Author Topic: Low temperature readout on CAT C7 gauge  (Read 20142 times)

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Offline LyleFikse

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Low temperature readout on CAT C7 gauge
« on: October 14, 2016, 04:41:53 AM »
My C7 Cat is giving me a lower than normal temperature reading.  It traditionally has read just shy of ¾ when at operating temperature.  About 2 months ago I noticed it reading ½.  At that time I had the engine serviced, had new thermostats installed, as well as a switch over to extended life coolant at the same time.  When returning home from servicing (100 mile drive), no change.  The temperature reading was still lower at about ½ on the gauge.   Yesterday on a travel day the reading was under 1/2, closer to 1/3.  I don’t think I have an engine problem as everything seems normal except the reading.   No change in fuel economy or performance.  What I suspect is an incorrect readout of the temperature.  Where should I start?  Bad sensor?  Bad gauge?   
Lyle Fikse
2007 Damon Tuscany  Cat C-7
2013 Lincoln MKS

Offline antiqueclockservice

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Re: Low temperature readout on CAT C7 gauge
« Reply #1 on: October 14, 2016, 05:07:30 AM »
Hi Lyle,

I have a CAT C7 in a Freightliner chassied Alfa.  MY gauge has always read as yours does now.  Runs about 1/3 of the way up.  When it gets to ¾ I get an overheat warning.   Seems you had a restriction in the coolant flow which was corrected with new thermostats or regulators as CAT calls them.  Sounds like the engine is running normally..
Best,
Phil

Offline Brett Wolfe

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Re: Low temperature readout on CAT C7 gauge
« Reply #2 on: October 14, 2016, 05:54:26 AM »
Lyle,

Do you have any secondary engine monitor on your coach:  Silverleaf? ScanGauge D?

If so, what does it read?

First thing I would do is insure that the on-engine coolant temp sensor (check with your chassis maker for location) is clean and tight.

If any other gauges are reading "off", that would point to a dash issue-- perhaps loose or poor ground.

Offline ziggyh

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Re: Low temperature readout on CAT C7 gauge
« Reply #3 on: October 14, 2016, 05:41:03 PM »
I would check the operating temperature of the engine with a thermometer, like a contact less one, and add about 5 degrees to your reading because you are measuring surface temperature,  also double check the coolant level, coolant sensors will read low if they are sitting in air.  That's one of the reasons why some gas engines are using cylinder head temp sensors instead.
ZiggyH

2007 Revolution LE
C9

Offline LyleFikse

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Re: Low temperature readout on CAT C7 gauge
« Reply #4 on: October 16, 2016, 05:39:45 AM »
Brett,
I did check the Freightliner digital readout yesterday during travel.  After traveling for several hours it read 156-158.  This seems low to me.  I still think it is not a correct reading as there is no change in performance or fuel economy.  We have owned this coach for 6 years and it has always read about 3/4 on the gauge until the last 3 months.  Could both the gauge and digital dash readout be hooked to the same sensor?  If this reading is correct and the engine is running cool, will I damage the engine if I continue to travel without a repair?  We are about 1/2 way on a 2000 mile trip to Southern California, where we winter.  I will have lots of time to work on it when we get there.  We only travel about 200 miles a day.
Lyle Fikse
2007 Damon Tuscany  Cat C-7
2013 Lincoln MKS

Offline Brett Wolfe

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Re: Low temperature readout on CAT C7 gauge
« Reply #5 on: October 16, 2016, 06:27:16 AM »
Lyle,

Yes, running a diesel under 160 degrees will do damage.

Have you cleaned the senders on the engine?  Any change?

If in doubt, replace the thermostat(s) called "regulators" by Caterpillar and the thermostat gasket.  Not a difficult job. And a lot less expensive than damaging the engine.

Were it mine and I did not have some other means of verifying operating temperature, in order, those two things are what I would do.

Offline WILDEBILL308

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Re: Low temperature readout on CAT C7 gauge
« Reply #6 on: October 16, 2016, 09:20:36 AM »
Brett,
I did check the Freightliner digital readout yesterday during travel.  After traveling for several hours it read 156-158.  This seems low to me.  I still think it is not a correct reading as there is no change in performance or fuel economy.  We have owned this coach for 6 years and it has always read about 3/4 on the gauge until the last 3 months.  Could both the gauge and digital dash readout be hooked to the same sensor?  If this reading is correct and the engine is running cool, will I damage the engine if I continue to travel without a repair?  We are about 1/2 way on a 2000 mile trip to Southern California, where we winter.  I will have lots of time to work on it when we get there.  We only travel about 200 miles a day.
Yes long term running the engine under temp will cause damage but I think you can make it to your  winter spot. It does sound like bad thermostat not closing.
Bill
2003 Bounder 38N,300 HP 5.9 Cummins
Allison 3000MH Trans.Towing 2014 Honda CRV. Home base Fort Worth, Texas
A man who carries a cat by the tail learns something he can learn in no other way.
-Mark Twain-

Offline LyleFikse

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Re: Low temperature readout on CAT C7 gauge
« Reply #7 on: October 16, 2016, 02:39:43 PM »
Please explain what you mean by clean sensor.  Can I pull it without losing a ton of coolant?  I have never pulled or replaced a sensor before.  How dirty can I expect it to be?  What do you clean it with?
Lyle Fikse
2007 Damon Tuscany  Cat C-7
2013 Lincoln MKS

Offline ziggyh

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Re: Low temperature readout on CAT C7 gauge
« Reply #8 on: October 16, 2016, 06:18:31 PM »
Lyle, when the engine is cold and the expansion tank cap is on, and if there is a small hose connected at the base of the filler tube pinch it off and you can remove the sensor with minimal coolant loss if your quick at it.   Coolant sensors are usually located toward the upper end of the engine. On some c7 they are around the top end of the crankcase breather just under the intake manifold.

As far as both the dash gauge and digital readout sharing the same sensor, that is entirely possible, my c9 temp sensor data is sent from the engine ECU over the j1939 network connection to the digital readout and from their to the instrument cluster.  Yours may or may not function the same way.  You would need to check with the chassis builder or the motorhome builder or wirring diagram.

When I read you initial post, it sounds like your problems started after or shortly after the coolant  was changed and the temperature regulators/ thermostats.  As posted previously, your problem could be a stuck open regulator, sensor or wirring connections ect.

Is the engine is actually running at the temperature your read outs indicate?Verify this with a thermometer, if it is low that tells me the gauges are reading correct and it points to the coolant regulators as a likely cause.

Should you have to replace the regulators, (you may have more than one in the housing) you should only need to drain off a minimal amount of coolant, as Brett indicated it is a fairly simple procedure.  There may also be a small checkvalve in the housing that is replaceable as well.

ZiggyH

2007 Revolution LE
C9

Offline Brett Wolfe

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Re: Low temperature readout on CAT C7 gauge
« Reply #9 on: October 16, 2016, 07:09:48 PM »
Lyle,

My "clean sensor" referred to the contact between the on engine sensor and the wire that goes to the dash. 

Sorry I did not make that clearer.  Most temperature sensors work on resistance.  Dirty, loose, wet or corroded connections can change the signal the dash receives.

No, I would not remove the sensor.  You can get from Freightliner the ohm readings for the dash temperature gauge sensor.  So, it can be checked in place.

But before going through all that, I would replace the thermostats.  Caterpillar recommends replacing them every three years.  There are a metal to metal wearing component.

Offline LyleFikse

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Re: Low temperature readout on CAT C7 gauge
« Reply #10 on: October 17, 2016, 05:06:28 AM »
I did replace the thermostats only a month and 1/2 ago.  This problem started when the old thermostats were in and has progressively gotten worse since the change. I saw no immediate change with the new thermostats.   I had the Cat dealer in Sioux Falls change the coolant at the same time since they were draining some of it anyway.  I don't think it is the thermostats.
Lyle Fikse
2007 Damon Tuscany  Cat C-7
2013 Lincoln MKS

Offline antiqueclockservice

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Re: Low temperature readout on CAT C7 gauge
« Reply #11 on: October 17, 2016, 06:31:34 AM »
Hi,

I still think the engine is running normally and temp is being controlled by the regulators.  I think the old regulators were stuck and the engine was running too hot.  ¾ of the way over on the gauge sounds too hot.  That said, until an actual temp reading is obtained for the water temp in the cylinder head or the radiator via IR sensor this is somewhat speculative.  When I was working for Ford engineering, every once in a while we would get an air bubble in the motor of one of the prototype vehicles.  When that did occur, the temp gauge would barely move off the cold peg...

best,
Phil
Best,
Phil

Offline wclogger1

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Re: Low temperature readout on CAT C7 gauge
« Reply #12 on: October 17, 2016, 07:56:47 AM »
And at the end of the day you still have to verify temperature at the block. Use a magnetic type analogue that sticks to the block. Or buy a handheld digital infrared thermometer from Harbour Freight and shoot the block in a couple of spots after running it fairly hard. You have to isolate whether you are chasing an engine problem or a gauge problem. Until you put that to bed you will chase your tail for days.
Bob

Offline LyleFikse

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Re: Low temperature readout on CAT C7 gauge
« Reply #13 on: October 20, 2016, 07:49:52 PM »
Took apart the electric connection at the sensor and hit it with electrical cleaner.  It did not look dirty, so I was not surprised today when we traveled with no change. Still cool on the gauge.   I'll get a infrared gun and check actual temp of block and the area around the thermostats next.  More updates to follow.  Did give me a good opportunity to lube the PAC Brake while I was in there.
Lyle Fikse
2007 Damon Tuscany  Cat C-7
2013 Lincoln MKS

Offline Brett Wolfe

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Re: Low temperature readout on CAT C7 gauge
« Reply #14 on: October 21, 2016, 05:45:55 AM »
  Did give me a good opportunity to lube the PAC Brake while I was in there.


Good idea.  For those not familiar with lubing the PacBrake: http://pacbrake.com/supplemental-brakes/prxb-exhaust-brakes/maintenance/

Offline Mutinyguy

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Re: Low temperature readout on CAT C7 gauge
« Reply #15 on: October 21, 2016, 11:40:11 AM »
  Did give me a good opportunity to lube the PAC Brake while I was in there.


Good idea.  For those not familiar with lubing the PacBrake: http://pacbrake.com/supplemental-brakes/prxb-exhaust-brakes/maintenance/


Where is the PacBrake located?

Offline Brett Wolfe

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Re: Low temperature readout on CAT C7 gauge
« Reply #16 on: October 21, 2016, 02:28:21 PM »
The PacBrake is usually bolted to the exhaust side of the turbo. It then connects to the exhaust pipe going to the muffler.

Probably easiest to see/reach from the bedroom or closet (i.e. from above). 

And, if your Cat 3116 or 3126 was built before 1/2003, you have a grease zerk on the fan hub that can also just be reached from above.

Come to a Diesel RV Club Rally and we go over this kind of stuff (easy to do, but if neglected can cost big bucks).  I also go over it (though MUCH faster) at the FMCA Convention Caterpillar Engine Maintenance Seminar. 

Brett

Offline Mutinyguy

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Re: Low temperature readout on CAT C7 gauge
« Reply #17 on: October 22, 2016, 03:33:01 PM »
Thanks Brett...I have a Cummins 8.9 ISL....

Offline Brett Wolfe

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Re: Low temperature readout on CAT C7 gauge
« Reply #18 on: October 22, 2016, 05:16:57 PM »
The Cummins ISL is the rare engine that could be ordered with either an exhaust brake (on/off) or an engine compression brake (much better and usually on low, off, on high).

So, do not know which you have.

Offline Mutinyguy

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Re: Low temperature readout on CAT C7 gauge
« Reply #19 on: October 25, 2016, 05:45:37 AM »
The Cummins ISL is the rare engine that could be ordered with either an exhaust brake (on/off) or an engine compression brake (much better and usually on low, off, on high).

So, do not know which you have.

I have an engine compression brake....low-off-high-like you mentioned...it works great!!

Offline Brett Wolfe

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Re: Low temperature readout on CAT C7 gauge
« Reply #20 on: October 25, 2016, 06:08:43 AM »
The engine compression brake (aka Jake Brake) is internal to the engine (located on top of valve train).  So, no exhaust brake to lube!

Offline LyleFikse

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Re: Low temperature readout on CAT C7 gauge
« Reply #21 on: October 28, 2016, 02:25:54 PM »
After traveling today I tested the temperature of the engine with a handheld digital infrared thermometer right on the housing that holds the thermostats.  183 degrees.  My gauge continues to show cooler temperatures.  Today it showed 145 degrees.  Now I know the gauge is wrong and the engine is operating at the correct temperature.  Could this be a grounding problem or do I new a new sensor?
Lyle Fikse
2007 Damon Tuscany  Cat C-7
2013 Lincoln MKS

Offline ziggyh

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Re: Low temperature readout on CAT C7 gauge
« Reply #22 on: October 28, 2016, 06:40:23 PM »
Lyle, next step is to determine where the reading is coming from, the data can come from the ECU or the engine has a dedicated sensor for the gauges and One for the ECU.

I suspect your ECU sends the temperature data to you gauges over a data buss.  With out a wiring digram as a reference the easiest way in my mind to determine where the data comes from is to unplug the coolant sensor on the engine harness going to the ECU and turn the key on, if the data comes from that sensor your display will blank out or the reading goes to one extream, probably very low.   The bad part of doing this it will set a DTC.  The sensor is usually just under the intake or near the temperature regulator housing, they are also usually a 2wire sensor that changes resistance based on temperature, I did have chart that had the ohm and temperature readings for a c9,  but I'm in the middle of a massive clean up I couldn't find it.  Inspect the connector for any corrosion or signs of coolant on the terminals.  On some of the c7 c9 engines the intake air temperature sensor and coolant sensor were the same part number, in that case you could switch them to see if your readings come back to normal.  Use your engine serial number and look up the sensor part numbers on a cat parts web page to make sure. The sensors usually use an o-ring seal.

If the gauges use a dedicated sensor, after locating the sensor check the connections, after that you would need to try and get a resistance temperature chart if a restive sensor was used and or wiring digram.

Because you have a temperature gauge and a digital display I strongly suspect the data comes from the ECU.
ZiggyH

2007 Revolution LE
C9

Offline Brett Wolfe

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Re: Low temperature readout on CAT C7 gauge
« Reply #23 on: October 28, 2016, 06:55:02 PM »
Your chassis maker can tell you exactly where the engine temperature signal comes from.  May be the engine ECU, or my supposition is from a temperature sensor installed by the chassis maker.

Let us now what you find.

Offline LyleFikse

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Re: Low temperature readout on CAT C7 gauge
« Reply #24 on: October 28, 2016, 07:47:37 PM »
Will do Brett.  Now that I know the engine is operating at the right temperature I will deal with this over the winter while we are in Desert Hot Springs, Calif  I will update, but it may take a few months. 
Lyle Fikse
2007 Damon Tuscany  Cat C-7
2013 Lincoln MKS