labrat Posted February 19, 2002 Share Posted February 19, 2002 I know you guys are probably tired of hearing about me and my problems, but here goes anyway... My 280ZX with a 350/TH350 is overheating badly on the highway. It does fine up till about 40 MPH, then the temperature slowly starts climbing. I'm running an aluminum radiator out of an 85 regal w/305, and a taurus fan (just the single speed, though). I also don't have a thermostat in right now, because the temperature sending unit for my cheap mechanical guage is too long to fit in the water neck with a thermostat, and i can't get the stinkin pipe plugs out to put it in one of the heads. My question is: would a lack of thermostat to slow the water down through the radiator cause this? I am turning about 3500+ rpms on the highway, so this is my first thought. Would timing (maybe the mechanical advance not working...) cause this? I have to have this car as a daily driver soon, and I need to get all these little issues worked out QUICKLY. Thanks, as always, for all the input, and all the input on my other problems... Bill Quote Link to comment Share on other sites More sharing options...
Guest Russ240z Posted February 19, 2002 Share Posted February 19, 2002 Very likely what is happening is the water is flowing through the radiator too fast to be cooled without the thermostat. I experienced this with my 400. It is race only so I went with a washer with a one inch hole to slow it down. Quote Link to comment Share on other sites More sharing options...
denny411 Posted February 19, 2002 Share Posted February 19, 2002 what type of belts do you have?serpentine/v-belts If you have v-belts, check to make sure that you have the proper width of belts. If they are too wide/narrow they will slip at higher rpm`s.it also could be your lower radiator hose sucking shut, make sure it has a spring in it to prevent this. If it is a serpentine belt,it is possible that you have too long of a belt, this will cause excess deflection and possible slipage. also be sure that the water pump is turning in the proper direction.somtimes when picking and chosing pulleys/belts and tensioners and figuring out where to put them,people can get the water pump turning the wrong direction. It also could be a problem with the thermostat.if it sticks open or opens too quickley it may circulate the coolant so fast that it doesn`t have time to disipate enough heat while passing through the radiator. this is the problem with not running a thermostast at all.if I think of anything else I`ll let you know Quote Link to comment Share on other sites More sharing options...
denny411 Posted February 19, 2002 Share Posted February 19, 2002 I guess I should have read the entire post Oh well maybe someone else can use the info Quote Link to comment Share on other sites More sharing options...
Tim240z Posted February 19, 2002 Share Posted February 19, 2002 I've had good luck just using a gutted thermostat to slow down the water flow. Just get an old one and cut it with some wire cutters so that the internals are gone. That should solve your problem until you can sort it out properly. Tim Quote Link to comment Share on other sites More sharing options...
Guest Aaron Posted February 19, 2002 Share Posted February 19, 2002 While this may seem overly obvious, make sure your fan is wired correctly. I have seen this before on a ford tempo. Someone rewired the fan and wired it backwards, so the fan was blowing out the front of the car instead of pulling in. Just like you described, the car was fine at low speeds, but above about 35MPH the car would overheat. AN Quote Link to comment Share on other sites More sharing options...
Modern Motorsports Ltd Posted February 19, 2002 Share Posted February 19, 2002 Labrat: -why no thermostat? (not even a 160?) -yes not having a t-stat (or restrictor) inhibits cooling bigtime as your coolant never stays in the heat shedding radiator long enough to reduce your temp enough -if you have a high flow waterpump and are concerned with allowing enough flow at idle/startup etc then I'd recommend a high flow Robert Shaw Tstat or drill two 1/8" holes in the flat area outside the bimetal valve on a cheaper Tstat -my setup requires no fan over ~25/30 mph for cruising (found that out when fan wiring kabitzed a few times with inferior fuse blocks/connections previously) and I forget what speed your fan is a non-issue but I'd suspect a Tstat may easily solve your issues (I run a 180 and would only go to a 160 if I had issues). hope that helps and glad you got it running:) Quote Link to comment Share on other sites More sharing options...
labrat Posted February 20, 2002 Author Share Posted February 20, 2002 Thank you all for helping me out, i definitely need someone who isn't staring at the beast with a knotted forehead to chime in with an opinion every now and then. I just get too frustrated to think sometimes, and if it isn't one thing, it's something else. I just got everything crossed off my list of things to do to get the swap finished, and since i drove it, the list is now twice as long! I'm kinda kickin myself in the behind for taking the cheap way out and just using the entire drivetrain from an old used truck. Now I have to redo everything, only with less ground clearance now. Oh well. Thanks a bunch fellas! Bill Quote Link to comment Share on other sites More sharing options...
Guest zthang43 Posted February 20, 2002 Share Posted February 20, 2002 There is another possibility. The radiator could be plugged, even if it *appears* to flow well. I had this problem with my Toyota pickup. I tried everything; removing the thermostat, using the really good radiator flush stuff, etc. nothing worked. It was fine until I went 40 or 50 for any length of time, then it would overheat. Also if it was under a load climbing a hill it would overheat. It turned out that some of the coolant passages in the radiator were plugged, but the rest flowed well enough that it seemed to flow ok when I stuck a hose in it. I replaced the radiator with a new one and it was fine. Quote Link to comment Share on other sites More sharing options...
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