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Author Topic: Need more help: 8V92 Cooling  (Read 4977 times)
Sean
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« on: August 04, 2007, 09:44:46 PM »

OK, we've been on the road for a full day since our in-frame at PEDCO, and we still have at least one problem still with us.

Before I get to that, thanks to everyone who helped with the problems thus far, including sources for the fuel pressure switch.  And, to everyone who has inquired about the in-frame, how we fared at PEDCO, and what the original source of that problem was, please check our blog.  I will post the information over there later tonight, just so I don't have to type it all in three places.

Now, as for the ongoing problems:  we are still overheating.  Originally, I thought that the overheating, black smoke, and low power were all related.  The low power and the smoke were easily explained by the fact that the engine was "dirted out."  This is a condition in which dirt particles have entered the engine through the air induction system, and, over time, have worn the cylinders smooth and the rings loose, just like sandpaper.  After enough of this, the rings no longer make a good seal, resulting in low compression (thus the lack of power) and excessive blow-by (thus the smoke).

The engine has now been completely rebuilt, at least as far as can be while still in the frame.  So I have eight new cylinders, pistons, and ring sets, two completely rebuilt heads, a rebuilt turbo, and all new bearings.  Also, four of the eight injectors were replaced, since they tested marginal.  So, in theory, I have an essentially new engine.

Nevertheless, we are still having a tremendous heat problem.  Now, the 8V92TA is probably the most heat-producing automotive engine ever built, and we've always had to slow down for the grades to keep the engine temps in the black.  But this is beyond the pale -- today, climbing Union grade from Laughlin to Kingman, a 12-mile, 6% affair, we had to slow down to 15mph in first gear, and, even then, I had to pull over and stop twice, where the high-idle still took close to ten minutes to bring the temperature back down into the 190's. So something is still amiss.

With that background, here are my questions:

(1) Can this be something other than a cooling system issue?  In other words, can there be some sort of, for example, combustion problem that is generating all this excess heat?  I am particularly worried about this because, during the rebuild, they found one cylinder with seized rings.  With different injectors and new liner, rings, and valves, it's hard for me to imagine what sort of problem could have existed before the rebuild that could be still with us, but, please, educate me.

(2) I am hoping that this is just a cooling system issue, that developed independently of the other problems.  In which case, I have to guess that the three most likely possibilities are thermostat problems, water pump problems, or radiator problems.  Where would you start, and what methods would you use to isolate the problem further?

(3) I am further guessing that the thermostats are OK, since I see the same temps on both sides of the block with my IR gun, and the temp eventually drops, under no-load, to 180 or so and stays there.  Does that make sense?

(4) I suspect the water pump.  That's because turning on my hydronic system's engine pre-heat pump *seems* to have helped (it's hard to say without truly objective data, meaning multiple load runs under identical conditions) a small bit.  So here's the $64K question: is there a way to confirm this suspicion without removing it?

(5) What is involved in R&R on the water pump?  I don't have a Detroit manual (other than the DDEC troubleshooting guide), so please don't just cite page numbers.  I'm already guessing I'm going to have to drain several gallons of coolant (shame we didn't look at this while the motor was still empty), but how hard is it to get to the impeller?

Thanks in advance for any and all help.

-Sean
http://OurOdyssey.BlogSpot.com
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Full-timing in a 1985 Neoplan Spaceliner since 2004.
Our blog: http://OurOdyssey.BlogSpot.com
Barn Owl
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« Reply #1 on: August 04, 2007, 10:18:43 PM »

Sean,

I am going to preface this and say I donít have a clue as to what to say, I am hoping others will have more experience with problems of this nature. But, it sounds like you are using the same logic that I would if it were me. I am going to throw this out there randomly, who knows, it might add something.

My grandfather bought a Cadillac new in í67. Every so many years that car would burn a valve in the same cylinder. It baffled everyone. Why after four or five years did he keep having to replace the same valve? Finally, sometime in the 90ís, some mechanic found that there was a casting defect in the head that caused a restriction in the cooling passage around that valve. It was not 100% blocked, so the valve would always die a slow death, and it was also not outwardly visible, so I donít know how they found it. After the head was replaced he never had a problem. Iím not saying you have a casting defect, but could something have happened that might be causing a partial blockage somehow?

Totally off subject, I just wanted to let you know how much I have enjoyed your blog. Your Odyssey page was one of the first I stumbled across back when I was just getting interested in busses, and one of the first to make it into my favorites. Thanks for taking the time to always share your adventures, good or bad. It has inspired at least one bus nut.

Good Luck,

Laryn
« Last Edit: August 04, 2007, 10:21:25 PM by Barn Owl » Logged

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« Reply #2 on: August 04, 2007, 11:00:49 PM »

Sean, what kind of shape is your radiator(s) in? Have you cleaned it (them) lately? Then there's the fan and shroud... they need to be in good shape, too. Once a DD is not loaded, it should cool down very quickly, assuming pump, rad., fan, and airflow are in good shape.

Something else to consider,
Brian B.
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Brian Brown
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Longmont, CO
Sean
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« Reply #3 on: August 04, 2007, 11:24:28 PM »

Brian,

The radiators were just cleaned (externally) by W. W. Williams in Las Vegas.  The fans and shrouds are fine, and the fans are spinning as they always have.  Belts were just tensioned at PEDCO.

That's why I've asked specifically about the water pump and what other steps I can take to isolate the trouble.

-Sean
http://OurOdyssey.BlogSpot.com
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« Reply #4 on: August 05, 2007, 05:06:32 AM »

Sean, I fabricated a coolant flow tester many years ago. Our engines had a male style quick release fitting  installed in the water jacket of the left bank head. This was called a Hanson fitting - as I was told.
The test device was a length of automotive heater hose with a hollow glass tube in the center of it. One end had a female style quick release valve - hanson valve on it, the other end remained open. I would connect my coolant flow tester to the male fitting on the head, put the other side into the coolant surge tank. Start engine, watch tube fill up with coolant, now rev the engine and look for faster coolant flow,air bubbles in system,poor flow,etc.This allowed me to determine if impeller was slipping on water pump shaft.
The water pump impeller is not keyed to the shaft, has a tapered fit.
You can probably use a length of clear hose today, not messing with a glass tube.
I'll look around to try to find you info on the Hanson fitting - transit bus applications and maybe others too.
It had a 3/4' id with pipe threads. Works great for me.
Good luck .
Sammy  Cool



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tekebird
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« Reply #5 on: August 05, 2007, 05:42:12 AM »

Hmmmmm,..................

I would suspect Radiator with all you have done.  Did this probelm just show up or did it creep it's way into being a problem.
Have you added coolant lately?
Have you tested your coolant lately?
mixing coolant types can easy FUBAR a radiator as it creates a nice sinus infection consitantcy snot that will clog a radiator in no time.

last cooling issue I had was due to this contamination.....and resulted in a radiator that was at testing 70% clogged ( symptoms only showed on grades)
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luvrbus
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« Reply #6 on: August 05, 2007, 07:18:51 AM »

Sean, does your bus have a fan clutch if so i would check it first
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edroelle
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« Reply #7 on: August 05, 2007, 09:13:05 AM »

I tried this with some small success.  - Just after initial start-up, IR the exhaust port of each cylinder for significant temp differences - especially the "bad" cylinder if you know which one that is. 

I don't know what is normal, but does radiator in vs. radiator out IR temperatures appear reasonable?

MCI's are noted for cooling problems.  Is the Neoplan known for marginal cooling?  If so, you may be looking for a number of items deteriorating rather than a silver bullet.

If you are unable to identify the cooling problem, you might try the Yahoo Detroit Diesel Group.  They have a couple of 2 cycle mechanics that frequent it.

http://autos.groups.yahoo.com/group/DetroitDiesel/

Ed Roelle
Flint, MI
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« Reply #8 on: August 05, 2007, 10:30:17 AM »

Sean- As to heating-that can be an internal radiator problem.  If the radiator is of the normal heavy duty design with bolted together top and bottom tanks, it isn't that big of a deal to have a radiator shop open it up to have a look-see.  Also, maybe you'd want to upgrade your core like I did.  I went from a 5 row straight fin to the more modern 6 row serpentine fin.  I'd like to know how big your core is-can you measure the actual fin area height and width?
Is this the first time you've had heating problems?  Remember too you have a new engine that is going to be tighter hence creating more friction with the associated heating.
Course the one thing you didn't mention was the outside temperature-what was it 100-110 degrees?  You might also have to set up a misting system like I did.  I found that when a big hill (like the Grapevine) comes up, I turn on the misters before hitting the hill.  Granted, I only went up the Grapevine at 32mph, but it stayed below 200 degrees and pulled it the whole way.  I am restricted to size of radiator-of which I now have the biggest.
As to your water pump, typically Detroit pumps will either not pump at all, like if the impeller severed from the shaft, or they will start leaking if the seals are bad.  They are a simply designed pump that rarely goes bad.  But with the placement of your engine, would be relatively easy to replace it since it is facing you when you open the engine compartment.
I believe that the seized ring was caused by the dirt.  As long as you're using sae40 Delo 100 type oil, you should be alright.  My first truck went 500,000 miles on its' 8V-92TA before overhaul.  So now without dirt induction, you should theoretically be alright for a few more years.  Good Luck, TomC
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« Reply #9 on: August 05, 2007, 10:53:02 AM »

Sammy has a good idea there - may even wan't to slap a pressure gauge on and test the pressure at that locale - if the impeller is damaged it won't be able to build vacuum/pressure to spec -HTH
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« Reply #10 on: August 05, 2007, 03:04:01 PM »

Sean I saw on the BNS group where you were talinking about dirt in the airbox and Silicates in the oil?

aren't you the guy who tools down desert roads and crosses sandwashes and dry creekbeds with his Neoplan....

Maybe it's someone else?HuhHuhHuh
At any rate...if thee is he than that would be where the dirt/silcates are someing from  no highway bus was ever designed to operate in such environments.

my guess is your radiator is restricted internally
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« Reply #11 on: August 05, 2007, 03:15:15 PM »

I have a MCI 7 with 8V92 and Allison 740 trans.  When I bought the bus it would overheat.  I put in new 6 row baffled radiators, new seals on the squirrel cages, smaller pulleys as well as a extra radiator.  It also has misters on all three radiators.  I still have to watch my speed on long grades and keep my foot out of it.  I found by opening up the rear doors on a long climb it will drop the temp 10 to 15 degrees.  Yes it look funny going up a hill, but I don't care as long as I make the top without going over 205 degrees.  I also don't care at what speed I make the top.
ED
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Ed Van
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« Reply #12 on: August 05, 2007, 03:22:36 PM »

I understand buses aren't designed as off road vehicles, but shouldn't the air filter be able to filter out the fine sand and dust?  The bigger issue could be any loose connections on the air intake lines.

I am planning to drive about 10 to 15 miles across a dusty dry lake bed every year.  I'm hoping this won't be enough to wreck a $20,000 engine.  I suppose I better check all of the air intake connections on my bus before I go this fall.
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« Reply #13 on: August 05, 2007, 04:04:42 PM »

one must remeber tyhat filter elements are speced for different applications.  it does not take buch to breach a paper filter that is not designed for off road, or poor environments or one that is worn to some extent already. and itdoes not take much to ruin an engine either.

problem is keeping your speed down can depending on how your bus is designed creat a huge dust cloud forward of your air intake.

conversly, higher speed kicks up more dirt from front and rear tires

ideally you need a roof mounted intake or a snorkle of some sort to get above this aerated dust for clean air.

back to the arguement for or against oil bath air filters........

I for one having had to service oil bath filters from my wee young years while forced into child labor for my parents Carter bus company that a huge ammount of dirt gets filtered by GM Style oil bath filters.  the ammount of dirt that was trapped in one service cycle 15k or so would have clogged a paper element of consideable size several times.......and this is highway intake air.

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« Reply #14 on: August 05, 2007, 04:07:32 PM »

Brian I would find myself a open non vegitated dirt lot and see what the charactristics of your bus create.

I know my A/C fans or my Genset both exhausting out the bottom will double the ammount of airborn dirt my bus creates (Each)
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