Fan pulley size and fan speed on MCI 5

[bevans6]

looked it up in my DD manual, apparently while the 12V engines had a viscous damper pulley ($$$) the others had either a solid pulley or a rubber damped vibration damper pulley, which I see on mine, come to notice it.  I've had the rubber dampers fail on race engines, from time to time.  they aren't cheap either...  So there is a possible difference to look out for.

Brian

[luvrbus]

The pulley and the harmonic balancers are 2 separate items some v12/71  just have a cap on the end of the crankshaft it all depends on the hp and application some have cam shaft balancers some don't. The 8v92 and the in line 671 use the viscous balancer also around 600 bucks from Detroit.  

good luck

[buswarrior]

Just to keep it straight, if changing the pulley on the engine crank, the goal would be a larger pulley on that end to speed up the cooling fans.

Smaller on the fans, bigger on the crank, or some combination of that is the goal for hiking the air flow.

happy coaching!
buswarrior

[mcilee]

I am confident the original was larger than the 9 3/8 we now have because it was a bit of a concern when I couldn't get the same size. It also was tough to get the belt between the pulley and the bumper stuff to change the belt. If these things happened fast it would be easier to remember but as most of you know these projects can stretch out for a few months and we have many other numbers running thru our heads!!! If the day is cool, say less than mid to low 80's it is usually not a problem. On one of the last outings I put new weather stripping in on the top door and made sure the gaps were sealed around the radiator. What are we towing? Last weekend was a 2004 F-150 with a jet ski trailer behind it weighing in @ probably 2000 lbs, ambient temp was about 90 degrees. On the way home at 75-80 degrees and not even a hint of over heat. Relatively flat ground with only slight  but long 1-2 miles uphills and down. I am about to the point that I will take some temp readings next time out and if they prove to be correct with what I have read on the board here I will machine out a pulley that will fit in the space allowed and get a new belt and see what happens. At least get back to the fan speed I think I had way back when before I started improving things. LOL
Lee 

[RickB]

Lee,

Think about giving ABC in Faribault MN a call to see if they can ship you out a new crank pulley. An earlier post from someone with an MCI 5 said they had the same one as I am running so it must be a good ground zero to start from.

If you kept the 7 and 1/2 pulley maybe try putting that back on and i'll bet you'll be just fine tempwise.

I know C&J coach have the smaller gearbox pulley in stock althought it will be considerably more than a used one.

Good luck and keep us informed as to how things work out.

Just to show you there is hope, I drove 350 miles a couple weekends back and I didn't look at the temp gauge more 2-3 times on the whole trip. That is a new concept to me.

Have a great day,

Rick

[Ed Hackenbruch]

From the parts book;  Pulley- Crankshaft (Std. Rear Axle)  8C-4-2.    Pulley- Crankshaft (3.7 Rear Axle)  8C-4-3.   Pulley- Blower Drive Prior to Coach Unit No. 5578,  6C-6-4.   Pulley- Blower Drive Effective With Coach Unit No. 5578,   6C-6-79.    Std. Rear Axle is 3.36:1 ratio,  Optional is 3.7:1 ratio.

[Ed Hackenbruch]

Forgot to add;  V-Belt - Blower Drive for Std. Axle Ratio,  111"   # 8B-27-2.   For 3.7 Axle Ratio, 110"  #8C-27-5