d-max fan questions

[Mikey von]

OK, I have a serp setup for my 6.2l. I am looking to put the d-max fan on it. I currently have easy access to a used stock 6.5l fan and clutch.


If I were to buy a used d-max fan and clutch, would it bolt onto my 6.2l with a '94 6.5l serp setup and HO water pump?

[Robyn]

IIRC the Dmax units are a screw on type hub on the clutch like the real late 6.5 (99 and later)

For most 6.2 applications a 6.5 fan and clutch will do fine as lon gas the clutch is in good shape.

Be sure the radaitor is top notch too.

Far too many folks start fighting a heating problem from the wrong starting place.

The 6.5 fan clutch will not engage until the air temp gets up to around 200F
Now this said, a used radiator thats got BOO KOO miles on it will be well silted in and have other issues that will prevent the heat from reaching the fan clutch sensor bimetal spring.

When this happens little will help to fix the issue.

You have the best of the best with the serp drive and the HO Pump.
Do you have a daul T stat Xover too with 180F stats.

If you dont have the dual stat Xover, this is not a huge issue but it is recommended with the HO Pump to take advantage of the flow changes.


If your radiator is old, I would save the $$$$ on the DMax fan and clutch and get a fresh Visteon radiator instead.

Avoid the cheap units advertised on the web in places like ebay.

These will (or likely could) have an epoxy coreed unit. (The tubes are set into the head plates and then epoxied in place.

The epoxy cracks in time (sometimes short time) and they leak, then they are junk.

The biggest issue with the cooling system on these rigs, even the older square bodied trucks of the mid 80's is that the cooling system was sized too close to the minimum needed to cool things when the going gets tough.

Now as time and miles pile up the cooling system slowly looses its ability to reject heat.

Granted a good fan is essential to a good system, but the stock fan from a 94 serp system will move more than enough air when it hooks up right.

The DMax Fan is a great piece and along with its attendant clutch do a fine job.

Just be sure that your system is otherwise top flight.

When fresh, clean and working properly, the stock system will cool fine.

Another area of neglect is in many cases the AC condenser and the other cooles out front.
These become plugged (or partially) with little creatures such as bees etc along with road dirt from the winter water spray off the highway.

All this stuff sticks to and eventually slows down the airflow through the frontal area as it heads to the radaitor.

Be sure to spray all the coolers and AC unit with something like simple green cleaner, let soak and then flush with a good stream of water.

Be sure and backwash the coolers to get any an all crud back out the front and then blow dry and look them over to be sure things are clean.

The area between the radiator and the AC unit collects leaves and all sorts of crap in fairly short order.

Removal of the top shroud half or the retaier cap (depending on the model) and then unbolting to two top radiator clamps will allow the radiator to be leaned in towards the engine a little and any crap cleaned out from between.

This is a good anual preventive maintenance item.

Removal of the grill is essential to doing a good job.

Now all this said.

If you still decide to do the DMAX fan, be sure that the blades will clear the shroud with at least 3/4" on a side to avoid the blades hitting under engine torque loading.

DON'T ever be tempted to "TRIM" the blades if the fan is too big, instead trim the shroud carefully so things clear.

IMHO
The earlier steel fan of the 94 0r so 6.5 is plenty to do the job as long as the other details are in good order.

GM likely did not switch to the plastic fan in the DMAX because it was just sooooo super, but instead more likely because it was far cheaper to produce.

Those steel blades are not cheap compared to a plastic fan.

The plastic fan is much lighter and will probably place less stress on the waterpump bearing.


Have fun

Missy

[DmaxMaverick]

It won't fit. You will need a later model water pump, too. Earlier clutches attach with 4 bolts to the pump flange. Later models thread onto the pump shaft. John Kennedy has some solutions to fan/clutch improvements on his site (http://www.kennedydiesel.com), with a better description of the above.

[Mikey von]

Where I am right now is no fan or clutch. I have the serp setup, ho water pump, dual thermostat x-over with 180 degree stats. My rad is in decent condition and will be thoroughly cleaned while I have it out. The rad will be replaced and upgraded when I eventually go with a NV4500 and external oil cooler (next summer hopefully). This truck hopefully will be my "forever" truck and I do not mind spending money on good products. I am short of cash at the time though (see my engine thread). I am just looking for the best value for my money right now.

I can buy, for $20, a '94 6.5l well used fan and clutch that I was expecting to come with my cooling upgrades (long story). I am weary about buying this as I am unsure of clutch condition and the older fans look highly inefficient. I am also unhappy with the whole situation and would rather not dump more money into this guy.

I have also been looking at some used d-max setups. It sounds like the used d-max setups are not the way to go as the clutch wont fit.

Will a used d-max fan fit a 6.5l clutch with the 4 bolts mounting it to the water pump?

Are the later model 6.5l fans better than the '94s?

How much are new fan clutch setups at places like napa (i get a discount) or summit?

What would you do?

[EWC]

As has been previously posted , the Dmax fan clutch is a screw on design . The HO pump , later years , does come in the screw on design . The early HO pump has the 4 bolt holes . I have an 85 that is going to be serp drive and I went with a Kennedy fan clutch and the later 6.5 9 blade fan . What you have , with the 94 fan , may work with your combination depending on the condition of the radiator . You could try it and make adjustments later on if money is tight .

[DmaxMaverick]

Napa and Summit both have online catalogs, and list their prices.

As far as what I would do??? Not sure. I haven't had any significant cooling problems with all my 6.2/6.5's. Maintenance is key, and most issues, even those you read about here, are remedied with repair of failed components. Most overheat issues involve poor coolant flow, thermostat/clutch failure, or overreaching in the power department (without taking into consideration and accommodation of the additional heat generated).

I haven't tried to fit a late fan onto an early clutch, so I don't know if it'll fit. I'm sure some have tried, so you should get some feedback on it here. If not, I'll pull up the diagrams and compare them, as well as make some comparisons on my equipment (I don't have an off-vehicle Duramax fan clutch).

Still, check out Kennedy's site. He's posted up some good info, and not just "parts for sale".

[Mikey von]

Napa and Summit both have online catalogs, and list their prices.



As I always do, i searched all the diesel sites (kennedy, ect.), plus summit and napa right after I posted.

It looks like the best deal is at ssdiesel with a clutch and fan going for $200.

[More Power]

Kennedy is the only vendor who offers 6.5 fan-clutches that are calibrated for a lower engage temp. His cost more because they are special... These would be recommended if you're getting late engagement with a stock, off-the-shelf, variety. That said, it's heat that causes a fan-clutch to engage. Even factory fan-clutches are designed for a specific application. Installing a 6.5 fan-clutch in a formerly 6.2 truck might not produce the same result because of a potentially different airflow through the cooler stack, which could fudge the calibration. Might work fine... then again...

While I haven't measured them, the 2004.5-2005 LLY Duramax is supposed to have a 19" diameter 9-blade composite fan. The original 2001-2004 LB7 Duramax was equipped with a 21" fan. The 2006+ Duramax is reported to have a 23" fan.

I've trimmed a 21" Duramax fan to 20", and didn't have a problem. So, it can be done, if you're careful... The tips of the blades are very thin and lightweight - and there are 9 of them. The factory fans are not spin balanced after manufacture.

[Robyn]

If you dont have a fan and clutch, I would look at the used setup and if there is not any oil leaking around the bimetal spring then it likely ok.

Just be sure it turns stiff and smooth when cold.
A loose or leaking clutch is junk.

Acfar as triming a fan goes , I am still flinching from one that came apart on a local fellows truck.
He trimed the blades and seemingly did an ok job.

Was over there looking at his finished work, the engine was running, he reved it up and the blade disintegrated showering us with pieces only after destroying the fan, radiator, shroud and denting the hood too. :eek:

Was a real FUBAR for sure.

The 19" Dmax fan should fit in the hole fine.

The biggest issue is getting that clutch locked up at around 200F water temp.

Once the clutch locks on and the fan spools up it will cool the little beast..

The late HO pumps have the threaded hub and will probably accept the DMAX clutch and fan.

Do some searching of the bone yards and see if you can find some parts that are not trash that you can check to see what will and wont fit.

Then you can scrounge up some good stuff.

John Kennedy though is the hot ticket for his low temp fan clutches.

They are the definately a good option.

Best

Robyn

[rogers]

If you want a duramax fan on the cheep, buy the 1998+ fan thermostat and the 2001+ fan at Rockauto for $138. The 1998 thermostat bolts on to the regular water pump and will allow the duramax fan to bolt up too. This is the set up I have.

[Mikey von]

If you want a duramax fan on the cheep, buy the 1998+ fan thermostat and the 2001+ fan at Rockauto for $138. The 1998 thermostat bolts on to the regular water pump and will allow the duramax fan to bolt up too. This is the set up I have.


just to be clear, do you mean the 1998 fan clutch instead of fan thermostat?

[rogers]

Yes, yes, yes! I am not sure where I pulled that from. I do need to get a set of thermostats though. Must have had that on the brain at the time. Thanks for getting that cleared up!

[Mikey von]

Looking at rockauto, they list 3 fan clutches for 1998 6.5L's (1 is way too much $$$$).

ACDELCO Part # 154674 - $85.79

or

HAYDEN Part # 2839 - $141.79


Which one is correct?

[rogers]

Looking at rockauto, they list 3 fan clutches for 1998 6.5L's (1 is way too much $$$$).

ACDELCO Part # 154674 - $85.79

or

HAYDEN Part # 2839 - $141.79


Which one is correct?



ACDELCO!! The Hayden one must be filled with liquid gold!?!