Odd overheating problems

allstaruk · January 24, 2006, 04:25:40 PM

Cool but why would the be dirrectly affected by pressin the air con button as soon as I do the temp goes up and as soon as its turned off it starts to drop.

nikp · January 24, 2006, 04:34:51 PM

Well, if it\'s a screwey gauge and sensor, then maybe its misreading the temps. Not saying that thats the problem, but i think thats the first place to start looking - as the symptoms are so wierd!

allstaruk · January 24, 2006, 04:42:57 PM

Just started her up with the radiatior cap off and after about 20 seconds the water level rises apprx 5mm then stays where it is there is some vibration in the coolant but deffinately no bubbles coming through.

I then took the kettle outside set it up under the bonnet and dropped the sensor in it turned it on the kettle boiled at exactly 100 on the gauge so there is no fault there.

What should I check next? Is it worth changing the thermostat and coolant before I try anything more extreem, where would I get a theremostat from quickly?

Alan

nikp · January 24, 2006, 04:49:25 PM

Yeah, get a new thermostat in there, and flush the coolant system. Then re-fill. Use a coolant flush too to get out any crap thats lying in the rad.

allstaruk · January 24, 2006, 04:54:26 PM

Cool what the best way to go about this, should I just pull the lowest pipe I can find on the radiator off and drain the coolant that way.

iaint · January 24, 2006, 05:46:08 PM

Could be a dodgy water pump - it\'s mechanical (not electric) and may be past it\'s best. Not sure how to check though.

allstaruk · January 24, 2006, 06:14:37 PM

You could be right I don\'t know how to check either and I have an MOT of fri.

iaint · January 24, 2006, 09:18:36 PM

Shouldn\'t fail the MoT for high temps

Mave · January 24, 2006, 09:35:52 PM

Problem with an MoT is that they might leave it running with the engine on to help with emissions and then overheat it.....

When you\'ve got high temperatures, are the radiator and bottom hose warm? If the thermostat is stuck closed, the bottom hose will be much cooler.

shaunwil · January 24, 2006, 09:45:32 PM

Just out of interest has the front bumper been modified for the numberplate ? There may not be enough air getting into the engine bay to allow it to properly cool down. Have you always had this problem, or is it a new problem ? Have you warmed the car up and checked to see if both of the fans kick in, there is a thread with a fan mod somewhere that lets you control the relays to get the fans to kick in when you want them to.

Shaun

nikp · January 24, 2006, 09:51:49 PM

Quotethe bottom hose will be much cooler.

Thing is, if I understand Allstaruk correctly, he has his temp gauge plumbed into this bottom hose - so the high temps are reading off this.

Ok, so the gauges appear accurate - next guess would be clogged rad, or something blocking the air cooling the rad. However, still don\'t know why when the fans come on temps get higher!!!!

allstaruk · January 24, 2006, 11:51:10 PM

Hi,

The sensor is plumbed into the coolant filler neck (the piece infront of the alternator that you remove to get to the thermostat).

I am still very lost, tomorrow I will try and get some coolant flush tried halfords todays as it was the only place open but they didn\'t have any, also if i can get a thermostat I will change that.

How would I check the waterpump?

The fans come on when its parked on my driveway surely it doesn\'t matter if the fans come on during driving as the air flow should be good enough.

A

Martiny · January 25, 2006, 08:12:34 AM

I would only use a genuine Mazda Thermostat, so you would need to get one from Mazda, or perhaps one of the vendors on here would supply a Mazda one. Else, call Roteckniks.

There are 2 places to drain the coolant.

1 - there is a plastic plug in the bottom of the radiator.
2 - There is a plug in the engine just underneath the sparkplugs.

Download the factory service manual and it will show you these 2 places, plus it will tell you how to replace the thermostat.

Question - do you have the big plastic tray under the engine fitted?

iaint · January 25, 2006, 08:46:49 AM

Could the water temp sensor be suffering heat-soak? I know it\'s an issue with the standard air temp sensor - it\'ll read much hotter than the actual intake air temps in the stock location... Could be picking up very high temps if it\'s situated too close to the engine block...

nikp · January 25, 2006, 09:25:13 AM

QuoteCould be picking up very high temps if it\'s situated too close to the engine block...

That seems plausible.

You could try relocating the sensor to the entry to the radiator, instead of below the filler neck. Thats where most people put their after market coolant sensors.