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I just ordered an OEM replacement fan clutch for my '80 L48. I thought the screaming sound was a fan belt (replaced). After, I was still getting some sound like a fan slipping when I would hit the pedal. But, after a test drive, I suspect the fan clutch. While speeding up or slowing, I was getting a 'metal scraping/screeching' noise from front of the engine. Also, I was getting it right at start up. The fan clutch is the original 39-year old unit. I am also going to install a new a/c belt as I had removed it in the search to solve the noise at front of engine.
Another symptom of fan clutch was when I would accelerate from dead stop, the engine really had to 'work' to get up to speed. Like something was dragging (fan clutch fully engaged). It is the original thermal fan clutch.
Will advise on outcome.
I am also having to clearance the starter. Will advise on that also.
An update: I ordered the non-thermal Derale fan clutch P/N 21037.
From the Derale site: There are two types of fan clutches, non-thermal and thermal. Non-thermal fan clutches engage the fan based on the shaft speed of the water pump. Thermal fan clutches engage the fan based on a bi-metal thermostatic coil, which senses the under hood temperature.
All original GM fan clutches are thermal and you should always use a thermal clutch..
I suspect a non-thermal fan clutch was installed on my engine (I have owned since 1997) before I bought it. It has no external coiled spring on front like most that are pictured in searches. I probably ruined my fan clutch when I left the fan assembly sitting in a box for several months allowing the silicone fluid to drain out the back of the unit. I hadn't driven the vette much since the top-end refresh of cylinder heads and carb and the clutch doesn't turn very well and is very noisy when slowing or starting up. Also, it slows the engine down under acceleration.
I intend to order the Derale (Made in USA) thermal fan clutch from Jegs for my 1980 Corvette.
Ted, there is a lot of good info in this brochure about fan clutch operation and troubleshooting. It may help you decide which direction you want to go.
I have a complete 1980 unit that I removed intact that I don't need (1980 4-speed L48). PM me if you are interested. I was waiting until I finished removing parts before I posted them all.
The Derale (US Motor Works - Made in the USA... it matters!) THERMAL fan clutch (P/N 259-22037, $43) from Jegs arrived Friday. Installed it Saturday. It is working great. Still getting a scraping sound when I am coming to a stop. Sounds like fan blades. If I had a bad motor mount, I would probably have engine rocking issues. Next stop is the area of the torque converter cover on the 700R4. Hoping it isn't the poly cam button on the timing cover. Really hope it isn't torque converter blades. Car runs fine otherwise.
Use a thermal clutch! My ACDelco/GM L-82 fan clutch is rated at 195 degrfees before in fuly engages the fan and does not operate engaged dragging on the motor 99% of the time since my engine NEVER goes above 185-190 degrees on the highway or in the city.
Use a thermal clutch! My ACDelco/GM L-82 fan clutch is rated at 195 degrfees before in fuly engages the fan and does not operate engaged dragging on the motor 99% of the time since my engine NEVER goes above 185-190 degrees on the highway or in the city.
When fully heated and driving in the city, my temp gauge hovers 190-195. It pretty much sits at 190 when I am driving in the country. Going to take it for another spin now to see if I can run some of the old gasoline out of the tank. I've added 18 gallons (13 last week and 4.7 yesterday) of Shell Nitro 93-octane. So, there should be more good fuel in the tank than the old E10. Will advise on behavior and road manners after this test drive.
The Derale (US Motor Works - Made in the USA... it matters!) THERMAL fan clutch (P/N 259-22037, $43) from Jegs arrived Friday. Installed it Saturday. It is working great. Still getting a scraping sound when I am coming to a stop. Sounds like fan blades. If I had a bad motor mount, I would probably have engine rocking issues. Next stop is the area of the torque converter cover on the 700R4. Hoping it isn't the poly cam button on the timing cover. Really hope it isn't torque converter blades. Car runs fine otherwise.
Ted, I'm sure that you've already verified this, but it is critical that the pilot diameter of the fan clutch be the same as the pilot shaft on the water pump.
I also suspect you would quickly notice this if were not, because the tip-path of the fan would move in an orbital path and likely vibrate.
Ted, I'm sure that you've already verified this, but it is critical that the pilot diameter of the fan clutch be the same as the pilot shaft on the water pump.
I also suspect you would quickly notice this if were not, because the tip-path of the fan would move in an orbital path and likely vibrate.
Good luck... GUSTO
Yes. It works perfectly. Really good quality and correct sizing.
Next on the list is R&R of the PS pump. It is leaking and I suspect the impeller inside is damaged and causing noises (It had run dry before I realized it). It is over 20 years since I installed the VB&P rebuild kit.
03-16-2019, 01:08 PM
Replacing Fan Clutch - 80 L48
