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Old 08-01-2018, 10:18 AM   #1
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Normal temps/testing gauge?

OK, I'm puzzled and would love to hear from folks who know what they're doing.

Dash gauge says 180 after some minutes of idling. Using my Spaceman Spiff IR Non-Contact IR Thermometer I found:
  • 225-250 degrees for the exhaust manifold;
  • 175 for the top front of the engine just below the hose going to the radiator (where autos - and perhaps buses - have their thermostat);
  • 170 for the coolant overflow tank up near the firewall ;
  • 130 or so for parts of the engine; and
  • 77-88 degrees everywhere else (hoses, radiator, engine).
To the touch, the radiator felt only slightly warmer than ambient temperature.

The bus is on its way to the mechanic as soon as UPS delivers the new fan clutch, but I'm wondering what else to ask him to check. Any ideas? Of course, telling him "Please fix the cooling system" will probably do.

Thoughts?

By way of reference, this is part of an overtemp alarm problem I want to address before I drive my Cummins 5.9 bus across the country and over the Rockies. See earlier "How to test a fan clutch?" thread.
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Old 08-01-2018, 12:05 PM   #2
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Do you know what the rating of your thermostat is or should be?

Maybe someone with that engine does but after a short warmup, 180 doesn't sound too bad.
I do get the feeling that you are expecting this mechanic to do a great job and I hope he does. Not all mechanics and shops are capable and/or reputable.

My thinking is you are going tripping and will have a bus that isn't really tested before you go.
You should drive a fair bit to know it's working well before you head out and get stuck because of...any number of issues somone overlooked in haste.


John
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Old 08-02-2018, 12:52 AM   #3
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...My thinking is you are going tripping and will have a bus that isn't really tested before you go.

You should drive a fair bit to know it's working well before you head out and get stuck because of...any number of issues somone overlooked in haste.
Possibly so, John. Pray for us. Events have forced my hand - gotta be across the country by a certain date for the memorial service for my mother who passed away a couple of weeks ago, and to start a new job. I've had one mechanic go over the bus an another will fuss with the cooling system tomorrow. May God have mercy on us. Thanks for your concern, and given a choice I would certainly take another few months for shakedown.
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Old 08-02-2018, 06:17 AM   #4
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My most sincere condolences Dapple. Yours is a difficult decision and you can bet I will be praying for you brother.
Good luck today and keep us up to date as you can.
All the best wishes for a safe and uneventful journey,


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Old 08-02-2018, 06:40 AM   #5
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My condolences, stressful times for sure.

I'd bet all the money in my pocket that the clutch will solve your problem. Wait... I'm only wearing my underwear...

Assuming the new clutch does not solve the problem...

The thermostat is "usually" an easy item to get at and test (not positive of that in your case). Testing it is a matter of dropping it in a pan of water and heating it. When water reaches thermostat temp, it should open. If easy to access, I would have the mechanic test it - or just replace, they are not usually expensive.
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Old 08-02-2018, 02:04 PM   #6
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Mechanic confirmed fan clutch bad, replaced it. Engine runs cooler, but still gets up there (245 degrees) according to the gauge. According to the mechanic, over 240 and the top of the radiator explodes, so he suspects a bad sensor. I see about 20 degrees less on the engine near the thermostat using the IR thermometer, so I'll likely replace the sensor. Got the diagnostics computer dude looking at it tomorrow morning, too, as well as a new belt to put on. Yay!
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Old 08-02-2018, 02:07 PM   #7
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Quote:
Originally Posted by Dapplecreek View Post
Mechanic confirmed fan clutch bad, replaced it. Engine runs cooler, but still gets up there (245 degrees) according to the gauge. According to the mechanic, over 240 and the top of the radiator explodes, so he suspects a bad sensor. I see about 20 degrees less on the engine near the thermostat using the IR thermometer, so I'll likely replace the sensor. Got the diagnostics computer dude looking at it tomorrow morning, too, as well as a new belt to put on. Yay!
Gauges on buses are so sketchy!
Modern stuff runs a good bit hotter than older machines for sure. My Cat runs like a top but the scale on the gauge is really hard to read. It looks like I'm at 200-220 depending on speed and incline.
I like Chris' super-tech-ninja gauges. They work!
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Old 08-03-2018, 12:24 PM   #8
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Replaced the engine coolant temperature sensor (and the fan belt, just for good measure): same incorrect high readings.

Looks like I'm going to live with the false readings (and alarms, presumably). Probably will install a mechanical aftermarket temperature gauge so I know what is going on with the engine.

Thanks for your comments!

-Tim
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Old 08-03-2018, 12:52 PM   #9
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are you sure the thermostat is opening? the water pump is circulating? if you open the heater valves do the heater cores get hot without the booster pump on?


the idea that your radiator is MUCH cooler than your thermostat housing would indicate to me that possibly the stat isnt opening.. most of these newer engines run 190 Tstats from the factory.. when you go out and drive and it reads hot, then yopu pull over and let it idle, and hit the inlet and outlet of the radiator (tanks) with the gun do you get VASTLY different readings? lime inlet is 245 and outlet is 130? while the dash gauges are known to be inaccurate at times, the temp gun reading 20 degrees difference still puts your engine at 220-225.. which is way hotter than i like to see a diesel.. id expect the fan to be blazing and wicked hot air out of the radiator at that point...



just wondering if theres a circulation issue here somewhere..
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Old 08-03-2018, 03:13 PM   #10
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you are in virginia headed which way?

In topeka kansas if you end up needing roadside help...

highest temp of the radiator should be the metal just below upper radiator hose.The upper hose has the hottest engine water, flows away from there, does not really matter if cross flow radiator or down flow, hottest water should be just below the upper radiator hose. Take a reading there. The lowest temps should be where lower hose attaches to the engine. read there at the neck the hose attaches to. if the metal is not black, get a magic marker, or a bit of paint. reading from shiny aluminum surfaces, white, plastic, rubber and such will give you lower readings.
as a back up...might be able to find a thermometer you can put into the fins of the radiator and make contact with a cooling tube. might be a cheap cross check of gage.
hope this helps you.

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Old 08-03-2018, 03:46 PM   #11
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I would definitely change that thermostat before you head out Tim. Surprised they didn't do it yesterday. Or at least pick one up so you can do it on the fly if necessary.


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Old 08-03-2018, 05:24 PM   #12
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I would definitely change that thermostat before you head out Tim. Surprised they didn't do it yesterday. Or at least pick one up so you can do it on the fly if necessary.
Well, so far as the mechanic is concerned, the engine is nice and cool and it's a wiring harness or computer problem. I do have a thermostat with me, and plan on adding a mechanical temp gauge as soon as I can.

I was hesitant to change out the thermostat just because of the pain in the neck factor of losing all of the coolant and needing to replace it. Likely a bad call. Will keep you posted.
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Old 08-03-2018, 07:53 PM   #13
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thermostat change and loss of coolant

Seems to me you could catch the coolant in a five gallon bucket or two and not loose a bunch, I usually use a paint filter in the funnel when I pour it back in.

five gallon poured into one gallon one gallon poured into coolant system......

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Old 08-03-2018, 07:57 PM   #14
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cummins 5.9

That is on the top of the engine.... you should not loose a lot of coolant.

does the radiator have a drain? drain some off .. no need to dump all the coolant. - some engines have the thermostat in the lower hose - different story.

I'm putting a 5.9 in my bus, I needed to know this anyways.

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Old 08-04-2018, 07:05 AM   #15
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Quote:
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Seems to me you could catch the coolant in a five gallon bucket or two and not loose a bunch, I usually use a paint filter in the funnel when I pour it back in.

five gallon poured into one gallon one gallon poured into coolant system......

william
If you don't have a paint funnel, shop.towel in the funnel will.strain the coolant. Might be good idea to turn heater lines off before draining
To hold coolant in cores so system will fill to.max capacity. Pinch off with vise grips if necessary.
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Old 08-12-2018, 04:54 AM   #16
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I think I am missing something in this saga.

If I understand what is going on, after running the bus the factory gauge says one thing but an infrared thermometer says something different. The IR thermometer also indicates that hot water is going into the top of the radiator and much cooler water is coming out of the bottom of the radiator.

If an infrared thermometer indicates much lower temps than what the gauge says, unless the gauge is hooked to an overheat alarm/engine shut off, I would use a piece of tape and make a new scale reflecting what the IR thermometer says what the temps are. And then head out and not worry about it.

I would trust even a cheapy Harbor Freight IR thermometer more than I would trust a factory in dash gauge.

In all of the years I have trained drivers I have always told them the gauges are only really good to tell you what is normal. Once you determine what is normal the gauges can tell if something is too low or too high. But betting that the factory gauges are telling you the truth is a bad bet no one should take.

When I started in the bus business over 40 years ago almost everything had 160* thermostats and we would get excited if we saw 180* on anything. On my 1995 Suburban it has a 195* thermostat and the fan clutch doesn't kick on until almost 240*. You can only imagine how those numbers makes me nervous climbing a grade will pulling our travel trailer in the summer.

Just find out what is normal on the gauge and you should be fine.
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