MCI rad shutters - how do they work?

bevans6 · October 27, 2009, 11:03:37 AM

the rad shutters on my MC-5C bus are always open. it just occured to me that maybe they should close from time to time. I've read the manual but I don't think I am connecting the dots - can someone do a 'hip bone connected to the thigh bone" step by step on how they work? When should they be open vs closed? Where should they be if the bus is off, it's cold out (50 degrees or less) and there is no air pressure?

thanks for the help!

Brian

JohnEd · October 27, 2009, 12:11:19 PM

Brian,

They "fail" to the open position. They are CLOSED by air pressure so after the bus sits and looses air they will drift to the open posit. There is a thermostat air valve "somewhere" that senses engine coolant temp. When the engine comes up to temp that valve opens and applies air pressure to the cylinder that moves the shutters and opens them. They are a subsystem that gets ignored as when it fails it doesn't create a problem. It is mechanically complicated and wasn't cheap to make. DD did it for a reason and getting the engine up to temp quickly was sufficiently important for them to install the sys. Unlike the coolant thermo, the air flow shutters also shut of the cold air being blown across the engine and oil galley surfaces. Oil takes a good long while to warm up and cold oil isn't good for the DD or any other. Working or not the shutters don't impede air flow thru the rads so removing the system will not aid cooling in any way. Once repaired I suspect the system will function without any hassle for 20 years...just like it did originally. I would suggest that you recondition the shutters and run the air line that has been removed.

And the thigh bone connected to the hip bone soos u be HIP.

Wish I was there,

John

bevans6 · October 27, 2009, 12:14:52 PM

how do the big dampers on the squirrel fans figure into this, if at all? Mine just are forced open by air pressure on their cylinders, they just stay open.

thanks for the explanation!

Brian

JohnEd · October 27, 2009, 12:29:08 PM

Brian,

I have never looked at the sq cage rotor shutters. I imagine they operate the same as the rad shutter system...in parallel. "Imagine" was the key word there. What I do know is that a sq cage blower will run with much less resistance if the air flow is choked off....shuttered. Given that it takes something like 30 horse power to run the cooling fan alone, cutting the power consumed by the blower should give you appreciable/measurable MPG gain. I didn't think the bus' came with both systems so I guess I am wrong again.

Please post what you discover in inspecting the system and what you had to do to repair it.

Thanks,

John

bevans6 · October 27, 2009, 02:38:19 PM

Well the first update is that all of the parts appear to be there (and they are very dirty - I have to wash this engine bay). The air feed is from a manifold on the wall of passenger side engine bay, right near the ping tank, and appears to get it's feed from the manifold on the other side that feeds the air clutch and other engine bay stuff. So first assumption is that there is air available. From there it goes to a filter arrangement, with a water drain on the bottom and a tee fitting with a shut off valve as the output. Lookee there - the shut-off valve is shut off, perhaps that's why nothing works... Of course it's equally possible that's why nothing leaks too, but a clue is at hand...

From there it goes to a valve on the water manifold, presumable the shutter-stat, and from there goes off to the various air cylinders that work things. I think I will study the manual and start by turning the shut-off valve on and see what happens...probably not till the weekend.

cheers, Brian

Lin · October 27, 2009, 03:28:56 PM

The arrangement is similar in the 5a. My valve was off too, so I thought opening it would tell me something. It did--that there was no air coming into it. If I remember correctly, the book showed it as on the same air circuit as the air assist for the clutch also which did not work either. I suspected that the whole branch had been disconnected, but never looked further. We do not really run in cold country, so I was not that concerned about getting the system back to working. I did test the shutters with air though, and they snapped shut when fed.

jhaggerty · October 27, 2009, 03:32:01 PM

brian,

You are right. The shut off valve , if opened, will let air get to the rad shutters and they will be then controlled by the engine temp. .. If everything works correctly! I shut mine off in the summer and start using i once it turns cool.

Jim

RickB · October 27, 2009, 04:44:29 PM

The tee valve on the side of the filter housing (the figure eight looking thing on the passenger side bulkhead) turns on or off the air. The one on the bottom purges the air from the system as a failsafe so if the system fails you can still have the shutters in the open position to allow you to not br stranded because of overheating. It get's its air from the shutterstat on the main coolant line between the engine thermostat and the radiator supply line.

The squirrel cage shutters are basically designed to accomplish the same final goal. Which is operating temp ASAP.

The shutter stat is marked with a temp # on the back. I have a 195 in mine currently but Brian Diehl gave me a 180 degree one. Just haven't put it in yet.

My shutter assemblies and shutterstat work great but they don't leave me
enough comfort zone before hi temp shutdown

RB

gus · October 28, 2009, 07:24:57 PM

Brian,

Same story on my 4104. I found the valve closed, opened it and the shutters worked perfectly for a couple of years.

Then all of a sudden the engine started running up to 200* before the shutters would open. I found the shutter thermostat is adjustable, adjusted it and decreased the temps 10*. Not enough, so adjusted it again and will know the results the next trip.

According to the book one turn of the adjuster = 10*.

JohnEd · October 28, 2009, 09:33:17 PM

May I be so bold. I would not disable the warm up system in the summer. The faster she gets up to normal op temps the better for the engine. Even in the summer I would preheat the engine and oil if I could. That way when I can't the wear will be as low as I can make it and there is a lot of caution/warning info out there about wear rates and "cold" engines.

I would also augment my block heater with an oil heater. I think that would be less critical if using synthetic. Another reason to go that way.

My thoughts.....BK, what are yours? You have a ton invested and start and stop more than any trucker. Given that I think your rigs would spend an inordinate amt of time in the "warm up phase".

John