Medium and Heavy Trucks

Have Truck Repair Questions? Ask an Expert

Ask an Expert,
Get an Answer ASAP!

Medium and Heavy Trucks
This answer was rated:

I have a 2006 Freightliner with cat c7 engine. just start

experiencing an unusual behavior. In...
I have a 2006 Freightliner with cat c7 engine. just start experiencing an unusual behavior. In mornings when ignition is switched on all clocks go through the usual pre-check movements. When engine is started it revs up and down on its own and temp guage goes dead.
Up and down rev goes away when engine warms up but temp guage does not move. Also radiator fan will not come in.
Show More
Show Less
Ask Your Own Medium and Heavy Trucks Question
Answered in 27 minutes by:
8/17/2017
Pete
Pete, Automotive Mechanic
Category: Medium and Heavy Trucks
Satisfied Customers: 29,610
Experience: Performed various automotive repairs on several light duty and medium duty vehicles over 15 years of service.
Verified

Hi my name is ***** ***** I will be happy to assist with this today.In some cases I may need more info to assist better.I apologize for any delay.

From what you have described here with the engine revving up and down on its own and the temp gauge not registering on start up or when running this sounds like a fault with the engine coolant temp sensor itself.If the temp sensor is not sending a signal or is sending a false signal the computer will try and compensate or will try and run with the way the gauge reads and can cause the engine to rev up and down like this.

I would have the engine coolant temp sensor tested to see if it is faulty and if found to be at fault it will need replaced to resolve this issue here.

If more help is needed, use the reply tab to continue our conversation. If no further assistance is needed, kindly rate my service,your 5 star rating is appreciated ( should be a link to click on here or above).You can rate at any time and we can continue to work on your question as this will not close out your question.Keep in mind in some cases it can be difficult to fully diagnose or help repair your vehicle without seeing it and I work on delivering the best possible answer from what I see to work with.

Thanks Pete

Ask Your Own Medium and Heavy Trucks Question
Customer reply replied 3 months ago
Thanks...will check to see if that's the issue.

Your welcome

Let me know if you need anything else and feel free to rate my help here or above ( should be a link to click on ) as this is how I receive credit for my time,this can be done at any time and you can still come back here and reply if needed.Your 5 star rating is appreciated

Thanks Pete

Ask Your Own Medium and Heavy Trucks Question
Customer reply replied 3 months ago
Pete...checked engine coolant temp sensor connected at coolant reservoir and its ok. Also switched sensor from and similar truck and the problem remains. Would appreciate any other suggestions to try and remedy this issue.Thanks.

O.k.,if the sensor is o.k. and the temp is reading cold all of the time when running and with this running issue and the cooling fan not coming on this indicates that either the wiring leading from this sensor the computer has damage at some point and the wiring needs traced and inspected for any issues or there is a fault with the engine computer itself with it needing replaced.I have seen both cause this type of fault here.

The wiring needs checked first for any issues and if found to be o.k. it can be the engine computer that is not seeing the coolant temp signal properly causing this fault needing replaced.

Let me know if you need anything else and feel free to rate my help here or above ( should be a link to click on ) as this is how I receive credit for my time,this can be done at any time and you can still come back here and reply if needed.Your 5 star rating is appreciated

Thanks Pete

Pete
Pete, Automotive Mechanic
Category: Medium and Heavy Trucks
Satisfied Customers: 29,610
Experience: Performed various automotive repairs on several light duty and medium duty vehicles over 15 years of service.
Verified
Pete and 87 other Medium and Heavy Trucks Specialists are ready to help you
Ask your own question now
Customer reply replied 3 months ago
Hi Pete....sorry for the delay in updating you. I'm happy to report that the problem has been resolved and that your first suggestion of the coolant temp sensor was in fact the problem. We've replaced sensor and all is well with our unit again.
If it was possible I would give you a 6 star rating ******. Thanks

That is great to hear.If there is anything else I can help with here on this let me know.

Thanks Pete

Ask Your Own Medium and Heavy Trucks Question
Ask Pete Your Own Question
Pete
Pete
Pete, Automotive Mechanic
Category: Medium and Heavy Trucks
Satisfied Customers: 29,610
29,610 Satisfied Customers
Experience: Performed various automotive repairs on several light duty and medium duty vehicles over 15 years of service.

Pete is online now

A new question is answered every 9 seconds

How JustAnswer works:

  • Ask an ExpertExperts are full of valuable knowledge and are ready to help with any question. Credentials confirmed by a Fortune 500 verification firm.
  • Get a Professional AnswerVia email, text message, or notification as you wait on our site. Ask follow up questions if you need to.
  • 100% Satisfaction GuaranteeRate the answer you receive.

JustAnswer in the News:

Ask-a-doc Web sites: If you've got a quick question, you can try to get an answer from sites that say they have various specialists on hand to give quick answers... Justanswer.com.
JustAnswer.com...has seen a spike since October in legal questions from readers about layoffs, unemployment and severance.
Web sites like justanswer.com/legal
...leave nothing to chance.
Traffic on JustAnswer rose 14 percent...and had nearly 400,000 page views in 30 days...inquiries related to stress, high blood pressure, drinking and heart pain jumped 33 percent.
Tory Johnson, GMA Workplace Contributor, discusses work-from-home jobs, such as JustAnswer in which verified Experts answer people’s questions.
I will tell you that...the things you have to go through to be an Expert are quite rigorous.

What Customers are Saying:

Wonderful service, prompt, efficient, and accurate. Couldn't have asked for more. I cannot thank you enough for your help.

Mary C.Freshfield, Liverpool, UK

This expert is wonderful. They truly know what they are talking about, and they actually care about you. They really helped put my nerves at ease. Thank you so much!!!!

AlexLos Angeles, CA

Thank you for all your help. It is nice to know that this service is here for people like myself, who need answers fast and are not sure who to consult.

GPHesperia, CA

I couldn't be more satisfied! This is the site I will always come to when I need a second opinion.

JustinKernersville, NC

Just let me say that this encounter has been entirely professional and most helpful. I liked that I could ask additional questions and get answered in a very short turn around.

EstherWoodstock, NY

Thank you so much for taking your time and knowledge to support my concerns. Not only did you answer my questions, you even took it a step further with replying with more pertinent information I needed to know.

RobinElkton, Maryland

He answered my question promptly and gave me accurate, detailed information. If all of your experts are half as good, you have a great thing going here.

DianeDallas, TX

< Previous | Next >

Meet the Experts:

Daniel Wilson

Daniel Wilson

2,139 satisfied customers

Owner at DJ Wilson

Cat Man

Cat Man

Cat Engine Expert

4,151 satisfied customers

I am ASE Master Truck Certified.

Wayne

Wayne

Journeyman

2,495 satisfied customers

worked on, Gmc, Macks, Freight liner,Mercedes Benz,,Ford, sterling

Jeremy

Jeremy

Certified Truck/Bus Technician

1,974 satisfied customers

ASE Med/HD Truck Technician, NATEF Diesel Engines and Electrical/Electronics Technician, EPA 608/609 HVAC Certified, Steering/Suspension and ABS/Brakes Technician

cumminsdr

cumminsdr

Mechanic

1,195 satisfied customers

All types of Cummins applications

Curtis B.

Curtis B.

Technician

770 satisfied customers

Technician turned service manager on multiple lines of trucks and engines, used in industry.

dieseldan55

dieseldan55

Contractor

74 satisfied customers

Road Service mechanic for Volvo Construction.

< Previous | Next >

Related Medium and Heavy Trucks Questions
I have a 91 freightliner with a Detroit 60 series. it
i have a 91 freightliner with a Detroit 60 series. it recently had been abused and the solenoid was ruined and in turn ruined the batteries. I have replaced the starter and batteries. Now when i start… read more
Daniel Wilson
Daniel Wilson
Auto Mechanics 1&2/diesel mech
2,139 satisfied customers
I have a c10 with seriel number #3CS28501. I am having
I have a c10 with seriel number #3CS28501. I am having problems with the fault code 4-11. I have replace the injector and the engine harness and the problem still continues. Can you help me out.… read more
Cat Man
Cat Man
Cat Engine Expert
Vocational, Technical or Trade Scho
4,151 satisfied customers
Have a 2005 in line Magna 230 it will ignite heat up to
Have a 2005 in line Magna 230 it will ignite heat up to temperature and only once in a while.. Will it reignite until it cools way back down in material and oil temp… read more
Daniel Wilson
Daniel Wilson
Auto Mechanics 1&2/diesel mech
2,139 satisfied customers
I have an '05 Winnebago Journey 39k with Freightliner
I have an '05 Winnebago Journey 39k with Freightliner chassis and 350hp Cat C7. It is blowing coolant out the reservoir tank overflow while running normal temps. Over time, once coolant level goes low… read more
Cat Man
Cat Man
Cat Engine Expert
Vocational, Technical or Trade Scho
4,151 satisfied customers
I have volvo truck 4V4Nc9RJ41N311503, model and serial no:
i have volvo truck 4V4Nc9RJ41N311503, model and serial no : DDS60 430/ 500HP … read more
Daniel Wilson
Daniel Wilson
Auto Mechanics 1&2/diesel mech
2,139 satisfied customers
2009 Freightliner Columbia 120, keeps regening and lights
2009 Freightliner Columbia 120, keeps regening and lights still flashing and spraying deisel in the exhaust.… read more
Daniel Wilson
Daniel Wilson
Auto Mechanics 1&2/diesel mech
2,139 satisfied customers
I have code 3719 for high soot level and my doser wont dump
i have code 3719 for high soot level and my doser wont dump fuel during regen … read more
Daniel Wilson
Daniel Wilson
Auto Mechanics 1&2/diesel mech
2,139 satisfied customers
I have a 2008 KW W900L with a Cummins that won't crank over.
I have a 2008 KW W900L with a Cummins that won't crank over. We replaced the starter in April for the same problem, and it's worked fine till now. Starter solenoid has battery voltage to it. 12.4 V. W… read more
Daniel Wilson
Daniel Wilson
Auto Mechanics 1&2/diesel mech
2,139 satisfied customers
I have cat 299c ser # CAT0299CCJSP0L554 that has developed a
I have cat 299c ser # CAT0299CCJSP0L554 that has developed a steering problem. When started the machine seems to be fine but it soon starts jerking to the sides. This is followed by the exclamation ma… read more
Daniel Wilson
Daniel Wilson
Auto Mechanics 1&2/diesel mech
2,139 satisfied customers
I am looking for the SFC of a 3412C, 500kW marine generator
Hello I am looking for the SFC of a 3412C, 500kW marine generator set … read more
Cat Man
Cat Man
Cat Engine Expert
Vocational, Technical or Trade Scho
4,151 satisfied customers
Lever at governor suddenly will not rotate .engin only will
Lever at governor suddenly will not rotate .engin only will idle cannot increase engin speed.what could be broken? … read more
catmastertech
catmastertech
Field service technician
Vocational, Technical or Trade Scho
1,287 satisfied customers
1999 Sterling L7500 Vin: 2fwkajcb2yag07836 Model: Y101042
1999 Sterling L7500 Vin: 2fwkajcb2yag07836 Model: Y101042 The issue is warning engine light will come on after a while. Truck does not seem to run poorly. Also if let sit light will flash repeatedly v… read more
Wayne
Wayne
Journeyman
Vocational, Technical or Trade Scho
2,495 satisfied customers
I need to no what the rods and mains torque on as well as
I need to no what the rods and mains torque on as well as the head bolts and cam caps … read more
Daniel Wilson
Daniel Wilson
Auto Mechanics 1&2/diesel mech
2,139 satisfied customers
After my fl cascadia 2012 finish doing the parking regen
After my fl cascadia 2012 finish doing the parking regen then come two code EEC 061 SPN003719 DPF SOOT 31 AND EEC 061 SPN520249 SCR IN TEMP HI 04. WHAT IS THE PROBLEM STILL SHOW ME THE REGEN LIGHT AND… read more
roy
roy
Associate Degree
3 satisfied customers
I have a 2000 Ford Van E-350 with a 200AV Altec 35' boom.
I have a 2000 Ford Van E-350 with a 200AV Altec 35' boom. The truck is always outside. When it gets cold I warm up the truck and the system in the back and when I use my turntable for the first time i… read more
Daniel Wilson
Daniel Wilson
Auto Mechanics 1&2/diesel mech
2,139 satisfied customers
Why will the pot not come out of gear when hot. Model number
Model number is ***** not with tractor to see serial no. … read more
Curtis B.
Curtis B.
Technician
Associate Degree
770 satisfied customers
Wayne, Wonder if you can supply me labor time standards to
Wayne, Wonder if you can supply me labor time standards to perform a 250, 500, 750 & 1,000 hour service 972H, D8R, 349E, D6R, and 777D machines? … read more
Jeremy
Jeremy
Certified Truck/Bus Technician
Vocational, Technical or Trade School
1,974 satisfied customers
My 2010 international prostar with maxxforce engine has the
Hello, my 2010 international prostar with maxxforce engine has the engine warning light and buzzer on and I'm trying to reset it. It had a coolant leak yesterday and we replaced the leaking hose and a… read more
Wayne
Wayne
Journeyman
Vocational, Technical or Trade Scho
2,495 satisfied customers
Disclaimer: Information in questions, answers, and other posts on this site ("Posts") comes from individual users, not JustAnswer; JustAnswer is not responsible for Posts. Posts are for general information, are not intended to substitute for informed professional advice (medical, legal, veterinary, financial, etc.), or to establish a professional-client relationship. The site and services are provided "as is" with no warranty or representations by JustAnswer regarding the qualifications of Experts. To see what credentials have been verified by a third-party service, please click on the "Verified" symbol in some Experts' profiles. JustAnswer is not intended or designed for EMERGENCY questions which should be directed immediately by telephone or in-person to qualified professionals.

Disclaimer: Information in questions, answers, and other posts on this site ("Posts") comes from individual users, not JustAnswer; JustAnswer is not responsible for Posts. Posts are for general information, are not intended to substitute for informed professional advice (medical, legal, veterinary, financial, etc.), or to establish a professional-client relationship. The site and services are provided "as is" with no warranty or representations by JustAnswer regarding the qualifications of Experts. To see what credentials have been verified by a third-party service, please click on the "Verified" symbol in some Experts' profiles. JustAnswer is not intended or designed for EMERGENCY questions which should be directed immediately by telephone or in-person to qualified professionals.

Show MoreShow Less

Ask Your Question

x