www.RX7fb.com

It's been a frustrating few weeks trying to chase and rectify issues. My initial diagnosis of a faulty viscous fan was only partly correct.

Step one was installing an electric cooling fan


And a fan controller to monitor the actual coolant temps rather than trusting the OEM temp gauge. Thanks Jesse for the great deal


Early static testing had the OEM guage still reading unusually high while the fan controller proved that radiator temps were fine. So best try a new sender then, more on that a bit later.

Next stage was a short drive. Within ten minutes, OEM guage is 3/4 up the scale but a quick engine bay check reveals coolant temps are still good. I decided to head back anyway as the traffic was going nowhere fast.

Turned out to be a wise decision ...







Things had gotten a litle melty for some reason!










For reasons yet to be understood, this connector didn't appreciate being used as a 12v ignition source


It was a wire from the connector that I used that got hot inside the main connector block. That block was resting on a cable tie and it was the plastic cable tie that melted, caught fire and started to melt other stuff. Damage looks a lot worse in the pics.


Black blob in the center is the melted remains of a cable tie. That is what burned and caused the melted mess although I probably got off lightly.






So began the unwrapping of the loom section to establish damage. The heat damage made the wiring closest to the plug unusable, First thought was to unpin the plug and replace the wiring with a stripped down section that I already had.



Turns out, the pins on there were not compatable with the plug anyway so I had stripped the damaged loom for nothing. Plan B was to source an entire loom section. One call to Tim at RX Motors had that sorted.

So ... while I'm busy with refitting wiring and getting the fan to not melt anything, I have a curious dilemma to sort out with regard to the coolant temp sender. Having replaced one before on my previous motor, I know that it should be M8 diameter thread. This duly arrived from RockAuto and turned out to be too small.
Thanks to Pete (DKWW2000) for sending what should be the proper item, nah, thats also too small

The sender that I've removed from the rear plate / iron is M10 diameter and it has me stumped.

The one on the right removed from the car. Left from RockAuto and Pete.


You can see the difference here M10 (R) vs M8 (L)


edit ... a little more investigating has turned up some helpful photos with what might be a potential solution. Quite expensive as a mazda part from Mazdatrix / Atkins but a quick cross reference on Rockauto gets me an OEM eqivalent for 1/4 of the price so it's worth the gamble.

Let's hope you have sorted all the problems now, sounds like you may have got off lucky.
Dibs

Lucky to catch that before any more damage occurred aye bro! Damn temp senders in these hahaha

Looked like you dodged one there Dave!
As you say could have been worse.
The Temp sensor.......perhaps a previous owner stripped thread & Tapped out the larger or was it another Mazda change prior to FC?

Damaged loom section replaced. Electric fan working fine and doesn't melt stuff now.. 12v ignition source from the unused A/C fuse and manual control using the aerial switch.

Used a infrared thermometer to prove some temps. Seeing high 90's at the factory temp sender area (rear iron), the rear of the water pump, top of the thermostat housing and top of the radiator so I'm not holding on too hard to the temp sender theory but there is a replacement coming anyway

There's not too many options left, water pump and radiator are next on the list. Strange that temps have just increased without warning. There's no evidence of coolant levels dropping, no steam at the tailpipe, no mess in the oil filler cap.

The Goodwood weekend proved that temps do come down once the car is moving at a decent speed and in decent airflow.

I'm considereng flushing the cooling system but everything that came out when I changed the thermostat gave no cause for concern. No rusty stuff at all, just a nice blue color. Next update when the sender arrives.

DKWW2000 wrote: ↑Mon Jul 05, 2021 7:40 pm
The Temp sensor....... was it another Mazda change prior to FC?

It is looking that way Pete. Hard to speculate until the thing turns up. I was lucky to find pictures and it was easy then to compare. Of course, thread pitch could be the ultimate spoiler but lets not go there just yet.

High 90's is getting pretty warm imo. Isn't the thermostat fully open at 90C? I set my fan to come on about 90 from memory

What does the fan controller say the temp is in relation to the infrared gun?

KiwiDave wrote: ↑Mon Jul 05, 2021 10:21 pm Damaged loom section replaced. Electric fan working fine and doesn't melt stuff now..

The high amp from the e-fan have had demage the loom section Dave?

spirit r wrote: ↑Thu Jul 08, 2021 10:05 pm

KiwiDave wrote: ↑Mon Jul 05, 2021 10:21 pm Damaged loom section replaced. Electric fan working fine and doesn't melt stuff now..

The high amp from the e-fan have had demage the loom section Dave?

The fan feeds directly off the battery so that's where the amps are. The offending wire is just a 12v ignition source so should be pulling very small amperage. It is still a mystery Thomas. I still think it was just the wrong connector choice on my part.

Hobbawobba wrote: ↑Tue Jul 06, 2021 9:44 pm High 90's is getting pretty warm imo. Isn't the thermostat fully open at 90C? I set my fan to come on about 90 from memory

What does the fan controller say the temp is in relation to the infrared gun?

There is some difference in the readings but Davies Craig do point out that a probe into the radiator fins is not the most accurate method of measurement so I will need to bring my target temperature down on the controller.

I have discovered today that the fan is not working properly. It's not the controller, it is a faulty fan. The fan motor was getting up to 112 deg C in testing this afternoon. It's for the bin.

Just managed to get a replacement unit fitted before the darkness arrived. Final testing tomorrow