4108 Radiator Shutters

Templar52 · May 11, 2018, 06:28:38 PM

Shutters are very important. And they have to be free operationals. They permit the engine to get to his operational temperature more quickely. The only concern is to watch them if they open beafore the fan kik in. If the fan start and the shutters are closed,the shutters will not open beacause of the suction from the ventilator. Overheating will soon beacome. The shutters should open first,then the fan can start working full blast.

richard5933 · May 11, 2018, 06:53:56 PM

Quote from: Templar52 on May 11, 2018, 06:28:38 PM
Shutters are very important. And they have to be free operationals. They permit the engine to get to his operational temperature more quickely. The only concern is to watch them if they open beafore the fan kik in. If the fan start and the shutters are closed,the shutters will not open beacause of the suction from the ventilator. Overheating will soon beacome. The shutters should open first,then the fan can start working full blast.

I'm guessing that this doesn't apply to my bus then, as my radiator fan is not on a clutch and spins all the time. The fan on the 4108 is not set up like it is on the 4106. That's the reason there are shutters from what I understand.

buswarrior · May 12, 2018, 04:38:59 AM

No and no.

Shutters that are freely moving and springs in place, they will not be kept sucked closed by the fan.

Notice their clever shapes, and the geometry of their movement and linkage, there is aerodynamic and engineered design involved here, those aren't just slabs of metal hanging in there...

MCI fan sucks full speed, full time against them. Just fine.

Happy coaching!
Buswarrior

richard5933 · May 12, 2018, 05:41:59 AM

Buswarrior - Have you seen the shutters mentioned in a GM manual at any point? I can't find them in my manual and would love to see what the manual entry looks like, if there is one.

chessie4905 · May 12, 2018, 09:05:43 AM

My manual has a little about the shutter system. The air cylinder and shutterstat itself are non serviceable. The shutter stat is mounted in coolant passage of engine. One lines connects to shutter control air cylinder. The other line goes to shutter air control unit on firewall. It receives it's air supply that also supplies the engine control solenoids. The shutter air control unit filters air and injects small amount of shutter fluid to shutter air cylinder along with the air. There is also a shut off valve that will allow shutters to stay open when desired for servicing or in hot weather if desired. There is a cap you remove to add specific shutterstat fluid to reservoir periodically. It is absorbed into felt packing in reservoir which allows a light mist of fluid along with air to the shutter cylinder. Their is a fuller explanation in the GMC 4104 shop manual when they were standard equipment. On the later GM's shutters were optional. My 1975 parts bus has shutter system with mechanical fan. Someone removed shutters, but left rest of system. They are useful for maintaining engine temp on light engine loading on level or slight down grades, especially in cooler temps. The 04 had an adjustable shutterstat. Newer ones were fixed at 175 degrees, I believe.

richard5933 · May 12, 2018, 09:28:52 AM

Shutterstat fluid?

Any ideas where one can get such a thing or if there is an alternative which is currently available?

richard5933 · May 12, 2018, 10:05:38 AM

Here's a catalog entry that looks like the control on the bulkhead above the engine. If my understanding is correct, the T-handle on the face is the on/off valve for the air flow. The T-handle on the bottom is the drain petcock. Maybe what Luke was saying is that for summer use the air is closed and the drain is opened, and that for cold-weather use the air is opened and the drain is closed.

The brass nut on the top of the left-side part looks to me where I'd add the shutterstat fluid. Correct?

Maybe someone with a 4104 manual (or any manual showing the shutter system) can verify this?

The parts all look to be in clean and relatively good condition. I'd like to see if they work, but before I start just turning knobs and adding fluid I'm hoping that someone can confirm.

When we ran the bus this past winter, it seemed to take forever to get the engine up to temp. Now that I've got the shutters themselves freed up, I'm hoping that the shutters system functions and will help.

richard5933 · May 12, 2018, 10:57:26 AM

Found a 4104 manual on another bus site. Was able to answer my questions about the hardware. Copy of manual pages attached for anyone wanting to take a look.

Only question left is where to find either Shutterstat fluid or a suitable replacement. Thoughts?

chessie4905 · May 12, 2018, 11:15:01 AM

Since it is air controlled, the bottom petcock is to occasionally drain any accumulated moisture. Our 04 spent off road time in the shop when not in use. You could hear and see shutters open when air in system dropped off after a couple of days. When they are closed and engine is running, shutting off the valve, they would come open after a few seconds