I took the 240 out today and noticed that the temp was a little high, 3/4 the way over, mainly at idle (a long red light). I have always had the opposite in that before the temp would never go past 120-130. Three months ago I replaced the thermostate with a courtsey nissan 190, everything seemed fine until today, when I hit about 220 or so on the gauge.

I searched the forum and noticed alot of post about the fan clutch, one post said that if you can turn the fan blades with ease at normal operating temperture then somethings wrong with your clutch. Well, I can turn the fan blades very easy, with no effort at all when the engines hot, does this mean I need a new fan clutch?

Any advice would be appreaciated.

Randy

Hi Randy:

Oh boy... this should be fun.

I would say that the "test" you conducted is certainly an initial indication that perhaps your fan clutch is weak, if not shot. But in my mind it's only an indication to check farther.

True that a Fan Clutch when new, will give resistance to spinning when it is warmed up to normal operational temps... but with the engine stopped. True also that a fan clutch that is shot - will spin easily under the same conditions. The big HOWEVER is that a fan clutch that is not new, nor shot, but somewhere in between the two extremes can do its job for a long time before it actually does wear out, or leak out.

Given the expensive and difficulty of finding, buying a new fan clutch - you don't want to change one out until it is really necessary.

Before I forget - - - -

Did you write that wrong? "the temp would never go past 120-130" and for some reason you installed a 190 thermostat? I'll guess you meant 220 to 230 degrees F.

I don't understand why you would be using a 190 degree thermostat in Knoxville this time of year. The first thing I would do, would be to replace it with a 160 degree thermostat, and add a bottle of Red Line Water Wetter.... then see if the engine returns to its more normal operating temp.

In the middle of the Winter in one of the very Northern States, I might be running a 190 degree thermostat to maintain a normal operating range during severe cold....

About the fan clutch.... the "method" used by at least six of the professional "Datsun" mechanics I knew back in the day (the 70's) goes as follows.... YES IT IS RISKY - YOU HAVE TO BE CAREFUL... I'm not TELLING ANYONE TO DO - only reporting the procedures and processes that worked well for the guys you pay to work on your Z -

1. Start the engine and make sure it is up to normal operating temps for at least 15 minutes. This will allow enough time for the fan clutch itself to heat up (ie to catch up with the block temps). This is important. The fan clutch is activated by the hot air coming off the radiator, as well as by the hot water flowing through the water pump. All this has to normalize before the fan clutch - engages. Centrifical force driving the hot and expanding silicone fluid toward the outside of the fan clutch also plays an important roll (part of the reason the "static" test of spinning the fan on an engine that is stopped can give you a false indication).

2. While your waiting for everything to warm up - get a piece of thin cardboard, typically used for product packaging...not the type used in heavy cardboard shipping boxes.... Fold the thin cardboard until its about three or four layers think, two to three inches wide, and about 10 to 12 inches long....

3. With the engine idling - push the cardboard on a downward angle into the spinning fan, in the direction of rotation, when the fan blades are moving in a downward motion. If the fan simply pushes the cardboard out of the way, and keeps spinning - the fan clutch is fine. If on the other hand if you can stop the fan from spinning by using moderate resistance - the fan clutch is shot.

If course replacing a serviceable Fan Clutch with a new one - can't hurt anything. But it might mask, at least for a while, some other problem with the cooling system.

FWIW,

Carl B.

I had the same problem, and did the same test, the blades turned really easy when the engine was hot, and also the fan wasn't blowing hard enough when i rev'd the engine, so i replaced the fan clutch and all my problems were gone.

Camilo

If you decide that your fan clutch is indeed bad, do yourself a favor and avoid the Autozone cheapie replacements, they seem to have a 3 out of 4 failure rate right out of the box, according to several z-pundits. Get the Nissan factory unit, about $100. Now me, being the cheap son-of-a-gun that I am, followed the directions in this link and successfully rebuilt my fan clutch.

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

5000 miles on my backyard rebuild and no issues.

or sya the hell with it and go electric from black dragon

What? And lose that signature Z-fan sound??? Whirrrrrrrrrrrrrrrrrrrrrrr!

, I figure I'll go electric eventually. The Black Dragon kit is not cheap though, and I was thinking there's got to be a close fit in the local pick 'n pull I could massage into place. Ever hear of anyone using a different elec fan setup?

Fred

Tampa, FL

'74 260Z 2+2

I'm getting rid of mine and installing an electric fan. Not sure which type or model yet but I'll tap the temp sensor into the rad somewhere and run cables from the battery via a relay off the ignition.

It will free up a tiny amount of HP and stop that noise. From memory, I recall that sometimes I could swear that the fan produced more trust than the L24, just by the noise it made at high revvs.

Thanks guys,

I was thinking about going electric, now may be the time.

Carl, thanks for the input. Yes I did right the wrong so to speak, I took the old thermostate out which was stuck full open, so I'm assuming thats why I was always running cold. Why I put in a 190???.....because I didn't pay attention when I ordered it and thats what was sent. Stupid mistake, I know. I'll change out to a 160 and see if that fixes the problem.

Thanks again.

21200-F3160 is the part number for the 160 deg. thermostat. I run them year round here in California in both the Z and the 810. Both have stock clutch fans, AC, and auxiliary fans on the front side of the condensor that run whe the AC is on. Neither on goes past the center of the guage even on the hottest days with the AC running. And, Carl, I also use the 'cardboard test' to test clutch fans and have for years. Anyone who wants to try that: just make sure you fully understand #3 in Carl's explanation!

get a piece of thin cardboard, typically used for product packaging...not the type used in heavy cardboard shipping boxes....

Would that be the kind of cardboard around a 12 pack of bud light in cans or the the cardboard around a 12 pack of Sierra Nevada bottles?

Now me, being the cheap son-of-a-gun that I am, followed the directions in this link and successfully rebuilt my fan clutch.

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

Brilliant link, thank you.

Ever hear of anyone using a different elec fan setup?

I've heard that the Ford Taurus or Mercury Sable fans are a decent swap. I think I read it over on Hybridz.

Would that be the kind of cardboard around a 12 pack of bud light in cans or the the cardboard around a 12 pack of Sierra Nevada bottles?

Perhaps this test isn't a great idea for you to try anytime soon. :dead:

I have been thinking of going to an electric fan setup ,I thought it might sound better without fan noise in lower to normal operating temp conditions.

Letus know if you have converted and what the sound difference was like,

and any thing else you noticed.

Roger