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i was driving home from homebush to the central coast today im my 98 mx5 and noticed my temp guage was moving closer to the hot end of things.i was sitting on 4000rpm in 2nd, ready to dart into a gap as i merged at the freeway on ramp.

This had me puzzeled as it usually sits at half way and never moves, even on the hottest of days and the right foot on the floor.

after a very nervous drive home+1 stop to check everything, i still have no idea whats causing it. the temp seems to come up when im between 3700 and 7000rpm or sometimes when im going up hill in 5th. BUT when im crusing at around 110-120km/h (3500-3900rpm) its fine.

The car has plenty of water as i topped it up before i left work (there may be more water than coolant in the radiator as i had a minor leak that stopped its self) . the water pump was change at 100k, but the non oem replacement was making noises after 20k of use so i put the original back in, no dramas untill now

would be very greatful for any help

cheers Ben

I'd still say water pump. I had temps hitting 65% on \"spirited\" drives long before it finally broke and dumped rusty water everywhere.

jonno.

the original pump was perfect when it went back in. not a spot of rust. im getting a replacement tomorrow from mania.
could it be the thermostat???

thanks jonno

Could be any number of things. Thermostat, radiator cap, fans, head gasket, water pump, blocked radiator core, obstruction in airflow...

Note though that the gauge has a deadband in the middle where it doesn't move over a range of temperatures. It only creeps up when things start getting significantly warm. It's only a real danger when it gets to H though (but if you see it start to rise, take action! it shouldn't move normally).

thanks for the check list matty, fans are fine, cap is good 2, air flow to radiator and intake are all clear 2.

if the head gasket was gone wouldnt my oil be creamy??

any way i can check thermostat with out replacing as money is really tight at the moment???

might check the core tomorrow night.

would more water than coolent be adding to the problem at all???

more water than coolant should actually keep it cooler...
how long after you start to drive \"hard\" does the temp start to climb.... if it takes a while then it might just be the typical NA6 overheating problem.

its a 98 nb, it was dríven from homebush, to the start of the f3 plus a petrol stop, before i noticed it

it only has to be above 4k for a short time(60sec max) before it starts to climb,

im rather worried as its my only trasport

mmx005 wrote:any way i can check thermostat with out replacing as money is really tight at the moment

You can put the thermo stat in a sauce pan with water and heat the water until it reaches the temp as marked on the thermostat body (90 c ?) if it opens at that temp it is ok. They are reasonably cheap to replace, under$20. Same as the radiator cap, it might look fine but until it is pressure tested you won't know and it is cheap to replace as well.

J

your prob best off to take it down to mazda and ask if they would do a quick cooling system pressure test... takes all of 5mins.

Sounds like the same symptoms I've only just solved after nearly 12 months by doing - you guessed it - a water pump change.

See the Brisbane dodgy day thread in Events.

Juffa wrote:

mmx005 wrote:any way i can check thermostat with out replacing as money is really tight at the moment

You can put the thermo stat in a sauce pan with water and heat the water until it reaches the temp as marked on the thermostat body (90 c ?) if it opens at that temp it is ok. They are reasonably cheap to replace, under$20. Same as the radiator cap, it might look fine but until it is pressure tested you won't know and it is cheap to replace as well.

J

Genuine thermostats are $66 with gasket. I bought one last week. Be wary of non-genuine thermostats if you have to buy one as the second valve on the ones I looked at were very inferior looking. I doubt your problem is a thermostat however, as I think that when they break they either stop in the open or closed position.

Spranga wrote:

Juffa wrote:

mmx005 wrote:any way i can check thermostat with out replacing as money is really tight at the moment

You can put the thermo stat in a sauce pan with water and heat the water until it reaches the temp as marked on the thermostat body (90 c ?) if it opens at that temp it is ok. They are reasonably cheap to replace, under$20. Same as the radiator cap, it might look fine but until it is pressure tested you won't know and it is cheap to replace as well.

J

Genuine thermostats are $66 with gasket. I bought one last week. Be wary of non-genuine thermostats if you have to buy one as the second valve on the ones I looked at were very inferior looking. I doubt your problem is a thermostat however, as I think that when they break they either stop in the open or closed position.

not necessarily spranga, last one i had go took over a week to finally not open at all, (while all the mechanics checked everything else with me jumping up & down in frustration saying "it's the f&^%$g THERMOSTAT)..............the spring just gets progressively weaker on some of them...........the USUAL way is the shaft of the valve corrodes & sticks the thing either open or shut, but not always

Sometimes they only partly open.

I've heard of people having trouble with non-genuine thermostats. If you are going non-genuine then make sure you get one with a bypass valve in it.

Take the thermostat out.
Go for a drive at 4,000+ RPM as before and check if the temperature still rises. If it doesn't then it's a pretty good bet it will be the thermostat.

Note of warning. Don't drive for too many days without your thermostat in. It's there to keep the engine at a constant temperature rather than going through a series of heating and cooling cycles.