Hello All, regarding the attached, this is about as far as the temp gauge on my 2007 MK3 gets, can I assume this is a sign of a stuck open thermostat?
temp gauge by Fitzer1, on Flickr
Cheers
Ian
FWIW…my 2006 2.0l runs at half way on the guage
A stuck-open thermostat is the most likely cause - it should read more-or-less in the middle of the gauge.
Do you notice the car taking a long time to warm up - silly question really, because it is obvious that it is not warming up at all, but I’m sure you know what I mean !
Short Answer - Yes, probably…
Slightly longer answer - But it might be the temerature sender unit instead.
Even longer answer - Try feeling the temperature of the top rad hose and the bottom rad hose when it’s been running for a while - how different are they? Should be a at least 25 degrees diference - warm enough to feel it. Has the system been drained recently? Could be an air lock. Tried removing the expansion tank cap (Slowly!)? Is it pressurising?
Does the heater give a good strong blast of really hot air when set fully on? If not, it’s probably the thermostat.
Just my free advice - money back if not happy!
Aldi
Argh, lost all I posted, pressed wrong button.
Many thanks all, haven’t checked the rad hoses, will do so. The heater ‘seems’ warm enough but then I have nothing to compare it to (had the car 6 weeks), warm up time seems fine, gets to the position shown in about 3 miles. It’s a 1.8 and has full Mazda service including the last in Jan and has 75k miles so I don’t know when it would have been last drained etc. I’ll check the suggestions inc. expansion tank if it ever stops raining and the heater tonight. Thanks again.
For what it’s worth, mine never goes above “4 o’clock” on the gauge i.e. just about 1/3rd of the way up. It’s been the same since new.
H’mmm…interesting that…!
How long does it take to get to ‘4 o’clock’?
Mine gets to about halfway point from cold in about a mile of gentle driving, as does my friends same model (2.0 NC).
That warm-up time will readily show if the 'stats working properly, I think.
I’d say that mine doesn’t get much higher, maybe 4 oclock sames Andy.
For what it’s worth, I just looked on Google images for MX5 MK3 Heater Gauge, and the ones I found were between 4-5 oclock, so I don’t think that i’d be overly concerned.
Yep mid position is the norm on these, well 2lr engine.
The car is not due an antifreeze change until 2018. Therefore it is unlikely the coolant has been changed.
My 2008 1.8 runs with needle in the middle.
Yep, about five minutes or three or four miles driving, and my temperature gauge climbs up to mid-point on the dial, and stays there all day.
Well, you learn something new every day; mine has been at the same position (5oclock) since I’ve had it. assumed it was normal. the heater is toasty after a very few miles so presume the sender is slightly orf
Naive question, perhaps…
Do all NCs have the same thermostat setting? I notice the ‘older’ (NC3.0) model owners who have replied all say - halfway. The later ones (NC3.5+)seem to say less than that. There were some engine mods between the two models - was the t’stat setting one of them?
I don’t think so, but stand to be corrected.
Aldi
I heard that convertibles have very hot heaters (for obvious reasons) and on my MX5 it’s true: It’s like a furnace!
If it doesn’t get very hot on full blast I’d say the thermostat is stuck open too.
My 3.5 is halfway if it was less than that thermostat or sender needs attention.
My 2.0L SportTech 3.5 goes to about 4pm too. No higher than a third of the way up. Not had any issues with in cabin heating. Always been like that.
Interesting subject his.
With mechanical and electrical equipment of any kind, there is bound to be certain operating tolerances - leeway if you like - to the way the different components interact, and therefore the readings they give are bound to vary a little from car to car.
I would suggest that getting to know your own vehicle, and in this case, the readings that the dials and gauges normally give, would be a good idea. If your temperature-gauge needle only climbs a third of the way up the dial, it may be normal for your car. I suppose the only way to prove this one way or the other, is to have the thermostat changed and see what happens.
Of course, if you have to actually pay a garage to do this (and cannot do it yourself), especially a main dealer, you could very well be letting yourself in for a not-inconsiderable bill - all for an experiment…
If your particular temperature gauge only takes a few minutes to climb to its ‘normal’ position, and your heater is nice and ‘toastie’, as MX-5 ones tend to be, then there may very well be nothing wrong. Only conducting the experiment is likely to prove it one way or the other I’m afraid.
A usual symptom for a stuck open thermostat is that the temperature increases if the engine is left idling for an extended period of time and drops if the car is driven at speed. The air flow through the radiator over cools the complete contents of the cooling system as the thermostat doesn’t close to regulate the flow of coolant.