Ive got an over heating problem and dunno what i should do next.. Ive read through all the tech articles and probably most of the threads here on overheating.. ive got the following mods: fmic, air filter, bov, TWD and autometer temp gauge Ive recently had a mechanic do the 100k service (package by K-zed)... which means all the belts, water pump, thermo stat, bearings etc.. i've also recently did the under plenum water by pass. and changed all the water hoses including the heater hoses and all the fuel hoses.. Being paranoid while i did the plenum pull i took the radiator to a specialist and got it rodded and replaced both end tanks... I got a new nismo radiator cap, installed an air guide, vented nose panel and the splash guard under the car.... ive also replaced the bottom and upper radiator hoses.. Now the problem is when im going about 70 to 100km/h the temp will stay at about 80c... but after about 20 mins of driving and if im stuck in normal traffic (not bumper to bumper, not a hot day and aircon off) the temp would go to about 95c - 99c, and if i pull over it will drop back down to about 85 in about 5 to 10mins.... and if i keep on driving at higher speeds it would go down faster... I religiously check my coolant level and i don't lose coolant.. theres no leaves blocking air to the radiator (except the FMIC ), i know im missing the sub fan relay fuse.. and theres no oil in the coolant... So what should i do next?? help please... its driving me NUTSSSS... should i change the CTS (ive replaced the plug but not the sensor itself)? Should i remove my fmic?
I tried removing my front mount when I was having problems and it made little difference. I'd say it's not the problem given the amount of people that run them without drama. Only thing I could suggest is maybe there's air in the system. Was the coolant fill procedure followed when it was replaced? Also, are you running the factory fan and shroud? That was the main cause of my problems. My car came with a thermofan fitted from Japan and it turned out to be completly useless. I got hold of a factory fan and shroud and bob's your uncle. Ben
yes check if your thermo fan is kicking in. also do you have the plastic undertrays under the front bar and the engine? these help with directing the air to the radiator instead of escaping out underneath the engine. a Koyo 53mm radiator will also help big time.
I assume your running the stock clutch fan. Clutch fans by nature are good when the engine is revving but poo when at idle, especially with aircon. What you need to do is get a new subfan relay from any nissan at a wrecker. The aux fan will then turn on at 90degrees and off at 88. It helps alot with aircon in traffic. However if you're not running aircon then there must be something else wrong.
While filling up with coolant i made sure that there was no air left in the system... and im still running with the factory fan shroud... ive got the plastic under tray as well.. maybe ill try to source a sub fan fuse and see how that goes... BUT im not running the car with air con on..?? Though does the factory fan shroud have an under piece to it? i remembered that when i told out the fan shroud there was no like a missing piece at the bottom of the shroud.. i hope that makes sense??? Thanks for the replies everyone...
then could that be the culprit to my problem? i mean my car only slighty over heats at idle and without the bottom half of the shroud, the air would be pushed down and under the car rather than towards my radiator? does anyone have the bottom part of the shroud they wanna part with? thank you
ok maybe the clutch fan So youve replaced the water pump and cleaned out the radiator and the coolants full, so theres coolant in there and its doing its thing. Which leads to airflow, you say when youre moving temp is good. When you idle or crawl in traffic no good. That points to an ineffective fan. The auxiliary electric fan should only ever operate if your using the ac so yeah get a subfan relay but thats not the main trouble. Check the fluid coupling of the belt driven fan, when the car is off if you try to spin it does it free spin or is there lots of viscous friction? You should not be able to get more than half a turn. If it free spins replace it its the big hub that the plastic fan bolts onto. Its there to let the mechanical fan slip a bit at high engine revs.
few things that might help .. Try flush ur ur system with CLR a few times.. also have a look at the fins on the radiator make sure they are all straight as ..
I dont know where you got that, the fan practically serves no purpose at speed and its primary use is to keep the car cool when at idle and in traffic.
One possibility I haven't seen this problem on a 300ZX but I have experienced the same problem on another car after changing the thermostat to a new one. The issue was that the new thermostat sealed so well that it did not allow the water to heat up the delivery end of the thermostat that causes it to open so it stayed closed and overheated the engine. The solution was to drill a small hole in it allowing a small amount of flow all the time ensuring the thermostat would open as necessary.
Thanks for the replies everyone.. WHen the car was off i manually spun the clutch fan and it only rotated about 3/4 of a spin... i went and brought a sub fan relay fuse.. turned on aircon and after a while the aux fan kicked in.. in a way atleast i know my aux fan is working .. but thats not the problem.. Yeah with the radiator i had it rodded and when i installed it.. the fins were pretty straight.. well as striaght as possible.. So then any other ideas anyone?
check flow of coolant thru rad Well its likely youve got enough air flow. So back to checking coolant; Thermostat was changed during your 100k service? When its getting hot the top and bottom radiator pipes should both be hot as the thermo should be fully open, if the bottom one is cold then theres poor flow through the radiator, probly because the thermo isnt completely opening. Coolant system flush is a good maintenance task to do. Remember H on the stock dial means the car is extremely hot and the guage doesnt move much at all from 80 to 100C.
I think this might be your problem i remember reading some articles about overheating and some guy had the same problem he checked and replaced everything in the cooling department and yet his car was over heating until he put back on the original radiator cap and everything was fine after that so i would recommend to put the original cap back on or try a new genuine cap
I dont have data scan.. so im checking my temp thru a gauge that is conected to the top rad hose.... thermo stat was changed when teh 100k service was done.. and i checked that the top and bottom hoses were quite hot... But its not over heating to the point that the stock temp gauge is hitting H.. the stock temp gauges didnt even move... well in a sense the zed seems to running on the hotter side rather than over heating.. hope that makes sense.. the rad cap seems to be an idea... anyone know where i can get one besides nissan? im in the process of getting a lower fan shroud... so ill change that and see how it goes...
just a thought. have you tried another temp gauge? iit could be out a few, maybe even 5 degrees, especially if its an el cheapo. I'd say that 95 is an acceptable temp on a hot day with the aircon on.
2nd'd That was my thought too. It can be checked>correlated with datascan or a laser temp guage. [Tip: aim laser at the brass head on CTS for accuracy] TWD will come on ~93 -95 degrees, pretty normal in traffic with moderate to hot ambient air temps.
