Series 60 DDEC II Mystery

[RichardEntrekin]

Got a little mystery that maybe one of the experts can tell me where to start looking.

The pertinent info is this. I monitor all the temps with a VMSPc so the temps I quote are coming straight from the ECM and the problem is not a gauge problem.

Sometimes my engine water temp runs right at 200 plus or minus 3, the oil temp is about 5 degrees cooler, and the tranny temp runs about 210 to 215. I can watch the temp cycle up and down like the thermostat is opening or the fan is cutting on and off.

Other times, the engine runs at 180 plus or minus 2, the oil runs at 179 plus or minus 2, and the tranny runs at 175.

I am figuring either a thermostat issue or something amiss with the circuitry that activates the hydraulic fan.

Do you guys want to venture a guess or theory about what is going on here?

One last clue. The last time it ran at 200, I pulled over. Shut the engine down at a rest stop, and when I restarted it ran at 180 for 500 miles,

[Ace]

Not really a mystery! Not all detroits run the same temps such as 180. If you check with any good detroit certified mech. or a good manual you might find that the series 60 runs best at 200-210. You never said what speeds your temps are at but my 8v92 runs 200 easily while hitting 75-80 mph but at normal 180 temp at 60-65 mph. Its also a DDEC 2!
Ace ... Having a blast in Arcadia!

[Ed Hackenbruch]

Change in ambient temperature could make a difference too.

[belfert]

My S60 runs very consistently at 195 degrees.  It will climb close to 200 on the steepest grades out west.  BK told me a long time ago that every S60 bus he has dealt with runs between 190 and 200 consistently.  More recently he said he did some cooling system work on on one of his older Setras with S60 and it now runs under 190.

My bus has had the water pump, thermostats, and radiator replaced so I doubt anything I do will ever lower the temp.  I am happy at 195.  Before I replaced the radiator I was overheating on the slightest hill.  When I first got the bus I hit the DDEC shutdown temp on a grade in Pennsylvania.

[luvrbus]

Do you have a fan clutch , a drop in turbo boost will add heat to a 60s, the air to air could be dirty a lot of things could cause the problem.
You take the heat out of a series 60 with turbo boost a different animal than a 2 stroke.
Do you have 11.1 engine if so they run around 195 all the time 180 is a little cold 




good luck

[RichardEntrekin]

I didn't do a good job of explaining what the issue is. SOMETHING is controlling the temp to either 180 or 200. I see no temps in between. The computer shows accurate readings coming out of the DDEC and both the oil and tranny temps follow the coolant temp, so I tend to think it's real. It doesn't change under load or between 55 and 70 mph. It is NOT a cooling system capacity or dirty radiator issue. SOMETHING is controlling the temp to either 180 or 200. The engine will hover at one of those two temps with very little fluctuation. I just wonder what it is. I would never have even wondered about this IF it didn't flip back and forth between the two. The key to the flip is ignition off and a restart. It NEVER has changed from one temp to the other while it was running. It is a mystery to me why sometimes it runs exactly 180 and sometimes it runs exactly 200, nothing in between, nothing lower, nothing higher.

Does that explain my curiosity better.

Thanks for the info on S60 temps. All along I was thinking 180 was better than 200, but apparently it's the other way round.

Thanks for all your ideas.

[luvrbus]

Richard, if you have the hydraulic fan there is a wire from the fan clutch to the thermal valve that comes lose or the plug gets corroded. 
let us know what fan setup your Newell has 


good luck

[belfert]

Could you have a two speed fan clutch that is acting up or a faulty temp sensor?  Not sure if the DDEC II can even control a two speed clutch or not.

[RJ]

Richard -

I'm not familiar with DDEC engines, but, as seems to be a common issue with all kinds of electrical gremlins, you may have a bad ground or a loose connection somewhere.

However, what's intriguing is that apparently, with whatever temp is showing, it doesn't fluctuate.  If I'm reading your message accurately.

When it comes on and says 180, it stays at 180, regardless of driving conditions.  Ditto with the 200 reading.  Is this right?

If that's the case, I'm wondering if maybe it might be a temp sensor that's dying.

FWIW & HTH. . .

[RichardEntrekin]

I do have a hydraulic fan, so fan clutches are out.

It can't be a dying temp sensor because both the oil temp and tranny temp track exactly the two different coolant temps.

SOMETHING is controlling the temp either at 180 or 200 without fluctuation. The question is WHAT?

I am thinking something in the DDEC that controls the fan, and here is why. The tranny temp tracks the temp in the engine. However, the only place the tranny fluid and the engine coolant are in  proximity is the radiator. When the engine temp is running at 180, the tranny temp will run anywhere from 150 to 180 depending on ambient, when the engine temp is running at 200 the tranny temp will run 200 to 215. Curious that when the engine temp is running at the 180 setpoint the tranny runs at that temp OR COOLER, and when the engine is running at the 200 setpoint, the tranny runs at THAT temp OR HOTTER.

Does anyone know if the DDEC turns the hydraulic fan off and on, or better yet runs the fan at different speeds?

Thanks again.

[luvrbus]

Richard, the DDEC doesn't control the fan speed if you are positive you do not have a 2 speed fan clutch and some hydraulic systems do.
Then you have a thermostatic valve somewhere in the cooling system that tells the switching valve how much oil to flow for fan speed. 
Check and see if you have a thermostatic unit it will look like a sender somewhere in the piping for cooling or could be on the engine even on the side of the radiator tank.
It will have a hose about 3/8 of an inch in dia (or it could be electric controlled) going to the switching valve close to the fan.


good luck

[RichardEntrekin]

I am not positive at all about the two speed fan. That makes the most sense of anything. I will check the connections to the "box" that controls the hydraulic flow to the fan.

Thanks to all of you for your help.

[rv_safetyman]

Richard, building on Clifford's comments,  I am pretty sure that the Series 60 DDEC system would not control the hydraulic fan system.  It does have the ability to control an air type fan clutch on trucks, but nothing specifically for a hydraulic fan.  I guess someone could have gotten cleaver and used the air clutch signal to do something with the hydraulic system (shift speeds).

I bring this up, as it would let you focus on just the hydraulic system and not have to deal with the DDEC system.

I would think the Newell folks could give you the details of the hydraulic fan design.  I would also suspect that there are forums specific to Newells that might also help.

It has been said already, but none of the information you have given us would be cause for concern.  I suspect you are asking from an academic standpoint.

Jim

[RichardEntrekin]

There is a control box that the hydraulics pass through on their way to the fan. It is getting a 12V signal, but I do not know how it is supposed to function. I'll give Newell a call on Monday.

I am guessing the solenoid on the control box changes speeds on the fan, and the solenoid is not working properly or perhaps working sporadically.

The fan speed did not change when I unplugged the voltage to the solenoid, so that was a clue.

[buswarrior]

Nothing but a wild a** guess...

By your test, the fan fails safe by running when the controls fail (by taking the wire off and fan runs)

If we assume for the minute the fan has some sort of set point, or points in a multi speed fan control, there would be set points for engaging each speed...

Could there be an intermittent fan control glitch, so that sometimes the fan runs flat out (broken), taking the temp down to the thermostats, and sometimes it works right, letting the temp run up at the higher temp?

I think finding out would be prudent, so you may ignore it with confidence, or take action to prevent further deterioration.

happy coaching!
buswarrior