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Damien

Engine Cooling System - alot of heat

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Hi everyone,

I am totally new to Rotary and have just invested in a mid year 2006 RX8.  Perhaps a little the worst for wear, but mostly it appears to be cosmetic at this point. I have just completed an oil and coolant change and both done without a hitch.  The car has 158,000kms on the clock but starts within the first second and appears to run very sweetly indeed.

When the car arrived (seller delivered it after a 3hr drive) the cooling fans were really at full blast and after engine shut down took about 10mins before silence.  This spurred me to change the coolant (as I don't accurately know the history and care I like to start from a clean slate)  Tonight (its 0 degrees out there) I took it for a quick drive - 10min drive and after start up 5mins sitting - but upon my return the cooling fans were on and didn't shut off for maybe 5-7 mins after engine off.  I can appreciate that this is the car's system for cooling but my question is after such a relatively short journey should the fans be needed to come on?  Temperature gauge is indicating that all is well and exactly where it should be so really nothing appears wrong but the car just seems 'hot'.  Perhaps the RX8 runs hot? Any 'this is normal' or 'you need to check this or that' would really be helpful.  Piston/Cylinder I totally get but Rotary - so interesting!

Thanks for your time.

Damien.

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Hi and welcome to the forum Damien, does sound strange how it would be on for that long as the weather is quite cool, hopefully just something small triggering the fans to stay on like a faulty switch.
A code reader would help to see if you have any codes and how hot it is but If you don’t have a code reader where about are you and someone might be near by with a code reader for yah. Fair play for changing the coolant but any harm asking which coolant it was:)

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muck and Aido - thank you both so much for replying to my query.

I 'invested' in an OBDII reader - a cheap nasty ebay bluetooth units for a big sum of €9.  So I ran some tests tonight - let it warm up from cold (its 0 deg outside) and then took it for a quick spin (2miles) and never let the revs above about 3k.  Temperature on return was reading 99 deg C - the fans hadn't come on but I'd say it was only a matter of a minute or two and they would - in all fairness 99 deg the water is boiling - so this can't be right! So it is good to now know where the temperature really is and armed with that I am now thinking perhaps the thermostat has seen better days - the RX is an 06 so I suspect it has never been changed. 12 yrs of opening and closing and now just isn't opening enough - would that sound about right do you think? (temp gauge never moved so muck I am bearing in mind your thoughts on this.)

Aido, unfortunately I do not have the luxury of having a Mazda dealer near me to get the correct coolant so I depend on the local auto factors in Sligo. I got a bottle of Prestone Antifreeze Coolant Concentrate - it is supposed to be safe to use on any car..(paper and labels never refused ink!) but I know that even before the coolant change the whole heating issue was there - as the 'careful previous owner' delivered it after a 3hr drive and the fans were going crazy when he arrived - this is the same 'careful owner' that left it to me with oil a mins (I did an oil change too - put in Halfords 15W-40 Mineral Oil.)

The way I look at it with this car is I am, as such, starting from scratch - its history and care is somewhat questionable - have new plugs to go in at the weekend and brakes (pads and discs all round) so maybe I should add thermostat to this list? - what would you think?  The car is a 'project' so if I break something - it just means I have to fix it - no biggie, as that was the reason for buying it in the first place - to 'mess', experiment and learn with and maybe make a somewhat reliable car out of it...looking good so far!!:P:wacko:

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Look I’m in Sligo to and a bit like yourself I am trying to learn bits. So, I bought a second rx8 for parts but can’t get time to break it although I have a little bit done. If you are feeling confident enough you are welcome to come to take whatever parts you may need, I guess with cars it’s all about having the right tools so I may not have all of what you need regarding tools.  That coolant is fine do shoot me a pm if you want to arrange to come down to pull a part or 2 to see does it help you.

 

Also, Marcin in MG Motors is fairly clued in on Rx8s and does Diagnostics for about 50 notes. Again you are welcome if you want to trial so parts:)

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Hi Damien ,

Any chance the Rx8 has been re-mapped check with @littlefeck and see if he has done any of the Fan mods on it ? ,

Other than that they are staying on quite long would maybe check Thermo sensor on the block they rarely go wrong but just and idea ! 

Regards

Dale !

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Bradyy - I don't think so but I can't confirm 100% that is hasn't been re-mapped.  I'm not convinced that there is any issue with the overall cooling system in the car from the point of view of the fans because it is in essence doing what it is supposed to - the bigger issue now is the fact that after a 2mile spin, without any pressurized revving or 'spirited' driving the coolant temperature is reaching 100 deg C!

I am going to try a new thermostat just to see if that makes and difference and will of course report back.

Aido - delighted to see another RX8 owner within the county and will compile a PM for you and thank you ;)

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9 hours ago, Damien said:

Bradyy - I don't think so but I can't confirm 100% that is hasn't been re-mapped.  I'm not convinced that there is any issue with the overall cooling system in the car from the point of view of the fans because it is in essence doing what it is supposed to - the bigger issue now is the fact that after a 2mile spin, without any pressurized revving or 'spirited' driving the coolant temperature is reaching 100 deg C!

I am going to try a new thermostat just to see if that makes and difference and will of course report back.

Aido - delighted to see another RX8 owner within the county and will compile a PM for you and thank you ;)

 I’d swap your thermostat and water pump for starters so ! 

Otherwise I’d start doing a coolant system pressure test etc ! 

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So just to update and close this thread.

Ordered the relevant thermostat from the local auto factors (82 degree unit) and installed it at the weekend.  A reasonably straightforward install

(have to admit I found this youtube invaluable: https://www.youtube.com/watch?v=TrNG5z0vUcw&t=415s )

and the nuts on the tube on the manifold from the air pump valve loosened with just a little spray of penetrating spray.

So I am glad to report that the replacement of the thermostat appears to have solved the over heating issue. (I suppose it does not seem like there is an issue as the only indicator is that the cooling fans are running at full blast - because the temperature gauge seems to happily sit just below centre irrespective of temperature!

Using an OBDII Bluetooth adapter I monitored the temperature and I never seemed to climb above about 93 degree C - this was just sitting - no driving - however a quick drive (speed slow but revs up a touch!) and at no stage did the cooling fans come on - before this after two or three mins they would be on - and persist as the temperature would not decrease.

I hope I have this solved - my only concern is what other damage has been done because of this issue and when will it raise its ugly head - and I do not know for how long it has been like this :huh::( oh well I am sure time will tell but for now onto the next job - new discs and pads all round!

Thank you to everyone who has contributed and helped solve this first problem - ( I suspect one solved of many to come :D ) 

 

 

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15 hours ago, Damien said:

because the temperature gauge seems to happily sit just below centre irrespective of temperature!

Apparently it can move past half way. But I think the temperature needs to be approaching that of nuclear fusion :lol:

Anyway, glad you're sorted

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