I am getting ready to replace my newly installed temperature gauge. We were not sure what was really bad, the gauge or the sending unit, so we replaced both. As it was the only thing readily available locally, we have installed a Sunpro Temp Gauge and sending unit. It works, but I do not trust it as it already seems to be reading lower than actual temperatures. I am replacing this with a VDO gauge/sending unit.
I tried to do a search on this site and also looked through all the literature in our Breakaway, but cannot find an answer to my questions......
First, what is the maximum temperature and maximum SAFE temperature for a 1993 Cummins B5.9 diesel? This will help determine what graduations I am going to have on the gauge.
Second, what should the sending unit warning light contact be rated at? They no longer manufacturer the one that was in the motor and I have a choice of a 217 degree or 230 degree contact for the warning light. Both units are +/-5%.
Thanks for your help and input!

I never run mine over 220 under the worst conditions. My over temp switch will go off at about 222 or so. I would probably opt for the 217 degree switch. Have you checked with Spartan on the switch replacement?

I wish VDO still offered the same style gauges with white pointers that were in the original panel!!

quote:

Originally posted by Bruce & Kathleen:
They no longer manufacturer the one that was in the motor and I have a choice of a 217 degree or 230 degree contact for the warning light. Both units are +/-5%.
Thanks for your help and input!

I would read This Post, And All Of The Replies, as it has part numbers and info on the sending unit that does both. This part is readily available and we go into detail on how to wire it up.

Ed---They do still make the gauges that are in our Barth's, or at least in mine. Go to egauges.com and click on VDO. My big question was whether I would go with the original Cockpit Black Series (#310-039) or go with the Vision Black Series (310-105), which gives a better graduation on the dial. Also, the Vision Black has thru the dial lighting where the Cockpit Black is side lit. I don't know if one is better than the other...

Bill--- Thanks for the input. I had read that posting previously, whch is why I could recognize the sending unit when we removed it. My mechanaic couldn't find one, so he kind of rigged up the Sunpro with two seperate sending units for my recent travel, as I wanted to make sure I had some sort of temperature gauge that worked.

I'm still interested in the operating temperatures of a Cummins B5.9. I cannot find that information ANYWHERE! Even doing an internet search I come up with no answers. I wonder why? And though Ed has run his at 220, I can say that I have turned on my high temperature light three times (last time was the water pump going southbound) in my ownership. All the times it did, I pulled over immediately. Since replacing the water pump it seems to be running much cooler than before. But, I want to know exactly what is going on with the temperature of the motor at all times. Thus, the changing of the gauge and sending unit. The light seems to come on around 230 degrees. I do not know if that is standard for these motors or not.

Here's the deal... Normal operating temperatures really shouldn't exceed 200. Pulling 210/215 on a long grade probably isn't too bad on certain occasions. The idiot light coming on at 220 might be correct. The trick is knowing what the item is designed to do.

Anybody can rig anything up. But, the rigging could/will give you out of range readings in this instance.

In the case of an idiot light it is a "make or break" scenario... When it gets "Too Hot", it completes a circuit. Simple wiring really as all it did was ground out the idiot light thus illuminating the red light and/or causing the buzzer to sound off.

This is considered the point at which serious damage occurs if driven farther. The question now is if you're close to cresting a hill and if you can allow your forward momentum to cool off more efficiently going down hill or if its better to pull over and rev the engine to cool it off.

It is usually not a good idea to just "Shut Off" the engine as the excessive heat in the engine compartment will start a process known as "Heat Soak" What this is, is a degregading condition that will eventually turn the rubber pieces into hard brittle items.

If you pull over (or crest the hill) and it keeps climbing, then it is far better to turn off the engine as you might now have a blown hose, broken/slipping belt, seized water pump or a broken idler pulley.

The trick is in knowing what the temperature gauge was doing before. A 5.9l pulling a hill in our application should always be done with one eye on said gauge. This gives you a basis for knowing what is considered normal or what is considered a failure or an impending failure mode.

The fact that you have a newer gauge that might not take into account the correct sending unit is cause for very real concern. If all you did was just change the gauge and the sending unit has a different resistance then nothing I tell you will matter.

Remember, you've changed the known factors by replacing the water pump. Did you change your belt too? maybe its not slipping like it "could have" been before. Newer belts tend not to slip.

Now, you'll need to relearn the characteristics of how the engine heats up pulling long grades. By your own admission, it seems to be running cooler with a new water pump.

I know you just recently cleaned the radiator too. Didn't you say then that the temp was running cooler after that was done?

My suggestions are geared towards longevity and operational ranges as was intended by that specific sending unit. Keep in mind, these work off of a known resistance to that gauge. Some gauges use a different range of resistance than others.

They might use 217 or 230 for an idiot light to make the circuit complete. They use resistance range to make your gauge work. One gauge can not be put in place of another gauge if electrical resistance isn't figured in too.

The typical "gauge range" is around 140-280 on a water jacket - the typical "gauge range" on an motor or trans oil passageway is 160-320.

The mechanic who rigged this up MIGHT be doing you a disservice. He's not the one who has to replace or buy you a new engine when it goes "BOOM" if he already has you convinced that what he did beforehand was correct.

Get the correct sending unit for your gauge. Buy the correct item for your application. Make sure there isn't resistance in the electrical line from the gauge to the sending unit. Resistance in this wire will give you an "out of range" reading.

Contact Spartan, ask them what ranges (temp & resistance) this sending unit controls, find out what the idiot light is set for. It might be 225 for all we know... not the 217 to 230 he quoted you.

If in doubt, and all you have is an idiot light, I agree with what Ed said... "I would probably opt for the 217 degree switch"

Part of being a mechanic is researching things. Contacting Spartan and insisting that you buy the correct sending unit might have been the better play here if Spartan will not give him the specs of this sending unit.

The reason for this really long response is I wanted to cover all the bases because I have no idea what this means and if he took into account all of the other variables...

quote:

Originally posted by Bruce & Kathleen:
My mechanaic couldn't find one, so he kind of rigged up the Sunpro with two seperate sending units for my recent travel, as I wanted to make sure I had some sort of temperature gauge that worked.

Many years ago (10-15) when we still had our bus (35' GM106) at a bus rally there was an old time engineer for Detroit Diesel. His comment was "Don't make vapor". With a 50% mixture this is about 240+ at sea level. The 2 stroke engines were noted for cracking heads if you over heated them. The four stokes are a little more tolerant.

In summary the over heat sensor need to come on before you make vapor. If you are running plain water you make vapor at 212 at sea level and lower temps at altitude.

Don't make vapor and you will be fine.

212F is "vapor" only at atmospheric pressure at sea level (14.7 psia, where "a" is "absolute", the only figure used when determining boiling point).

Cooling systems are pressurized, so the boiling point is raised. 220F is generally safe for most engines. But running near redline isn't usually wise. Downshifting will lower the need for throttle and speed up the water pump and fan speed.

quote:

Originally posted by Rusty:
212F is "vapor" only at atmospheric pressure at sea level (14.7 psia, where "a" is "absolute", the only figure used when determining boiling point).

Cooling systems are pressurized, so the boiling point is raised. 220F is generally safe for most engines. But running near redline isn't usually wise. Downshifting will lower the need for throttle and speed up the water pump and fan speed.

And antifreeze isn't used just to keep the cooling system from freezing up either...

A 50/50 mix further raises the boiling point to about 230 without any pressure. Add a 15psi cap and it increases the boiling point to around 265.

Vapor is just that... the point at which the head becomes a teakettle. This is where the first area of failure happens in a low coolant level or higher engine temp scenario.

Vapor, or air in a head, is the point at which you'll probably crack or warp your head because the actual temperature is now even higher than that.

quote:

Originally posted by Gary Carter:

Don't make vapor and you will be fine.

quote:

Originally posted by Rusty:
212F is "vapor" only at atmospheric pressure at sea level (14.7 psia, where "a" is "absolute", the only figure used when determining boiling point).

Cooling systems are pressurized, so the boiling point is raised. 220F is generally safe for most engines. But running near redline isn't usually wise. Downshifting will lower the need for throttle and speed up the water pump and fan speed.

If any gasser Barthers are following this thread, the above is very good advice for gassers, as well.

I will add that, in my gasser RVs and tow vehicles, Red Line Water Wetter inhibits the formation of vapor pockets (hot spots) very well, and keeps temps down.

This is going to be a little long winded, and for that I apologize to those who are reading this posting. I also apologize for spelling mistakes (no spell check here? ).
First, I thank all for your input and welcome more on this subject. I believe it to be valuable to anyone following this because diesel pushers seem to be prone to higher and fluctuating operating temperatures in certain running conditions.
As some of you already know, I have been concerned about my operating temperatures since I purchased our Breakaway. It seemed to run on the hot side of normal. I have done some modifications to try keep it running at 180 degrees or so including adding a trans cooler, since the trans fluid is normally cooled thru the radiator and I believed that keeping the trans fluid temperature cooler would help keep the water temperature in check. That modification did help the water temperature somewhat but more so, it certainly helped keep my trans fluid at a much lower temp therefore prolonging it's life. I also have been following the threads from Ed (MWrench on this site) as he has gone thru many stages of keeping his operating temps in check. When I was searching this site and the internet for some answers to operating temperatures it occurred to me that many folks with diesel pushers have heat related problem. Some of the answers are as simple as flushing and cleaning your radiator, changing your radiator cap to the proper PSI or making sure your water to antifreeze mix is correct. Some are related to a water pump getting ready to go bad, as was in my case. (By the way---that has DEFINITELY helped). Other answers are more complex as it could be an indicator of cracked heads, blown head gaskets or ???....
But this takes me to my point. Since I have always been concerned with the operating temperature of our Breakaway, I find that when I am looking at the dash I am checking the water temp and oil pressure gauges mostly. Some of that has to do with knowing what the speed is because my coach will do 60ish on flat land. And that corresponds to about 23-2400RPM. I was having problems with my water temperature gauge BEFORE my water pump decided to give up. It would run erratic at times during my travel. But I knew that the warning light always worked. And by my VDO gauge that was existing, it was about 230 degrees when it came on. Since I replaced the water pump (and yes, the belt too) I figured I need to also replace the gauge. And that is how the Sunpro got installed. We ran out of time to get the VDO replacement and I wanted SOMETHING THAT WORKED. Now I want to remove that and put the proper thing in place. I will call Spartan on Tuesday and get the information on the "stock" sending unit and gauge. I will also try to see if they have the information on "normal operating temperatures". I am aware that the low end of the scale should be around 180, I just don't know what the max is. My concern is having the correct information so I know what I am looking at once I install the new gauge and sender. And if 220 is the temperature to really concern myself with, then I want a gauge that is more defined that the one that was installed previously. If the temperature of this motor should never see 230, then I better hope that: (A) my gauge was wrong or (B) I was lucky and didn't hurt anything..... The new Sunpro says I am now at 160-170 running temperature. I know that is wrong, but it isn't 200 anymore!

anyone with temp concerns should boil water and stick the temp sensor in it to be sure it reads 212. If not, make out a correction card so you always know what is what.

quote:

Originally posted by Bruce & Kathleen:
I will call Spartan on Tuesday and get the information on the "stock" sending unit and gauge.

Here is a list I made up of the most common chassis setups in our Barths.

Thanks Bill!!! You might want to also copy these and put them in an easy accessible post.

quote:

Originally posted by Bruce & Kathleen:
Thanks Bill!!! You might want to also copy these and put them in an easy accessible post.

That is an image that is permanently located at the very bottom of the Data Tag Project. On that page, the links to their respective website work when you click on the image.

Bruce & Kathleen, To try to eliminate some of the variables in your temperature delema, did you replace the thermostat during the water pump replacement or any time during your exploration of high temperatures?

How long after you opened up the water system, either to replace the pump, sender or other radiator issues, did you run the engine before you made the temperature recordings?

The first question comes from the fact that Cummins have replaced the style of thermostat from a high flow design to a standard design. I have found quite a large difference between these thermostats and temperatures during operation. Individual thermostats vary, I have seen as much as 7 degrees difference between brand new thermostats.

The second question has to do with bleeding the system after antifreeze is removed for any reason. Unless the engine is bled thru the bleeder valve at the top of the engine,near the radiator hose but located on the head, it will take a few hours for all the air to find its way out of the block, this will cause some temperature variances for a period of time.

If you have a infrared non-contact thermometer, you could aim at the water hose, preferably the top hose, better the metal where the hose attaches to the engine, and get a pretty good idea of what temperature the engine is operating at, and how well the dash gauge is reporting.

Thanks for the egauges.com tip, I have bought from them before BUT they don's have gauges with the white pointers, only red pointers. All of my gauges have white pointers except the boost gauge and EGT gauge,(which I bought from them) these are red pointers, also trans temp gauges are only a few styles and they are thru lighting as opposed to edge lit and it is very noticeable when side by side.