Overheating

[Reverend]

Have you always bleeded the cooling system after changing parts? I had spooky overheating too, caused by air bubbles in the system.

[Bonzi Lon]

A well experienced Datsun mechanic has always said, "If you can stop the fan at idle with a 'TV Guide', the clutch is not working." I would assume any magazine you didn't like would work.

Bonzi Lon

[Wade Nelson]

Pressure testing is the way you get started diagnosing overheating. Even a simple loose hose clamp can allow the system to lose pressure, and then, instead of boiling at 260 degrees and 7 psi, it boils at 212 degrees and 0psi. Result: You overheat. Buy or borrow a pressure tester. Check engine cold, then warm up the engine with the radiator cap off, and see if it holds pressure hot.

Next is to perform a block test, seeing if you have a blown head gasket. There are chemical tests your mechanic can do, it changes colors if combustion gasses are getting pumped into the coolant. The chemical goes "stale" fast, so have him TEST the chemical before testing your block.

Driving WITHOUT a thermostat in is how you determine total cooling system CAPACITY. If it can't stay cool doing 30mph, or climbing hills, you've got other problems. Leaves/dirt plugging the radiator is one.

Just replace ANY thermostat with a new Stant and call it good. Never re-use an old radiator cap either. And excess flushing only causes problems. The steel/aluminum in your engine/radiator form a battery, when you flush it with caustic acid, you expose lots of shiny new metal, and the battery action starts up all over again.

A lot of drivers MISTAKENLY put 100% antifreeze in the system once they start having cooling system problems. Bad, wrong! Ethylene glycol has LESS heat carrying capacity than water. Use a 50:50 or a 60 water 40 antifreeze mix.

Gauge problems mislead SOME drivers into THINKING they have an overheating problem.

If you run the engine, till warm, with the radiator cap off, any air trapped in the Z's engine should bleed itself out. Some other cars don't work so well and require special tricks to get the air out of the system. And the most frequent cause of bubbles, air, is....blown head gaskets. (And the most common cause of blown head gaskets is plugged up catalytic converters, btw...)

To remain cool a car needs only a few basic things, sufficient coolant, sufficient pressure, sufficient flow (waterpump) and sufficient airflow.

Looking at when and WHERE your car overheats should tell you which of those you don't have.

And no, I would not stick ANYTHING in a spinning radiator fan unless you like buying new fans. Those plastic blades are brittle now, not flexible like 30 years ago when your mechanic USED to stick a magazine in 'em.

[Wade Nelson]

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

Flushes, in general, are a BAD idea. They often make the problems worse, oil OR radiator flushes. Save them as a last ditch effort before a tear-down.

Edited August 27, 2012 by Wade Nelson

[MotoManMike]

If you are certain your cooling system is up to par, your fan is good, oil flow is good through the motor. I suspect and intake leak causing a lean condition. Its a thought worth investigating. I know you said you have a holley on it, that doesn't mean its flowing the right amount of fuel. Lots of thoughts I would spout off have been mentioned above but reading all the posts this is what comes to mind.

On another thought, how do you "know" the gauge is good, have you used a infared temperature meter on the engine? Those little tools are handy for just this purpose of testing heat.

[madkaw]

Overheating + not charging= loose belt

I am also very confused here, you have 2 260's and one that doesn't have a clutch on the fan?

You might want to be clearer to get good help

[boosd]

Overheating + not charging= loose belt

I am also very confused here, you have 2 260's and one that doesn't have a clutch on the fan?

You might want to be clearer to get good help

tension in belt was more than adequate

seems to be just a bad alternator and added more weight to the fan clutch as well replaced water pump/gasket and some old hoses, now getting a better result with a 60/40 water antifreeze mixture.

Not sure how you got so confused that you read 2 260s and one that doesn't have a clutch fan... i guess that is irrelevant, but I received plenty of good help regardless

Thanks for yalls help, took the z out for a drive for about an hour, with stops and various traffic/speeds and did quite well

[Zed Head]

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?

Probably from your writing. Above you said that you're working on the fan clutch, then said that your early 260Z doesn't have a fan clutch. You're either talking about two different cars or just not explaining things clearly. I thought that you had two cars also.

Now you said that you've added more weight to the fan clutch which also doesn't make much sense either. Overall, it's hard to tell what caused the over-heating and why it would be better now. But, if it works for you, good luck with it.

Edited August 28, 2012 by Zed Head

[72 OJ]

[boosd]

Probably from your writing. Above you said that you're working on the fan clutch, then said that your early 260Z doesn't have a fan clutch. You're either talking about two different cars or just not explaining things clearly. I thought that you had two cars also.

Now you said that you've added more weight to the fan clutch which also doesn't make much sense either. Overall, it's hard to tell what caused the over-heating and why it would be better now. But, if it works for you, good luck with it.

Now it is clear why I caused the confusion, I should have typed fan shroud instead of clutch. My apologies.

My assumption is that the fan clutch on my 260 was aftermarket since it only had 4 bolts and 4 rivets which had to be drilled out and it seems most have 4 bolts on each side that can be removed.

I read some information about rebuilding the fan clutch and there was no real clear indication of how much "goo" from www.hammondsplains.com/newtechtips/cooling/index.htm that should go into the clutch, unless I missed something. I have read a few posts that said 10w30 was to low, and to add 90w or lucas oil smoke additive.

Since there was clearly some thick liquid still inside the clutch, I at first thought it was not the issue, but after turning it over a couple times and it being clear that it did not need to be done quickly to prevent any from leaking out I assume that it was possible some of the liquid had leaked over time so I added a good amount of 10w40 into the clutch and bolted it back together.

On my way out have the electrical tested the car did quite well, slightly over mid way on the temp gauge but did not shoot up like it use to at stops.

Once I arrived to have the electrical tested, I shut the car of, (for the 3rd time on the trip from other stops) and the car would not start.... It kept trying, and would start to fire up only to die a second or less later.

After probably 30 attempts she fired up and I revved the engine to about 6k and off went one of my newly replaced hoses that apparently had not been tightened down... :/ (Up to this point I was running a 50/50 mix)

Still unclear as to what caused the failure to start but possibly something in the line causing a blockage or issue with the electric fuel pump.... Nevertheless, I lost about a quart of 50/50 and after thinking about some of the previous posts I decided to add just water to try and bring closer to a 60/40 mix.

The 60/40 seems to be working better, I let it idle for a good 10 minutes after driving for a while and had no over heating issues at all.

Thanks much for all your help, may have fixed a few things that weren't the direct root of the problem, but nothing wrong with a little preventative maintenance.

[71Nissan240Z]

Flushes, in general, are a BAD idea. They often make the problems worse, oil OR radiator flushes. Save them as a last ditch effort before a tear-down.

Coolant flushes are fine. Prestone works great and take years of calcium off from running with tap water. There is a lot less to go wrong than an engine flush....those I dont like either.

[esmit208]

Do you have a fan shroud? Many underestimate the importance of a shroud. Without it air goes around the radiator matrix instead of through it. elementary my dear Watson..........Elementary