Loss of Power after New Fan Clutch

[jonaz]

Hello Everyone,

I have a 2007 Dodge Ram 1500 5.7 and it blew the water pump and fan clutch at the campsite. Got it towed to a auto repair store in San Diego and they replaced the fan clutch, water pump, and thermostat.

Since they replaced everything, I noticed that new the fan clutch is unusually loud and tends to stay on a lot (yes, it was a very warm day in Southern California). The fan clutch seems to be matched to my throttle acceleration...meaning the fan clutch roars more with when I apply the gas pedal. Going up into the mountains where I lived, I noticed a significant loss of power..I really had to floor it to maintain 40mph when I could easily do 50mph before.

I hate towing my trailer now and the new fan clutch engages a lot. Ive owned this truck for three years now, and it ran great, never even noticed the fan clutch before. I read that there are thermal and non thermal fan clutches? Do you think they put in the wrong fan clutch? Looking for some advice.

Thanks in Advance

[ScottG]

Roy, Neighbors truck is 5L. I don't think one can assume everything in back of the fan is the same though. Different engines have VERY different thermal efficiencies and thus, different cooling needs. Shape of rad probably dictates fan type and configuration too. Calculating cooling requirements is over my pay grade!

Devo, that is a complicated question. Under the conditions you state, it probably takes no power at all - fan can be disconnected. But When conditions are at their worst, like climbing mountain w/AC and heavy trailer, it takes a lot of power My truck uses up to 23 HP just to turn the fan.

My advice to the OP is to live with it for a while. Better to have ample cooling than more speed. Also, don't jump into doing some kind of modifications when what you have works.

As a side note and I don't know if this is true for 1500's, but when it comes to clutch fans for Ram/Cummins, only the OEM will do. Aftermarket clutches are notorious for having performance problems.
If the problem is really bothering you, ask if they put an OEM clutch on. They are stupid expensive but work great because Ram continues to revise them for both better cooling and AC performance. Last year I replaced mine and it works better than when it was new (but again, it's a diesel).

[Devo_the_dog]

How much HP is needed to turn the fan to transfer heat at highway speeds, if the radiator, water pump, thermostat are working properly and there isn't any blockage in the cooling system (airflow or coolant)?

[RoyJ]

ScottG wrote:
But even newer 1/2T's have clutch fans. My neighbor has a late model F150 with HD towing pkg and it has a large clutch fan - because that's what it needs to keep temps down.

Also, you do not want to add an electric fan to a system that already has a clutch unit. The electric fan will block airflow and cause performance issues. Besides, pusher fans don't work nearly as well as pullers.

What year is the F150? Every model I've seen (at least the EB engine) uses twin e-fans. Fuzzy photo, but you can barely make out the fans behind the rad:



Not saying that's the solution to the OP's problem, just that there shouldn't be a perceivable power loss on a modern 1/2 ton. 1 - 2 mph loss, maybe, not 10 mph.

My 2014 Ram hemi uses a shroudless e-fan in front of a mechanical fan. I've since deleted both and installed a brushless e-fan from a Pentastar. Not overheated once towing 8500 lbs, though our temp don't get that high.

The modern 1/2 ton Ram has a higher GVW with only a brushless e-fan (higher wattage than mine). And we know how strict OEM cooling certification is!

[ScottG]

Cummins12V98 wrote:

ScottG wrote:

Devo the dog wrote:
Put on an electric fan.

No electric fan can move as much air as the stock clutch fan on these trucks. That's why they use them.

I agree on that if he had a Diesel. Some of the electric fans do a great job on gassers.

No difference between the two when it comes to cooling. The truck was designed with a 15~20 HP fan to move enough air. That HP is directly proportionate to air movement. The clutch doesn't take more power because it's inefficient, it needs more power because it does more work. No electric fan will move as much air and if the truck is operated near its limits, it will overheat with one. Not talking about any other truck than the OP's. If he takes off the clutch and cobs on an aftermarket unit, it will overheat at its limits.

But even newer 1/2T's have clutch fans. My neighbor has a late model F150 with HD towing pkg and it has a large clutch fan - because that's what it needs to keep temps down.

It would be a mistake to try and get rid of perceived parasitic losses at the expense of cooling power.

Also, you do not want to add an electric fan to a system that already has a clutch unit. The electric fan will block airflow and cause performance issues. Besides, pusher fans don't work nearly as well as pullers.

[Devo_the_dog]

RoyJ wrote:

ScottG wrote:

Devo the dog wrote:
Put on an electric fan.

No electric fan can move as much air as the stock clutch fan on these trucks. That's why they use them.

As of 2021 all domestic 1/2 tons come with OEM e-fans. The much smaller fan to shroud clearance has a decent increase in efficiency, hence Ram gets away with 900 - 1000 watts instead of the 5 - 10 hp mechanical fan.

But in the OP's case, something is not right. Even a 10 hp parasitic draw shouldn't decrease speed from 50 to 40 mph, that's closer to a 50 hp draw.

Furthermore, the e-fans used on autos for the last 15-20 years typically outlast the radiators, hoses, etc.

I agree with RoyJ. Something's not right. If the fan clutch is kicking in often and you can't maintain speed, you have other problems.

[RoyJ]

ScottG wrote:

Devo the dog wrote:
Put on an electric fan.

No electric fan can move as much air as the stock clutch fan on these trucks. That's why they use them.

As of 2021 all domestic 1/2 tons come with OEM e-fans. The much smaller fan to shroud clearance has a decent increase in efficiency, hence Ram gets away with 900 - 1000 watts instead of the 5 - 10 hp mechanical fan.

But in the OP's case, something is not right. Even a 10 hp parasitic draw shouldn't decrease speed from 50 to 40 mph, that's closer to a 50 hp draw.

[Cummins12V98]

ScottG wrote:

Devo the dog wrote:
Put on an electric fan.

No electric fan can move as much air as the stock clutch fan on these trucks. That's why they use them.

I agree on that if he had a Diesel. Some of the electric fans do a great job on gassers.

[beergardens]

I also think that they may have replaced your standard duty clutch with a heavy duty or “trailer tow” fan clutch. It may end up being a better choice overall, but if you really can’t stand it, get an OEM one to replace it with. The dealer should be able to find out the part number of the one the truck was originally equipped with.

[BenK]

On electric radiator fans...make sure your alternator and battery are in good to excellent shape.

It moves the HP source from the water pump shaft to the alternator/battery system.

Have read articles stating that fan clutches 'can' draw more than 10HP when fully on and even more (25HP) for HD/SD fan clutches.

Benefit of electric is that when 'off', there isn't any parasitic draw from the water pump shaft

[ACZL]

ScottG wrote:

Devo the dog wrote:
Put on an electric fan.

No electric fan can move as much air as the stock clutch fan on these trucks. That's why they use them.

I think the reason he mentioned it was to get air moving thru the rads so the main eng fan wouldn't be engaging as much

[_1Flyboy]

If they did NOT put on an OEM Dodge Fan Clutch you will get different results with an Aftermarket!!!!!!! I used to be a distributor for different brands of Fan Clutches….

[ScottG]

Devo the dog wrote:
Put on an electric fan.

No electric fan can move as much air as the stock clutch fan on these trucks. That's why they use them.

[Devo_the_dog]

Put on an electric fan.

[BenK]

Agree and add that they might have installed a HD fan clutch assembly, which couples more water pump shaft RPMs

OEM for most half ton's couples water pump shaft RPMs in the 50%-60% when they turn on.

HD and Severe Duty fan clutches couple water pump shaft RPMs in the 80%-90% range when they turn on.

They R.O.A.R compared to OEM fan clutches and they turn off sooner than OEM, as they do such a good job of cooling the cooling system down.

[Grit_dog]

If it runs fine, I’d question any issues with power loss being a problem, but Likely just a 10-15hp drain due to the added accessory load.