shutterstat question

[bevans6]

I aired up the bus today with my shop air and tested the shutters.  I think I have a bad shutterstat but I will describe what I have, in case I am missing something.  I aired the bus up, and opened the needle valve on the shutterstat air filter.  Immediately the shutters closed and the fan baffles closed - exactly what was supposed to happen,  good so far.  But the shutterstat leaked air out of the end of it's body constantly, quite a lot of air.  I didn't think that it should do this, I  thought that it should allow air through to activate the air cylinders but that it's shouldn't leak constantly.  I think that where it's leaking is an exhaust port to vent air from the air cylinders when it shuts off air to them at 180 degrees hot.  So I think it's bad.  I didn't warm up the engine to check warm operation, I just kind of decided it was bad and to change it out.  Right call?

When I vented air from the shutter stat manually, by shutting off the needle valve, the shutters returned to open but the dampers on the fans kind of hung closed, or only went half way open.  What is supposed to open them, is there a spring somewhere I should look for?  Just lack of use and needs a little lube and TLC?

Thanks, Brian

[Doug1968]

Brian,

I'm not sure how the MCI 5's shutters are designed but my 102A3 shutters have a return spring attached to the shutter linkage just above where the cylinder attaches. This spring is very strong and it returns the shutters as the cylinder is deactivated.

Looking from outside the shutter this spring or the linkage cannot be seen. You must remove the shutter to see the spring and linkage. You should be able to tell if the spring is operating correctly as with the air drained you will be able to move the shutters by hand and they will return with the spring force.

It seems as though the cylinder operating the shutter needs to be in good condition as it takes a fair amount of force to move the linkage.

Hope this helps,

Doug

[Tenor]

Brian,
On my MCI 7, I don't have any air leaks from the shutterstat or any of the other components.  If I understand the shutterstat function, it does not release air from the system, it just closes and blocks air from entering the shutter part of the system or opens and allows air into the shutter part of the system. 

I found that the shutters on the squirrel cages needed a good deal of lube to get them to return to a fully open position.  The linkage doesn't have zerk fittings so lot's of oil was put to use and worked in manually.

Hope this helps!

Glenn

[RickB]

Brian,

The shutterstat should definitely not be leaking air. Wonder what might have fractured it? Might want to check your antifreeze if you're in an area that feeezes. My filter housing leaked like a sieve when I started using my shutters. What temp is your shutterstat? If you are interested I have an extra 195 degree shutterstat you can have.

Let me know if you're interested,

Rick

[gus]

I presume MCI shutterstats are not adjustable?

The one on my '54 GMC 4104 is adjustable by a small knurled knob inside a brass sleeve over the stat.

[buswarrior]

The piston on the damper doors is supposed to return the doors to fully open. Internal spring.

However, the pistons aren't the best.

The damper doors must move freely, disconnect the piston and move the doors by hand to check. Trouble with lubing the doors or their hinges, the lube will clog up with dust/dirt and you're back into it again later. Any trim/seal around the edges contributes mightily to the resistance to close.

We just want obstruction to airflow, not a seal.

A damper door hanging as little as 1 inch from fully open will trigger an overheat.

I just pulled the pins on my pistons and leave the doors fully open. The shutters do a good job of blocking the airflow sufficient for my operation.

The only shutters that close going down the highway are up in the arctic, so no worries for most busnuts to somewhat compromise the performance.

happy coaching!
buswarrior

[JohnEd]

If I am wrong about this I sure would appreciate being corrected.....  The shutters are held closed by air pressure.  In failure mode, air gone, the shutters move to the open posit.  NOW.....When the engine comes up to heat the stat will pinch off the air supplied to the shutters....right?  If there isn't some provision for the air pressure to be bled off then the shutters will stay closed and over heat the engine.  Right?

Now if it were up to me to design that system(just imagine that!) I would install a stat that has pressure passed thru when the engine is cold and I would employ a stat that shifts the output to "vent" when the engine comes up to temp.  I think there is a "dump" feature needed.  An air bleed in the shutter system that would bleed it off would work, it seems.  Like an "unloader" for an air compressor.

I have stood next to the open engine bay of an 8V92 in a Pre.  The shutters were closed when the owner started her up.  He ran her briefly and shut her down.  While we talked, the shutters mysteriously "opened" with a sharp hiss of escaping air.  As we talked and he expressed his confusion as to why it did that, the shutters then hissed and closed. The owner just frowned and shook his head.  I figure the brief heat soak after a short run period eventually opened the stat and and allowed the shutters to open.  As it cooled in front of our very eyes, the stat closed again and shut the shutters.  What say you all?

POINT?  I would be careful when I started "fixing" the air "leak" in the shutter stat.

John...ever confused

[RickB]

John,

I have never heard my shutterstat vent but that sure doesn't mean that it doesn't operate that way since I am normally driving when it opens. Good description of the way it probably works John, and it does match up with what happens when I dump the air out of the filter assembly through the tee valve on the bottom of the filter assembly which is essentially bleeding the system thereby allowing the shutters to open.

I would venture a guess that if Brian's shutterstat is leaking at startup and with a cold engine that he has found the culprit in the shutterstat and if it is doing it at the specified temp stamped on the back of the assembly then it is working correctly.

Thanks for the input. Made sense to me.

Brian, let me know if you need/want the extra shutterstat that I have although I'll warn you that 195 degree temp shutterstat made me uncomfortable when my shutdown is at 210.

Rick

[bevans6]

Thanks guys.  I spoke with Luke this morning and he confirmed that it should not be leaking at cold position.  It should vent air from the cylinders to atmosphere when up to operating temp, or they would stay closed, but it should never vent system air  directly to atmosphere.  It was a decent leak, 20 psi in less than 10 minutes.  I ordered a new 175 degree unit from Luke, we talked about the higher temp option and he didn't think it was a good idea.  Now I have to make sure the dampers reliably open, or disconnect them per Bus Warrior's suggestion.

Cheers, Brian

[jackhartjr]

Brian, how much did the 175 unit run you?
Thanks
Jack

[bevans6]

It was about $75 I think.  In stock.  I think in colder weather having this system work is worthwhile, but maybe only for faster warm-ups and if you are stuck in traffic or something.  I got thinking about it because I was out the other day, temps in the 50's and the bus gauge didn't show over 170 or so.  Of course, who knows how deathly accurate it is...

Brian

[lostagain]

This has been discussed before, but I don't think shutters are really necessary unless you're going to use your bus at 30 below with a North wind. Or iddling it all night at that temp for fear it wouln'd start again. We used to do that back when, if the hotel didn't have any plug ins. The 102D3 with S60 doesn't have any shutters. But it has a Webasto that keeps the engine near operating temperature when needed. Or preheats the engine in the morning before starting. When I overhauled my engine and radiator last winter in my '57 Courier 96, I removed the shutters. Mind you I don't use that bus in the winter.

JC

[gus]

I live in a mild climate and my engine never got up to 180* until I got the shutters working properly, now it holds whatever the shutters tell it to.

I would not like to do without them!!

[buswarrior]

lostagain raises an excellent point of decision for the designing busnut:

Keep and maintain, or remove?

To be fair, the 102D3 with S60 has a fan clutch to stop the fan spinning when it is cold, and with the reduced heat output of the 4 stroke, if it wasn't for Webasto, an empty S60 coach is only just keeping the interior warm (and engine up to temp) in everything except a hill climb when it is a few degrees below freezing.

Regardless of engine type, to one degree or another, if a busnut is using some form of engine heat for the interior and drives around in an urban area with stop lights, on a cool day, the engine will be pulled below operating temperature with a combination of unrestricted fans and/or the interior heat.
The colder the day, the colder the interior starts creeping.

Whether this is important depends on the busnut's orthodoxy of Detroit care and where the coach will be operated.

Southern coach? rip it all out, not needed.

If the coach has a northern home, a compromise is to keep the shutters, and scrap the more problematic damper doors and their pistons.

Shutters only screw up if somebody bent them, tried to lube the exterior moving parts(leave them dry) or the thick return spring broke. All easily seen, and only need fixed once. Those darned pistons and doors however...

Yes, if idling all night to stay warm, the shutters are good.
My orthodoxy is heretical...

happy coaching!
buswarrior

[bevans6]

My further thinking is that they will warm up the engine faster, contributing to fuel economy and generally good things.  I don't think the big old DD loves to idle along for 10 minutes as cold as it can be in the frosty mornings....   The shutter and damper combine to stall the air in the squirrel fans.  The stalled fans consume significantly less power to spin.  That can't be bad either.  I'm planning a trip next month where half of the travelling will be in freezing or below freezing weather, god willing no snow though!  I think it's a good system to get going if I can.

Brian