Marbles In A Can noise. If you don't have the RB gauges or similar, the ONLY sign of a similar main fan failure would be the very loud version of the MIAC noise as it won't show up on your main temperature gauge... so my caveat here is if you experience a very loud MIAC, its very likely caused by a failing fan and / or imminent destructive overheating.

Where we went after that. I considered several options... my main aim was that if the radiator had to come out anyway (pig of a job), it was going to be replaced with something better, and of course I needed fans. Cost was a concern as was availability in Australia.

In the end I went for the Mizu double core radiator and fan shroud / fans set. The radiator is a beauty - well made and correct placement of all pipes and fittings - dual core as mentioned and the finned mesh is, I would estimate, about 25% less dense than the factory radiator - so unlike some aftermarket radiators - air flow through the radiator should be good (I keep seeing that Koyo for example, are too finely finned for the RX-8). The shroud itself - also well done but after we fitted all I found out that the fans themselves are not up to the task in the RX-8. With the Mizu fans installed the car was running in the mid 90s all the time in mild autumn weather.

The Mizu supplied 12" fans are actually something more like 10.5" in a bevelled rim, and they're weak - 80 watt motors only. So I sourced a set of Italian designed SPAL fans which are a true 12" fan, at 350 Watts per motor, and after hours of dremelling and grinding the Mizu shroud to fit the actual 12" diameter of the SPAL fans, we now have excellent cooling performance and the behaviour as per the gauges has been better than the original setup.

So a word of advice to all on the Mizu arrangement - if I had to do this again I'd go the Mizu radiator but use the RX-8 second generation fans as detailed on here by Ash8. By the time you pay the extra for the Mizu shroud and fans, then chuck the fans and buy the SPAL fans, you'd be better off spending your dollars on the Series 2 fans and shroud, and bolt that to your lovely new Mizu dual core radiator. Pic below of the lot installed!

Update - apparently the standard OEM fans are 1700 and 1300 CFM respectively - the Spal model used above is VA10-AP10/C-61A and they move 1540.0 cubic metres per hour or 909.0 CFM each.

Twiztog43

iTrader: (15)

i agree that the Mizu Radiator is a good deal, but i disagree on the fitment.

a friend of mine also got the Mizu radiator, and we both ran into the same problems. we got our radiators from 2 different vendors and about 6 months apart.
1. fitment for the fans was off. i believe the right upper bolt hole did not align right with the OEM fans.
2. the right upper bracket did not match up with the bracket on the car. so we only bolted it with the 2 lower brackets and the upper left.
3. we needed to use washers as spacers so that the OEM fans would not make contact with the Mizu radiator and cause a leak.

but overall, it does the job. no issues so far, other than the install. but at least you wont have to worry about the plastic becoming brittle, because its fully aluminum

SARRAS

Hmmm that's interesting - so with the Mazda shroud the fitment is off - definitely something to keep in mind then. Since I used the Mizu shroud fitment was good and the other advantage is that the way the fans are mounted with bolts and two nuts, I can remove each fan and then the shroud out through the top should the need arise in the future. That you cannot do with the factory shroud - its all got to drop out the bottom in one piece with the radiator AFAIK.