Air in coolant line on 6v92

[niles500]

Why can't we just replace a $5 cap and see if that doesn't work first ?

[vwb11356]

I will try to find a cap.  It should be easy to fix, but I need to find one.

[RickB]

Vince
Do you have bubbles in your coolant when the motor is running?

Rick

[luvrbus]

A cracked head or head gasket is a easy thing to spot on DD check your air box drains steam or water you have a problem up top



good luck

[RickB]

Vince,

I don't know about you, but since we both have some weirdness going on in our cooling systems, that last post by Clifford made me feel alot better!! I have no water in my airbox but man I have alot of oil that seems to be enjoying passing through that particular area!!!

Rick

[vwb11356]

I will check the air box drians.  I need to find them first.  I will check the manual and see if I can locate them.

Rick, I do not have bubbles in the line when running.  When bleeding the coolant comes out steady.  The sight-glass level rises the falls to normal after turning it off.

Does anyone know if their 6V92 coolant level in the sight-glass rises and falls the same way?  I am still am not sure if this is normal.  JR has had his for years and said he doesn't know if his does it.  I think you check this unless you have a problem.  Is that why is has the "Cold Level" in the sgiht-glass"?

Thanks for all the help.

[RickB]

Vince the airbox drains are located on both side of your engine below the exhaust manifolds in the side of the block. They are rectangular in shape about 1" wide by 3" long with a tube that drains onto the ground or is rarely run back into your crankcase. you can't miss them because almost every Detroit leaks out of them while running. I think what Clifford was getting at is the puddles that you leave behind on the ground after idling for 10 minutes or so should be oil only. black in color with no white or milky color to them. Otherwise you could pull your airbox access ports on the sides of the motor just below the exhaust manifolds (little rectangular shaped covers with 1/2" or 7/16" bolts in them. They will probably have some oil and gunk in them but it should be all black in color.

The no bubbles thing is a good thing.

As far as whether or not all our motors momentarily drop in coolant level at startup I'll try and check that later today but it's pretty obvious that they don't drop far enough in our motors to trip the low coolant sensor.

I'd consider checking your low coolant sensor as well. If you can pull it out and clean it. Just a thought

RB

[JackConrad]

Here is a photo of the air box drains on our 8V71. Yours should be similar in appearance and location.  Jack

[RickB]

Jack,

you are da man!

HEY I need a clean spot to do some brain surgery on a relative. Mind if I use your engine compartment.

Thats a sterile clean environment if I ever saw one. You're gonna have to drive that thing more so it looks like the rest of ours!

RB

[vwb11356]

JR

Here are the codes I am getting in order.  It went into shutdown again tonight.

16 System Running with High Coolant Sensor Output
312 Injector Response time too long
313 Injector Response time too long
315 Injector Response time too long
43 Coolant Low Level for 7 Seconds while Ssytem Running.

I have a DDEC manual now!!!!!!

This is disturbing since the sensor is not connected to the DDEC.  I think the same sensor gives high and low level.  I will try to find out.

I also put a pressure gage on the coolant pressure test fitting we talked about and it does not build pressure.  I used a fuel test pressure gage (0-10 psi) and a tire valve with a lock on it.  It would show about 1psi while running and with the engine off.  I think it works ok since there was no coolant coming out around the fittings and it would go to "zero" when disconnected.  Not sure if this tells us anything, but I am trying to give you as much info as possible.

When I started it today it smoked really bad white smoke,  I know this doesnt sound good.  It didn't run bad it just smoked.  Then it almost stalled.  It then stopped smoking and ran fine until I turned it off.  Still had the same coolant fluctuation issues, but ran fine.

I have not been able to check air box drains or find a new cap yet.



Thanks



Vince

[vwb11356]

Are there only 3 places the coolant can be coming from in the surge tank?

1 The left overflow from the radiators
2 The right overflow from the radiators
3 Backing up from the engine

Could I tell anything by disconnecting the radiator overflow one at a time and see if it is coming from one side or the other. And if it is neither side then it must be backing up from the engine.  I am not sure how it could "back up".   I am just trying to isolate the problem.

Sorry for the long replies.  I want to give as much info as possible.

Everyone here has been great and I appreciate the help.

Thanks
Vince

[RickB]

Vince,

If you have an IR gun I would IR each cylinders exhaust to see if you have one cylinder acting abnormal. Try and shoot it at non reflective surfaces. I wish I was DDEC savvy and could help more.

Rick

[NJT5047]

Ignore the "pulse width" codes (312, 313, and 315).   A DDEC I will set 'low voltage" and "injector response" codes when they are running perfectly.  Those won't shut the engine down.    They may indicate issues, but they'll likely clear up once the bus is run a hundred miles. 
The sensors for both low and high water are removed....? Right? 
Is the low water module still mounted next to the ATEC ECM?   Small black module that probably has "low water" logo inprinted on the unit.   Maybe 3" by 2"...
The low and high water sensors have probably been shunted.   I'd try to locate the wiring terminations and see what the PO did to fool the DDEC unit to ignore the coolant sensors.   I would recommend repairing the low water senor by installing a low water sensor.   Might need to find a plug. 
The DDEC manual you've ordered will give you details on how the system works and color codes (numbers) so that the wiring can be traced. 
If you replace the coolant sensors, be sure that the surge tank is grounded.  It had a wire that grounded the tank to the frame member to the left of the tank.   
No matter what else is going on with the cooling system (maybe nothing), the low coolant code problem must be repaired.  The bus won't go with a low coolant code set.   It can be made to operate for 30 seconds by holding the 'Override' switch located to the left of the ignition master.  Has a red bomber door cover.   
As mentioned, the cooling system could be checked for sudden increase in pressure when the engine is started.   There's some expansoin due to normal engine heat, but the pressure should not suddenly begin to rise.  The engine will idle all day without a rad cap. 
It'll run down the highway with the cap loose too....don't ask how I know this..      The radiator fill cap isn't a 'pressure' cap anyway. 
Overpressurization of the cooling system on an '87 NJT MC9 is handled thru a pressure relief valve mounted on the surge tank.  Upper LH (looking at the tank) so don't waste a lot of time hunting for that oddball fill cap.   
There's also a small pull valve that releases whatever residual pressure may be in the cooling system when adding coolant to a hot engine.   It's located just below the filler.   If you see water oozing on the curb side bumper, the valve is stuck open.  Just push it in.
BTW, on an unrelated subject, your coach has a transmission retarder that should be 'ON' unless operating on wet or slick roads.  The retarder is controlled by a switch with a bomber cover towards the rear of the drivers side switch panel.   When turned off, a light may light up on the RH front (above the RH headlights) of the coach.   Probably doesn't work, but that's what the little jeweled light above the RH headlights is for.   My understanding was that the supervisors could monitor the use of the retarders by looking for the light.   

JR
   

[vwb11356]

JR

I still am not sure about rising level in surge tank.  I put a clear tube on each side of the radiator "overflow lines" to see if coolant was going through there and filling the surge tank.  It is not coming through either line.  This means the level is rising through the large line going directly to the engine.  As I stated before I put a pressure gage on the schrader fitting and it is not building pressure.

I think there is only 1 sensor that shows the level in the surge tank.  It provides a signal to the DDEC based on level and then the control has setpoints to determine high and low.  The DDEC manual I have does not show how the sensor works, but I think it varies the resistance based on the level.  If it has a signal based on the level it would probably need a resistor instead of a jumper.  I am using an educated guess since I do not have enough info on how it works.  I am pretty comfortable with the electrical part since I deal with that kind of thing at work.  I will try to get this bypassed for now and then see if there are any other issues.

The engine is not getting hot.  And seems to run OK.  The white smoke at the start is different.  I hope you read the previous post with the other details.

I appreciate everones help.

[NJT5047]

I'll check the level sensor readings in a short.    Get back to you this evening. 

JR