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Author Topic: Muffler Question  (Read 1870 times)
Busnut83
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« on: September 22, 2006, 08:55:50 AM »

Howdy,,, Just wondering if a muffler can be part of the overheating on the mc-9s Huh??
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Sammy
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« Reply #1 on: September 22, 2006, 01:19:09 PM »

A defective muffler does not usually cause overheating problems.
Try to describe the problem your having in a bit more detail, might be able to help.  Cool
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Happycampersrus
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« Reply #2 on: September 22, 2006, 01:40:01 PM »

Busnut83,

It depends, if the muffler has been damaged or crushed and the flow restricted enough excessive backpressure can cause a heating situation.  Cool

Can you go into more detail of your heating problem?? Is it on long grades?? Is it all the time?? Has your engine been "suped up" with larger injectors?? When was the last time your coolant system was flushed and serviced?? Fans ok?? belts ok??

Dale
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NJT5047
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« Reply #3 on: September 22, 2006, 01:53:58 PM »

If you have a "clean air" bus, you may have a catalytic converter.  It'll soot up eventually. Then you got an eternal pac-brake.   Seems as though it would cause overheating...? 
The buses used by major cities such as NJT had these mufflers.  The cat is inside the regular muffler.  It can be removed without much trouble on an MC9.   The cat is heavy, so look out if it falls out as an assembly...and it will.
Mine was mounted in an additional  6" section inside the muffler.  Removing the clamps from the muffler will allow the unit to be disassembled. 
Check all of your rubber seals around the radiators and, upper rear blower doors.  And look at the blower assembly.  The inlet molded parts may be missing or damaged.  The air cylinder may not  tighten the blower belt properly.
Thermostats, water pump may be faulty.  Hope that the radiators are good.  They're sorta expensive.
Are you sure that the bus is heating up?  May wish to check the dash gauge and verify that the engine is overheating.
 
JR
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JR Lynch , Charlotte, NC
87 MC9, 6V92TA DDEC, HT748R ATEC

"Every government interference in the economy consists of giving an unearned benefit, extorted by force, to some men at the expense of others.”

Ayn Rand
Busnut83
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« Reply #4 on: September 23, 2006, 10:49:49 AM »

I have posted,,,earlier this year... Radiators---questions--- then I changed them,,, 2 new radiators,,, you guys told me about shifting,,, this helped,,, but it still reaches 210* and shuts down,,, 20-30 seconds,,,then starts. July I took a trip from Dallas to Ohio going to Ala. and Ga.
At night I can run the bus hard and long.... but during the day with sunshine it will reach 210*   I Ohio I took the bus to Williams Diesel and they ran a rack,,, new injectors,,, took the delay start off,,, raised the governor from 70 . The bus runs better than when I bought it in 2003. BUT in 90+ weather climbing a hill (not very steep) it will reach 210*... also with the new radiators I used premix anti-freeze from ABC bus co...
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Beatenbo
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« Reply #5 on: September 23, 2006, 06:32:31 PM »

I have owned a MC 8, MC 9 96A3, and now a C3. The 8s and 9s were designed and built when the speed limit was 55 mph. I bet at 55 it does OK  My 8 would run all night (auto) but if temp was over 80 I couldn't run over 60 daytime. My 9 was a stick and ran around 185-190 perfect. This was a poor MCI design in these models. I,ve seen biggger pullies to turn fans faster, scoops, rear doors louvered, heard of misters, In my opinion the only real answer is BIGGER radiators, more coolant. My C3 came with the largest rads for a 8V92 and has 6V92 It will run all day at 185 no AC,  190 with AC any temp Just my dimes worth
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Busnut83
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« Reply #6 on: September 23, 2006, 06:46:30 PM »

I am looking for a way to cool the engine compartment... I think this is where the problem is !!! I respect you guys opinion???
I have the loovers on,,, the compartment can reach 280*... I am condersidering extending my tailpipe past my bumper,,, then I thought maybe the muffler is old and restricted,,, next I am thinking of a fan to blow hot air out or pull cool air in... also when the engine reaches 210* my radiators are 190 at the top and 140 at the bottom?Huh
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Dallas
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« Reply #7 on: September 23, 2006, 07:12:51 PM »

I am condersidering extending my tailpipe past my bumper,,, then I thought maybe the muffler is old and restricted,,, next I am thinking of a fan to blow hot air out or pull cool air in... also when the engine reaches 210* my radiators are 190 at the top and 140 at the bottom?Huh


The tailpipe needs to be past the bumper anyway, just for safety.
Have you checked your Thermostats? If the engine is 210° the radiators should be close to that also. If you have an automatic transmission, I don't remember what transmission you have), do you have a separate heat exchanger for it or is it plumbed into the radiator? If it's plumbed through the radiator you may need to put in a seperate "oil to air" heat exchanger with it's own fan.
Another thought is that the fans may not be working at capacity. Check the belts and tensioners to see if they are where they are suppose to be.

I hope some of these suggestions help!

Dallas
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NJT5047
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« Reply #8 on: September 23, 2006, 07:55:36 PM »

I'm not aware of an MC9 with the tailpipe beyond the bumper.  There's a "turndown" tailpipe that exhausts down and back.  If the tailpipe ran under and beyond the bumper on a 9, it'll soon be flat from grounding.   If the turndown was not on the pipe, exhaust still shouldn't be a problem when running.  The engine picks up combustion air thru the LH rad inlet....I assume nothing is interfering with the inlet tract?   
I don't believe my MC9 engine compartment gets anywhere near 280*.  You don't have "louvered" rear engine compartment doors?  They may cause problems.. The blowers push the hot air out the bottom of the coach....is it possible that (if you have them) your louvered doors are allowing the engine cooling air to fail to cool the turbo and such since the air shunts out (is drawn out due to low pressure zone immediately behind the bus) before cooling the exhaust and turbo...or is not removing the hot air from the engine compartment.  Don't believe you could blow into the engine compartment or significantly alter the engine room temp if the squrrel cage blowers are working correctly.  They move a lot of air.   Engine compartment should be at radiator temps. 
An MC9, automatic with engine coolant cooler, with good radiators will operate at around 190* at a steady speed.   Something's wrong if it doesn't.
If you have shutterstats make sure that they are opened and stay open...block them in the full open position.   Check the temp of the trans lines going into the oil cooler.  If they are excessively hot, you may have a trans failing...that would likely present as a high-speed heat failure...wouldn't explain the boarderline cooling when ambient is cooler.   
Do you have the same temps all over the radiator cores?  Is there any cool spots on the core?   Be sure that the rads are properly installed and sealed around the body.  There cannot be any significant air leaks in the radiator fit.
If you are shutting down from a highway run and measuring engine temps near the turbo, you may be reading the heat from the exhaust pipes and turbo..which would run up on shutdown..even idling, the blowers should push the hot air out of the engine compartment.   
You may have radiators that are improperly sized.   8V71 rads probably won't cool a good 6V92T, nor would 6V rads cool an 8V92T.  Maybe you can find an MC9 with a powerplant similar to yours, that isn't heating up, and check the radiators for dimensional issues...number of tubes, core thickness, area of the core.  Perhaps someone has the information and could post it. 
What engine do you have?  There are a lot of MC9s operating at normal temps.  You have a problem that can be resolved.
Post more details on what has been modified on your engine.   HT740 transmission?
JR
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JR Lynch , Charlotte, NC
87 MC9, 6V92TA DDEC, HT748R ATEC

"Every government interference in the economy consists of giving an unearned benefit, extorted by force, to some men at the expense of others.”

Ayn Rand
DrivingMissLazy
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« Reply #9 on: September 23, 2006, 08:01:13 PM »

I do not understand how the radiator temperatures you indicate could allow the engine temperature to reach 210 degrees. Have you checked your thermostats?
Richard

I am looking for a way to cool the engine compartment... I think this is where the problem is !!! I respect you guys opinion???
I have the loovers on,,, the compartment can reach 280*... I am condersidering extending my tailpipe past my bumper,,, then I thought maybe the muffler is old and restricted,,, next I am thinking of a fan to blow hot air out or pull cool air in... also when the engine reaches 210* my radiators are 190 at the top and 140 at the bottom?Huh

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JackConrad
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« Reply #10 on: September 24, 2006, 04:37:43 AM »

We have an RV Safety Systems alram system on our MC-8-8V71/740 that monitors ambient temperatures in the generator and engine compartments. Our engine compartment sensor is above the center of the engine and has never exceeded 160 when driving, ususally runs about 135-140. We do have the louvered rear engine compartment doors and an auxillary transmission cooler installed in the right engine compartment side door.  Jack
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« Reply #11 on: September 24, 2006, 05:46:26 AM »

Make sure you are picking up CLEAN COOL air.    Not the air that has come through the radiator, or from the exhaust.     I know from experence, if you have a leek in the intake hose, or are picking up air that is already heated, the temperature will raise in the coolant, as the engine can not expell heat quickly enough.
Make sure you are getting that cool unheated air.
Just athought.
Steve
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Sammy
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« Reply #12 on: September 24, 2006, 09:07:29 AM »

Check the water pump coolant flow. Might have a slipping impeller when pulling real hard.
Impeller is not "keyed' to shaft, just a tapered fit with a nylock nut.
Found this a few times, poor flow, aerated (air pockets).
Does your engine have a large fitting to pressurize the cooling system (Hanson valve)?

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Busnut83
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« Reply #13 on: September 25, 2006, 09:45:56 AM »

THANKS!!!! your replys have great merit,,, this heating problem is very disturbing,,, I can add that if the wind is blowing a certain way the heat from my condensor will also make it over heat???

As for the thermostats,,, I was TOLD they wouldnt open as quick as they do when it overheats...

The radiators are new rebuild just like the 2 removed,,, njt original...

The rubber seals that were around the radiator were rotten,,, so,,, some I put on and some I left off
HuhHuhHuh? (a light in my brain just came on,,,,,,,Thanks
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