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Well, its summer and I have noticed some cooling issues when I take my na6 mx5 around the twisties. Had a look at the radiator and it looks pretty beat up and the plastic tanks look ready to die (brown colour) so I went about ordering an oem replacement because I just can’t afford to pay $450+ for an alloy dual core and new fans.

As I went inspecting my radiator I noticed I only have one cooling fan on the passenger side (right side drive car) when I have seen others online and in tutorial vids with two! Am I missing one, did the previous owner not replace a broken one? I can’t find wiring for where the second fan would plug in? Where can I get a second fan from?

Second fan is for air con.

It runs independant just to pull air through the air con and make sure the interior is cool.

Fans dont do ANYTHING AT ALL WHATSOEVER hen the car is moving.

Look elsewhere.

Dann

This is correct only 1 fan spins when car activates the fans when the car is to hot. The other Fan is activated by the A/C.

The tutorial you have seen with dual fan when the car is hot is a diy which slices into the 1st fan wiring which activates the 2nd fan; i wouldnt recommending doing this because it can cause your high-amp fuse to blow.


edit: you beat me Dan

revhead wrote:Well, its summer and I have noticed some cooling issues when I take my na6 mx5 around the twisties. Had a look at the radiator and it looks pretty beat up and the plastic tanks look ready to die (brown colour) so I went about ordering an oem replacement because I just can’t afford to pay $450+ for an alloy dual core and new fans.

As I went inspecting my radiator I noticed I only have one cooling fan on the passenger side (right side drive car) when I have seen others online and in tutorial vids with two! Am I missing one, did the previous owner not replace a broken one? I can’t find wiring for where the second fan would plug in? Where can I get a second fan from?

Replace the thermostat and radiator cap. Most common problem with all old cars is these two items failing. They are cheap and easy to replace.

G

Thanks for clearing that up guys, i had a suspicion it was for AC as my car does not have AC. I’m fitting a new radiator so that should come with a new cap, if not il buy one from the local auto parts store. Out of interest, how does the rad cap cause overheating if I’m not losing any coolant? Is fitting a new thermostat something a DIY would cover or should I just get it done at next service (2 weeks from now) thanks

revhead wrote:Thanks for clearing that up guys, i had a suspicion it was for AC as my car does not have AC. I’m fitting a new radiator so that should come with a new cap, if not il buy one from the local auto parts store. Out of interest, how does the rad cap cause overheating if I’m not losing any coolant? Is fitting a new thermostat something a DIY would cover or should I just get it done at next service (2 weeks from now) thanks

Thermo is really 2 bolts and doesn't really require much effort, but if you are not confident, get it done at the next service.

The cooling system is managed by the thermo, ensuring the correct flow of hot water gets to the radiator via a wax filled valve that, when hot, fully opens. If this item is not opening correctly it can cause problems.

Also, the cap is designed to hold water under pressure. Water won't boil to steam when held under pressure. The caps are designed to hold pressure and therefore ensure water stays as a liquid. If the pressure is lost, then steam is a poor transfer agent for heat, and the system won't work as effectively.

G

The cap has 2 seals one at the top which seals the cap to the radiator and one at the bottom which is spring loaded for the overflow. The bottom seal usually deteriorates first but if either do you lose steam slowly and therefor the system builds no pressure which it needs to increase the boiling point.

Dann

If neither of those help, then look into the water pump.

They can sometimes go rubbish after not a very long time if the wrong collant/water is used.

(for example: my Water pump was 1/2 blocked up with calcium and other sh*t because the previous owner must have used straight tapwater rather than distilled)

Thanks guys, and gslender, that was very helpful and informative, now I have learnt something new thanks! I have ordered a new oem replacement radiator which comes with a new radiator cap which is good, should be arriving tomorrow. I have also ordered a new thermostat and thermostat gasket which is arriving soon-ish. Hopefully these will fix my slight cooling issues.

A bit off topic here but I have noticed my oil pressure gauge is giving me some different than normal readings. Before I changed to semi syn oil the gauge would move the full spectrum under hard acceleration up to red line which is normal and sit about mid point when cruising. But lately on start up the gauge jumps all the way over to just under 5ish and go up to 6 when accelerating only to 3.5k rpm!! But then after some time and warming up will drop down to somewhat normal range again, if not a bit past midpoint? Is this normal for semi syn oil? I changed the oil about 3 weeks ago but only now noticing this??

What rating is the oil? 10W40 etc?

gslender wrote:

revhead wrote:... how does the rad cap cause overheating ...

... the cap is designed to hold water under pressure. Water won't boil to steam when held under pressure...

Ummm, sorta It will actually, if it gets hot enough. The pressure only increases the temperature at which water boils, so that the water may get to, say, 105 degrees but at 106 it will start boiling.

You will be aware that you can get caps with different pressures, so that boiling point can be 'tuned'. Remember too that the higher the pressure, the greater the pressure inside the cooling system - and this will expose weaknesses in the system, especially in old hoses.

I didn't say which pressure, and if held to an unlimited pressure it won't boil to steam. But hey, I wasn't answering your question! Thanks

yeah i just changed to 10w40 semi syn engine oil, and i also filled the gear box and shift turret with some nice nulon (i think thats how you spell it) gear oil. a couple of weeks after that i noticed the increase in oil pressure on start up..

revhead wrote:Thanks guys, and gslender, that was very helpful and informative, now I have learnt something new thanks! I have ordered a new oem replacement radiator which comes with a new radiator cap which is good, should be arriving tomorrow. I have also ordered a new thermostat and thermostat gasket which is arriving soon-ish. Hopefully these will fix my slight cooling issues.

Remember that most thermostats have a right way and a wrong way to install them! They always let a little bit of coolant flow otherwise heat would not be moved around and the thermostat would never open. There will be a small hole in the thermostat that coolant trickles through and sometimes these have a one way valve of some sort, they are generally marked for flow direction.

Just installed a Mishimoto X line radiator today and was testing it and noted only one fan turned on. Panic stations for a while until I read this thread.