Cat 3126 overheat

WIDGET33 · 07-29-2011, 01:59 PM

I know there have been many discussions about the slobber tube and plugged radiators on this forum. I have one more question. I have an Ultimate Advantage 40j with 52k on it. Recent trip to Flagstaff Az at about 6000 ft and temp about 90 degrees temp gauge climbed and warning buzzer went off. Pulled over put in neutral and idled about 1500-2000 rpm. Within 30 seconds temp went back to normal. Started out again and about five miles down the road same thing happenned. Pulled over once again and temp went back down. After that temp was fine to our destination. Drove home two days later, back to Phoenix, everything fine. Last month had coolant changed, fuel filters replaced and air cleaner changed. Freightliner says to put it on a dyno for $180 to determine cause. Then wants 1400 to pull radiators and clean. I considered cleaning with Simple Green as discussed but both radiators are so close together it is impossible to get in between. When looking at the engine from under the bed it looks like one big radiator. Could it be a slipping belt? Nothing was being towed at the time. I have driven the coach in town when the outside temp was 118 recently and no problems. I hate to just start throwing money at it until solved. Your thoughts? Thanks

skigramp · 07-29-2011, 03:08 PM

The first hint I can give you is to keep your RPM up in the 2000 to 2250 range on long climbs ... you may have to manually downshift in order to do this. I have only driven from Phoenix to Flagstaff once and I recall that is a huge change in elevation (so it is all more or less uphill) and there are some significatn long uphill pulls; if you watch your tachometer and your temperature gauge you will see that the temp climbs as the tach falls ..

The second hint is I clean my radiator twice a year.

When I am home I use a garden sprayer with Simple Green (or Jungle Jake) and hot water. I spray the solution into the radiator from the rear (without the engine running) ... I then start the engine, crawl underneath and direct the spray up into the fan housing {before I did this the first time I crawled underneath and make sure I understood where the fan and flywheel were before starting the engine}

I let this set for about 10 or 15 minutes.

Then I get my garden hose and spray the radiator from the rear and from underneath ... I keep spraying with the garden hose until the bubble go away.

When I am away from home I buy an aeresol can of "Gunk" engine degreaser and spray the radiator from the rear ... and spray with clear water from the rear.

WIDGET33 · 07-29-2011, 04:12 PM

Thanks. I will try Simple Green this weekend. According to Freightliner the cause could be several things. Guess I will try the cheapest fix first. Anywhere you go from Phoenix is an uphill drive. Just didn't want it to happen next trip as I get a little nervous when I think how easy it is to damage a very costly engine. Phoenix is 1200 ft and Flagstaff is 7000 ft. Distance about 125 miles.

1ciderdog · 07-30-2011, 09:44 AM

Also back off the fuel pedal a bit - yes it'll slow you down and you'll have to down shift but going slower & gearing down do help keep the engine cooler. This month I left Texas, went up to colorado Springs and am now in Albuquerque and I have climbed several long grades in third gear running the engine above 2000 rpm to keep the temp gauge under 217. Driving in the right hand land with the trucks and flashers on - Seems to work - Outside temperature was above 100 on several days. I also turned off the dash air and used the generator and house A/C to keep the coach cooler.

WIDGET33 · 07-30-2011, 04:50 PM

So if I understand you I need to push the mode button on the transmission so the light comes on and then down shift to third gear when climbing. I have been leaving the gears up to the tranny. It usually downshifts automatically. I was going between 35-45 mph with my foot to the floor. The light always stays on 6 but i feel it downshifting just not sure what gear it is in. Never looked at the tachometer as I thought the rpm and speed would tell the tranny what gear was needed. Thanks I appreciate your help.

skigramp · 07-31-2011, 06:43 AM

It is my understanding that the mode button will SLIGHTLY change the shift points when you are driving in rolling terrain or into variable headwinds ... that is supposed to adjust the normal shift thresholds slightly ... the mode button has very little to do with climbing a long hill.

I travel I-80 often ... between Cheyenne, WY and Grand Island, NE there is a 4000 foot drop and it is roughly 250 miles ... the wind generally is out of some westernly direction ... so when I travel west (uphill and into the wind) my transmission will sometime shift more than I want it to when there are rolling hils ... so I press the MODE button ... and let the transmission shift automatically.

But when travelling eastbound on I-80 between Laramie, WY and Cheyenne, WY there is a 5 or 6 mile hill that has about a 6% grade ... I build up my speed as I reach the bottom ... I pay no attention to the MODE button ... I watch the tach ... when it falls to 2000 rpms I manually downshift ... I think I generally make it to the top of that particular hill in 4th gear going about 45 mph.

On some hills that are longer or steeper you will need to be in gears lower than that ... I remember being in 2nd gear on one particularly steep hill in Utah.

jimmccreary · 08-01-2011, 03:37 PM

I agree with skigramp but with one exception. To get the front side of the radiator I crawl underneath without the engine running and spray directly onto as much radiator surface as I can get. By manually turning the radiator fan slightly, I can see and spray about 2/3 of the radiator and count on dripping solution to get the lower part of the radiator. This process is done on the passenger side of the radiator. I cannot get spray into the driver side of the radiator from underneath because the fan blade does not allow sufficient clearance.
So my question for skigramp is "can you get the cleaning solution uniformly over the radiator by spraying when the engine is running and the fan is moving?"

Also, I use a pressure washer to force solution from the rear of the radiator (outside) back to the inside. Have to take care not to bend the radiator fins but this can be done by picking a tip for the pressure washer so that the spray is over a larger area.
You know that the radiator is clean when you can feel a uniform flow of air coming out of the radiator.

Also, the key when driving is to slow down and shift down to keep rpm at 2000 (or more). Also agree with skigramp on this one.

Also, I did extend slobber tub and seems to help too.

hope this helps

jim & debbie, 04 Journey 34H

cmercer · 08-02-2011, 11:48 AM

Widget33, I also live in Phoenix and take the Flagstaff (or Payson) route often during the summer months. My Horizon seems to handle the heat better than my previous 04 Journey DP. The Journey would struggle when temps reached 95+. I also used the 'simple green' soaking twice a year and it helped. However, what I found to be the most effective is to drive the hills using the tachometer and not the speedometer. I will manually downshift the tranny to make sure I keep my rpms around 2000. I then drop road speed as necessary to maintain the rpms. If I keep the accelerator 'on the floor' then I am just asking for an 'over-heat issue'. Best is to back-off the accelerator and downshift as necessary. As I get passed I just remind myself that by going 35mph up a long climb it will only cost me a few minutes to my destination...but not require me to pull-over to cool off.

sgtjoe · 08-02-2011, 12:16 PM

Do you have access to your engine from inside the coach?? If so before you start spraying check it out to see if the radiator is clogged by having someone (at night) run a brite flashlight around the back of the radiator while you watch for the light from the inside. Most clogging will be to the outer portions of the radiator as the fan pushes the flow that way. If the flashlight is as brite to you all around then you have another problem.
My wife and I do this after long trips especially if we have been on dirt roads. I use Dawn dish soap through a garden sprayer and then my power washer set on a fan spray.

When I bought my MH in Tucson it was in the winter, the overheating showed up in the Summer in Utah climbing I-80 towards Park City. It cost me 756.00 to have freightliner disassemble and steam clean the whole mess. Freightliner did cover the cost of the longer slobber tube which caused the problem. 20 bucks. The guys that did the work told me how to avoid the problem in the future and how to check the radiator with the flashlight at night. 6 years later, no problems.

Good luck and keep us posted on the outcome. Do the flashlight inspection tonight and let us know how it came out. If I had known about that and the Dawn dish soap I may have saved the 756.00.

bdpreece · 08-02-2011, 12:22 PM

I did not read every word of each post so if I missed it I apologize but I did not see where anyone suggested changing the thermostats. I am assuming the 3126 is the same as my C7 was and it had two thermostats. If one were to stick closed you will most probably not have any overheating problems unless you were working the engine harder than normal. since I no longer have my Cat coach I can't check the manual but there was a section that said you were supposed to install new thermostats at I believe around every three years.

jimmccreary · 08-02-2011, 04:30 PM

BDPREECE,
I had the same overheating problem caused by a clogged radiator that others have had. During the initial stages of repair, freightliner changed both thermostats at my request even though they thought that was not the problem. They recommended changing the air filter. After doing both of these repairs, I still had the overheating problem. It was unaffected by thermostat replacement.
After reading this forum, I cleaned by radiator---problem solved.
Hope this helps.

jim & debbie, 04 Journey 34H

bdpreece · 08-03-2011, 12:27 AM

I would agree it is most probably a clogged radiator/CAC and that a good cleaning is probably the first thing I would do. When I had my Cat rear radiator coach I cleaned them faithfully every year. I was just adding that Cat states thermostats need to be changed every three years and I have heard of them failing.

rvarner · 08-03-2011, 11:40 AM

Quote:

Originally Posted by WIDGET33

I know there have been many discussions about the slobber tube and plugged radiators on this forum. I have one more question. I have an Ultimate Advantage 40j with 52k on it. Recent trip to Flagstaff Az at about 6000 ft and temp about 90 degrees temp gauge climbed and warning buzzer went off. Pulled over put in neutral and idled about 1500-2000 rpm. Within 30 seconds temp went back to normal. Started out again and about five miles down the road same thing happenned. Pulled over once again and temp went back down. After that temp was fine to our destination. Drove home two days later, back to Phoenix, everything fine. Last month had coolant changed, fuel filters replaced and air cleaner changed. Freightliner says to put it on a dyno for $180 to determine cause. Then wants 1400 to pull radiators and clean. I considered cleaning with Simple Green as discussed but both radiators are so close together it is impossible to get in between. When looking at the engine from under the bed it looks like one big radiator. Could it be a slipping belt? Nothing was being towed at the time. I have driven the coach in town when the outside temp was 118 recently and no problems. I hate to just start throwing money at it until solved. Your thoughts? Thanks

Be sure to check that belt. Mine was really loose and had it replaced. Made quite a difference coming from Nevada over I-70 into Denver. With RPM at 2000, only hit a little over center gauge once. I slowed down and went to 3rd and 2200 rpm and temp went right back down. I used to see temp guage readings all over the place but the belt seemed to stabilize the readings to below center. Hope this helps. Nothing more frustrating than an overheating problem.
Richard

bachler · 09-29-2011, 02:04 PM

We also have an Ultimate; It over heated; I tryed all That crap everyone said to spray into the Rad;; It didn't work. Here's why . They have an Intercooler Then the Rad; There is about 1 inch space between them. The only way to cure the over heating Problem, Is remove the rad. and intercooler Clean them replace them AND don't forget to Extend the Crankcase Vent. That is what caused the problem In the first place;; I even Had some IDOT said to steam it out ; then I had to streighten the fins. Have it removed cleaned. Ours cost Appx. $3500.00, Now it works as it should. Don't take any shortcuts. They will come back and bit you.. Life is good.