Hey guys. So for a long time my Pontiac runs 180-185 all day driving, but I hit traffic or a long light and temp creeps up and up and up. As high as 220. Once I move again it drops down to 185 again. So I'm getting the radiator cleaned out and notice that at an idle the mechanical fan is not moving any air! Some out the sides but just nothing. Lots of dead spots. I took a pic of how the fan was and it looked backwards to me. I take it off, flip it and it's the same amount of air flow. Hardly any, lots of dead spots and no roar of air going thru. The draw feels very low on the front of the radiator. Before I get fed up and go dual electric fans, what am I missing on this simple issue?! My set up; 65 Pontiac bonneville. 389 4bbl stock. Pertronix 3 with pertronix relay. 6 or 7 steel blade fan. Fan clutch. Desert cooler high efficiency 4 row radiator, fan shroud. Hi flow water pump. Spring in lower hose. Fan is 1/2 in and 1/2 out of shroud. Clutch sits maybe 1- 1.5" from radiator core. Sent from my iPhone using The H.A.M.B. mobile app
With a spacer I will have to install the radiator after the fan. There isn't anymore room. How is it possible for this fan not to move any air? How can u tell the pitch and difference of this fan from any other? Sent from my iPhone using The H.A.M.B. mobile app
If it's spinning slower than it ought to, it wont move much air, but it will look like it should be moving air. The clutches do wear out over time. If it's old, try replacing it. That setup should move a bunch of air, if it's all working properly. When the engine is not running, can you spin the fan easily? or does it take some effort to turn it, and it stops right away when you let go? also when you shut off the engine, does the fan keep spinning for a little while, or stop sort of quickly? (you need a helper to check this)
It doesn't spin easily when engine is off. Does the fan in the pic look backwards? The leading (longer) edge wasn't on the direction the fan was going. Sent from my iPhone using The H.A.M.B. mobile app
can you find a smaller water pump pulley, it looks really big. a smaller water pump pulley or larger lower pulley will speed the fan up.
Two types of clutch fans. One is the cheaper version that is not thermostatically controlled, the other has an exposed coiled spring facing the radiator. Spring is bimetallic so it controls a valve inside. T-ones, when the car is stone cold, the fan roars till you get a block or two away. Then runs silent until very extreme temps of air, brings the roar back on. Takes a very high temp to kick it back on.
Pulleys are all original. Interesting point. Don't think this one had the spring facing the radiator that u mentioned. Maybe it's a cheaper one that is finally going out. Just seems strange that the would be no air moving thru it at all. Didn't seem like it wasn't spinning slow or anything. If that's the case I guess this is my first bad fan clutch. Didn't think these things "wore" out. Sent from my iPhone using The H.A.M.B. mobile app
If you get a new one, see if they can get the correct thermo one for your car and your blade. They work well, and you have piece of mind, knowing it will "kick in" when it gets too hot, before boiling. It's nice not listening to a high pitch fan if it's not needed. The old add-on A/C conversions in the 60s-70s, had a solid non clutch with very aggressive pitch and was awful to hear all the time.
Alright guys, thank u for the info. I'll look into a new clutch. Was wondering why there wasn't enough draw. And this explains why my buddy with a 65 bonneville with no shroud and a 4 blade fan could sit in traffic and I couldn't. Ugh, cars Sent from my iPhone using The H.A.M.B. mobile app
This may sound iffy ... let engine warm up take a piece of heater hose 2ft long double over hold ends in hand slowly and i mean slowly push it in to fan ( from the angle that you took the picture of the fan) the back side of the blades ! The fan wont catch it . If the clutch is weak the fan will slow down . DO THIS ONLY AT IDLE!!!! If clutch is ok it wont slow down. Now dont just stick the hose in fast and deep or the fan may get you (not good) or you my need a new radiator and fan water pump etc... Saw this test done many times . always worked . BUT do it SLOW and CAREFUL!!!!!!!!!!!!!!!!
I was having the same problem with my '39 convertible,I had the same size water pump pulley as the crank pulley,I installed a smaller W/P pulley and the water temperature dropped dramatically. HRP
X2 Pully size do matter , Also try what RTP suggested , BUT BE CARFUL, especially if the clutch is good !!
You can make it work by putting sheet metal screws in the front of it. That Locks it up and makes a good test.
Thanks HRP & eddy, I'm gonna look into that as well! Sent from my iPhone using The H.A.M.B. mobile app
Thanks for reminding me! This trick really helped my OT Jeepster so it should help my 50 The top one is 5" off an 82 s-10 with the goofy little v6, and is sitting on top of my original 6" The original s10 one is actually 4 groove. Drill out 2 spot welds and you get 2 try's to get one to fit. The one shown is the deeper 1/2. The front shallow one is on my car now Good luck with yours Sent from my iPod touch using The H.A.M.B. mobile app
And here is the front 1/2 of the s-10 pulley on my mid 70 Pontiac 350 Sent from my iPod touch using The H.A.M.B. mobile app
When cold take the rad cap off and start the engine. Let it idle until it his hot and you are sure the thermostat has opened. Look in the rad see if there is any movement of water if none raise the idle slightly, I mean 100rpm or less, if you see water movement a smaller pulley will solve the problem. YBlock guys do it all the time. This 15% methanol gas doesn't help either..good luck.
Poked my head under the hood after work. The water pump pulley measures 8" !! I'm sure a 6" will help that out. Anyone know a good place to find a 5-6" pulley, 2 groove that's about 1 3/4" overall depth? Sent from my iPhone using The H.A.M.B. mobile app
NAPA has 3 grades of fan clutches for 60's-70's GM engines. Standard, heavy duty and severe duty. I put a severe duty on my 67 GTO w/AC, and never looked back. The only problem is that it is noisy (like a big truck) before the clutch warms up. A heavy duty clutch probably would have been quieter at start up.
Are you sure the radiator fins are not just plugged up with dust, dirt and other stuff and the air can't flow through it? Its seems pretty strange the current system has worked for all these years, and now somehow the pulleys are the wrong size? Either the clutch has gone bad, or the radiator fins are plugged up and the air can't pass through, or a combination of both. Wash the rad fins out with a pressure washer from under the hood towards the front bumper. If that doesn't do the job, change the fan clutch. Gene