Fan clutch staying locked on.

[L31MaxExpress]

Common 6.5L diesel upgrade is an early Duramax fan about 2002ish. It has enough drag to allow a severe duty clutch to freewheel most of the time. It moves a ton of air as well even freewheeling.

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[618 Syndicate]

Common 6.5L diesel upgrade is an early Duramax fan about 2002ish. It has enough drag to allow a severe duty clutch to freewheel most of the time. It moves a ton of air as well even freewheeling.

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Is that a viable option for a big block as well?

 

[smdk2500]

Common 6.5L diesel upgrade is an early Duramax fan about 2002ish. It has enough drag to allow a severe duty clutch to freewheel most of the time. It moves a ton of air as well even freewheeling.

Stop Your 6.5 Diesel From Overheating

You CAN stop your GM 6.5 from overheating! We show you how 3 simple parts can solve any overheating issues so you can tow most anything that you want!

www.65turbogarage.com

It is a upgrade but I am not going to go that route until I have to replace my water pump. I'm not going to replace a prefectly good pump until it is not good. Mainly because its not 4 bolts a couple hoses and its off like a small block. And I may not then. I might go with the late 96 to 97 pump so that I can get the HO pump. I don't have any overheating problems so I dont really need the extra cooling a DMAX fan provides. But I will cross that path when it comes.

 

[smdk2500]

Is that a viable option for a big block as well?

I don't see why it wouldn't be. I don't know how big the diameter of fan they use but the DMAX fan is about a inch bigger in diameter then the 6.5's and it fits in the hole the 6.5's does. And off the top of my head I don't know big the 6.5's is I think its 19"

 

[L31MaxExpress]

Is that a viable option for a big block as well?

I have a Duramax fan on my 8.1 in my 99 Tahoe and had one on my 350 in my 97 Express.

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Moved a ton of air and my ac was colder at idle then when I had Tahoe electric fans.

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[eran tomer]

I'm noy sure about diesels but I love electric fans controlled by the ECM. Less noise and definitely better engine performance. I don't know what the newer diesels have on them.

how do you make the ecm control the electric fans?

 

[1998_K1500_Sub]

how do you make the ecm control the electric fans?

On the 1996 and later models (I think all, but certainly 1998) one can wire a relay to the ECU (there's an unpopulated pin in one of the connectors which can be dedicated to controlling an aux fan relay), and then re-program (aka "tune") the ECU to control the relay and hence fan.

The "tunable" control parameters are (from memory):

(1) high and low speed thresholds -> cause fan to be enabled (e.g., speed is less than low-speed threshold) or disabled (speed greater than high-speed threshold)

(2) high and low engine temp threshold -> turn on aux fan if engine temp greater than high-temp threshold, turn off if less than low-temp threshold, and I believe only if conditions from (1) enable it

(3) AC high pressure switch closed -> triggers aux fan on, and I believe only if conditions from (1) enable it

(4) Plus a few others of similar function

See the attached images from JET's DST tuning tool for a 1998 L31 ECU config.

 

[GMTMark]

On the 1996 and later models (I think all, but certainly 1998) one can wire a relay to the ECU (there's an unpopulated pin in one of the connectors which can be dedicated to controlling an aux fan relay), and then re-program (aka "tune") the ECU to control the relay and hence fan.

The "tunable" control parameters are (from memory):

(1) high and low speed thresholds -> cause fan to be enabled (e.g., speed is less than low-speed threshold) or disabled (speed greater than high-speed threshold)

(2) high and low engine temp threshold -> turn on aux fan if engine temp greater than high-temp threshold, turn off if less than low-temp threshold, and I believe only if conditions from (1) enable it

(3) AC high pressure switch closed -> triggers aux fan on, and I believe only if conditions from (1) enable it

(4) Plus a few others of similar function

See the attached images from JET's DST tuning tool for a 1998 L31 ECU config.

That’s the way it’s done.

 

[Rcj1]

What are the parameters of a stock fan. Kick in at temp. ,disengage at speed etc....?

 

[smdk2500]

What are the parameters of a stock fan. Kick in at temp. ,disengage at speed etc....?

Good question I do not know for sure but I'm sure it is not as low as 90 degrees. I will have to look it up to be sure.