75 Clutch Fan (and Other Overheating Reasons)

[azopelnut]

you guys are super
How about a clutch fan for a 1975?

[David McCollam]

What about a fan clutch? Do you need one or a part number or what?

[azopelnut]

yes a clutch fan (for a 1975 Opel with a 1.9 engine)

[David McCollam]

Paul,

Is yours locked up? I'll need to look at the house for the part number. It has the same number as a 1975 Triumph Spitfire.

Good luck.

[azopelnut]

I am trying to eliminate an overheating issue.
Radiator (3 core)-ok
thermostat-new

[David McCollam]

Paul,

The car wil not overheat if the fan clutch is out. The clutch would lock up and the fan would spin all the time.

Check the timing, temperature sensor on the engine, voltage stabilizer on the gauges, see FSM for other potential causes.

[azopelnut]

I thought that if the clutch fan is not engaging properly that it could overheat the engine.

[tekenaar]

Originally Posted by azopelnut I thought that if the clutch fan is not engaging properly that it could overheat the engine.

Common misconception about how it works . . . it's actually a declutching fan, meaning that water pump pulley is not locked to fan blade, i.e. pulley turns faster than fan. When this "clutch" fails, it freezes up to the shaft causing "locked" operation, i.e. like a normal bolted on fan blade, as David said in earlier post. Never seen one fail where fan blade has no drive from center hub, i.e. free wheel.

[namba209]

Otto, et. al., On my old motorhome with a GM 454, I had two fan drives fail in the free wheeling position. The failed part on both was the bimetallic temp sensor spring in the front of the hub. As long as the sensor thought the air was cool coming through the radiator it never engaged the viscous drive of the clutch. Both went back to the manufacturer because, like you, no one had ever seen a failure like that. Needless to say, I did receive two new drives free. BTW the first was purchased here inSANe DIEGO, the second I got in Sacremento, when the first on failed, and the third one, again inSANe Diego, when the second one failed. What was wierder, and caused the concern and replacment on both was that neither one would engage at low engine RPM as they're supposed to. Murphy was alive and well on that motorhome, continuosly. It earned the nickname, Murphymobile, the motorhome from hell.

[azopelnut]

(found this on Google)
The clutch works by shearing a viscous fluid, the drag from which couples
force from the driving shaft to the driven hub. The clutch consists of
two sections, a fixed drag section that provides a minimum level of
torque and a variable drag section controlled by a bimetal thermostatic
coil visible from the outside.

The most common failure, indeed the only failure I've ever seen, is
from the viscous fluid leaking out. Typically this happens over
several years and is not noticed because it doesn't leave a nice wet spot.
If the unit goes completely dry, the clutch will sometimes seize.
More common is that just enough fluid leaks out that the variable side
no longer functions. The fan still turns at idle but there is insufficient
drive to cool the engine.
(sounds like my problem)

Generally the seals are still OK and don't need to be replaced. Rebuilding
consists of opening the housing, cleaning it and refilling with fluid.
Opening the housing involves removing the clutch from the fan and removing
the 4 6 mm bolts that hold the housing together. Then gently pry the
housing open. There is an O-ring so a little force is needed. There is
nothing to fall out and no springs to surprise you :-)

Pour out any remaining oil and clean with brake cleaner or something
similar. Then completely fill the shaft-side housing with 90 wt gear
oil and add about 5 cc of laquer thinner. This slightly swells the
rubber in the seals and makes them more leak tite. Make sure all air
bubbles are eliminated. Then assemble the housing, replace the bolts
and the job is finished.

[tekenaar]

True of most other viscous fan clutches, but not Opels . . . ONLY failure of Opel fan clutch is that the clutch shaft bearing seizes, making it operate the same as a bolted fan blade. Opel clutch has no external thermal coil and cannot be disassembled to repair.

[Paul]

The Opel fan clutch doesn't have the bi-metal spring. Its just provides slip via viscous shear of the torque transfer liquid (heavy silicone ~20,000Cst) that circulates between concentric rings of the rotors. Failure can actually occur in two ways. The first, as Otto described, is by bearing lock up. The second is by the silicone fluid leaking out. In this case the fan would spin freely since there would be no viscous fluid to transfer the torque. The telltale signs would be a real mess and the fan blades freewheeling.

HTH

[David McCollam]

Paul,

In all of the need to definite and explain, we've forgotten to ask you what is occuring in your situation? Does the engine overheat at low speed in stop-and-go driving, at cruise, etc? Please describe the problem and your effrots to date to diagnose the cause.

Thanks,

[azopelnut]

In moderate Arizona temperatures (45-80) the temp stays in a normal operating temperature both city and hiway driving. In the summer when temps are 100+ and especially when AC is running the temps climb rapidly in town and eventually in hiway driving also. Even shutting the AC off on the hiway only brings the temp down only slightly. My other ascona also with a 3 core, (160 thermostat instead of a 185) and a mechanical fan operates very comfortably in extreme heat so my thought is that my 1975 must have a improperly operating clutch fan.

[tekenaar]

Originally Posted by azopelnut In moderate Arizona temperatures (45-80) the temp stays in a normal operating temperature both city and hiway driving. In the summer when temps are 100+ and especially when AC is running the temps climb rapidly in town and eventually in hiway driving also. Even shutting the AC off on the hiway only brings the temp down only slightly. My other ascona also with a 3 core, (160 thermostat instead of a 185) and a mechanical fan operates very comfortably in extreme heat so my thought is that my 1975 must have a improperly operating clutch fan.

Not your clutch fan, IMO, change thermostat to 160 deg and run 20-25% antifreeze in your radiator. OOC, extra coolant holes in head gasket?

[N61WP]

Also add a bottle of Red Line's Water Wetter. About $7.00 at a parts store. It really works.
Jc

[tekenaar]

Originally Posted by N61WP Also add a bottle of Red Line's Water Wetter. About $7.00 at a parts store. It really works. Jc

I know, but we still get a bit of winter here, though not much. 20-25% mix eliminates having to add antifreeze for winter months and provides enough pump lubricants and anti corrosion properties required.

[David McCollam]

Paul,

In a hot climate like AZ or TX, the 160 thermostat is the more appropriate year round choice. Typically, the thermostat only begins to open at the indicated temperature and is not fully open until about 10-15 degrees later. Try the 160 degree unit for the '75 and see if the car does not operate cooler on the whole. If the car has a 3-row core, I'd think that it would cool just fine with the 160 thermostat.

Good luck.

[Paul]

In my 75 Manta, I've never had luck with the standard type thermostats the 74 and old models run vs the 2 stage version. The FI system hates them, It kicks and bucks until the temp rises (if it rises). Also, I've seen these two stage thermostats with two different water passsage diameters. I use the larger of the two which has helped my problems.

I suggest using the correct 2 stage t-stat....

...A Different Paul

[kwilford]

Split this to a different thread....

And I am not back, just visiting.