Question about Mazda Protege

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Pressure cooling system

My mazda protege5 is overheating the temp gauge goes up and down while driving

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Classic sign of a leaky headgasket.

Posted on Nov 29, 2013

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    _-__-___-_ Nov 29, 2013

    or just a leakig hose! (why go extreme:?), ignored, and coolant is low and all coolant that is way low, at the temperature sender causes the gauge to surge, (it cant measure air) so what to do?, well, cold engine only. take off the Radiator CAP, i'd bet it low on AF fluid. fill it back to the top, put back the cap, and run it (no driving) and as engine warms, look for leaks to the ground, or spraying or squifting of coolant. Also listen for engine misfire, if it is, do a compression test., on the engine, now, ( a $20 tool)

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    _-__-___-_ Nov 29, 2013

    the coolant runs at near 12PSI as the egine warms, the pressure goes from 0 psi to 12-14 range, this magic, allows you to see leaks 10x more easy, if there is a bad hose, or bad water pump, or leaking radiator, now is the time it will show its face, do not drive it, just run it and watch ! IT. This beats guessing, no?


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OUCH, no year.? what country, it is the WWW, right, im clueless.
you have air below the thermostat , the gauge, does not work right with air . Water then air then water then air. oops?

the air is caused by, 3 things.
1: bad service (bad flush and fill)
2: bad engine. (say bad head gasket or far worse)
3: total cooling system failure and overheat and you turned the engine cooling to steam , called boil over. did you?

if you boil it over and keep driving, say goodbye to the engine.
sorry of all this is boring, or OLD HAT, truly but other will like it.

as always, the first question is the engine, overheating.
yes, then fix that first , find the cause.

In pure physics (and ASE classes,) you learn that
it can be 2 things. (or both , weak cooling plus excess heat nets boil)
1: a bad cooling system (yes, the rad cap fell off is one)
2: engine producing too much heat, (EFI ECU in limphome does that on many years of car, worse in USA pre 96 year)
(or bad engine in some way)
This limp mode cause gross spark retardation and huge heat is
blasted in to the water jackets. (ASE 101)

the cooling system is complex , lots of parts.
really no part is excess or useless.
one guy said, a loose rad cap, well gee dont you thing the huge green flood on the garage floor is a clue?
all parts are important.
I have in fact, seen every failure. 1 by 1.
the top failure is engine is ok (no cracked head /block or bad head gaskets) easy and common.:
1: clogged rad tubes. use an IR Pyro gun ($15) to find this so very easy, ask.
2: bad water pump, seen impellers. rusted to nothing or by electrolysis.
3:A bad thermostat , or put in upside down or the jiggle pin bleed hole not up hill , making air burping out ,very hard.

now there are some cars, that have even more odd problems.
i had car (friends) that had a 1.8L and reverse flow RAD.
and the pump is mounted, external to the engine block. odd.
it turned out the hose to the cab heater was blocked
and this hose returns water to below the thermostat.
this blockage made the thermstat go quite nuts. (yoyo effect)
some cars and engine have some real nasty tricks,
to find those harder problems try a real mazda forum. (best practice)
there are other failures and tools to find them, i will not elaborate.
1: the green/blue test, its a tool that finds exhuast gases entering the cooling loop.
2: the RAD LEAK DOWN TOOL, finds cracked block/head or
even early signs of bad headgasket failure or fully bad.

Posted on Oct 15, 2013


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Posted on Jan 02, 2017

  • 110 Answers

SOURCE: 96 honda civic lxi overheating.

The car is not overheating if the temp gauge goes up and down by turning the lights on and off.  The gauge is giving you bad information.   You can confirm this by starting the car from cold, sitting in the driveway, let the temp go to somewhere BEFORE normal operating temp, then turn on headlights and fan blower on high, watch the gauge, then turn them off.   If the gauge moves significantly from the electrical load, you probably have a short or a bad ground connection.  

You have a short circuit or bad wiring somewhere in the front half of the car.  I don't know what thermostat switch you have replaced ... but it's not the problem .. stop buying them.  
If you are the original owner, was there an accident that may have damaged some wiring?  If you bought the car second hand,  get a carfax and find out where the thing was hit ... concentrate your wiring trouble shooting in that area.

I think it is something OTHER than the temperature sending unit or the gauge

Posted on Oct 29, 2008

  • 3 Answers

SOURCE: 2000 Mazda 626 LX V6, temp gauge goes dramatically up, then down

the thermostat needs replacing

Posted on Feb 12, 2009

  • 68 Answers

SOURCE: temp gauge bouncing up an down

i would say if the fluid is full and the thermostat is not sticking it would be your engine coolant temperature sensor (ect) sensor

Posted on May 23, 2009

  • 27 Answers

SOURCE: overheating

I am not an expert on Mazda vehicles but sounds like your fan temperature sensor is not working properly. My fan comes on low speed when the temp hits 205 and goes to high speed at 220 or when the air conditioning is on. You had better get it checked by your dealer or service tech.

Posted on Aug 03, 2009

  • 104 Answers

SOURCE: 2003 Mazda Protege5. Cooling fan on radiator is

First, check the relay for the cooling fans. Not sure about Mazdas but Fords have two coolant temperature sensors. One for the gauge or light on the dash and one for the fan relay. Check and make sure the sensor hasn't went bad or come unplugged. If these don't fix it the fan itself may be bad.

Posted on Sep 11, 2009

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I am not an expert on Mazda vehicles but sounds like your fan temperature sensor is not working properly. My fan comes on low speed when the temp hits 205 and goes to high speed at 220 or when the air conditioning is on. You had better get it checked by your dealer or service tech.

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