Air dampers are puzzling....

[NCbob]

I'm finding the operation of air dampers puzzling.
The air dampers have an air cylinder on them which is spring loaded to keep them open. Even in the absence of air pressure...they are open.

Da Book only pays lip service to the dampers in that it says the purpose of them is to close when the engine is cold, like before startup, and during startup to restrict the flow of air over the radiators (MCI) and facilitate fast warmup.

I could understand this if the spring in the cylinders would force the dampers closed and when the shutterstat allows air to flow to open the shutters it would also open the dampers for max air flow.

Could it be that at some time, someone has disassembled the air cylinders for the dampers and reversed the springs?

It's not keeping me awake at night but I feel that if the Engineers who designed this cooling system felt the need for the dampers, in addition to the shutterstats, they must have had something in mind where they'd close when the engine is cold.

Might I have the cart before the horse here? I sure wish someone would explain this to me.
Inquiring minds want to know!

NCbob

[belfert]

If the shutters are open by default, this will allow the engine to cool even if the system broke somehow.  It wouldn't be good if the shutters were stuck closed when the engine was hot!

Brian Eflert

[NCbob]

I believe what you're telling me Brian, but question me an answer.... if the spring is loaded to push the damers open when the engine is cold...and the air cylinders (when air is aplied, push in the same direction...how and when can the dampers ever close? 

NCbob

[NCbob]

Perhaps they're not as puzzling as I originally thought.  After working on the right side damper yesterday for a few hours, freeing up the frozen fittings and adjusting the cylinder...this morning I went down, changed the air cleaner elements and started the engine to air up the bus to check for leaks and....Voila!   Everybody's working as they should.  On warmup the Shutterstats are closed and the dampers as well.

Beats me...but I'll take it! 

NCbob

[gumpy]

The shutters and dampers require air to CLOSE them, and they are normally open when air is lost. The shutterstats shut off air supply to the cylinders when the engine warms up, and the springs cause the dampers and shutters to open. The reason, as stated above, is because if you lose air pressure to them, they will open automatically, and still allow cooling (good) as opposed to staying shut and allowing overheating (bad). When you start your bus with no air in the system, you'll notice they don't close immediately, but as air pressure builds, they will gradually close. When you start the bus with air pressure already up, they'll close immediately (actually, they're already closed  )

BTW, there's a valve in the engine compartment that you can turn off the supply of air, which has the same effect as the shutterstats tripping and shutting off the air. That's in case you get a leak in the shutter or damper cylinder or air line, you can isolate them in an open position and continue till you can get it fixed. If they remained closed, you would burn up the engine or be stuck making repairs.

[NCbob]

Gumpy, you should have been a College Professor!  I ruly thank you for clearing the fog in my brain. 

As a normal practice I try and noodle thing out.. but in this case I was 180 degrees off.  Your explanation makes sense with what I witnessed this morning.  Now I'm happy I too the time to straighten them out.

And a bottle of Jack to you sir!

NCbob

[gumpy]

Gumpy, you should have been a College Professor! 

Who said I wasn't?  I am a Certifiable Professor in the College of Hard Knocks! 

And a bottle of Jack to you sir!

Will take a rain check on that, and hold you to it!

Now, as long as someone who knows better doesn't come in and contradict what I said....