How hot?

loosenut · July 14, 2009, 11:44:45 AM

I have a 6v92. After a moment to air-up it is about 3 miles to 180^oish on the dash guage. After a 14 mile trip with a lot of hills that starts with 2 miles of surface streets, 10 miles of highway finished by 2 miles of surface streets at idle; the mechanical gauge on the engine shows 220^o, the dash gauge shows approximately 195-200^o no numbers between 180 and 210 the indicator is just touching the 2.

On the same test run at the same idle; the heat gun on the freeze plugs shows 183-187^o depending on which plug, the right thermostat housing 176^o, the left 184^o(is closest to the radiator), the top of the radiator is 172^o and the bottom 96^o.

The question is am I going?

Er what is my temperature and is it too hot?.

One more thing, these temperatures are fairly consistent except when I run my generator. Then the dash needle stays pegged just above 180^o. I've not recreated that anomaly to test the engine with the heat gun. While the generator doesn't interact with the engine I guess it signal the webasto heater to circulate water.

Utahclaimjumper · July 14, 2009, 01:03:27 PM

A lot of this discussion depends on ambient temps as well as load. Those temps are not bad if ambient is high, absolute high engine temp in my book for that engine would be 220 with shut-down at under 230.>>>Dan

loosenut · July 14, 2009, 02:44:57 PM

Ambient temperature was 78^o.

niles500 · July 14, 2009, 09:52:25 PM

Change out your T-stats (cheap fix)
Have your rads rodded and flushed - HTH

Chopper Scott · July 15, 2009, 05:30:31 AM

Are the 71's different as far as max temps? I was under the impression that 210 was getting about as hot as they could handle. Later

luvrbus · July 15, 2009, 05:40:52 AM

210 is the max on a 92 series and even at that temp is a crap shoot never would I go above 200 on a 92 series. good luck

Utahclaimjumper · July 15, 2009, 05:41:26 AM

71 series will tolerate more heat than 92 series engines.>>>Dan

NJT 5573 · July 15, 2009, 12:14:39 PM

The gauges are bad.

The oil cooler is on the left side so that could contribute to it being a little warmer. The temps look OK to me. Put it on a grade, go a couple miles up, stop on hi idle and see what you have at the thermostat housings. (Just want to make sure the L thermostat is opening right). It could be a 185.

The rad looks real good, thats about all you can ask for.

Do you have any kind of a hi temp shutdown?

Try improving the grounds on the dash gauges or run a mechanical one from the left head to the drivers area. My gauges are off too, but I know Mr. DDEC will take over if it gets hot so I don't even pay any attention to them for the most part.

Tim Strommen · July 15, 2009, 05:45:05 PM

100C = 212F

Water boils at 212F at open atmospheric pressure (sea-level). I'd be warry, even with a 30PSI cap, of going much over 200F simply because of that impending phase change. You get 3deg/PSI in a closed system before boiling starts, but if your system had even a pin-hole leak (like in an aging radiator), you could be in serious trouble before you knew what hit you.

The temperature rising above the normal steady state means that your cooling system is starting to have difficulty rejecting the heat to the atmosphere fast enough. If your temp gauge starts to climb you should really start to back off the throttle, and seek a lower gear. On a hot day, my truck reads the same as a cool day, but when it starts to climb (usually because I put my foot through the floor trying to pass someone), it usually doesn't stop until I do something different (I'd call this a potential thermal runaway...). It just means that the return water isn't cold enough even with the fan running max and the thermostat all the way open, to absorb the heat that's being added to the water by the engine. There is a possibility that there can be another equalibrium point at the higher system temp, but you would be rapidly approaching the boil-over point while reducing your safety margin.

-Tim

P.S. of course after re-reading the first post, I'd say - yes there is probably something wrong with your gauges. Do you have the option of digital at all? I hate interpreting a needle-width or more of change, I'd rather see a number... -T

loosenut · July 17, 2009, 01:08:09 PM

Thanks all for the help. If I understand all the responses it seems that it wouldn't hurt to put in a lower temp thermostat. Detroit Diesel said I needed a special tool to change the thermostat. Do you know where I would find the tool? They were mum on what it is and where I would purchase it.

I've assumed I have a DDEC setup. If I do have DDEC how do I find out its settings? Can I ala NJT count on it to shut down in time to save the engine?

Again thanks for the help. I hope to eventually make it to one of the fine sounding get togethers.

Mike

NJT 5573 · July 17, 2009, 10:43:52 PM

Look on top of the engine just behind the water rail for a good sized square box with alot of wires going into it. No box, no DDEC so make sure what you have. I doubt a thermostat will make much difference. If the old ones are opening and closing thats all that really matters. Could you have radiator shutters?

There is nothing wrong with the temps you took manually, I would just run it once I reconfirmed the real water temps at the thermostats and water rails a few times.

If you have DDEC and you want to know about the settings the easiest way to start is by taking the engine serial number in to a DD Dealer and getting a print out for that engine.

JohnEd · July 17, 2009, 11:08:36 PM

Loose,

I think you are wrong on your lower temp stat statement. The engine expands with temp- and it has run its entire life at 180 -185. If you start running it at 170 I think you will induce wear and shorten the engine's life.

I sure hope Luvr and others have something to say about this cause I want to know what the last word is.

You should have a (switch)sender that cuts the fuel when you hit the danger level....207 or something. I say that you need one of those in BOTH heads. Wire them in parallel and all the rest of the circuit stays stock. There should be a (analog) sender in each head that drives a separate dash gauge. If you only have a single gauge and sender and the "other" thermostat sticks closed when will you discover this failure? Ans....when it is too late. You can put a delay circuit in the fuel cut out circuit and give your self 20 seconds to find the side of the road. OR install a bypass switch that overrides the cut out in case you have a situation where a $15K overhaul is preferable to stopping traffic. Maybe use full to get her off the tracks, however. I would still have the delay so a uninformed driver couldn't wreck your power plant.

Or so they tell me.

John

buswarrior · July 18, 2009, 08:01:20 PM

Go with the temp gun, the gauges are suspect.

Is there a way to shoot some temps down through an access from inside the coach while underway?

By the time you pull over and get back there, it can dump a lot of temp from what it was while operational.

On an MCI, the pipes leading to the heater core come off the back top of the engine and can be shot at close range through an access panel in the floor by an assistant.

Be warned, it is loud, windy and dusty when you crack that open at speed!

happy coaching!
buswarrior

loosenut · July 19, 2009, 02:29:15 PM

I can't open the engine compartment from the top. The PO lined the floor with lead and insulated the engine compartment for sound. Not sure he insulated for heat. The bed storage compartment over the radiator is hot to touch.

The wife won't let me bungee her to the bumper or the engine compartment cover either. I told her the bungee was the best way but she is adamant no bungee, no bumper, no nothing. It didn't even help when I pointed out that I was only thinking of her comfort with the bungees. She could move around and get temperatures from both sides on one hill. Nope still mad. I'll never understand women. Try do something nice for them...

Mike