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Old 10-14-2016, 12:45 AM   #1
Almost There
Join Date: Jun 2016
Location: Canada eh?
Posts: 99
Year: 1991
Coachwork: Corbeil - RAMROD
Chassis: IH 3800 66 Pass
Engine: 7.3 IH IDI NA w AT545 hyd
Exclamation 6V92 with DDEC II ENGINE HELP needed!

My friend bought a new to her bus that has no temp or oil pressure gauges and is trying to drive it home. The only gauges are at the back of the city bus when you pop the rear door open.

Long story short - she blew a belt on the way home, and luckily caught it right away without a major overheat. Bought the 3 new single belts and put them on, checked everything and it ran great for another 100 or so km where she overheated. Opened up the bay, belts are gone, coolant had overflowed and a bunch of oil from the left side bank just under where the exhaust is routed ( my guess from her pictures).

How bad is her situation and besides a tow to a shop where she can tear into it, what is the best advice you guys can give?

I'll try to post her texted pics asap. THANKS IN ADVANCE!!
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Old 10-14-2016, 01:04 AM   #2
Almost There
Join Date: Jun 2016
Location: Canada eh?
Posts: 99
Year: 1991
Coachwork: Corbeil - RAMROD
Chassis: IH 3800 66 Pass
Engine: 7.3 IH IDI NA w AT545 hyd
Ok here goes. My guess is the belts she put on were not quite tensioned enough and they popped off based on the rub marks on the pulley shaft closer to the engine.
Then it clearly overheated and I'm guessing that is the left side head gasket that blew the oil out of it?

Hopefully we have a DD mechanic or knowledgeable folks in here. Her goal is to try and get it towed tomorrow am, but knowing what the damage is, the likely cause, and the likely fix would sure help.

Engine bay before issue.

Left side oil leaking - went from 1/2 full on the dipstick to just on the add line so not a ton of oil lost but definitely not a good thing.

The pulleys that caused the overheat once the belts were gone.

And the stupidest place for gauges ever. What kind of setup is this that you have to wait for a warning light on the dash, pull over and shut down, then go run back to the bus to see what the issue is.

Hoping for any knowledge to help get this healthy again. Thanks!!
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Old 10-14-2016, 01:38 AM   #3
Bus Crazy
Join Date: Jul 2011
Location: Winlcok, WA
Posts: 2,198
Most 2-cycle DD's in buses had shutdown alarms that would shut the bus off before you could do any damage to them. Which is probably why your bus has gauges in back and idiot lights up front.

The oil leaking on that DD doesn't look particularly bad. 2-cycle DD's leak oil until they are dry inside. When she adds oil to it, make sure she does NOT use any multi-weight oils or and LE rated oils. The ONLY oil she should be using is Delo 100 40w if the ambient temps are over 30* and Delo 100 30W if the ambient temps are below 30*.

REMEMBER: DELO 100 40W!!!!

Delo 400, Rotella, Ursa, or you name it will make the oil consumption go up and you run the real risk of breaking rings.

As far as the belts are concerned, losing belts can happen only one of a couple of ways. The first is if the belts were not tightened properly. There should not be any more than a 1/4" deflection when the belts are tightened properly. After the belts have been on there for an hour or so you need to go back and retighten them--they will stretch a little bit. Make sure the belts are a matched set--if they are not a matched set they will stretch at a different rate. Allowing one belt to be looser than the others can cause it to throw the other two. Not know what all the three belts turn, in a crunch you could get away with just two belts.

The second reason why you may have lost the belts is that the pulleys may not be lined up in a straight line. A lot of stuff can happen to make the pulleys not line up. But if they are not almost 100% in line with each other you will throw a belt.

In your picture you do not show how the belts are tensioned. Some had an air cylinder to put tension on the belts once air pressure is built up. Letting them flop around loose while building up air pressure means the starter isn't having to turn all of the belts and accessories when it turns the engine over to start. But loose is a relative term--they are tight enough that they won't jump off, just not tight enough to turn the accessories.

I also can't tell in the picture what the belts are turning. A lot of 2-cycle DD's had gear driven air compressors, gear driven alternators, and gear driven power steering pumps with about the only belt driven accessory the A/C compressor.

I also can't tell what is driving the fan on the radiator. It would appear to be a hydraulic fan. If it is you need to find out why it didn't start to turn when the engine got hot. Most of those hydraulic fans really make noise when they start to spin. It almost sounds like someone turned on an industrial sized vacuum cleaner.

Good luck and keep us posted to what you discovered to be wrong and how you fixed it.
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Old 10-14-2016, 07:30 AM   #4
Bus Geek
Join Date: May 2009
Location: Columbus Ohio
Posts: 12,859
Year: 1991
Coachwork: Carpenter
Chassis: International 3800
Engine: DTA360 / MT643
Rated Cap: 7 Row Handicap
it looks like from the silver pipes in the one pic that someone may have removed an A/C compressor? so maybe with the missing device the belts cannot be retensioned properly or the belt routing is now different than it used to be so the tensioners cant do their job?

all it takes is one belt to get loose and it will yank the others off..

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Old 10-15-2016, 01:38 AM   #5
Almost There
Join Date: Jun 2016
Location: Canada eh?
Posts: 99
Year: 1991
Coachwork: Corbeil - RAMROD
Chassis: IH 3800 66 Pass
Engine: 7.3 IH IDI NA w AT545 hyd
Thanks guys! Your posts were very helpful.

The belt runs from the crank to the hydraulic pump I am told which also runs the water pump. No A/C on it, not sure if it ever had it.

Apparently the belts keep tightening and when she pulls a big hill (lots of them) they snap. I'm wondering what the hydraulic pump would be doing creating a load or drag that big that it snaps the belts. I'm not entirely sure if they are the right belts being put on but I'm far away.

I'm also wondering why it has a hydraulic pump in the first place and what that system would be powering other than the raise/lower function when you come to a bus stop.

She mentioned it has an air system leak and that at idle it will bleed down the pressure, but when you rev it up it builds pressure. Pretty easy to track that down and fix that, but the key is to get it out of the snowstorm and to a place where you can spend time looking everything over.
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Old 10-15-2016, 02:15 AM   #6
Bus Crazy
Join Date: Jul 2011
Location: Winlcok, WA
Posts: 2,198
The hydraulic system operates the radiator fan and the power steering. Off the top of my head I can't think of anything else would run off of hydraulics on a transit bus. Most wheelchair lifts are electric but I suppose it could be hydraulic. But even still I wouldn't think you would need three belts to drive a pump big enough to do those tasks.

The kneeling function is done with air pressure--increase it goes up, decrease it goes down.

If it has an air cylinder that tensions the belts it may increase the pressure to the point it breaks the belts.

An air pressure leak that the compressor can't stay ahead of while at idle is a red tag out of service sort of driver gripe. I hope it doesn't get worse before the bus makes it home.
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Old 01-07-2017, 09:44 PM   #7
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Join Date: Jan 2015
Location: Oakland, Ca
Posts: 57
Chassis: Crown Supercoach
Engine: Detroit Diesel 6-71 Mid-ship
Rated Cap: 78
I don't know, that oil leak doesn't look that bad from the photos. I mean, it's a Detroit, it's going to leak. Can you quantify how much oil you're loosing over how long?

The worry with overheating is the head gasket failing. Check for oil-in-coolant or coolant-in-oil. If they cross contaminate, it would look "milky" "frothy" "creamy" and opaque. Coolant should be neon green but transparent, oil in a detroit will be inky black.

I think you're on the right track. Belt failure means the radiator fan isn't turning and in a pusher that means little airflow across the radiator, and then overheating. Overheating can cause head gasket failure, so check oil-water cross contamination, and then compression if you want (or just try to run it if the oil water sitch is ok).

So you need to figure out why the belts are failing. cowlitzcoach summarized stuff to check on the belts well in the post above. Additionally, belts will fail if the thing they are turning is seized or not spinning correctly, so check that stuff, eg air compressor, hydraulic pump, etc. There are a crapton of ways this engine could be configured, so I can't tell you what exactly is in there. Find the pulleys, tell us what they turn and how they spin, and we can help from there!
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Old 01-07-2017, 11:28 PM   #8
Bus Nut
Join Date: Jun 2016
Location: Orange County, CA
Posts: 913
Year: 1990
Coachwork: integral
Chassis: Crown Supercoach II (rear engine)
Engine: Detroit 6V92TAC, DDEC 2, Jake brake, Allison HT740
Rated Cap: 37,400 lbs GVWR
A DDEC II Detroit will shut down for three reasons - high coolant temp, low coolant level, and low oil pressure. They are codes 43, 44 and 45. Because 2-strokes are prone to overheating if the entire cooling system is not up to standard, you MUST make sure everything is working to factory original standards. You must also have an accurate temperature gauge in the front - I can't imagine any bus, transit or otherwise, not having such a critically-important gauge. If your gauge doesn't work, fix it or replace it, now! I changed my original Teleflex coolant temperature gauge to a Speedhut gauge which has far better resolution because it's a full-sweep design, and I mounted it front and center so I can see it all the time. How many gauges do you have in the front?

Use a straight-edge to accurately align the belts' pulleys precisely to each other, and keep a spare set of belts with you at all times. You may need to move the fan one way or the other to get everything to line up right - I did this recently for my alternator that was slightly misaligned by about 1/4".

DDEC is good, but it won't save your ass if other things are neglected or sub-standard - you still need to take care of basics, even with an electronic-controlled engine. PM me if you have any other DDEC II questions (am I the only forum member here with a DDEC bus?)

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