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Bus Discussion => Bus Topics ( click here for quick start! ) => Topic started by: Bryan on February 08, 2014, 12:57:52 PM



Title: Uh oh! Engine knocking?
Post by: Bryan on February 08, 2014, 12:57:52 PM
hey guys, I have a 8v71 engine. Today, it started making a loud knocking sound. Basically, when we start it, after about 3 to 5 seconds of idling, it starts knocking. Here is what we know, the water lines and heater lines are warm (not hot, not cold), and the oil pressure is at about 12lbs. What could this be?


Title: Re: Uh oh! Engine knocking?
Post by: luvrbus on February 08, 2014, 01:11:01 PM
12 lbs at what rpm,any white smoke ?


Title: Re: Uh oh! Engine knocking?
Post by: Bryan on February 08, 2014, 01:23:22 PM
12 lbs at what rpm,any white smoke ?

basic idle so aprox 1,000 rpms, we haven't started it in about a month or 2, so there was some white smoke at the very beginning, but seemed to go away


Title: Re: Uh oh! Engine knocking?
Post by: luvrbus on February 08, 2014, 01:28:55 PM
If it was only 12 lbs at 600 rpm which is the idle speed without the fast idle engaged on a cold engine you do have a problem any idea what the engine temp was ? 12 lbs is not bad for a hot engine at idle


Title: Re: Uh oh! Engine knocking?
Post by: grantgoold on February 08, 2014, 01:40:30 PM
Have you gone back to the engine compartment and tried to take a video? This might help the experts on this board, watch the video and could perhaps be more specific in their help! 

Grant


Title: Re: Uh oh! Engine knocking?
Post by: Bryan on February 08, 2014, 01:46:48 PM
If it was only 12 lbs at 600 rpm which is the idle speed without the fast idle engaged on a cold engine you do have a problem any idea what the engine temp was ? 12 lbs is not bad for a hot engine at idle

I'm not sure what is considered a hot or cold engine. We had it running for about 10 minutes and then cut it off, Then we started it again to move it, it was during this time that the sound started.


Title: Re: Uh oh! Engine knocking?
Post by: Bryan on February 08, 2014, 01:47:46 PM
Have you gone back to the engine compartment and tried to take a video? This might help the experts on this board, watch the video and could perhaps be more specific in their help! 

Grant

great idea! working on the video right now, will post it in 5 minutes.


Title: Re: Uh oh! Engine knocking?
Post by: Ace on February 08, 2014, 01:48:04 PM
Sounds like a bad air compressor


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Title: Re: Uh oh! Engine knocking?
Post by: Len Silva on February 08, 2014, 01:58:46 PM
Is it a stick?  I had broken flywheel bolts sound just like an engine knock..


Title: Re: Uh oh! Engine knocking?
Post by: Bryan on February 08, 2014, 02:01:57 PM
here is a video!

http://youtu.be/q1CyitEufWU (http://youtu.be/q1CyitEufWU)


Title: Re: Uh oh! Engine knocking?
Post by: luvrbus on February 08, 2014, 02:06:51 PM
Sounds more like a clutch to me try depressing the clutch and see if it goes away


Title: Re: Uh oh! Engine knocking?
Post by: Ace on February 08, 2014, 02:12:43 PM
Sounds louder on the fan side than on the clutch side


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Title: Re: Uh oh! Engine knocking?
Post by: luvrbus on February 08, 2014, 02:18:02 PM
Behind the fan there is a disk to drive the fan maybe the springs have broken and are rattling around in the housing check for slop on the fan


Title: Re: Uh oh! Engine knocking?
Post by: TomC on February 08, 2014, 03:57:42 PM
Without a doubt-it is one of your Jake brakes firing off. Make sure the Jake brake is off. Good Luck, TomC


Title: Re: Uh oh! Engine knocking?
Post by: OneLapper on February 08, 2014, 04:34:57 PM
I agree with Tom, sounds like a Jake.  The oil pressure comes up and the Jake actuates. 


Title: Re: Uh oh! Engine knocking?
Post by: Utahclaimjumper on February 08, 2014, 05:51:39 PM
 Jake brakes will activate UNCOMMANDED if the seals (three each) in the solenoids are bad or non-existent. Easy to check by removing the wire to each and unscrew the solenoid.>>>Dan


Title: Re: Uh oh! Engine knocking?
Post by: Bryan on February 08, 2014, 05:54:23 PM
Update: we tried messing with the clutch inching the bus forward and backwards, after about 5 minutes, it quit doing it and hasn't done it since. We took it for a spin, no issues. Looking back on the situation, when we started it for 10 minutes and didn't hear the knocking, it wasn't until we moved the bus until the knocking started. That made me thing possibly it could still have something to do with the clutch. What do you think? It's like we got it warmed up and it quit. Does to make sense.

On another note, I've always read that this manual transmission is known to grind when switching gears but it's pretty dramatic, and sometimes hard to get it into hear to start with, sometimes even hard to get out of gear into neutral. Is this normal? Thanks!


Title: Re: Uh oh! Engine knocking?
Post by: luvrbus on February 08, 2014, 05:56:13 PM
Isn't that a wet clutch ? it may need oil


Title: Re: Uh oh! Engine knocking?
Post by: luvrbus on February 08, 2014, 06:03:42 PM
The Jake will activate with out command when the spring breaks in the solenoid,easy to check push the plate or pin down on the solenoid if it doesn't return the spring is broke   


Title: Re: Uh oh! Engine knocking?
Post by: opus on February 08, 2014, 06:57:13 PM
It sure sounded like a few cylinders dropping off, I agree....Jake.


Title: Re: Uh oh! Engine knocking?
Post by: Bryan on February 08, 2014, 07:00:19 PM
Ok I will check that. can you tell me where the solenoid is? Thanks!


Title: Re: Uh oh! Engine knocking?
Post by: georgemci102a2 on February 08, 2014, 07:19:50 PM
How bout trying the old stick to ear method to start with ???...George


Title: Re: Uh oh! Engine knocking?
Post by: luvrbus on February 09, 2014, 01:26:31 AM
The 4 solenoids are under the valve covers the problem should have been worse if the solenoids or seals are leaking with the higher oil pressure while driving JMO,before you go removing the solenoids you better get the o-rings first those are not easy to come buy with out buying the $$$ kit

It will make it a lot easier on you ordering the 0-rings from DD if you don't mention 8v71 just tell them you want the o-rings for the 760,760A or the 765 heads the 60 series uses the same o-rings and solenoids and you won't get the blank look when asking  8)

good luck


Title: Re: Uh oh! Engine knocking?
Post by: RickB on February 09, 2014, 07:13:27 AM
My jakes have never been functional until the low air pressure switch has turned off. Don't you have to have at least 90 lbs of air to engage the hi idle and the buffer?

RB


Title: Re: Uh oh! Engine knocking?
Post by: luvrbus on February 09, 2014, 07:27:38 AM
Jakes are not going to work on fast idle unless something is wrong fwiw


Title: Re: Uh oh! Engine knocking?
Post by: sledhead on February 09, 2014, 08:39:59 AM
Last time out my jakes worked fine but my hi / low / off switch on the dash is not working ? any thought's

thanks     dave


Title: Re: Uh oh! Engine knocking?
Post by: luvrbus on February 09, 2014, 08:57:11 AM
It probably not getting any juice very seldom does both sides of the hi/lo switch goes out at the same time turn the Jake on you should have power to one side of the buffer switch, that is another thing I don't like about the 2 stage Jakes always electrical problems 1 forty ft wire is better than 4 lol


Title: Re: Uh oh! Engine knocking?
Post by: bevans6 on February 09, 2014, 08:58:46 AM
Jake heads need only two things to turn on - oil pressure and electricity to the solenoid.  How you control them adds to the complexity.  Most factory installations have a buffer switch that only sends electricity to the solenoids when the master switch on the dash is turned on (and the trans is in gear if automatic or the clutch is out if manual), and the governor (mechanical engine) is at no-fuel.  It's going to no-fuel that extends the push-rod in the buffer switch and engages the micro-switch.  If the engine is at idle or with fuel being applied for power the buffer switch does not engage and the jakes are not allowed to work.  If you have a fast idle buffer switch engaging fast idle uses the same push rod to add idle spring pressure for the faster idle, so by definition the jakes cannot engage.  Fast idle does need air pressure to work, but the jake control in the buffer switch is not affected by air pressure.  If the jakes work but the hi/low/off switch does not turn them off then you have a broken switch, most likely the buffer switch.

If you have a single control jake setup, on/off, then the flow of electricity is from positive in the front electrical bay to the dash on/off master switch, to the clutch/neutral switch, to the buffer switch then to both banks of solenoids.  If you have a Hi/Low/Off setup, the flow of electricity is from the rear engine compartment bus to the solenoid switch, then to the clutch/neutral switch, then to the master switch, then two runs back to the solenoids.  In high both banks are engaged, in low only one bank is engaged.  Since the flow of electricity is to the buffer switch first and then all the rest of the control switches a broken or mis-adjusted buffer switch can be always engaged, and just a gummed up pushrod inside the buffer switch can do that.

If you want to test if the jakes are working, you can warm up the engine, turn the jakes on, rev the engine to 1800 - 2000 rpm and release the speed lever.  You should hear the jakes engage as the engine falls back to idle, then disengage as the engine reaches idle.  While the speed is falling the engine is at no-fuel, then it goes to idle.  The engine might stall as it tries to recover from no fuel to idle with the jakes on.  If you have an automatic with a neutral switch in the control this test won't work unless you bypass that switch so the jakes work in neutral.


Title: Re: Uh oh! Engine knocking?
Post by: luvrbus on February 09, 2014, 09:07:43 AM
The Jakes can be wired so many different ways some of these bus people amaze me with all the complex wiring they do for Jakes that is not necessary


Title: Re: Uh oh! Engine knocking?
Post by: bevans6 on February 09, 2014, 09:13:47 AM
My bus, when I got it, had some funky Jake wiring that didn't work at all.  I pulled it all out and put it back to the stock setup from the MCI manual for single stage on/off jakes using the factory wires.  That worked fine, but the jakes still didn't work - but I couldn't tell because I didn't know what they were supposed to feel like, I just thought the advise that they didn't work all that great in the first place was right so I stopped worrying about it and forgot about them.  Later, when I pulled out the engine to replace it I looked into it further and they were not only adjusted to around 1/8" clearance, the bridge pipes had all backed off so there was no oil pressure to them...  On the new engine and adjusted right they work OK, but I still rarely use them.  I like them in town mostly, or in stop and go traffic.

Brian


Title: Re: Uh oh! Engine knocking?
Post by: gus on February 09, 2014, 08:32:01 PM
Check the unused pulley at the end of the cam on the left side (Fan).

This thing takes a lot of torque and likes to work loose and is noisy. Watch it with the engine running to see if it wobbles. Been there!!


Title: Re: Uh oh! Engine knocking?
Post by: TomC on February 09, 2014, 10:34:27 PM
Listen to which side of the engine the noise is coming from, then remove that valve cover. Start the engine and when it makes the noise and see which Jake brake is firing off-can tell by it push down onto the exhaust valve. All others-quite guessing what the noise it. Good Luck, TomC


Title: Re: Uh oh! Engine knocking?
Post by: luvrbus on February 10, 2014, 04:39:16 AM
Does he have Jake ?


Title: Re: Uh oh! Engine knocking?
Post by: opus on February 10, 2014, 08:40:24 AM
Does he have Jake ?

Awww....you're going to ruin all our good advice by asking a common sense question!  LOL!!


Title: Re: Uh oh! Engine knocking?
Post by: TomC on February 10, 2014, 11:11:35 AM
Since he has tall valve covers, I assume so.


Title: Re: Uh oh! Engine knocking?
Post by: zubzub on February 15, 2014, 06:14:30 AM
seems to me he posted the problem has gone away....
but my2 cents..IMHO... FWIW.. it's the main bus nut working loose.


Title: Re: Uh oh! Engine knocking?
Post by: expressbus on February 15, 2014, 10:05:11 AM
Speaking of nuts, I for one can't wait to get this new technology where all our vehicles talk with each other. Maybe then we won't have so many wing nuts cutting us off and then throwing out the anchor or loosing the accelerator pedal. This will be the first safety innovation that will actually tighten up the loose nut behind the steering wheel. Yeah, bring it on.


Title: Re: Uh oh! Engine knocking?
Post by: Jeremy on February 15, 2014, 11:39:10 AM
Speaking of nuts, I for one can't wait to get this new technology where all our vehicles talk with each other. Maybe then we won't have so many wing nuts cutting us off and then throwing out the anchor or loosing the accelerator pedal. This will be the first safety innovation that will actually tighten up the loose nut behind the steering wheel. Yeah, bring it on.

The technology is already there - it's the change in legislation to allow it that we're waiting for. I'm looking forward to it too - not so much because of the safety benefits but because I have better things to do with my time - driving a car, like riding a horse, should be something you do occasionally for fun, not something you have to do because the machine hasn't really evolved since the 19th Century

Jeremy


Title: Re: Uh oh! Engine knocking?
Post by: Dave5Cs on February 15, 2014, 04:19:32 PM
And just like any vehicle if you don't keep up the maintenance on the system it will at one point not work anymore and I don't want to be next to that vehicle. Just another system they can charge for and make the outrageous cost of vehicles even higher.


Title: Re: Uh oh! Engine knocking?
Post by: challenger440 on February 15, 2014, 08:10:44 PM
And of course your older vehicle will be unsafe and the gov. will MAKE YOU replace it.  At lunch today I sat and watched people parallel park their cars .  It was embarrassing to even watch.  Maybe we should spend more on driver training and worry less about a new gadget that will only make drivers worse. 

Did the OP decide on and engine?  JM


Title: Re: Uh oh! Engine knocking?
Post by: Bryan on February 15, 2014, 09:00:34 PM
seems to me he posted the problem has gone away....
but my2 cents..IMHO... FWIW.. it's the main bus nut working loose.

Yes, it hasn't made that sound since that day. I don't know what it was other than laying hands on it and praying (seriously!) Once we got the bus to moving forward and backwards a few feet a few times, it quit. We have drove it a couple times since. Prior to that it hadn't been drove in a few months. Thank everyone for their help.  ;D