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Discussion Starter · #1 ·
My 88 GT, which just recieved a new turbo, redone cylinder head, flushed radiator, new thermestat, new hoses and antifreeze....has a gauge problem(has to be, or a wiring problem) i will be driving along, no hard driving, it warms up like it should, but then i glance at the gauge a second later and its 5 or 6 needle widths right of center! it really worries me. then it will fluctuate to 3 need widths left of center. Its all over the place. and the fan switch is good, and it is not running hot because the fan shuts itself off when needed. nothing boiles over. another owner, a tech at my shop owns another 88 GT, with over 200k, and he says it does the same thing, and hes got a NEW radiator, and the engine has freshly been overhauled. Any ideas? is the car running hot, just not that hot? im out of patience :confused:

is this a whole deal or is it just me and this other guy????

Eric
 

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I have never had this problem, and i've replaced my engine, replaced the turbo twice, replaced the water pump, radiator, thermostat, etc.
 

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Could also be your thermostat is sticking. It stays closed too long (your needle goes up), then opens up and won't close quick enough (and your needle goes down). Just a thought.
 

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pre-1989's have different Temperature Sensors ( they wont interchange and the mid-89 and after ones have a lower resistace when showing the same temperature....) So its obviously supplying too much voltage to your old 88 temp guage. The cylinder head being from a 1989 or after.
So basically youre kinda stuck with it unless you get a 89+ guage or intrsu' cluster.
Have fun!
 

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I have a new long block that reqired that I put in the post 89 temp sensor. I have not had this problem with my temp guage.
 

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Discussion Starter · #7 ·
well the my father(whos a mazda master tech) read a bulletin on the subject, there was one, that said the gauge it self occasionally shorts out. the cylinder head is original to the car, i just had it gone over by the machine shop. the thermestat is a BRAND new mazda OEM thermestat, so its not that. Also that modification done to most during the warranty period(grinding down that hump that didnt allow the thermestat to open wider) was done to mine. I dont get it:confused: :confused: the guy at my work has an 88 gt produced within a month of my own, he has the same problem and has new radiator, the whole shabang, and still the problem persists.


Eric
 

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You're probably going to have to test the temperature with an external guage. It'll be the only way you can tell if the factory guage is faulty.
 

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mazda meister
when my temp gauge became erratic and finally failed to move above cold(never did indicate overheat) solution was replace temp gauge sender. fix about $10. location is thermo housing.
i might add that the wagner sender failed within 2 weeks, but w/receipt got a replacement which has lasted more than 2 years.
good luck.
 

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There is also two sensor ratings as well regular and GT. I believe the GT sensor handle much higher temperatures where the regular one might be too sensitive for the gt engine. Just my $.02
 

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I replaced the temp sensor on mine and now my normal operating temp is just above 1/4, fan comes on at half. Problem solved. (for me anyway)
Anyone else have a problem with both fans staying on all the time when the A/C is on????? Is this normal, just had A/C fixed so not used it. :confused:
 

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Discussion Starter · #13 ·
replaced temp sensor, little change, made it worse?

Ok i replaced the temp sensor, the one in the car measured 440ohms, the one i put in measured 560ohms. it takes longer to warm up. BUT i was going down the highway at 70mph... 5th gear....temp was 5 needle widths past center!!!!! that is not supposed to BE!!!!!!!!! ive got to test the car with an external temp gauge to see if it is running that warm, i sure hope not :mad: :confused: :mad: :confused: :mad: :confused: :mad: :confused:
 

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Discussion Starter · #15 ·
The main fan comes on at alittle above center, the secondary fan doesnt come on until 2-3 needle widths before the end of the bar. Im testing the gauge tonight with a variable resistor pack to make sure its ok, it really doesnt matter if the gauge is messed up because im going digital!

Eric
 

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Discussion Starter · #16 ·
FOUND THE PROBLEM!!!

Hey all, using the factory workshop manual, and a variable resistance box....I tested my gauge....At 21.1ohms the temp gauge should read at the end of the temp bar, on that white line towards the H. mine burried the needle!!!!!!! then at 31 ohms it reads on the line. The gauge is faulty, its shorted out and burned up!!!! the car never ran the least bit warm!!!!!!!!!to fix this im throwing a digital cluster in...FINALLY i figured it out!

Eric
 
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