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Thread: Fan clutch or other issues?

  1. #1
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    Default Fan clutch or other issues?

    Guys

    This weekend was supposed to be wonderful. A group of friends and myself were going to meet up at a lake and have a wonderful camping trip. Well as expected there were issues from the start. On the way to said lake I forgot some things at home and decided to head back. As I drive into my neighborhood I notice my temp gauge is not where its normally supposed to be, to be exact its a notch or so past the midway point, it normally runs at like 1/3. Freakout I pull into the spot and open the pressure relief on the radiator cap - yes I know you're not supposed to do it I wasn't in the right state of mind - steam comes pouring out for a good five minutes. Stumped I attach my laptop to my computer (I run aftermarket EFI) and see what the temp read;, 208 is what it see. I let the car cool off for a while, refill the radiator and off I go keeping a close eye on the temp.

    While driving in the city it hovered around 195, way above what I'm used to but nothing that I would worry about. As I get stuck in traffic and move inches per hour the temp begins to rise, when it hits 210 I open the heater valve (don't actually turn the heat on though, no vents) and watch as the temp drops to 198 and stays there for a while until I get moving again. I drive on to the freeway and continue to montior the temp, which slowy drops to the mid 180's at 75ish mph. I pull the pull into a gas station to fill up and make sure the radiator fluid was in good shape. When I reenter the car the temp gauge is roughly in the middle and the temp on my computer reads 219, but drops rapdily once I start the car. From then on it gets interesting. The road to the lake is rather long and windy through southern Arizona. Outside temp sits at around 85 or so. I'm driving the usual 50 or so and the temp, as if nothing had happened before, goes back to where it had run before. The rest of the trip to the lake and back this evening the temp never exceeded 175, dipping in to the low 160's at times.

    So here's my question. From my knowledge of cars - which isn't amazing but I know a bit - it sound to me as if my fan clutch maybe giving out. I'm not an expert and have reviewed a few posts here about cooling but if I had a pressure issue wouldn't the temp always be high or at least elevated and not fluctuate like it did? I run a 160 degree thermostat, the radiator is about three years old, the water pump is 2 years old. All the hoses are new, there are no leaks and since I added fluid into the overflow it has remained constant. There is no white smoke (or sweet smells) - had the friends drive behind me, the oil is oil (needs a change but is oil) and the coolant is nice and green. Any ideas on what this could be?

    Sorry for the book
    Thanks again
    Jan
    Last edited by Pomorza; 08-10-2013 at 11:40 PM.
    1976 280Z
    HLS30288273

  2. #2
    Registered User siteunseen's Avatar
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    If the fans spins too easily with the car off it very well could be the clutch. It shouldn't even make a complete rotation when spun by hand, in my experiences.
    1972 240Z #918 New Sight Orange
    1977 280Z #305 Light Blue Metallic
    1972 240Z #110 Persimmons Red

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    Registered User siteunseen's Avatar
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    I've tried them both and the 6 month old clutch will barley go 1/2 of a round while the one on the 280, that was on it when I bought it, goes 1 and 1/2 to 2 turns but cools just fine. Hope that helps you out.
    1972 240Z #918 New Sight Orange
    1977 280Z #305 Light Blue Metallic
    1972 240Z #110 Persimmons Red

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    Registered User madkaw's Avatar
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    I second the look at the clutch fan. Maybe thermostat got hung up?
    Steve
    71 240z,bw-5sp 2.4-40 over,balanced,e-88,big valves,ported&polished, stage2,header, triple Mikuni's 40's
    3.90 Subaru STI LSD

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    Thank lads

    I will confirm the diagnosis later this week. When the car is cold there is a bit of resistance in the fan, haven't tested it at operating temp just yet. I do have a question though, should I replace the stock clutch with a new one (which is roughly $50) or spend slightly more and get a dual speed electric fan? The one(s) I've looked at have a 1500 cfm rating on high, I don't know how that compares with a stock Z fan so suggestions are welcome.

    Thanks
    Jan
    1976 280Z
    HLS30288273

  6. #6
    Barn Find Daily Driver Captain_Zeros's Avatar
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    I've got a dual electric fan out of a late model junkyard altima that I got for like $18 at the local self service yard. Both fans on the low setting will overcool my car on the hottest of days. I don't even have the high speed windings wired up.

    If originality isn't a concern and you don't mind wiring up electric fans, it's the way to go in my opinion.
    1973 240Z w/ roundtop carbs, 280zx e12-80 distributor, 280zx alternator, late model Altima junkyard electric fans. 115 Blue Metallic & white side stripes.

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    Registered User rcb280z's Avatar
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    Thats too big of a fluctuation in temp. 50 degrees to be exact. Too much. You are running a 160 thermostat and you still get up to 210 and it sounds as if it would keep climbing if you don't open the heater core. Are you sucking air anywhere? Have the system pressure tested. I had an over heating problem once due to a leak. You can also check the fan clutch by running the car up to temp and with a rag balled up in your hand VERY CAREFULLY try to stop it from spinning. Apply just a little pressure on the fan and you will know. If it slows down it's no good. If it fights you and will not slow down it's good and then at that point I would look for a leak, (air) in the system. Just be sure before you go buying things that you may not have to buy you have verified the cooling system is working properly.
    Last edited by rcb280z; 08-11-2013 at 06:53 PM.

  8. #8
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    Thanks guys

    I'm pretty sure my system won't be "air" tight as the front cover has a lot of silicone where the waterpump is - it was eaten away by electrolysis. Ill check both tomorrow

    Thanks
    Jan
    1976 280Z
    HLS30288273

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    Update:

    Ran both tests today. Took the car from my house up to my brothers (~3 miles way) to get the car to operating temperature. Arrived at my brother's place and the Z sat at 173. Let it idle for about 10 minutes and checked temperature again was now at 177. Step one, check the fan. Took a new paper, rolled it into a tube and attempted to stop fan. Fan nearly took newspaper AND my arm with it, so that would be a pass. Turned car off. Step 2. Tested pressure, hooked up pressure tester, took it up to 13 psi (per rating of cap) and check for leaks. Pressure kept steady at ~13 for about 15 minutes while I checked around. Step 3. Checked flow of radiator. Took off pressure tester and started the Z. Temp after sitting was 194. Two things I noticed. 1. The flow was amazing, the coolant was moving so fast from one side of the radiator to the other that it nearly came out of the damn radiator. Secondly the fan was ON, as it sounded like I had a messerschmitt sitting under my hood. Step 4. Drove car back home. After placing everything back to where it needed to be I closed the hood and drove back home. Even in the 100+ degree heat of Tucson the temp never exceeded 175. The fan was also on most of the drive home - as I could hear it.

    So, it seems that everything checks out in my cooling systems. I have the suspicion, that my fan wasn't on the day it over heated as it didn't seem that loud for what I remember. I don't know exactly how these fail - if its a gradual loss of function or if it can fail and not fail. Would like to hear your opinions.

    Thanks
    Jan
    1976 280Z
    HLS30288273

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    Update:

    Ran both tests today. Took the car from my house up to my brothers (~3 miles way) to get the car to operating temperature. Arrived at my brother's place and the Z sat at 173. Let it idle for about 10 minutes and checked temperature again was now at 177. Step one, check the fan. Took a new paper, rolled it into a tube and attempted to stop fan. Fan nearly took newspaper AND my arm with it, so that would be a pass. Turned car off. Step 2. Tested pressure, hooked up pressure tester, took it up to 13 psi (per rating of cap) and check for leaks. Pressure kept steady at ~13 for about 15 minutes while I checked around. Step 3. Checked flow of radiator. Took off pressure tester and started the Z. Temp after sitting was 194. Two things I noticed. 1. The flow was amazing, the coolant was moving so fast from one side of the radiator to the other that it nearly came out of the damn radiator. Secondly the fan was ON, as it sounded like I had a messerschmitt sitting under my hood. Step 4. Drove car back home. After placing everything back to where it needed to be I closed the hood and drove back home. Even in the 100+ degree heat of Tucson the temp never exceeded 175. The fan was also on most of the drive home - as I could hear it.

    So, it seems that everything checks out in my cooling systems. I have the suspicion, that my fan wasn't on the day it over heated as it didn't seem that loud for what I remember. I don't know exactly how these fail - if its a gradual loss of function or if it can fail and not fail. Would like to hear your opinions. Also the coolant is coolant, nice and GREEN. The oil is still oil, dirty and in need of a change but its oil.

    Thanks
    Jan
    1976 280Z
    HLS30288273

  11. #11
    Barn Find Daily Driver Captain_Zeros's Avatar
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    Sounds like a Messerschmidt eh? I have limited experience with fan clutch failure, but mine failed in the "on" position and that'd be an apt description of the ruckus coming from under my hood. I'm just making a guess here, but I wouldn't rule out the possibility failing fan clutch going from "slipping too much" to "seized in place" and giving you the problems you described. Try and move the fan by hand with the engine cold and stopped, if it is seized in place like it's bolted to the water pump then it still needs replacing.

    Alternatively if you had the coolant system drained recently, a bubble in the coolant can give you a world of overheating that suddenly goes away when the bubble burps out.
    1973 240Z w/ roundtop carbs, 280zx e12-80 distributor, 280zx alternator, late model Altima junkyard electric fans. 115 Blue Metallic & white side stripes.

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    Barn Find Daily Driver Captain_Zeros's Avatar
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    arg doublepost, damn internets.
    Last edited by Captain_Zeros; 08-12-2013 at 02:22 PM. Reason: doublepost
    1973 240Z w/ roundtop carbs, 280zx e12-80 distributor, 280zx alternator, late model Altima junkyard electric fans. 115 Blue Metallic & white side stripes.

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    Captain Zeros

    The fan will move about 1/3 of a turn when the car is off and cold. When the car is hot and off it will maybe move a blade or two over before stopping. Wouldn't say it was "seized" but its pretty hard to move. I didn't drain the system recently but I could have a bubble in there from the heater core maybe, it has a small leak which could cause air to enter I guess.

    Thanks
    Jan
    1976 280Z
    HLS30288273

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    Registered User rcb280z's Avatar
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    If air is entering the system it will get hot.

    But that would have showed itself during the pressure test if you had the heater core "open". I think. Now I'm second guessing myself. Long day at work. But I do know for a fact that "air" in the system will make it run hotter.
    Last edited by rcb280z; 08-12-2013 at 04:41 PM.

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    I had the heater closed. I'll keep you guys updated.
    1976 280Z
    HLS30288273

  16. #16
    Registered User siteunseen's Avatar
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    Aren't the clutches filled with grease or some type of oil? If it spins less freely when it's hot it's doing the opposite of what it is supposed to do, right?
    1972 240Z #918 New Sight Orange
    1977 280Z #305 Light Blue Metallic
    1972 240Z #110 Persimmons Red

  17. #17
    Registered User siteunseen's Avatar
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    I knew I'd read this Tech Tip for the fan clutch but had trouble remembering the wording of the site, not atlanticz.com.
    240z 260z 280z 280zx Datsun Fan Clutch Rebuild
    Last edited by siteunseen; 08-15-2013 at 10:26 AM.
    1972 240Z #918 New Sight Orange
    1977 280Z #305 Light Blue Metallic
    1972 240Z #110 Persimmons Red

  18. #18
    Barn Find Daily Driver Captain_Zeros's Avatar
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    Quote Originally Posted by siteunseen View Post
    Aren't the clutches filled with grease or some type of oil? If it spins less freely when it's hot it's doing the opposite of what it is supposed to do, right?
    It's a little more complicated than that. It is a fluid coupling that is designed to slip when cold, and then stiffen up when hot, but still allows some slip so it doesn't spin at 7000 RPM and explode when you pin the throttle.

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    1973 240Z w/ roundtop carbs, 280zx e12-80 distributor, 280zx alternator, late model Altima junkyard electric fans. 115 Blue Metallic & white side stripes.

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