foxlovescars

Hi everyone:
Was leaving for the Olds Nat'ls in Nashville early tomorrow and have been working on my car all week. The car starts and idles great, but when I press the accelerator and the engine revs up, I have a loud "roar" coming from the front of the engine that I can't find. I would guess the problem would be mechanical as the driveshaft and and trans don't move in Park. The fan turns clear of the shroud and is not hitting it.

Here's the list of things I did on the car this week: New transmission pan, speedometer gear at transmission, trans filter and new modulator. New distributor cap and new spark plugs, (I have electronic ignition module so no points). Oil and filter change.

Any ideas?
Thanks in advance,
Frank in Florida

no1oldsfan

I might guess possibly the clutch on your clutch fan.

foxlovescars

no1oldsfan:
I'll check the service manual to see how to test it.
Thanks for the quick response.
Frank

Sugar Bear

X2, If the car has a fan clutch it is seizing or has seized. It is easy to replace, you could probably drive it like it is, , it will drink a lot of fuel.

Good luck!!!

foxlovescars

I walked out to the garage and the fan spins freely with the engine off. It has a relatively new clutch fan, for the miles I've driven. I replaced it in 2017.

Koda

Quick method. If the engine is hot, and off, it should not spin much, like 1/8 turn. If the engine is cold and off, it should spin 1/2 turn.

Locked is bad. Free wheeling is bad. This is all with a decent heave from your hand.

Don't test with engine on, that method is for super samurai.

foxlovescars

Didn't know free wheeling was bad.
Frank

no1oldsfan

It can be very loud. Sounds really strong.

69HO43

If original, general rule- start engine, get to operating temperature, turn off engine while watching fan/clutch. Should only turn less than 1/2 turn more. This is if you have a factory-style spring-type thermal fan clutch.

AFAIK, all factory fan clutches were all thermal, noted by a coiled spring on the front. Meaning they don't lock up until the spring reaches a certain temperature from the air moving through the radiator and opens the ports to allow fluid to flow to lock up the clutch. When it cools down, it closes down the port to cut off the locking action. So when cold, they should be fairly easy to turn, but you can still feel a little bit of resistance. If it is difficult to turn when cold, or fairly easy to turn when hot, it's likely failed. Check the shaft for evidence of fluid leakage, or wobble.

There's the non-thermal clutch style (and usually cheaper) fan clutches that came into aftermarket use so make sure to check which you have as they operate "backwards". They usually have a flat face and are thinner. The idea behind them is that they are always on and release at certain RPMs regardless of temperature. These will fake you out if you're not used to them because they're supposed to be resistant to turn when the engine is off. I've always referred to them "rev-limiting clutches".

foxlovescars

no1oldsfan: (and others)
You were right (actually "fan" is in your name). Read the service manual and it mentioned how in a/c cars, the clutch operates. I turned on the a/c and the roar went away. Will purchase a new clutch fan locally and store it in the trunk for the journey in case I need it.
Thanks for your help.
Frank in Florida

rocketraider

Frank, if it's at all questionable replace it before the trip. Might save a radiator or water pump job on the side of the road.

Enjoy your JWO articles.

cfair

If you’re going to replace it, be aware that Hayden has a very wide selection of clutch fans that fit our Olds’s. You can get standard duty, heavy duty, short, long and so on.

Easiest fix, if the car runs cool and right, is to direct replace with the same number. If you’ve modified things or it runs hot, you might look for an HD clutch fan that kicks in at lower temperatures or keeps the “taller/longer” fan clutch that holds the fan just a bit closer to the radiator core (while being about 1/2 the blade out of the shroud).

Fan pitch matters too on noise. Deeper pitch pulls more air across the core, but runs louder. It took me many years and experiments to get mine right, but I went with 7 blade fans and non-stock clutches with 180F thermostats and the cars run cool and correct, even on hot days.

I ultimately went with moderate fan blade pitch and I think an HD fan clutch for my 455 A/C 66 Starfire. After all that, gotta say I’m a fan of mechanically driven clutch fans over electric, but you have to have the shroud and front rubber curtains right for it to really do the job.

Cheers
Chris

matt69olds

Fan clutches will sometimes roar on a cold start. That’s just due to the heat sensitive liquid settling in the bottom of the clutch. After a few seconds the roar should stop.

There will be a noticeable roar when the airflow thru the radiator gets hot enough to engage the clutch.

There is a procedure outlined in the service manual to testing clutch function. If I remember correctly, you put a blanket over the front of the car to block airflow, start the engine, turn on the air conditioning, and slightly race the engine. After certain amount of time, abd a certain temp, you should hear the fan roar and feel a increase in airflow. Remove the blanket, turn off the A/C as the engine cools down the roar should slowly cease.

no1oldsfan

Right on. I suggested what I did because I have lived it. So loud so strong. Keep checking your items. It will be an easy fix. Shakes the entire front of the car. Been there.

Koda

I will clarify, the clutch, when not engaged, allows a whole lot of spin, but not ALL. ALL spin, where it's just turning loose, is what I meant by freewheeling. The fan would not turn at all when the engine is running and cold if it spun completely free, it would be like those sliders the rap stars have on their wheels.

Fun71

Imhotep, eh? Invoking Egyptian chancellors is what makes the fan clutch operate?

no1oldsfan

Clutch fan can also start spinning way to early or late after whatever it's life has been. Not that it is locked up but the clutch of the fan can get gummed up etc so it spins at the wrong speed. Trying to simplify. When you mentioned a Roar. That explains it exactly. Pulls from the motor too. Hope you get it worked out. I feel your pain. My 70 442 came with a non clutch fan. 455 Oldsmobiles run hot. I replaced that four blade fixed blade fan instantly. My first clutch fan acted up like you are describing. You will get good help here even if I am not correct.

Greg Rogers

I replaced both clutch fans on my 71 Cutlass and 70 Vista Cruiser. Both roared terrible. I can hear it roar as I take off down the road and can hear when it disengages. I think that's the way those cheap clutch fans are. The original on the 71 had failed, free wheeled and car overheated once when left idling. The clutch fan was gone on the Vista when I got it. You guys who bought the more expensive Hayden clutches happy with them???

matt69olds

Shaddup!!!


I know. I fat finger a lot of my reply’s. I’ll never understand why I don’t notice them as I’m typing, but it’s so obvious when I go back and reread them.




I corrected my spelling mistakes. I think we can all agree that now the world is a better place. 😏

foxlovescars

Sugar Bear:
I drove to Nashville from Florida yesterday and you were CERTAINLY right about the car using more fuel. Does the bad clutch make the engine work harder?
Frank

no1oldsfan

Yes

rocketraider

Takes horsepower to run that fan! That's one reason they were developed, to reduce engine load.

Greg Rogers

Just ordered a Hayden 2747 standard fan for my Cutlass. I can't remember what brand the last one was, but knowing me it was a cheap one. Anyway I hope the Hayden stops the roaring. We'll see....

oldsmobuser

If you turned on the A/C and the noise went away then the bearing in your A/C Compressor Clutch is bad.

Greg Rogers

I changed the cheap generic fan clutch to the standard duty Hayden. It is better but still roars though less. I guess if it never roared it would be freewheeling. I guess I am happy....

cfair

In case it helps, here’s how I arrived at my current ‘66 Big Car setup of Hayden 2765 & 7 blade fan. Not claiming that it’s relevant to Cutlass/442, just in case it narrows the fan clutch search for someone down the line.

These are my notes from long ago, just so I didn’t repeat a previous mista…, uh, setup: +++++++++++++++++++++

Hayden clutch fans 2705 SD, 2747 HD, 2765 SD, all fit ‘66 big cars.
On my ‘66 A/C equipped Starfire the 2747 has .5" radiator clearance against a 4 core copper/brass radiator. It is both cool and very noisy. Hayden 2765 runs quieter but the engine runs hotter. 2747 with 7 blade deep fan runs noisy. Check Hayden 2772, it may fit. Hayden 2797 seems like it will be too long in overall length.

Ultimately I added 2747 to 6 blade quiet fan 4/16. Switched to 6 blade and 2765 in 12/16

++++++++++++++++++++++