NA Overheating Issue after total Engine Rebuild...

[NMX516]

As well as the under tray, there is also a plastic "splitter" type piece between the front bar and the bottom of the radiator which helps direct air through the radiator. With a thicker rad like that one, you've got to be very certain that air can't go around the outside of the radiator - it will take the path of least resistance. I had similar problems when I first fitted my cooling pro radiator, and the solution was to both fit rubber foam around the front edges of the rad so that no air could escape around past the edges, and to remove the front "bling mesh" grille. Doing that solved the problem.

[sabretooth]

If you're overheating at speed then you'll need to look at more than just the fan.

The radiator's thickness is excessive so I'd check the ducting to the radiator.

[Stu King]

Guys thanks heaps for all of your input and opinions... from everything I read it is pointing to airflow through the radiator. Given the Cool pro is about 50mm shorter than OEM, it is my bet (confirmed by many) that the air is simply flowing under neath the cool pro radiator.
I have spent some time today filling in the gaps underneath and the side of the radiator as well as getting a MOSS polished radiator cowl.... I will be testing over the next couple of weeks and will let you know the results...
Once again thanks for all your help...

[Mr Morlock]

seems very odd to me that you buy supposedly a higher performance radiator and it does not work properly?? When you buy the thing don't the instructions or the seller tell you that special care has to be taken with ducting. If Coolpro make it for MX5's surely they have the engineering expertise to include "instructions"- so much for aftermarket.

[manga_blue]

I wouldn't focus on airflow alone. It mostly looks to me like a coolant flow problem. Airflow restrictions cause problems more at the extreme use end but water flow restrictions have much more impact in normal use. If the water goes round and round then 99% of the time the thing will stay cool enough on the highway.

I still can't see where you've satisfied yourself that you actually have coolant flowing through the radiator at any reasonable rate.
When you put the engine back together did you match the new head gasket to the old one to see if it had all the same holes? Was there any risk of wrapping plastic or surplus sealant or anything like that being jammed in the waterworks? Have you tried running a hose through the new radiator to see if water comes out the other end without back-pressure?

BTW fans do nothing above about 10kph. They're for stop/start traffic. At driving speed the volume of air pushing through the front is much greater than what a fan can move.

[Stu King]

***Update***

I fitted the foam beneath the radiator and either side as well. So far the needle has not moved above "1130", and after some normal trips the fans are not running...

Running down the freeway the needle does not move either.... sounded a little good to be true so have triple checked all the basics...

Water is flowing, no leaks, thermo switch works....

Unless anything else pops up I think this is case closed.....

Thanks.

Stu

[sabretooth]

Great result!

[manga_blue]

Yeah, good result.