Update : some around the block testing and extended idling for 30 mins and the oil temp is 92 deg C which is good for this M5 , normally it's at 95 to 100 deg C so the fan is showing an improvement.
There's a track day next Saturday 4 July and we'll give a further update then.
For the first time the M5 didn't lose any coolant but he temperature starting increasing at the end of the day.
We tracked the fault , the electrical connector for the fan couldn't handle the heat and vibration and was intermittently failing to supply power to the fan.
Tony, how about hooking your factory electric fan to a 318i fan switch? This fan is very powerful, and well ducted. But to our conversations on another thread, , the fans become relatively unimportant at higher speeds. Above ~70 mph , a well ducted system will likely be hindered by the fan, and the shrouding which makes that fan work well at low speeds.
Have you watched for the operation of the factory electric fan, and checked for correct correlation between temps and fan operation? An infrared temp gun is extremely important.
Losing coolant? Oh crap, that's not good. (I lost coolant once on the track....nozzle of aux water pump broke off)
I'd have to say you need that big Summit rad, suitably modified. Hose fittings are perfect for stock BMW hoses, on the M30 engined cars. almost certainly the M5 too.
I don't promise that this is the exact radiator I modified; I remember 27", and Chevy pattern....and you really can't beat that price!
Before the coolant loss was from the overflow on the coolant header tank on both the M5 and the 530 which means the cooling system was at the limit, this has been cured on both cars now.
On GA25331 both fans are being triggered by a standard M5 temp sensor at the moment.
In the next few weeks we are having an aluminium radiator fabricated with bigger side tanks and 2 temp switches similar to what is in my 530i M60B30.
A summit radiator will cost us over $500 by the time we ship it and put cash into the hands of a long line of officials.
The custom radiator works out at around $400 and getting cheaper with the falling Indonesian currency.
The set up in the 530 uses a 318i 80/88 temp switch for the pusher fan and M5 91/99 switch for the puller fan.
On the 530i this car never gets past the needle tangent to the centerline on the temp gauge even at the track day yesterday.
I've only seen the puller fan switch to high speed once which was yesterday at the track day. Normally the puller fan will come on at low speed , run for 2 mins and switch off , run for 2 mins , switch off.
The 530i is my DD hack and test mule , it's using a stock M5 M5 pusher fan in the puller position because 1. We had one laying around the workshop and 2. it fits.
It won't fit on an M5 , there's not enough space , if it did fit I would have used it again on the M5. We had to use a slim SPAL fan.
That's a very pretty radiator; you obviously have a very talented welder there, the welds are gorgeous. Unlike your big Spal, those slim-fit Spals don't pump much air.
Do me a favor; put a piece of rubber under the hooks holding the radiator. Aluminum hates direct vibration in stressed locations, and that location gets stressed. (Ask me how I know)
A small rubber mat was put in under the hooks a few days after these photos were taken , this was the first trial fit.
I'm using an M5 pusher fan in the puller position on the M60 and that moves a lot of air , more than the SPAL , that fan won't fit in the space on the M5 so we're using the SPAL
Oh YES, the factory pusher fans move a LOT of air.
I think you've likely pinpointed your issue, to fuel quality. In 100F heat, my engine cooling has never really been an issue, in heavy traffic, or in full tilt track use..
In fact, I've never even had cause for concern; my coolant does not run hot, and I use the oil temp or tire greasiness to tell me when I need to rest my only car. (Full-tilt Track Use, after ~40+ minutes) I am very gentle on oil temp, because I can't afford to fix the motor if I break it.. Other than that, I am extraordinarily abusive to my lovely car.....And it likes it, too.
As for the rubber mats; THERE YOU GO! Great minds think alike.
How did you use the factory electric fan backwards? Does it run backwards when you wire it backwards?. I'm sure it would, but I've never tried it, because, well, there's no room there! (On an S38 or M30, anyway) Great fix, though! Factory stuff is more reliable than aftermarket, when it's possible to use it).
Oh YES, the factory pusher fans move a LOT of air.
How did you use the factory electric fan backwards? Does it run backwards when you wire it backwards?. I'm sure it would, but I've never tried it, because, well, there's no room there! (On an S38 or M30, anyway) Great fix, though! Factory stuff is more reliable than aftermarket, when it's possible to use it).
The pusher fan is running in the normal direction , the 'nose' of the fan is next to the radiator core making it a puller fan.
It's not ideal but it WORKS well.
I've also removed the rubber strip at the back of the bonnet on the 530 , to let all that hot air out. Yes it's a low pressure area at high speed but it hasn't caused any problems.
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