Heat build-up in engine runbox

[Richard Dangel]

Hello  All,
I am new to the forum although I have been browsing this site for 6 years.  I seem to be having a heat build-up problem in my engine run box. I have a 2009 Marquis, Lapis IV with a Cat C-15 purchased 2 years ago from Beaver Coach Sales.  I have had to replace the Big Boy and the smaller solenoid twice each along with the run circuit board (EXPENSIVE). I have to keep the cover off the runbox or the heat builds and I go into downrate. Gerald mentioned on another post that the voltage going through the Big Boy drops after it pulls in to reduce heat. How do you check that it is really dropping? I am considering punching a couple of holes in the runbox and installing a small 12 volt fan and a screened vent. Any and all help, thoughts and consideration would be greatly appreciated.

[Steve Huber Co-Admin]

Richard,
There should be approximately 4 VDC on 1 of the 2 small terminals of the Big Boy solenoid after it has been engaged for a minute or so. Alternately you can check the voltage at the "Solenoid" pin of the BIRD controller since that is the source.
I highly doubt that the Big Boy is the source of your heat issue however. I don't have a C15 so not sure of the layout but if the muffler and exhaust run under the run box they would be my first suspects.  An IR temp probe might help you locate the source of the heat.
Steve

[Richard Dangel]

Thank-you for the prompt reply. I hadn't thought about using a heat gun (sensor). will definately look into that. Muffler and large burn box (?) are directly under the box. Should I pursue the fan and vent idea?

[Keith Moffett]

Richard
First, welcome!
Next if your engine compartment is like ours the amount of dirt would make me seal the run box up tight.
Last;
The engineer at Monaco who worked on the C15 is Scott at Source Engineering in Venetta Ore.  (There is a company of similar name in Seattle and google takes you there so be sure its Oregon. )
Jim and Scott are partners and may provide some help or insight.

[Mike Shumack]

If your Coach is going into a "derate" condition, there should be a code stored. Have you checked for codes? Does the Check Engine light come on when this happens?

[Richard Dangel]

Kieth, thanks for the info. I will try to contact Scott on Monday to pick his brain.

[Richard Dangel]

Mike, I have had codes and had them all checked out by Cat. Reset and currently have no codes. Definitely had all my warning indicators come alive, very disconcerting when negotiating in the mountains. My concern right now is how to keep things alive in the runbox. I did quite a bit of travel with the cover off and did not get any alarms or indicators.  Thanks. I'll try to post any efforts I do to alleviate my problems. Will be really nice to be able to post an "All Fixed".

[Mike Shumack]

How did you determine that the problem is due to heat in the Run box?

Why/how can a faulty "Run Circuit" board cause an engine derate? I see circuitry that could prevent the engine from cranking (neutral safety switch and starter relay) but I don't see anything obvious that would cause an engine derate. Maybe the wiring diagram I'm looking at is missing some pages or I'm just not seeing something.

[Steve Huber Co-Admin]

Richard,
Mike makes a good point. To follow up, do you know if the "high temperature" condition occurs only when traveling in the mtns or cimbing or does it also occur when running on the flats? Also what temp does your engine normally run at and what does it reach when climbing long grades? Some of our C15 drivers may be able to give you a comparison.
Steve

[Richard Dangel]

Engine has only gone into derate about 6 times.   Always on grades using lots of power. Opening the runbox and letting everything in there cool down has allowed me to proceeed with 2 exceptions. Once coming into Las Vegas at 2 mph and once pushing a big wrecker in Tennessee. I  may be all wrong about my heat problem and losing my solenoids in the runbox but I need to do something to keep me from worrying every time I leave the campground. I previously had a 2003 Marquis with a C-12 and had no engine issues. 85,000 miles on this one and wish I had my old C-12 back. I think it had more power too. The pollution control solution on the C-15 has been a costly headache and Cat hasn't said anything to make me think that  wont have more problems in the future. I know I may be rambling here but I am experiencing extreme frustration. Thank you all for your suggestions and listening to my rants.

[Richard Dangel]

Always watch the heat guage on uphills and never experience much of a raise in engine or transmission temps.

[Dave Atherton]

Richard, we are talking all around the block on your heating problem, first of all what is your Cat C-15
Serial number. Second did you have motorhome at a Caterpillar service shop and if so could you give
me any code that pertained to your heating and derate issue. I should be able to assist you with your problem. Dave Atherton Retired Cat Mechanic

[Fred Brooks]

   Hey Dave, is there a possibility of a fuel starvation issue and is there a code for that?

[Eric Maclean]

Fred
I was thinking more on the lines of DPF over heating on hills triggering a code and consentrating heat below / behind the run box
If Dave gets the codes it should shed some light on the derate
Eric

[Dave Atherton]

Fred, Eric, until I can get more information with Engine s/n number and ET codes we are only guessing.
I will say, the Caterpillar C-15 is a very good engine with very good history. Getting mixed signals
about what is really going but problem is within the engine itself and not within the engine compartment. Dave Atherton Retired Cat Mechanic