For years now I have dealt with an overheating problem and can not figure out what the cause of it is....

I just went through and replaced water pump, gasket, and thermo, cleaning radiator, replacing hoses i let it idle for a few minutes and slowly the dial starts to creep up towards the red....

I dont know what else to do any suggestions welcome.

Thanks

also, if i am driving the temp stays ok for the most part, but when i idle it starts to creep up, and once it gets up to high the only way to get it down is to shut the car off till it cools down, or maybe if im going 80 on the interstate

I had that same problem for a long time replaced everything i could think of and finally decided to pull the motor and when i did i thought about oil and so i pull the oil pan and there it was the oil pick up looked like a biscuit years of dirt and gunk had clogged the pickup and the motor was not getting enough oil you should check that it solved my problem

So what about adding an engine flush to the motor, might that help?

This requires taking the water pump off, but defintely needs to be checked. The condition of the cavity on the front cover where the pump vanes fit is critical to the pump efficiency. If there is any wear from a previously loose water pump vanes rubbing or cavitation damage to that area (looks like poc marks) the pump is simply not putting out the volume it needs to. Was the cause of my issues some years ago.

For years now I have dealt with an overheating problem and can not figure out what the cause of it is....

also, if i am driving the temp stays ok for the most part, but when i idle it starts to creep up, and once it gets up to high the only way to get it down is to shut the car off till it cools down, or maybe if im going 80 on the interstate

Sounds like the fan clutch is bad. At idle the fan is not pulling enough air into the radiator.

Details of the car and engine, and how far the needle gets toward red would help. The gauges aren't known for accuracy.

74 260z, mostly stock say for holley 4barrel, not just a bad gauge, will go all the way red after a couple mins at most of idling, once it goes past the halfway mark hwy driving will sometimes lower the temp a bit, but as soon as back down to an idle or low speeds temp shoots up fairly quickly

Sounds like the fan clutch is bad. At idle the fan is not pulling enough air into the radiator.

This was my first thought as well, do the "smoke test" hold a lit cigarette in front of the radiator and see how the fan pulls. Also feel the clutch resistance cold, then idle the car till it gets hot and recheck the resistance, should be much tighter when it's hot.

I don't know if anyone asked this but do you have a fan shroud? I know people that believe these don't do anything but they do indeed help cooling the engine. Check the fan clutch also as stated above

Jan

I also have another post up about electrical issues, the battery is not charging when my foot is off the gas; Does this add more to the possibility that the fan clutch is shot?

I have the clutch removed from the fan atm was going to try to rebuild, however mine is bolted to the fan, I removed the 4 bolts, but then the fan is riveted together where rebuild instructions say there should be 4 bolts....

Is this clutch not able to be serviced?

Also no fan clutch on my early 74 260z, havent had one since I have had the car, I assume this is typical of the year and model?

Edited August 26, 201212 yr by boosd

EDIT, Drilled rivets out, I guess this is an aftermarket fan clutch????

Looks pretty good though.... So im guessing this isnt the issue??

Edited August 27, 201212 yr by boosd

EDIT, Drilled rivets out, I guess this is an aftermarket fan clutch????

Looks pretty good though.... So im guessing this isnt the issue?? [ATTACH=CONFIG]55783[/ATTACH]

Its hard to tell from the picture if there was any oil inside the clutch, and if there was oil in it, was it thick?

No oil or too thin oil and it won't work very well regardless how it looks inside.

They riveted the halves together? I've never seen a factory datsun clutch thats rivited. There is no way to put it back together unless you put threads in one half with a tap but thats too much trouble. I'de just get a used factory datsun clutch off someone and add a heavier oil to it.

You have another early 260z without a fan clutch? can you swap out the fan that uses no clutch? That should tell you

if it was the clutch causing the overheating.

The alternator charging is another issue. One possiblility is the fan belt is too loose. If you can turn the alternator pulley

with your hand, its too loose.

http://www.hammondsplains.com/newtechtips/cooling/index.htm

Edited August 27, 201212 yr by hr369