I have a 1987 NJT MCI MC9. I am having a problem with the bus going into shut down. The coolant level is fluctuating, but I am not losing it anywhere. I am getting air in the coolant lines. There is no coolant in the oil.
Below are a list of things I have tried.
1. Shut off coolant line to the coach and driver heat to isolate the coolant to the engine.
2. Bled the lines from the petcock in the rear between the blower belt. I have done this with the bus running and off. I also have done it after any change to verify line is stable and clear.
3. Removed coolant lines to the air compressor to verify it is not blowing air into the coolant.
I have been talking to Luke (from US Coach) and JR (from NC) and they have been a lot of help. Just trying to see if anyone has any other suggestions.
I am new to this and I appreciate anyy help.
Usually, cooling systems on trucks and buses are self aerating- meaning they purge the air out of the cooling systems themselves. To accomplish this, there are small cooling lines at the highest points of the engine-typically on the top of the thermostats-that take the air out of the cooling system since air rises to the highest point. Check those small lines-I would suggest have them pressure tested to see if they are introducing air back into the system if they are old and cracked. Also, make sure they are not blocked. If working properly, air in the cooling system should not be a problem. Good Luck, TomC
Removed
The coolant shutoffs to the front of the bus are notorious for stripping out and you end up just turning the spigot shutoff handle without turning off the valve itself.
Rick
Is there an air bleeder on the top of the engine, rear end, down through the hole in the floor from inside, on the coolant pipe heading for the coach heater/defroster?
Check the bleeder on the top of the heater core in the dashboard too.
the air is in there someplace, chase it out!
happy coaching!
buswarrior
Check your cap for any signs of corrosion - replace if necessary - first things first - HTH
I have the coolant shut off at the 2 vales that allow it to circulate through the rest of the bus. I think it is isolated to the engine. I want to get a compression check done.
VW,before spending big bucks on a compression check I would check the water pump and make sure it hasn't sheered a key or lost a blade,if you have problems with water on the top it will show up in the air box drains.
good luck
A friend had a similar problem on a Saudi MC-5. Water level would not stay up in the sight glass and no sign of where it was going. He replaced the pressure cap, end of the problem. Jack
Clifford or Don,
Is this starting to sound like a cracked head or blown head gasket?? Coolant obviously leaking or burning and air in the coolant system. Would an IR gun pickup a bad cylinder thats burning coolant?
The compression check is expensive (around 1K) and has to be done right to be accurate. Motor warm and running at idle.
This one is nagging at me
Rick
I have found the compression check is not needed.
I am not losing coolant. It is air in the lines. When I start the bus the level rises. Then I bleed the air and the level returns to normal. It just continues to build pressure when I start or run the bus. It does not go anywhere else.
I have only replaced the coolant that has been lost by bleeding it. I use a tube and run it back into a jug.
How would the pressure cap or water pump cause this.
I am wondering if the only thing to do is check the head for cracks and bad gaskets?
I am new to this and learning a lot. Trying to find 6v92 manual now.
I appreciate all the help.
I feel like Chicken Little. "The sky is falling, the sky is falling". Since my last post I have started my bus and bled the air from the coolant while it ran. This caused the level to drop. As the bus ran the level began to rise in the sight-glass, but did not shut the bus down as before. I ran it for about 15 minutes after bleeding with no issues. The level in the sight-glass began to fall to the normal level after a minute or so. I think this is normal, please tell me if it is not. The level did not fall back to normal before.
Here is one difference from today:
I have needed to charge my batteries, but did not have a large enough charger. I purchased one today and now have the front battery to a higher level than it has been since this problem began. This all began after the bus sat in cold storage for about 1 1/2 months in the coldest time of the year. Could this all have been becasue the DDEC was at a low voltage? I am not sure about this and I know it is a reach, but I thought I would give as much info as possible.
Is there a thermostat or something that could have casued this also? It is starting to warm up here (around 40 the last couple days). Could this have any effect?
Sorry for the long post. I hope this may help point to the problem. Or did I just get lucky and it ran for a few minutes.
Thanks
Vince
Vince,
I got your email and after revieweing this post I'm not sure we're dealing with the same issue. I haven't actually been out to see what is happening with my motor but first off my motor is out of the bus on a stand. We filled the motor with water, it will just keep recirculating it inside the block until the thermostats open which we haven't ran it long enough to have that happen. But it seems that I may be getting pressure through a crack in the head or a blown head gasket. I'm going to video it for review later today and hopefully put a pressure gauge on the coolant system to see what kind of pressure we're getting inside. But my mechanic sure seems to think that all is not well in my motor. It is all specualtion until I can get out there and see it for myself but I will definitely keep you informed.
As far as your issue, I have never noticed alot of fluctuation between starting and running coolant levels but certainly the system pressurizes itself due to the rising temp of the coolant. I have read many time that it is a no no to run your ddec ecu to below certain voltages but I do not have a ddec so I'm not qualified to even venture a guess.
Sean is pretty darn knowledgable when it come to electrical issues. Maybe ask the question on the board what are the issues I can expect to have with lo voltage in my ddec.
Just a thought
Good luck with this
Rick
Vince, may not be your problem but a bad water pump or bad seals on the thermostat or anything else that causes a turbulence in the cooling system will cause air pockets
good luck
Vince's bus appears to be pumping air into the cooling system within a few seconds of firing up the engine.
The thermostats would have been closed, the pax heater gates are both closed, the air compressor has been shunted away from the cooling system, and the DDEC set a "high coolant level" code (16) and the water level substantially increased in the surge tank.
Also sez he can hear air bubbles 'boiling' up into the surge tank following cold shut down. My bus doesn't do that even when shut down hot...only noise is oil dripping back into the crankcase.
IHMO, the engine has been bled satisfactorily. I've got an identical bus and it bleeds within a few seconds. Some engine combos may not, but these NJT systems are easy to bleed.
For a time, as I understand, Vince would start the bus and it would shut down due to either high or low coolant within a very short period...long before heat expansion would increase the water column.
The DDEC isn't likely related to the problem. Nor the water pump or thermostats. Water pump isn't doing any great thing anyway until the thermostats open. Although, a DDEC sensor fault could be the problem. Ex NJTs are famous for setting bogus "Low Coolant" codes.
My bus is still in 'winter storage'...what Vince needs is someone to crank an MC9 and see what the water level does. I've never paid any attention to what the sight glass does when the engine is initially started...it may surge up and down. May not. I set it and forget it.
I'm with RickB....the problem sounds like a cracked head.
No water in the oil. That may change.
And maybe no problem at all...? Or maybe a faulty high water sensor?
The bus seems to be functioning for now, and my thoughts would be drive it and see what happens. Unless coolant becomes obvious in the oil or the engine begins to miss--or overheats, nothing will be worse for the wear.
If the bus does begin to miss, an infra-red tem gun will ID the cylinder.
Vince, make sure the dash water temp guage is working correctly. The dash sender is the automotive looking temp sender screwed into the pax side thermostat housing. One wire sender. Ground the wire and the guage should move to "hot" when the ignition is "on." The engine doesn't have to be running to verify that the guage works. It it doesn't move, check the wiring at the guage, if patent, change the guage (remember that it is a 24V guage). If it moves, but doesn't read when hooked up to the sender, replace the sender.
The DDEC will shut down on "Hot Coolant," "Hot or Low Oil Pressure," and "Low or High Coolant." It will shut down with bogus sender signals too.
See if you can read all of the codes. On a DDEC I, the codes are lost if the DDEC fuses are pulled or the batteries disconnected. Turning off the battery master will not depower the DDEC ECM. Keep in mind that some of the DDEC wiring is always "hot" if working on the bus wiring. This is true for the 'Distributor' (engine unit), and the ATEC and DDEC ECMs.
Whaddaya think bus peoples? ???
Good luck, JR
Why can't we just replace a $5 cap and see if that doesn't work first ????????????????
I will try to find a cap. It should be easy to fix, but I need to find one.
Vince
Do you have bubbles in your coolant when the motor is running?
Rick
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
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!!! ;D ;D
Rick
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.
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
Here is a photo of the air box drains on our 8V71. Yours should be similar in appearance and location. Jack
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
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
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
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
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
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.
I'll check the level sensor readings in a short. Get back to you this evening.
JR
I read and re-read the whole thread. Other than the fluctuating fluid level at run and start up how do you know you have air in there. Did I miss this?
I don't think it is air in the coolant now. I just have the level that rises. I do not seem to build pressure. I checked it with a prssure gauge on the schrader valve and it has about 1psi all the time when running.
Do you still have a shut down problem ? and you should have more than 1 # of pressure more like 4 or 5 lbs
I would say fluid is getting restricted and lowering the level at the point you can see it, raising it elsewhere in the sytem. Pressure finally takes over the restricting problem, allowing the fluid to move bringing the level back up. What in this system could open and close creating a fluctuation in the level? A large air pocket, a restricted automated valve perhaps?
Hi All,
I wasn't aware there is a high coolant sensor, or code. Is this DDEC I only, or am I missing something. DDEC 2,3, or 4 only lists code 43, low coolant level. Is there some other type monitor on this engine?
Just trying to clear the waters.
Dick Egler
OK first off it's been so long since I worked on a "9" I can't remember what they look like! ;)
OK, OK maybe not, but it's been a while! And I never worked on a NJT "9" that had a DDEC.
So far I ain't bat'n to good am I?
Well I do have a little insight or experience in this area.
Our first Setra '89 model S215 W/8V92 DDEC in it had similar issues as what your having prior to us purchasing it.
We listened to the head "tech" at the company that had it and were skeptical of a coolant sensor causing the shut downs. But he said "can't be that we already tried that!"
Well I just happened to have one laying on the desk that I needed to send back to Setra as they had sent the wrong one to me for a customers bus. (the customers bus had a 60 Series in it!)
So we took a gamble and took the sending unit (little black box like Jr describes, not the actual sensor!) with us when we went to look at it on a Sat. and first thing I noticed was that the sensor it had was the same as the one I'd put on the 60 Series. So 1st thing I did was asked if we could "test drive it." They said sure, but you ain't gonna get far before it shuts down and you'll have to wait until it restarts to bring it back.
I told them I'd take that chance. So as soon as we rolled out we found a large church drive to pull off at and unhooked the sender and hooked up the one I'd brought and left it hanging. We drove it for 30 miles or so with no issues. Went back and stopped and took our sender off and hooked the original back up. Just as I pulled into their lot it shut down.
They came out and met us as we got off the bus and told us "see that's what it does to us, if ya buy it you'll have to have it towed home.
Well long story short after the deal was made I switched it and drove it home 138 miles with no issues there. (others yes, but not there!)
OK now after we had it a little while I noticed the coolant low it the sight glass on pre-trip so I added some. While loading a passenger or someone told me yer bus is leaking anti-freeze!
So I went and checked thinking I had a "leak" but it was just coming out the overflow.
So next morning it was down again and I added some again. A little while later it was running out the overflow.
So after 3 or 4 times of this I decided to go ahead and start it and see what happened before adding any. After checking the oil, coolant, belts etc. I started it and finished doing my pre-trip just before taking off I took one last look at the coolant level and there it was right where it was supposed to be.
So I always waited to add after that and seldom had too. And anytime dad or another driver would drive it the first thing they would do is add coolant, and then complain it was "leaking" later! ::) (yeah they never listen to me! ;))
And we've have a newer Setra ('95) with a 60 Series that does the exact same thing!
So if it's not actually showing bubbles it may not really be a problem.
My guess is shut down is a faulty sensor or sender!
YMMV
;D BK ;D
Quote from: dickegler on March 11, 2010, 02:28:29 PM
Hi All,
I wasn't aware there is a high coolant sensor, or code. Is this DDEC I only, or am I missing something. DDEC 2,3, or 4 only lists code 43, low coolant level. Is there some other type monitor on this engine?
Just trying to clear the waters.
Dick Egler
I'm with Dick on this! Not aware of high coolant sensor. But I once thought I was wrong, only to find out I was
mistaken! ;)
YMMV (and Dick posted this while I was typing my book!)
;D BK ;D
wal1809,
I have an extra coolant level module that BK is talking about. I would be glad to send it to you to try out. I think I have a sensor too.
Let me know.
Dick Egler
OK. I have found there are 3 codes that I know of that are related to the sensor.
Code 13 that is a Coolant Level Sensor (CLS) Low Pg 134 of the DDEC I Manual
Code 16 that is a Coolant Level Sensor (CLS) High Pg 148 of the DDEC I Manual
Code 43 that is a Low Coolant Pg 148 of the DDEC I Manual
I think the 13 and 16 have to do with a "bad" Sensor. It tells the sensor either "open" or "shorted".
I misunderstood the 16 fault and thought it meant "high level".
The 43 is that the actual Shutdown fault.
I do not have a sensor connected and think that the shutdown I am getting is caused by the the wiring or the module as described by BK. Someone connected the signal to the +5v. I think this may work for a short time , but the sensor dwg shows it as a Pot. This may need some resistance to make it work. I am going to order a module and sensor. In the mean time I am going to try to get the correct resistance across the line and see what happens.
Dick,
I could use the sensor and module. Let me know how to contact you.
Thanks
Vince
Vince, sent you a pm
Dick Egler
I've got some 'wet' and 'dry' readings off of a Robertshaw low water sensor used on DDEC coolant tanks.
The sensor has 4 pins, but only A, B, and C are used.
Dry with meter on 20 ohm scale.
A to B = 7.3
A to C = open
Dry with meter on 2000 ohm scale.
A to C = 1570
A to D = 216
A to B = inf
Wet with meter on 200 ohm scale.
A to B = 156
Wet with meter on 2000 ohm scale.
A to C = 1598
A to D = 1604
Omitted readings were either infinity or open.
Robershaw low coolant sensors are used on both 2 and 4 stroke DDEC units. Should be pretty common.
HTH, JR
Man I hate to keep repeating it - BUUUUUUUUUUTT - replace the cap - FWIW and HTH