Fan Clutch

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NicolasB
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Years Owned: 1969 Oldsmobile Toronado

Re: Fan Clutch

Postby NicolasB » Thu Jul 15, 2021 7:53 am

Okay, I just bought a 180 thermostat and will see if that helps. Since first gen. Toronados tend to run hotter I think the 160 is acting the same as having no thermostat at all since it’s open all the time.

Does anyone use a 195? I feel like that one is too high but I believe that is what the stock one is rated, cause the service manual simply says to not use a thermostat over 195 degrees. Just curious.
Last edited by NicolasB on Thu Jul 15, 2021 8:07 am, edited 2 times in total.

NicolasB
Posts: 261
Joined: Sat Apr 25, 2020 9:27 pm
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Years Owned: 1969 Oldsmobile Toronado

Re: Fan Clutch

Postby NicolasB » Thu Jul 15, 2021 8:03 am

I also back-flushed the cooling system three times with this kit I had laying around and it seems like it removed some crud that I missed in the engine. It’s actually quite convenient and doesn’t require removing the thermostat (but I still have to remove it to install the higher temp one haha). I drove it three times in between these back-flushes and the temp would still increase so I’m hoping the thermostat would solve the issue. Good news is the water is now clear.
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NicolasB
Posts: 261
Joined: Sat Apr 25, 2020 9:27 pm
TOA Membership Number: 0
Years Owned: 1969 Oldsmobile Toronado

Re: Fan Clutch

Postby NicolasB » Thu Jul 15, 2021 4:17 pm

So upping the temperature for the thermostat didn’t do much, I pushed it quite hard on an incline (84 degrees today) and it went up to 233 degrees. Once I started going downhill, the temperature immediately started to drop a few seconds in the descent (dropped 10 degrees within 30 seconds and 20 in about 2 minutes). Within 5 minutes of just going downhill, the temperature gauge dropped almost 50 degrees.

Schurkey
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Re: Fan Clutch

Postby Schurkey » Thu Jul 15, 2021 4:51 pm

NicolasB wrote:So upping the temperature for the thermostat didn’t do much, I pushed it quite hard on an incline (84 degrees today) and it went up to 233 degrees. Once I started going downhill, the temperature immediately started to drop a few seconds in the descent (dropped 10 degrees within 30 seconds and 20 in about 2 minutes). Within 5 minutes of just going downhill, the temperature gauge dropped almost 50 degrees.

1. Are you sure the gauge is accurate? HOW do you know?

2. Fan clutches often get the blame when the radiator can't release heat into the airstream. The fan clutch won't engage if the air temperature blowing around it isn't hot enough. Folks look inside the radiator for scale build-up, but they don't look at the corrosion on the air fins that should be soldered to the coolant tubes. Air fins corrode away from the coolant tubes, often from the effect of salt spray in winter/spring, coming from the tires of the car ahead.

3. If the engine tune isn't correct--overly-retarded timing, lean fuel mix, etc. will drive engine temps higher. When was the last time the carb was rebuilt, and a "Tune-Up" performed? Does the vacuum advance work? Centrifugal advance?

4. Sparrows and crickets stuck in the fins of the A/C condenser, or folded-over fins will hurt airflow which hurts cooling.

5. Dragging brakes and low air pressure in the tires make the engine work harder, creates more heat in the engine.

6. Still have the OEM fan shroud?

7. A stuck heat riser valve will force screaming-hot exhaust gas across the intake manifold, leading to engine overheating and detonation problems. A restricted exhaust--crossover pipe on a single exhaust, or a restricted leg of a dual exhaust--does the same thing.

At idle or cruise, temperature more than 15 degrees beyond the thermostat rating means the thermostat has lost control of the engine temperature. The closer you are to the thermostat rating at idle or cruise, the better. Higher load/heavy throttle may drive the temp up--trailer towing, serious uphill grades, "beyond highway speeds", i.e., having lots of fun, etc.

NicolasB
Posts: 261
Joined: Sat Apr 25, 2020 9:27 pm
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Years Owned: 1969 Oldsmobile Toronado

Re: Fan Clutch

Postby NicolasB » Thu Jul 15, 2021 9:28 pm

Schurkey wrote:
NicolasB wrote:So upping the temperature for the thermostat didn’t do much, I pushed it quite hard on an incline (84 degrees today) and it went up to 233 degrees. Once I started going downhill, the temperature immediately started to drop a few seconds in the descent (dropped 10 degrees within 30 seconds and 20 in about 2 minutes). Within 5 minutes of just going downhill, the temperature gauge dropped almost 50 degrees.

1. Are you sure the gauge is accurate? HOW do you know?

2. Fan clutches often get the blame when the radiator can't release heat into the airstream. The fan clutch won't engage if the air temperature blowing around it isn't hot enough. Folks look inside the radiator for scale build-up, but they don't look at the corrosion on the air fins that should be soldered to the coolant tubes. Air fins corrode away from the coolant tubes, often from the effect of salt spray in winter/spring, coming from the tires of the car ahead.

3. If the engine tune isn't correct--overly-retarded timing, lean fuel mix, etc. will drive engine temps higher. When was the last time the carb was rebuilt, and a "Tune-Up" performed? Does the vacuum advance work? Centrifugal advance?

4. Sparrows and crickets stuck in the fins of the A/C condenser, or folded-over fins will hurt airflow which hurts cooling.

5. Dragging brakes and low air pressure in the tires make the engine work harder, creates more heat in the engine.

6. Still have the OEM fan shroud?

7. A stuck heat riser valve will force screaming-hot exhaust gas across the intake manifold, leading to engine overheating and detonation problems. A restricted exhaust--crossover pipe on a single exhaust, or a restricted leg of a dual exhaust--does the same thing.

At idle or cruise, temperature more than 15 degrees beyond the thermostat rating means the thermostat has lost control of the engine temperature. The closer you are to the thermostat rating at idle or cruise, the better. Higher load/heavy throttle may drive the temp up--trailer towing, serious uphill grades, "beyond highway speeds", i.e., having lots of fun, etc.


1) At idle, the gauge read 180 degrees and the thermometer read the same so I believe it’s accurate. Will confirm this once I have the thermometer gun with me again (and when the gauge reads close to 230).

2)The thermal fan clutch works fine and the air around it is pretty dang hot so I think it’s good. I also bought it a few months ago to replace the old non-thermal clutch. I also got the radiator cleaned and repaired at a shop so there shouldn’t be a problem there either (actually tested it with a thermometer and it’s performing quite well).

3) I performed a tune-up over the past several months and readjusted the carb multiple times. I adjusted the timing once about five months ago, so I’ll check to see if it’s still accurate (last time I adjusted it to 8 degrees BTC). The carb was rebuilt last May and the timing adjusts when I rev the engine so I believe the vacuum advance is working (I know that a vacuum tester would verify this but I don’t have one as of right now).

4) There are no bugs on the radiator and I removed the A/C condenser for more airflow.

5) Tire pressure is good (checked this morning) and the brakes are fine.

6) OEM fan shroud still on, but one of the top brackets broke off and haven’t been able to find a way to put it back on (glue wouldn’t work). There is a slight gap but it’s pretty small.

7) I addressed the stuck heat riser valve by using a wire to keep it open all the time so there is a sufficient exit way on both sides of the engine. Exhaust system also converted to dual exhaust (basically straight pipe with two resonators).

The temperature seems to stay constant at cruising and idle, but under load for a bit of time makes the gauge rise a good amount (drove uphill pretty hard for 25 minutes and the temp went up 50 degrees [need to confirm if the temp in the gauge at this point is accurate]. Highway speeds of 65-70 for some time also slowly increases the temperature.

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Otto Skorzeny
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Re: Fan Clutch

Postby Otto Skorzeny » Fri Jul 16, 2021 5:52 am

Hi Schurkey,

My exhaust heat riser valve moves freely through the entire range but living in Atlanta, I think it's not really needed.

What is the default position when the spring is attached? Does it stay closed and then open up when exhaust blows through it?

When the spring is removed from its peg, the weight moves the valve all the way to a new position - I assume that's full open. Is that correct?

NicolasB
Posts: 261
Joined: Sat Apr 25, 2020 9:27 pm
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Years Owned: 1969 Oldsmobile Toronado

Re: Fan Clutch

Postby NicolasB » Fri Jul 16, 2021 11:09 pm

Some “fantastic” news: after ruling out all the obvious problems that car could have, we finally used the combustion leak tester and discovered the head gaskets do have a small leak. We didn’t want to immediately come to this conclusion at the beginning in case it could have been something simple (and it wasn’t noticeable performance or exterior wise under normal use), but the liquid from the tester did turn green so the heads gotta come off. The engine gasket kit is $72 on RockAuto (minus shipping and taxes), but I’m not sure how much the job will cost. Our mechanic is going to help us when he has the time and mentioned that replacing them on these cars aren’t that difficult, but there’s going to be many parts on the floor. At least this will be a good excuse to remove the intake manifold and clean the carbon out of it. So top engine rebuild will happen, it’s just a matter of when. I’ll also have to find a machine shop to repair and clean the heads ($200 a pair at one place I called).

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Otto Skorzeny
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Years Owned: 1966 Toronado

Re: Fan Clutch

Postby Otto Skorzeny » Sat Jul 17, 2021 4:49 am

Buy the intake manifold gaskets that have the exhaust crossover passage blocked up to keep the base of your carburetor cooler.

Maybe your guy can plug the passages ?

NicolasB
Posts: 261
Joined: Sat Apr 25, 2020 9:27 pm
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Years Owned: 1969 Oldsmobile Toronado

Re: Fan Clutch

Postby NicolasB » Sat Jul 17, 2021 1:16 pm

Our mechanic said that it’s a good idea to buy intake manifold gaskets that block off the exhaust crossover, but I would need to clean out the carbon in the manifold first. It actually absorbs heat and can cause the car to get even hotter than normal, so by cleaning it and blocking the passage, it would make the manifold and car last longer.


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