Engine runs OK then hot

[Jerry Sanders]

Greetings to all of the Beaver guru's.  We have just returned from a 7,900 trip around the U.S. in our new to us 2000 Marquis.  The trip went well until we holed a transmission cooling hose.  One day in the shop for repair and we were off again.  At about 7,000 miles the surge tank sprang a leak and we lost a lot of coolant but an epoxy patch and some emergency tape fixed the leak and we had the coolant drained and ELC filled at a Caterpillar dealer in Elko Nevada.  All should have been good, right?  Not quite.  The coach runs great on the flat and slight grades but the temp hits 215 on any heavy grade and we have to stop to cool down before moving on.  Flat ground the temps run 188-192.  The coach is 14 years old and we have no information about how it was serviced. I checked the fan operation during the high temps and it is running.  I am concerned that the radiator may be plugged with scale. Does anyone have any experience with attempting to flush or clean a plugged radiator?

Jerry

[Matthew Harger]

Hi Jerry

I'm just over the hill from you in Oakley.

Took our coach to the Lodi RV Center in January for service and one thing I had them check was the radiator due to the same overheating issues you are experiencing.

They did their tests and found our radiator was 60% blocked up....apparently the previously owners did not believe in regular flushing or extended life coolants.

Anyways, they tried to salvage it but I wasn't so lucky.  Needed a new radiator put in and it was a pretty penny.  Anyways, have taken a several trips now and it doesn't get over 185.  On a steep climb last week up to Lake Almanor we reached 205 max....I'm happy with the results.

Hopefully your previous owners took better care of the radiator and yours is still salvageable.

[Edward Buker]

Jerry,

I am not sure depending on the grade, outside temp, and the load if 215F is actually out of range by much. Try when you see the temp climbing to drop a gear and run with RPMs up near to 2000 and see if you get the same results. The fan is driven faster and the coolant circulation is better and the engine should pull more air and run cooler at higher RPM. Also be sure that the radiator is clean on the outside. From the side of the coach you are seeing the intercooler first with the radiator behind that. Sometimes debris can get in between.

I am not saying that a flush and ELC coolant wouldn't be a good thing at some point just that you might be O.K. with a little modification to your climbing procedure.

Later Ed

[Terry Melot]

Hi Jerry, Lee and I were parked next to you and Nancy in Indio, last Jan.  Our 2002 Marquis also ran hot on it's first trip. Only on a steep hill at 100'F in the Cal mountains. At 230, the engine cut back in horsepower and the coach slowed to 45 mph.  Read on this forum about spraying some soap like Simple Green into the radiator (air side).  Let set a few minutes and then spray out with a garden hose.  I did this when we got to Oregon.  On the hot return thru Cal mountains it was better but still ran 210 - 215 up long grades.  But never hit the 230 and lost power.
Also, the first time I was a gallon or two low on coolant.  Might double check the coolant level.  Good luck with it.

[Jerry Sanders]

Matt, I'm sorry to hear about the clean and flush being unsuccessful.  Ed's suggestion on downshifting was the one thing that got us as far as we did.  We ran all steep grades in 5th gear and that did help some but the heat built rapidly and then once over the top it dropped like a rock.
Terry, thanks for the suggestion on cleaning the outside.  I should have mentioned that we had the radiator steam cleaned in Pennsylvania after we found dirt, grass and leaves between the air to air cooler and the radiator. It ran OK until the steep hills of Wyoming, Utah, Nevada and Cailfornia.
I would love to avoid buying a new radiator but I am hoping an internal flush/cleaning can fix the problem.

J

[LarryNCarolynShirk]

Jerry,

On some hills in hot weather you may have to shift down to 4th or 3rd gear to keep the temperature down.  Do not assume 5th is low enough.  Use your temperature gauge to determine when to shift down.  If it reaches 210 degrees, you should be in the next lower gear now.  Do not be concerned with keeping the speed up, just the temperature down.

Larry

[Steve Huber Co-Admin]

Jerry,
Since the problem occurred after you had the coolant drained and refilled, I'd check to see that you have a fully filled system. The system seldom gets fully filled when refilling it. Air is always trapped. Lower than normal fluid coupled with a marginal radiator per above may be the problem.
Steve

[Peter and Connie Bradish]

We have had a similar problem but it started slowly and built up over the years.  
Lots of diagnosis and parts later, we finally found that while the fan was turning it was not speeding up high enough once we were climbing a hill.
Suggestion.
Optical tachometer can be used. Check the fan speed at idle, then at several higher RPMs of the engine.
Our problem was a divider that controlled the amount of fluid going to the fan. The divider was because our fan motor and hydraulic pump use the same hydraulic fluid to run them. It was malfunctioning and not increasing the amount of fluid to the fan motor to increase the fan speed as the engine heated up.
While we are much older and a different design than yours, I would check fan speed at different RPMs. Also could be thermostats, coolant level, hoses, radiator, hydraulic fan solenoid.
We should know we have replaced most of these parts.

[Joel Weiss]

I don't see anywhere in this discussion that you had the thermostat replaced (if I missed that I apologize).  The thermostat is a ~every 3 year item on a C-12 even though I suspect few ever replace it.  I replaced mine last year and the change in the way the engine operated surprised me.  Even though the new thermostat was a 195F one compared to what I believe was a 190F for the older one, the general effect has been to keep the engine operating cooler.  These days I barely reach 200 degrees even when climbing Cabbage Hill and the temp falls fast when we get level.

If you haven't already replaced the thermostat I would strongly recommend it.  It was 1-2 hrs of labor at a CAT dealer.

[Lee Welbanks]

Jerry,

On some hills in hot weather you may have to shift down to 4th or 3rd gear to keep the temperature down.  Do not assume 5th is low enough.  Use your temperature gauge to determine when to shift down.  If it reaches 210 degrees, you should be in the next lower gear now.  Do not be concerned with keeping the speed up, just the temperature down.

Larry

I was thinking the same thing, if 5th is as low as you have to go you haven't found any grades yet, when we were up in Co I found a couple of 8 and 10% pulls, 3 gear required to keep temp down. Also loss of power at 9K ft elevation not as much turbo boost.

[Jerry Sanders]

My thanks to everyone with their experience and sugestions.  As always the group is a great help to beginners in the diesel adventure!  When we first purchased the coach we made several trips to BCS from the SF bay area and we towed a 4,500 pound truck up all of the hills in northern California and Oregon.  The temp never got over 205 so something has changed when we have to climb.  The thermostat is probably the original and looks like a good place to start and then we'll go from there.  I will also have an optical thermometer check the radiator to see if we can detect an unusual heat/cooling pattern on the core.  Again thanks to all for your interest and wish me luck.

Jerry

[Larry Dedrick]

Jerry:
            Laura and I are progressing on our 7500+ mile journey. In our second week of our travels we also had an overheat issue. We did not realize soon enough that we had a leak and thus lost considerable coolant. The leak was fixed, bypassed a leaking drivers heater core, and coolant added. It took four different times to get the coolant where it needed to be. Usually overnight the coolant would be drawn back into the engine and more would be added. Finally got it topped off and we now are operating at normal temps. Due to us being extremely low on coolant our radiator fan was not operating correctly either, but now it performs as it should. Due to a higher than normal temp during this episode we had Cat change the thermostat, and had the oil changed as a precaution. Even Cat did not get the coolant to where it should have been, but they were close, I added one more gallon.
           I also concur with downshifting to 4th or even 3rd, and in doing so RPMs were maintained within reason (2000) on a long climb and our max temp was 203 degrees.
           Good luck on your troubleshooting.

                       Larry D

[LaMonte Monnell]

Larry, I hope you are settling down and not having any more issues. Our HWH trip went well and we got home this am. Stay safe and keep in touch.

I will check on the jack removal pricing soon......

[Hassell McClanahan]

how do you know if thermostat is bad,mine coach is 2006 and I keep my radiator clean with a little high pressure about 40# and I never have any problem hill climbing,,I spraymy radiator with simple green let it set 30 min. then spray it off with high pressure washer about 40#

[Joel Ashley]

Whoa!  Hassell, don't do that.

Get some Simple Green Extreme if you can find some, or use Dawn dish detergent.  The regular Simple Green has been shown to react with aluminum.

40 lbs. is okay, but you should be able to get that out of a garden hose;  a pressure washer and all it involves shouldn't be necessary unless you happen to be using it for something else, and can guarantee 40 psi at the radiator fin impact point, and I'm not sure you can.

If you don't have an issue climbing hills, then if it ain't broke, don't fix it with a new thermostat.

Joel