M30B35 Cooling Conundrums

[E3Oggy]

Hello all,

I'm sure cooling questions come up time and time again and after reading dozens of threads online and spending countless hours tinkering I've not been able to solve this as yet - though I have my suspicions that I'd like some feedback on please. To set the scene it idles and drives fine. If I give it some gas on normal (30 mph) roads it will start to creep just over half way on the temp gauge but will soon return to half way as long as it keeps moving. If I pull up at lights or stop however it will start to creep up to the point where I panic and either turn off the engine or put the hot blowers on which seems to hold the temperature. I've bled the system more times than I care to remember and have tried every suggested method on the Internet; I'm confident there's no air in there!

This leads me to think that the cheap 14" eBay electric fan I'm using may not be efficient enough, which might explain why it tends to creep over when stationary.

However, before I commit to buying a better Spal (or similar) pusher fan (which is my intention for long-term reliability anyway), I want to make sure I've correctly identified all of the potential issues. The other component that I think may be contributing is the temperature switch. The only information I could find on this at the time was vague, and the wiki suggested use of a 91oC temp switch for single speed fans. Being a hobbyist and scientist by trade (but certainly not a mechanic or engineer) I thought this would be "wing-able" and opted for a universal inline temp switch which activates at what I thought was 88oC (but turns out to be 90oC) to control my crappy fan. I (perhaps wrongly) assumed that this was a fairly universal temperature as there was option to specify pipe diameter but temp was fixed for all models. Unfortunately I've more recently learned that the M30 thermostats open much lower at around 80oC.

With these points in mind is it possible that the fan is kicking in when the temp is too high to deal with? If so is a 90oC switch too high for even a decent pusher fan to deal with? I guess in most situations electric fans disengage when they've done their job but loosing the viscous makes this scenario different, i.e. the fan should be on permenently anyway to keep stable once the car is up to operating temperature?

For the record I'm using 50:50 water:coolant and have swapped the M20 brown sensor. My hoses are set up similar to those featured on the wiki using the appropriate T-pieces.

As such any advice/knowledge/reassuring stories would be very much appreciated!

All the best,

Oggy

[Rav335uk]

Hi Oggy,

A few questions first.

What radiator are you using?

Have you checked the thermostat opening temp, and whether it is working properly.?

Cheap ebay fan may be also an issue.There is an adjustable inline temp controller for the fan, this allows you to adjust the temp the fan kicks in.

The biggest issue on the conversions is the fan and radiator setup, and this needs to be spot on.

[jimbom30cab]

Agree with Rav. I had a 88/80 switch, e28 535 rad and 16inch kenlow fan and the temp never went over half way.

M30s make a lot of heat.

Also drilling a 5mm hole in the top of the stat helps bleeding

[E3Oggy]

Thanks guys, much appreciated. I'm using the 535i rad with recommended hose set-up. I've not had the thermostat out to check it as such but it seems to open when I'd expect it to by feeling the top hose and return and monitoring dash temp (crude method I know). I've suspected the cheap fan all along but after discovering the thermostat operating temps are quite low I started to get concerned about the temp switch may be too high also. I've never let it run to the point of actually overheating, but I know if I did the temp would go up and up whilst the car is stationary. I just want the cooling to be absolutely perfect before I take her out for any distance...

Thanks again.

[zaust]

Which hose have you located the temp switch in ?

[rob0r]

I've had an absolute mare trying to keep my E30 M30 conversion cool. I ended up buying a brand new 16" Mishimoto fan which was advertised for working in both directions, it also was rated at something like 1850 CFM. After I fitted it the car was still overheating... the fan was the issue. I think some aftermarket fan makers are very optimistic with their CFM ratings and even if more established makes (Spal/Kenlowe etc) rate their fans lower they are actually far more likely to keep the car cool.

In the end I fitted twin Range Rover (P38) fans which required trimming the front panel slightly and with no other changes the car never goes above halfway in traffic. Fans fitted as OEM from other cars are cheap off ebay, are likely to be easily powerful enough to keep an E30 M30 cool enough and be more reliable than CHEAP aftermarket fans.

[Rav335uk]

I'm using a Peugeot 307 diesel fan on my conversion

[E3Oggy]

Cheers for the input everyone, and apologies for the [very] late reply. I have a hectic job and rarely get time to work on my car at the minute, but I bought a 16" Spal 'pusher' fan and fitted it in replacement of the cheap eBay one. The car got to temperature and just as I thought it was up to its old tricks and about to creep over I literally watched the needle drop as the new fan kicked in. With a bit of tweaking of temp switch configuration sure enough the needle sits exactly where it should do now and has done for the last few weeks during all kinds of driving (and waiting in traffic).

I'm now one of them guys that can't recommend buying a decent fan enough!

Thanks again,

Oggy

[rob0r]

Good news, decent fans for all!