PanzerAce Posted May 16, 2008 Share Posted May 16, 2008 First, the problem. Today, with the glorious 100+ ambient air temp, I got in my Z, turned it on, and the tach claimed I was idling at about 2k rpm. I can hear that it is idling normally, but the tach has decided to bump everything up by just over a grand. When I have the power on but the engine isn't on, the tach is either at about 1000rpm (if the engine hasn't been run yet, since 'cold' doesn't really apply), to if I just shut the engine off, it'll bounce b/w 2750 and 3500rpm. I *think* this is related to heat, since it just started happening. Anyone have any advice on where I can start tracking down the problem on it? (Especially since I'm using the tach as my speedo for highway driving.....) Now for the question: Considering that this is the START of summer and it's already 100+, I was thinking of ways to run cooler. Does anyone know if there is some kind of ready made spray bar system for the radiator, or do I need to fabricate one myself? (As in spray water infront of the radiator to lower the ambient temp air charge). Thanks for the help guys. Quote Link to comment Share on other sites More sharing options...
ozconnection Posted May 17, 2008 Share Posted May 17, 2008 A few years ago I had this really strange thing happen to my tacho...similar to what you're describing. The problem was found to be a poor electrical connection between the battery post and the clamp...sure nice and tight but a poor electrical connection. Solution: Take off the clamps and give them a good clean. Baking soda and a post/clamp cleaning tool will do the job very nicely. Should only take you a few minutes. As far as your cooling system is concerned...make sure it's in perfect order before deciding you need to add water sprays etc. Do you have a fan shroud? When was your radiator/engine flushed out and new fresh coolant added, condition and tightness of fan belt, water pump age/condition, water leaks, collapsing hoses...stuff like that. Good luck. Quote Link to comment Share on other sites More sharing options...
PanzerAce Posted May 17, 2008 Author Share Posted May 17, 2008 I'll check the electrical connection, but I'm not seeing any other symptoms of electrical issues. No fan shroud/fan belt/water leaks/hose issues, checked those a little bit ago. I'm actually running an electric fan right now. Quote Link to comment Share on other sites More sharing options...
CArFAn Posted May 17, 2008 Share Posted May 17, 2008 This is happening to me to my tach goes all the way to 8k and stays on start up. But only when hot. My speedo bounces within 5mph of each number but its accurate enough to tell how fast i'm going.(im goin to give my battery post and cable ends a good cleaning) As for cooling i flushed my cooling system twice with fresh water then added antifreeze and redline brand wetter water. I have no problems with heat so far. Quote Link to comment Share on other sites More sharing options...
z-ya Posted May 17, 2008 Share Posted May 17, 2008 I've also seen that problem on hot days after sitting in the sun. I think it might have happened 2 or 3 times. Only on the hottest of days. Switch back to a mechanical fan with a good clutch, and find a shroud. Quote Link to comment Share on other sites More sharing options...
PanzerAce Posted May 17, 2008 Author Share Posted May 17, 2008 I've also seen that problem on hot days after sitting in the sun. I think it might have happened 2 or 3 times. Only on the hottest of days. Switch back to a mechanical fan with a good clutch, and find a shroud. What is a good fan to use? And what would the clutch do anyways? I was under the impression that fan clutches were mostly to regulate the temp, but doesn't the water pump on the L engines do that? Quote Link to comment Share on other sites More sharing options...
Dragonfly Posted May 17, 2008 Share Posted May 17, 2008 The fan clutch is a viscous (sp) clutch that controls the speed of the fan in relation to the speed of the engine. The clutch viscosity is controled with a bi-metal coil (spring) that you can see on the outside of the clutch, make sure it works smoothly or you will have problems. When I ran a mechanical fan I used the Nissan plastic one that comes stock on most L series motors and I would recomend you use that one as well if you go back to mechanical. A fan shroud makes a huge difference and should be the first thing you consider after insuring that there are no clogged passeges in your radiator. As for the tach issue also check the connections to your coil and the large resistor that sits just below the coil with the three wires on it. Make sure all connections are clean and look at the underside of the resistor to make sure the coil of wire on the inside is not damaged or broken anywhere, if the coil of wire inside the resistor is dirty or corroded be VERY cautous with cleaning because it can be damaged very easily. Dragonfly Quote Link to comment Share on other sites More sharing options...
PanzerAce Posted May 17, 2008 Author Share Posted May 17, 2008 Were there any Z models that came with a fan shroud stock that I could keep an eye out for at the pick-n-pull while I'm hunting down a fan as well? And not to be dense, but what coil are you referring to? Quote Link to comment Share on other sites More sharing options...
Dragonfly Posted May 17, 2008 Share Posted May 17, 2008 And not to be dense, but what coil are you referring to? Ignition coil. Dragonfy Quote Link to comment Share on other sites More sharing options...
PanzerAce Posted May 17, 2008 Author Share Posted May 17, 2008 Ignition coil. Dragonfy Got an aftermarket coil as well, but I'll check to make sure nothing is corroded there. I wouldn't have thought about that at all Is that where the gauge actually gets the rpm reading from? Quote Link to comment Share on other sites More sharing options...
ozconnection Posted May 17, 2008 Share Posted May 17, 2008 I too personally prefer the stock setup with the tempcoupling hub/fan and fan shroud. Keep an eye out for the larger 8 bladed version. The fan itself is slightly larger in diameter and has a slightly more aggresive pitch. It fits where the original one does no problemo. You might find one on an air conditioned Maxima with the L24? You are running a thermostat in your car right?? Cheers. Quote Link to comment Share on other sites More sharing options...
PanzerAce Posted May 17, 2008 Author Share Posted May 17, 2008 You are running a thermostat in your car right?? Cheers. Yes. I should have clarified, the issue with engine temp is only there at idle. At speed, it works just fine, but I was thinking of a spray bar to cool it back into the normal operating temp range (from the higher temp it gets to at idle), faster than just airflow would do (specially 100+ degree airflow) Quote Link to comment Share on other sites More sharing options...
ktm Posted May 17, 2008 Share Posted May 17, 2008 It is a known phenomenom with the 240z tachs and their inductive loops. Check over at www.classiczcars.com for more information. It only affects the 240z tachs. When I was running a 240z tach, it would slowly climb up to redline and then stay there when it was hot out. As soons as it would cool down, the tach would function normally. Quote Link to comment Share on other sites More sharing options...
Daeron Posted May 17, 2008 Share Posted May 17, 2008 It NEVER hurts to do a thorough cooling system flush. First, get some solution (if you keep your system in good shape its not THAT big a deal, just get something cheap) Run that through, drain the coolant, pull the radiator, remove the thermostat, and flush the block with a garden hose if nothing else... make sure you turn the heater on and make sure you backflush the heater core. I like to go back and forth in the heater core with the garden hose. To me, the heater core is the biggest reason to get a flush solution. I like to run the engine for a brief while with the garden hose running into the water inlet. You could also just get one of those flush kits if you dont want to do the garden hose thing The IMPORTANT part, to me, is removing, flushing, degreasing and clearing out the air passages of the radiator.. ALL the heat transfer happens on the surface of all of those aluminum fins, and road grime and bug carcasses make for a goo that is a horribly effective insulator. When all is said and done, make sure you reinstall a good fan shroud and thermostat. Having a fan placed in a shroud with the fan offset from the face of the radiator will blow air over the entire shrouded surface area. An electric that is zipped straight onto the rad only blows air on that one spot. You can use an electric fan standing off of the rad with a shroud as effectively as the stock mechanical fan as well. Quote Link to comment Share on other sites More sharing options...
Dragonfly Posted May 18, 2008 Share Posted May 18, 2008 Is that where the gauge actually gets the rpm reading from? Yes, the negative wire of the ignition coil is the source wire for your tach. I run an MSD ignition on my Z so I have to run an MSD tach adapter in order for mine to work so I have not experienced the phenomina of my tach behaving like that. Since the overheating issue is only when idling (stuck in traffic etc.) then you may want to look into the option of an electric water pump (as long as your electrical system is up to it). Some of the benifits is that it runs at the same speed no matter what your engine rpm is that way you have optimal flow at all times with no cavitation because the second part of keeping everything cool is transfering the heat from the source (engine/combustion) to the disipation point (radiator) and that is the job of the water/coolant. An optimal pressure and flow of coolant allows the best heat soak time and heat transfer time when combined with a properly functioning thermostat/radiator/fan and shroud assembly. The first part is of course the properly functioning thermostat/radiator/fan and shroud assembly. Dragonfly Quote Link to comment Share on other sites More sharing options...
PanzerAce Posted May 18, 2008 Author Share Posted May 18, 2008 Cool guys, thanks for the help. I'm going to have to figure out my options, since I can't just optimize this engine for hot weather, as I also have to be able to drive it in below freezing weather as well during the winter. Quote Link to comment Share on other sites More sharing options...
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