Original 5 blade red fan temp fix question

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After reading lots of posts on the cooling fan subject, I realize that there are a lot of upgrade options. I still have not decided which way to go. In part because I will be doing the M30B35 upgrade at some point so I am not too keen on spending too much effort and/or money upgrading the original cooling system.

So, just to get me through the upcoming summer months, and since my temp needle goes with alarming frequency to just below the red before the fan finally gets to work, I wanted to do a simple temporary fix which some people have mentioned on here. It involved "using longer bolts so the fan is always on". I imagine this is a way to lock the clutch out of the equation. Unfortunately I did not see any specific info on it such as which bolt to lengthen and which ones to use instead.

Would anyone have any info they would be kind enough to share?

Thank you

Bo
 
Replace with M6 x 30 bolts and you are good to go. Never heard that it fails in the locked position, I always thought when these failed it resulted in so many of the warped/blown heads back in the day.
 
I think they lock and are noisy. I'm amazed our 2800 still works. It had to get pretty warm before it locked on.
 
So why does the manual say to use the bolts in case of failure? The friction material and metal spokes are so thin I cant see how that ever got out of das laboratory

HB Chris said:
I think they lock and are noisy. I'm amazed our 2800 still works. It had to get pretty warm before it locked on.
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Stevehose said:
Replace with M6 x 30 bolts and you are good to go. Never heard that it fails in the locked position, I always thought when these failed it resulted in so many of the warped/blown heads back in the day.
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Thank you Steve. Do you mean to replace the existing bolts with M6-30's ? What size are the existing ones? M6-20?
 
Couple years ago I had a client come in with an overheating problem.
Seeing the fan was just barely spinning I grabbed it and explained the clutch was bad.
Told him I could lock it up so it wouldn't over heat again.
When he came in the next day to pick up his car he grabbed the fan to check it.
Let's just say 950 rpm on a sharp fan blade is really a bad thing....
 
Stevehose said:
Replace with M6 x 30 bolts and you are good to go. Never heard that it fails in the locked position, I always thought when these failed it resulted in so many of the warped/blown heads back in the day.
Click to expand...

Mine failed in the locked position. I could tell something was off since I could hear fan noise that was louder than usual, increasing with RPMs; almost like an electric fan was on.

I think that even at its normal temperature-driven maximum "lock", the viscous clutch always has quite a bit of slip because the sound I hear when it's working normally is never as loud as when it locked itself.
 
Luis A. said:
Mine failed in the locked position. I could tell something was off since I could hear fan noise that was louder than usual, increasing with RPMs; almost like an electric fan was on.

I think that even at its normal temperature-driven maximum "lock", the viscous clutch always has quite a bit of slip because the sound I hear when it's working normally is never as loud as when it locked itself.
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luis yours failed ? was it a friction or a viscous ?
i can not think of a reason why the friction would block when failing
 
DQ: mine was a viscous clutch that failed. I thought that's what we were talking about, my bad if not ...
 
old thread but I was pokin around trying to find prices for some red fans I found in the back and came across this?

I suppose there are almost as many solutions to overheating as there are owners. Fwiw, I know it's a problem for many, but my bav w/an 81 3.5 and 5 blade fan has never overheated.

I haven't tried this but... a microswitch somewhere on the throtttle linkage that turns the fan on at idle (or whatver throttle input you adjust the switch to activate)...so you not only have the viscous/temp control but anytime you are at idle the fan is on. You could also wire the switch to keep the fan on when the car is off. ( for those terrible emrergency situations ) Actually, don't new cars do that?

Like this thread and as the book state I would say locking up your fan is ONLY an emergency solution as stated above. I don't think the fan was made to run at high rims and aside from th extra vibrations causing a lot of wear on the water pump bearings it MAY, I dunno just thinking out loud, it may come apart at those speeds.

Ok, back to the search engine...
Al


Edit:the crazy spell checker in my iPad!
 
I remember back when the car was about four years old, the fan clutch failed with the fan disengaged. The replacement did the same thing a couple of years later and it's replacement a couple of years after that. I would get really nervous when stopped at a traffic light because the clutch could fail at any time, then the needle would start creeping up. One place where I gladly deviated from original in the restoration was to replace the friction clutch with a viscous clutch. It's a lot more likely to be stuck in bad traffic today than in 1974, and I don't want to risk it.
 
My fan was already locked with longer bolts when I bought it in 1980. It does make considerable noise at higher rpm but it has never come apart in the 36 years I have owned it. It has seen many excursions to redline. I don't recall ever changing the water pump either. It may have gotten replaced when I rebuilt the engine around 1983.
 
Me too I ran mine for a couple years that way. However it will create quite a lot of turbulence at lower rpms which for me caused the front carb of my triple webers to flood through the venturi. 9 blade is way to go for several reasons.


gwittman said:
My fan was already locked with longer bolts when I bought it in 1980. It does make considerable noise at higher rpm but it has never come apart in the 36 years I have owned it. It has seen many excursions to redline. I don't recall ever changing the water pump either. It may have gotten replaced when I rebuilt the engine around 1983.
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FWIW I do not run a fan. Just have the aux fan come on when temp gets just above midline on the gauge. Stays on about 60 seconds. Has been this way for decades, but keep in mind this a Canadian car, so limited super hot days, but I should add, when in traffic on a hot day, the aux fan does its thing and I can see the temp drop within the 60 seconds and then shuts off. As traffic and line ups have become more common, I have had my radiator upgraded to 3 core. Never think about coolant anymore. But of course there are other concerns....;) Mike
 
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