RPM engages clutch fan?

[Working K9]

I'm at a loss My humvee 94 6.2L if I Rev the engine up the clutch fan engages. And a get a huge air leak burst sound. No oil leaks what's so ever. It's clearly not temperature induced. I can start it cold and it will immediately do it from revs. Not sure where to look to find anything on the subject previously. Sorry I'm new.

 

[Andyrv6av8r]

Watch this and check out your system. Maybe your clutch is engaged already.

 

[Working K9]

Watch this and check out your system. Maybe your clutch is engaged already.

I believe you are correct the fan may be already engaged. I replaced the Cadillac valve already and have the temp switch and time delay switch on order. My concern is if the clutch is engaged why am I getting this burst of air at RPM? I see the hoses from the Cadillac valve flex when the burst occurres. It's not a constant air flow sound from the fan.

 

[papakb]

Why isn't this post in the HMMWV forum?

If your cadillac valve is kaput or the TDR or the clutch is on it's way out you'll get this issue. Where does the "air burst" appear to come from? The clutch system is hydraukicly operated. Are you referring to the sound of the fan blades make when the clutch engages? They sound like a small jet engine when they operate and it drags 10HP away from an already pathetically underpowered engine to boot!

 

[Working K9]

Why isn't this post in the HMMWV forum?

If your cadillac valve is kaput or the TDR or the clutch is on it's way out you'll get this issue. Where does the "air burst" appear to come from? The clutch system is hydraukicly operated. Are you referring to the sound of the fan blades make when the clutch engages? They sound like a small jet engine when they operate and it drags 10HP away from an already pathetically underpowered engine to boot!

I already replaced the Cadillac valve with a new one. I think the main question is whether it's engagement of the fan or not why is it engaging because of engine RPM? If the temp switch is bad then it's either on or not. If the Cadillac valve is bad then it's either on or not. Why is engine RPM causing engagement and not temp?

 

[Working K9]

I'm at a loss My humvee 94 6.2L if I Rev the engine up the clutch fan engages. And a get a huge air leak burst sound. Could just be the fan engagement but I don't remember it sounding like a air leak, almost like a wastegate on a turbo but I have no turbo. No oil leaks what's so ever. It's clearly not temperature induced. I can start it cold and it will immediately do it from revs. Not sure where to look to find anything on the subject previously. Sorry I'm new.

Temp sensor switch and TDM on order.

 

[Retiredwarhorses]

You need to take voltage readings, the fan engages when 24v is denied...I just Had this issue with a truck, fan engaged on higher rpm’s, was a bad Or clogged Cadillac valve...new valve and solenoid fixed it right up.

 

[DREDnot]

Id wait and see. When you get the sensor and switch, replace the temp sensor first and try running it and see if it goes away or not. Then replace the TDS and run it again to confirm a fix. Report your findings.

I'm sure we are all curious about the country of origin of your replacement parts. Since these parts are common problem areas of this cooling system, they are highly sought after and most of the ones you see are knockoffs with famously dubious quality. Did you chose your parts on best price, or did you try to find OEM/NOS cadillac valve/TDS/TS?

My money is on the Time Delay Switch making it geek like that. But a cheap cadillac valve could be defective out of the box i suppose.

Like I said, wait and see.

 

[Retiredwarhorses]

Id wait and see. When you get the sensor and switch, replace the temp sensor first and try running it and see if it goes away or not. Then replace the TDS and run it again to confirm a fix. Report your findings.

I'm sure we are all curious about the country of origin of your replacement parts. Since these parts are common problem areas of this cooling system, they are highly sought after and most of the ones you see are knockoffs with famously dubious quality. Did you chose your parts on best price, or did you try to find OEM/NOS cadillac valve/TDS/TS?

My money is on the Time Delay Switch making it geek like that. But a cheap cadillac valve could be defective out of the box i suppose.

Like I said, wait and see.

The fan can only engage from lack of fluid pressure or denial of voltage...so a simple check of the voltage into the Cadillac valve will tell your quite a bit....hard stop left and right turns will engage the fan when unlocked, this is due too denial of pressure at full lock.

 

[Working K9]

I appreciate the help everyone. I'll report back once I install the parts and test individually as I install. I just can't get past this air leak type sound. It's like an exhaust manifold gasket leak after 40 mph. Or at RPM

 

[Milcommoguy]

Trying to follow along here... on a Sunday, in the back pew.

Turn to your Humv hymm book > https://hummerhuren.files.wordpress.com/2013/01/hmmwv_test-diagnostics.pdf < Page 1 - 1 and a reading from pages 13-2

The clutch could be just stuck / gum-rusted up and on or off all the time. Air noises (Cadillac valve) just doing it's HISSY FIT thing might be throwing one off as to whats going on or NOT. (or clogged)

If fan is engaged when revved up off of idle, it will move a lot of air. V-RROOOM. Disengaged, works but a little puny vroom.

As stated the default to engage is the loss of voltage to the valve / system. Cold engine ( below 190 ish ) any fan wires pulled. Did that work to engage ??

(remember, fan ON - any fan circuit wires pulled on a cold engine, good fail safe logic / design and ass backwards as one might think)

Some simple electrical tests would clear up some confusion too.

Might be time to connect up the air compressor (90 psi) to the clutch line, looking for the slight fan disengage travel. Under pressure should free wheel like a top. That would clear up that mechanical assemble and get YA to see the light, going in the right direction and learn / see it in action. Then you can 'believe" (ENGINE OFF or be anointed in ATF )

Changing stuff ($$ shot gunning $$) could work for you. Not a real believer in this. Leaves me wondering.

I know the words, just on the wrong page. Passing the offering basket for parts now, CAMO

 

[Working K9]

So I installed the TDM today. Installed the new Cadillac valve last week, with engine off fan is locked. Tested the Cadillac valve for Ohm s and in spec. Disconnected the temp sensor and witnessed the fan move forward and engage. So it's clearly not engaged. Reved up the engine and witnessed the fan move forward and engage. Got off the throttle and observed the fan slid back and disengage. I'm at a loss.

 

[DREDnot]

Whats the generator output voltage at idle? When revved?

What are the individual batteries voltages when not running?

Is there any breaks in the wiring, or ground path that may be affected by the revving/torqueing of the engine?

Maybe P/S fluid pressure problem?

Just trying to think of out of the ordinary causes for a less than ordinary problem

 

[DREDnot]

Maybe the fan fording switch is out of adjustment? Should only switch continuity when at wide open throttle.

 

[Working K9]

Maybe the fan fording switch is out of adjustment? Should only switch continuity when at wide open throttle.

Where do I find that switch?

 

[DREDnot]

Its in the valley of the engine near the injection pump and throttle cable area. It has a little white plastic wheel that is part of the switch.

 

[Working K9]

Its in the valley of the engine near the injection pump and throttle cable area. It has a little white plastic wheel that is part of the switch.

Is it adjustable or does it need to be replaced?

 

[DREDnot]

I would at least inspect it to look for it being bent or boogered up, bad wires/connectors, and test that it switches continuity when you put the pedal to the floor.

Since its one of the components of the fan clutch activation system, you might as well check it and eliminate it as a cause. And you will learn what it does and how it does it for future reference

 

[Working K9]

I would at least inspect it to look for it being bent or boogered up, bad wires/connectors, and test that it switches continuity when you put the pedal to the floor.

Since its one of the components of the fan clutch activation system, you might as well check it and eliminate it as a cause. And you will learn what it does and how it does it for future reference

Thank you. Much appreciated

 

[Milcommoguy]

Little switch on IP pump is two fold. On the 3 speed transmissions (I don't have experience with 4 speed rigs) it controls the kick-down solenoid AND triggers the TDM to DISengage the fan to go for a swim.

Should give you about 20 seconds to get wet before fan comes back on.... IF the engine is above 190 ish ++ and fan temperature switch (in water crossover) is working properly.

(Note) fan temp switch is an OPEN switch when 220 ish hot or fan is running. Closes at 190 ish and below so fan should be off. This is the only switch that cycles fan on and off while happily going down the road.

OR

The kick-down switch (side of IP) triggers (momentary 24 volt pulse) to start the TDM to begin the 20 second +/- swim feature applying power to the Cadillac valve which disengages fan even if the engine is hot, overriding the temp switch. Confusing as heck, but it works well.

To pass grand-ma, the kick-down switch needs to be fully engaged, peddle to the metal to HOLD the solenoid engaged on the valve body in the transmission. Added bonus TDM get the trigger pulse too and off you go with a little more HP. All things working properly of course.

Those kick-down switches do go bad or could be out of adjustment. Pull one of the wires to it to check if fan STILL follows throttle position.

Does the transmission down shift correctly at peddle to the metal?

Question for you. Have you been reading the little book? >https://hummerhuren.files.wordpress.com/2013/01/hmmwv_test-diagnostics.pdf

Taking a survey to better serve, CAMO

An after thought... saw a picture posted a couple weeks back with a new fan temp switch that looked like a knockoff. SS was having fan issues. Just wondering here. You can set you clock by the humv posts. FAN problems in the summer. Start boxes in the winter.