# '86 z31 n/a overheating



## killsp1n (Jan 13, 2011)

hi, i bought my z a year ago and it drove beautifully for the first 4 months or so. after a while it began to run hot and eventually my heater core blew, also i had lost my license and so i just bypassed it for the time being. it pretty much just sat around for a couple more months and now that i have a license it still tries to run hot. ive replaced my thermostat, water pump and the fan clutch. im begining to think ive blown a headgasket or have a cracked head/block but theres no water in the oil and the coolant isnt milky looking. also when it idles the temperature is fine until i drive a couple miles up the road and then it suddenly shoots up and blows steam from under the hood. so my question is- is the heater core essential for the car to cool properly? or is there anything else i can do to determine if i do have a blown headgasket or cracked head/block? and if i do how can i find it?


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## Shadao (Aug 14, 2007)

heater core is just a mini radiator with a fan behind it. bypassing it will not cause over heating...

there could be a blockage some where preventing proper flow through the engine... also check your overflow bottle to see if there is any oil in it... oil floats in water and as such the oil you may expect to see (if there is a head/block issue) could end up in there...

do a full coolant system flush to start, remove the rad hoses and hook up a garden hose and flush it out... fill everything back up with the proper coolant/water mixture and add as directed the proper amount of " redline water wetter " i use it on my gtr and i got a friend to use it on his 350 swaped 280z, we both noticed a minimum of 10*c drop in temp, my buddys temps droped by almost 20*c and we just added it to his rad after one quick run up the mountain the temps droped and he nearly hugged me for saving his car...

did the car freeze at all? if the block fully froze a plug on the block could have popped out or partially popped out causing some weird issue...

also, there could be some kind of issue with the choke system, granted most cars dont have a mechanical choke but some do have a electronic choke and if the choke stays closed your fuel use will skyrocket and you will notice blackish smoke from the tail pipes... the added fuel in the AF mixture could cause added heat for the engine... and that heat has to go somewhere...


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## killsp1n (Jan 13, 2011)

ok thanks abunch ill try this and let yall know how it works


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## BeyondBiscuits2 (Jan 18, 2006)

The most definitive way to determine if you have a blockage, bad head gaskets, cracked cylinder heads / block, is to rent a pressure tester from a car parts store. You fork out the funds up front, but you get most of it back once you return the tool. A pressure test will tell you what you need to know.

On another note, do you have coolant leaks anywhere other than your heater core? My Z31 overheated one day on the way to university... turned out to be the coupler hose between the thermostat housing and radiator. Simple and easy fix... maybe $5 at the parts store. I'd also heat test your thermostat to see if it is opening at the correct temperature.


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