David K Posted July 5, 2003 Share Posted July 5, 2003 Long thread in the making. Lets start here. Ive had 2 actual road worthy 280zx's. The black one was the first, and the silver one is my current second. The black one never seemed to have a problem with overheating. Head gaskets, yes, but thats not the problem here. The black Z actually read 1/4 on the temp gauge on the freeway in the daytime, and it almost dropped down to the left side of the temp gauge on a cold night. It also ran rich. Faulty sender unit? Faulty gauge? The black zx always had decent power. I get a silver Z and ditch the black one due to rust. I swap over the 3 core radiator from the black z, install new water pump, new hoses, new thermostat, and flush on top of that. I did all of that as a precaution to rid of possible problems the car may have from the previous owner. Still overheating, and on a hot day, it runs 3/4 on the temp gauge. While on the hwy, the temp raises as i open throttle.... When i exit the hwy and drive streets, the temp goes down to about halfway, back to normal. Faulty sender unit? Faulty gauge? Its driving me nuts, and usually i wont post and make a big deal about general maintanance, but this has me stumped and irritated. I have a few possible explainations for the hot gauge id like to go over. The L series exhaust manifold is long and can heat up the engine bay signifigantly. The thermostat housing and temperature sender unit are right above #1 cylinder exhaust manifold corner. I feel that this creates enough heat to send faulty temperatures to the temp gauge. Poor design IMO. I also think that if the exhaust manifold is loose, the thermostat housing and temp sender unit get a case of 'heat soak'. It really irritates me. After parking the car, and coming back in a short period of time, the temp gauge is almost at its max! Here are a few ideas to fix this mystery problem. I plan on fabricating a heat sheild for the thermostat housing that will bolt up to the first stud for the exhaust manifold on the head. Thoughts? Should i make it thick, or should i make it thin? Any other ideas to rid my 280zx of its cooling problems? If my heat sheild idea does not work with me to cool down the car, errrrrr, give me a more accurate reading, how in the world do i fix my overheating problems? Ive done everything. Ive gotten the point where i have done so much to prevent the overheating, that i am ready to take investigating and fabricating steps to solve it Quote Link to comment Share on other sites More sharing options...
Tim240z Posted July 5, 2003 Share Posted July 5, 2003 What of fan shrowding, fan type, fan performance and probably most important, air movement through the radiator (or maybe it's going around the rad. at high speed.) Your soluitions above seem to be attaking the symptoms, not the cause. Tim Tim Quote Link to comment Share on other sites More sharing options...
Pop N Wood Posted July 5, 2003 Share Posted July 5, 2003 The lower radiator hose is collapsing. Faster the enging turns, the more suction the water pump makes, the more restrictive the hose. Make sure there is a good spring inside the hose. Also make sure you have the chin pan between the frame rails underneath the radiator. This smooths out turbulence under the car to increase air flow through the radiator. And like said above, make sure the air flow goes through the radiator and not around it. Quote Link to comment Share on other sites More sharing options...
David K Posted July 5, 2003 Author Share Posted July 5, 2003 Sweet! Ill get at replacing that lower hose tommorow. I remember looking at a z parts supplier a while back and they actually had a stainless steel pipe for z32's to prevent suckage during high rpms. Quote Link to comment Share on other sites More sharing options...
THUNDERZ Posted July 19, 2003 Share Posted July 19, 2003 If that doesnt fix it, get your radiator flow checked. It sounds like a classic clogged radiator. Flushing a radiator doesnt do anything to help clogging, it is more a preventative maintanence. Quote Link to comment Share on other sites More sharing options...
BQR280Z Posted July 20, 2003 Share Posted July 20, 2003 After the article in the last SportZ mag on stock aging Datsun temp guages, I would hook up a good aftermarket guage and see what you have. I took the fan off the motor and went electric, when I built my new motor. I connected one to a an automatic thermal switch and a second to a console mounted switch. With a 180 degree thermastat, I have never had to click on the extra fan, even in 90+ temps. The water pump and radiator are new, but stock Datsun. Bill Quote Link to comment Share on other sites More sharing options...
jeffp Posted July 21, 2003 Share Posted July 21, 2003 I was having much the same problems you are talking about and tried all of the above, except the new lower hose, that had not occured to me. I was not sure about the temp gauge and wanted to be sure baout it so I went to target and bought a 14.00 dollar digital thermometer and ran the car. I opened up the radiator after I got the car hot and got an exact reading of the temp and it was dead nuts on 190 The car gauge was right at center of the gauge. Then I let it sit in the radiator for a little longer and it went to 198-200 and the gauge in the car went about two needle widths above the center. I did not solve the problem, but I did verify the gauge. I then went to a 180 thermostat and that helped a little, but I was still getting a temp creep at the long lights, but it would come back down as soon as I was on the move. I tried all the various fans, flex, electric, and the stock fan. The stock fan worked the best. Now what I have done is say hell with it and got an aluminum cross flow unit from CR racing, that should cool down the engine and enable the thermostat to do its job correctly. I will find out here in a few days how it works. Quote Link to comment Share on other sites More sharing options...
Tony D Posted August 6, 2003 Share Posted August 6, 2003 my black car was similar, and found that by cycling my fans on a bit earlier (before thermostat was fuly opened) I could flow more than enough air over the radiator to bring the temp within limits. The problem with thermostats is that the rating you get is only an approximation. They crack around the temp listed, but are not FULLY open using total radiator cooling capacity until at least 10 degrees higher than what is stamped on them. Ergo, a 190 thermostat is actually a 200, and a 160 actually a 170. I have had good results on the early cars with a 160 thermo, and on FI cars with the 160 or 170 depending on if the sensor is tracking where it should be. For a stock EFI system, as long as you get near 177 degrees, all the "cold start enrichments" should be either totally off the ECU's map, or darn near off! Technically 200 is not "hot" but with the propensity of Nissan Aluminum to dance at that temperature, I'm more comfortable with a max temp of 190, and I get that with a 160 or 170 'stat as referenced above (which is actually a 170 and 180 full-open device) Quote Link to comment Share on other sites More sharing options...
denny411 Posted August 6, 2003 Share Posted August 6, 2003 You could also check to be sure you fan/waterpump belt is the proper size and properly tensioned. I had a similiar problem years ago with a Celica GT. I changed the belt to the narrower factory specified belt and never had another problem. The belt I had was too wide, and did not fit all the way into the groove. This reduced the contact surface area of the belt allowing it to slip at high rpm while cooling perfectly in slower and sometimes even stopped traffic. Quote Link to comment Share on other sites More sharing options...
Cody 82 ZXT Posted August 6, 2003 Share Posted August 6, 2003 Have you looked at your fan clutch. Most of the time they lock up when they go bad but, I've seen some that will not spin fast enough even when hot. If it's super loose wven when it's hot I'd try replacing it and see what happens. Quote Link to comment Share on other sites More sharing options...
Cody 82 ZXT Posted August 6, 2003 Share Posted August 6, 2003 I'm sorry you said you were having proublems while on the high way and not while at a stop. You should have plenty of flow then. I would have the radiator checked by a pro or just replace it. Also like ohers have said make sure your shrouds are in place. Quote Link to comment Share on other sites More sharing options...
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