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Bus Discussion => Bus Topics ( click here for quick start! ) => Topic started by: daveola on August 30, 2021, 04:36:29 PM
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My 1986 MCI 102A3 bus has been acting weird in the overheating department. First questions:
1) I can't tell for sure if it's a gauge issue or an actual overheating problem. The gauge is getting a little bouncy, so I'm not sure I can trust it. If I use an infrared temp gauge pointed at the engine, what kind of temps can I expect to see for a normal running engine?
2) What causes the engine cutoff? Is it using the same sensor as the gauge? (i.e., if my sensor is bad, could that make my gauge be off as well as cause shutoff?)
Failing that, I'm not sure what to do about the overheating. Almost two years back my radiator fan gearbox went out, and I ordered another one from Luke at US Coach. The one that arrived was smaller, but the mechanic put it in without checking with me, and it seemed to get us home (though we drove at night). The bus sat, thanks to covid, in storage. When I took it out, it immediately started to overheat and I had to stop driving. It took forever to get it back to storage.
I took it to Prevost Maintenance (there are almost no mechanics around the Bay Area who will look at an old bus). They kept trying things and claiming the overheating was fixed (flushed the cooland, blew out the radiators, but really not much of anything), but here I am, stuck on I-80. I am generally able to drive at night and keep it around 190, according to the gauge, but if I climb too much hill then it starts to overheat and I have to keep pulling over to cool off the engine.
So here I am, moving at a snails pace towards Reno. Any suggestions on what to tackle next?
Is it possible the different size gearbox is at a drastically different gearing and isn't spinning the fans fast enough? Any thoughts on how to check what my gearing is or is supposed to be?
Any thoughts on who in Reno can help solve this?
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There is some sort of sensor that is possibly involved. I noticed that a wire had come off of it. I tried reconnecting it and then my bus would immediately shut off when it got air pressure even when it was completely cooled.
Photo attached, or here:
http://tmp.davepics.com/Bus/Cooling-Sensor.jpg (http://tmp.davepics.com/Bus/Cooling-Sensor.jpg)
Does anyone know what this sensor is? It's right next to what the maintenance manual claims should be my temperature gauge - or perhaps this is the temp gauge?
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Here's the page from the maintenance manual:
http://tmp.davepics.com/Bus/Cooling-Maintenance-Manual.png (http://tmp.davepics.com/Bus/Cooling-Maintenance-Manual.png)
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Before anything, because it could be NOTHING wrong...
Confirm that the info you are getting is true.
Open the floor down the back, above the transmission. Identify the coach heater pipes, passing nearby, heading towards the tunnel. Have an assistant get comfortable with shooting that pipe with an infrared gun.
The gate valves in the engine room have to be open, and some coolant has to flow, some heat out of the defroster will be sufficient to get the heat into the pipes for accurate readings.
Go for a drive, and holler back and forth what temps each of you are getting.
The assistant will need eye protection, might get some hurricane blown sand, depending on your road conditions.
Confirm, or deny, that the dash gauge has caused a whole lot of trouble for nothing, or has saved your engine.
The gauge, like a clock, might be accurate twice a day... my MC8 was correct at 180, and then the dash climbed much faster than the "real" temp shot down the back. Take note what each indication on the dash gauge means for now, compared to the IR gun down the back.
None of this works, if you don't get some flow thru those pipes...
Report back.
Happy coaching!
Buswarrior
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Thanks Buswarrior, it may turn out that it doesn't matter, because I just talked to Don's Bus Repair in Sacramento (which I unwittingly drove past last night) and he believes that the squirrel fans were put in backwards (left to right and vice versa) so the fan blades are facing the wrong way.
Can anyone confirm that these vanes are facing the incorrect direction from their bus?
I'm driving back down to Sacramento and he's doing me a huge favor to work on it tomorrow, if this solves my heating problem, Don's my new hero!
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Can anyone confirm that these vanes are facing the incorrect direction from their bus?
Dave -
Those squirrel fans look correct to me.
Does the engine compartment temperature gauge match the dash gauge?
Are you sure you're getting sufficient tension on the fan belt?
Are the radiator compartments sealed properly, so that all the air coming in goes thru the rads and not around them?
Is the blower compartment sealed properly, so that the blowers aren't sucking air around the door seals?
Do you have a "mudflap" hanging off the back bumper? If so, get rid of it because it traps the hot air trying to escape the engine compartment.
Are the water valves controlling the flow to the OTR heater and defroster open, and thus getting heat out of both of those?
Just some thoughts off the top of my head. Hope Bob can help!
FWIW & HTH. . . ;)
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The speed of the blower will effect the cooling ,plus there are 2 different diameter sizes of blowere be sure the doors are open on the blower too
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Those squirrel fans look correct to me.
That would be a huge bummer - are the vanes going in the right direction? Can you take a photo of yours? I sent that to Bob and he said it was definitely wrong.
Does the engine compartment temperature gauge match the dash gauge?
I don't seem to have a temp gauge in the engine compartment - see the first photo in the original post.
I believe the radiator compartment is sealed. I don't have a mudflap anywhere.
The OTR heater works, so the valve is open.
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The speed of the blower will effect the cooling ,plus there are 2 different diameter sizes of blowere be sure the doors are open on the blower too
What do you mean by different diameter sizes - are you talking about the pulley connected to the gearbox?
And if by 'doors' you mean the radiator vanes, they are fully open.
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Those squirrel fans look correct to me.
Actually - I'm pretty darn sure that they are not correct. The scoops are supposed to be going forwards to throw air, but when I start up the engine I can see that the fan is rotating to that the curve of each blade is what is hitting air. I think this is the problem, and I think Don is right!
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Actually - I'm pretty darn sure that they are not correct.
Dave -
Looking again at the photo of the blower above, I have a question:
When the engine is running, are those vanes traveling "UP" towards the top of the photo, or are they traveling "DOWN" towards the bottom of the pic?
I don't have an MCI anymore, so I can't go out an look at mine, sorry.
RJ
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Dave -
Looking again at the photo of the blower above, I have a question:
When the engine is running, are those vanes traveling "UP" towards the top of the photo, or are they traveling "DOWN" towards the bottom of the pic?
I don't have an MCI anymore, so I can't go out an look at mine, sorry.
RJ
Be careful about this. Squirrel cage fans are a bit odd and will work both ways, and they are used both ways. I think maybe it has something to do with noise suppression. So be sure you have the right answer before you go changing it.
Jim
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Yup, backwards, you can't see into the fan blades usually, which is why so many people have fans full of dirt.
You can see into each blade.
Got a winner here!
Someone regarded installing the fans on the shafts as a mundane routine job... when it is a mission critical moment... and mixed 'em up side for side...
Tricky spatial sence thing when the fan assembly is out lying on a bench or the ground.
Happy coaching!
Buswarrior
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Looks backwards to me too.
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If they are backwards they would push air out thru the radiators instead of sucking it in, right? Easy test for that, fire it up and put a piece of paper on the outside of the radiator and see if it sticks to the grill or blows away from it.
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Yeah I vote backwards too, they need to be swapped left to right.
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Squirrel cage fans will always blow air out the outlet regardless due to centrifugal force. What looks right isn't always right. You have 4 possible configurations: Rotation towards the outlet, rotation away from the outlet, fins angled towards the outlet, and fins angled away from the outlet. All four will blow air out the outlet. The sound or noise will change and the volume of air will change, as will the load on the motor. It's not good enough to just say "It looks right" because sometimes that is correct and sometimes it isn't.
Now I do agree that it "Looks" like it'd blow more air if they were reversed. But you need to be sure, and I have seen fans that will blow more air the other way. I don't know how, I'm not a fan Engineer. But am I wrong in thinking that it is not a trivial exercise to switch the fans?
Jim
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It would be easy to get off the computer and start the engine to determine which way the most air is blowing by placing your hand at different points around the cage ..>>>Dan
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Yup - the blades travel 'down' as far as the image is concerned.
And yes, I thought that would mean they would reverse air direction (and push air out the radiators) but actually they don't, it just means that the blades aren't 'scooping' air, but going backwards and the curve is what is hitting the air.
So they are definitely backwards, I verified that when I started it up and realized the scoops weren't doing anything.
The trick to fan direction is to realize it's the inside of the blade that is catching air:
https://www.youtube.com/watch?v=OTNzd2dE2Oo#t=126
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Yes Sir! your squirrel cage blades are in fact mounted backwards - great find, easy fix, but a very huge risk as far as overheating the engine... :^
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I once took my snowblower to a mechanic as I couldn't get a broken shear bolt out of the auger shaft. It didn't blow snow worth a crap after that. I took it apart numerous times and replaced the belt at least once or twice. I took it to another mechanic who found the problem after two years of the thing barely working.
The original mechanic had reversed the augers from side to side! It was pushing snow away from the center impeller instead of towards the impeller. Mechanics sometimes make mistakes.
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Mechanics sometimes make mistakes.
What?
Well I never have, oh wait a minute that's not true.
Once I thought I was wrong but it turned out I was MISTAKEN!
;D BK ;D
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This is going to be a nasty job, the fan assembly is awkward, heavy and a very snug fit to drag out of there.
Is the offending party available to do pennance?
Happy coaching!
Buswarrior
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His pain is one most of us feel - lack of qualified and skilled mechanics to work on our old buses. From his original post it seems two places have had their hands in creating and failing to resolve the issues. The first mechanic put it in improperly and the second failed to determine it was put in backward and probably did unnecessary work.
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So according to the post on the other board... I'm guessing we need to replace all the humans with perfect robots that never make mistakes! Lol
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Just went out and looked at our MCI and yours are backward.
I took ours out years ago and the way I did it was to disconnect the four bolts that hold it in after taking off the belt and then opening the lower doors and setting two 2x10 across it. I then worked it out to the 2x's and then down a ramp to a metal table that the other end was on where I could work on it. :^
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Just went out and looked at our MCI and yours are backward.
I guess the guy got confused if right or left was from front or the rear those have a R&L in the parts number stamped on the blowers,not a easy job changing those the whole unit has to be removed
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Yup - the blades travel 'down' as far as the image is concerned.
Dave -
My apologies. From first glance, they looked correct. But when you made the above observation, I now agree with the others, that they're bassackwards.
It is a PITA to get the squirrel cage assembly out of the coach, but it's the only way to work on them. Here's hoping Bob comes thru for you!
FWIW & HTH. . . ;)
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Once again, grain of salt. Two things. Your video says the outside end of the blade should point in the direction of rotation. I don't know what that is in you photo but presumably you do.
Second thing. Not all squirrel cage blowers work that way. Depends on how the manufacturer designed it. Based on the video one would think this design is to maintain an engineered static duct pressure and may sacrifice flow to do that. The surest way to check would be to try it both ways and use instrumentation of some at least rudimentary type to see which gives the highest rate of flow. If you are set on reversing them it wouldn't take much to set that up before you start for a before and after comparison.
But so far you have no definitive answer. Just opinions, based on zero actual engineering or manufacturing history. I'd want more before starting in on what sounds like a BIG JOB.
Jim
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What Jim said! What would it take to unbelt the squirrel cage and spin it in both directions while it's in the bus?
Contrary to the 1st two sentences above was Dave's post confirming reverse blade orientation in comparison to his similar MCI set up! Soooo where do you go from here? I personally would try & spin them in place in both directions just to compare the difference if it's such a big job to R&R just for certainty & insurance.. IMO
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I offer no opinion as I am not a mechanic. Just encouragement. Just don't overheat it getting to the emergency room. On maiden voyage of my bus, engine run relay had gotten corroded and shut our bus down on the interstate. Three times! I'd wait 5 minutes and it would re start? It took 6 calls to 4 guys to diagnose it. I disconnected the engine shut off since all fluids and temps were good, and drove 2 hours (worried sick the whole way) to a good bus guy. New relay installed. Aaaaalll better.
You are in that worried sick part of this thing. They will solve it, but until then, you get a bad stomach, think about selling it since nobody can work on these old buses. Wonder why your fan was put in backwards and why a second mechanic couldn't see that.....
Hang in there. They will fix it, temp readings will be normal, you'll be back on the highway and all will be well in your world again...
It is just a fan problem. Not a tumor.
Hang in there! It will work out.
Best regards, Ted
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Update
Dave needed some fresh water, he offered to pay but my big heart let him use my faucet for no cost. Two big outcomes - he got his fan swapped back the right way and got it done inside 24 hours by a bus mechanic right here in Sacramento, just 5 miles from my house. Crazy! He's back on the road to the Burning Man location but no official event this year.
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. . . by a bus mechanic right here in Sacramento. . .
Don -
Please share the name and contact info for this bus technician - others may need his services, too!
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Please share the name and contact info for this bus technician - others may need his services, too!
Will do, happily!
His name is Don Zimmerman - Don's Bus Services a.k.a. DZ Tech
And the other Don in Sac was correct - he flipped the fans for me and it was a massive improvement in blowing air - there's still something wrong with my gauge (can't just have one failure at a time) but it's not overheating anymore (as verified with a temp gun and the fact that the shutoffs aren't engaging anymore). Made it out to the desert and back without an issue!
So high marks for Don.
Just don't take your bus there before I get mine in his shop!
+1 916-247-8796
1560 Juliesse Ave Unit C, Sacramento CA 95815
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That's great to hear. Any chance you could post a final photo of the fans showing the way they are installed? Could be helpful to someone later on.
Jim
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Will do, happily!
His name is Don Zimmerman - Don's Bus Services a.k.a. DZ Tech
And the other Don in Sac was correct - he flipped the fans for me and it was a massive improvement in blowing air - there's still something wrong with my gauge (can't just have one failure at a time) but it's not overheating anymore (as verified with a temp gun and the fact that the shutoffs aren't engaging anymore). Made it out to the desert and back without an issue!
So high marks for Don.
Just don't take your bus there before I get mine in his shop!
+1 916-247-8796
1560 Juliesse Ave Unit C, Sacramento CA 95815
Zimmerman is a good dude surprises me Zimmerman didn't make it good ,isn't he mobile now also
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I called and left a message Saturday, will call tomorrow and get the scoop.
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Zimmerman is a good dude surprises me Zimmerman didn't make it good
There must be confusion - he did make it good. I'm bringing my bus back there to fix all the other things that I need done!
And yes, he does some mobile too.
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I miss read it to many Don's sorry.I really like Don Zimmerman