Cleaning The Radiator & CAC

[sundancev]

Brett: We just completed 14,000 mile cross country east and west and north and south where we ran hot a couple of times with our 40' Diesel Pusher. I was told by one mechanic to simply drop in lower gear and slow down when climbing 9400 foot mountain at steep grade. Later I talked to Cummins Mechanic in Reno who told me to clean out radiator periodically essentially echoing your article. He suggest going to one of the car washes with a higher than normal pressure hose and spraying back from rear to front of radiator. We did so immediately and never had another overheat condition. It did get warm but not overhheat. Best to you and thanks for all your articles. Paul

[sundancev]

Brett: As a follow-up to my last entry relative to using spray hose at Car Wash, I have since gained entry to top of engine and radiator/fan housing and find any access to "rear of radiators" is effectively blocked by fan shroud. I had thought of having Freightliner clean when I went in for an oil change until I read about $600 cost from one of your writers. I am thinking the best and least expensive long term solution after re-routhing breather tube is simply spry Dawn on radiator from rear of motor home after warming up engine and spraying with hot water from a car wash again. At least try this method until I have an overheating event. Do you have any further thoughts on this idea. Mucho thanks for your wonderful forum responses. Paul

[wolfe10]

Paul,

While cleaning from the back (you are cleaning the back of the radiator) is fine, the vast majority of the dirt will be deposited on the FRONT of the CAC, since the air is sucked in by the fan and forced back through the CAC and then the radiator. As you saw, it is no fun to access the front of the CAC-- you have to work INSIDE that fan shroud/around the fan blades.

As I have posted before, use a strong flashlight inside the fan shroud and make sure that the lower PERIMETER is as clean as the center. Long before you experience overheating (i.e. radiator air flow insufficient), you will experience loss of HP and MPG, as the CAC is not able to cool the engine intake air sufficiently.

And no, there is no way with a sandwiched cooling system (CAC in front of radiator) to clean adequately it from the back only.

OK, that's the bad news. The good news is that you get to choose that outfit you got for Christmas that you REALLY don't like. Wear it to crawl in and clean the front of the CAC. And, with big apologies to the giver, it will be relegated to the "work clothes" pile.

[dickandlois]

Here are pictures of the radiator, CAC and the stack assembly.

Pictures #1 and 2 -- radiator

Picture #3 -- CAC

Pictures 4 and 5 -- engine

Picture 6 -- stack

Freightliner recommendations

On chassis equipped with a rear radiator, it is very important that the radiator and charge air cooler be inspected at regular intervals. Cummins® recommends inspecting the charge air cooler every 7,500 miles. This is because air and dust blown through the radiator and charge air cooler can build up and reduce the airflow through the cooling system. This is considered part of normal maintenance.

From the engine side of the radiator, use a flashlight to look into the fan shroud at the face of the charge air cooler. If there is any dirt buildup, this should be cleaned using a water hose and a mild solvent. If this is not done, the system can become clogged and can result in engine overheating.

I hope these pictures will help others understand the importance of keeping the area clean. The side-mount systems do not get dirty as quickly, but they still need to be cleaned.

[wolfe10]

Thanks for those great photos. A poster child for the importance of keeping the CAC/radiator clean. By the time it gets as bad in the photos, it is almost a certainty that you will have to pull them to get them clean.

If cleaned regularly, you can usually clean with a garden hose from back AND FRONT.

Brett

[jleamont]

Brett, thanks for the link from the other post.

I took your advice and bought two bottles of the Extreme Simple Green and cleaned mine out tonight. My coach has an aluminum fin assembled in front of the side mounted radiator stack. I removed the 6 self tapping screws and pulled the fin assembled off, next I removed the dash A/C condenser and supported it with a bungee cord so it didn't hang and swung it aside. My bed slide is just above so I put it out 3" to attach the bungee cord from the track.

I poured both bottles into a garden pump sprayer and hosed it down on both sides and due to the long nozzle on the pump sprayer I was able to get between the CAC and Radiator and soak them both down.

Here's where it got dirty, Mike Rowe could have made a show about this. I crawled under the coach in a position where the radiator was across my chest and lap area, and began to spray the garden hose from the fan side toward the outer wall, then on the outside toward the fan, then up between until I saw water bubbling out of the CAC (front side). What ran out resembled a light chocolate milk, I continued until I only saw water no matter where I sprayed.

I tried the light trick but I couldn't get my head behind the fan to look toward the outside so I figured I would clean it anyway for a good maintenance practice.

Needless to say wear swimming goggles and old clothes, you will be showering just after, I was completely soaked as if I jumped into a pool with my clothes on, with dirt all over.

The cleaning product had no effect on my skin. I bought the bottles at Pep Boys for $9.99 each.

I am not sure what to expect since I never reach 205 degrees on a 7% grade fully loaded towing, but if it's less I will take it, normally I run at 185 degrees.

[wolfe10]

jleamont,

Good write-up.

Sure hope you did this correctly. You are supposed to wear your LEAST FAVORITE outfit-- even if you got it for Christmas 2014!

You are free to blame me for ruining that purple pants suit!

With the amount of "light chocolate milk" you got out, I suspect air flow through your cooling package will be a LOT better.

So less overheating and lower intake manifold temperatures.

Good work.

[jleamont]

Thanks Brett!

I think this will become an annual PM and I might even give it another dose of cleaner this year just to make sure.

[obedb]

I received the Amazon ordered gallon of Extreme Simple Green today. Looks like a 1 to 1 ratio might be in order. I will use a 1 gallon pump sprayer for the application and I think that I have pretty much absorbed all of the helpful info available on this website concerning the need to do this. The pictures supplied by Rich really struck home. Backs up everything Brett has said.

[john kelley]

I have read the past comments, but have a new twist and question. My Freightliner chassis/CAT 350 rear radiator diesel is overheating on long mountain climbs. For the first 5 years we owned the new coach, we had no problems, anywhere. Then it first overheated on a long W Tx Interstate climb.

Steam cleaning the radiator from the rear seemed to fix us, for the time. I got home, had the radiator cleaned again, flushed, thermostats and bottom hoses replaced, and put on a crankcase breather extension (pointed down).

Following this, I began cleaning the radiator and CAC visible surfaces with water and simple green, prior to every trip. This solved things for a while, but, on a recent trip to the mountains, the dilemma returned. We only managed to get home out of the mountains by traveling in the cool of the morning.

Freightliner says that I must have non-visible dirt/solid blockage between the CAC and the radiator, untouched by all my efforts. They recommend removing the radiator for cleaning/soaking. This is a major job, and seems extreme.

Any thoughts or suggestions?

John Kelley

Georgetown, TX

7/6/15

[obedb]

Welcome to the forum. Brett Wolfe is the resident Cat expert and also a moderator. Hopefully he will respond shortly. Sounds like you have done everything that could be expected from a careful owner. Our Cat330 has a separate belt for the water pump that is manually adjusted. Learned that from Brett. Could it be out of adjustment or badly worn? One other thought/ local RV shop recently told me they occasionally find debris between the CAC and the radiator. I haven't crawled around under mine enough to tell you how that could even happen. Maybe when I get to the CAC cleaning I will know more.

[wolfe10]

Sorry for the delay-- driving today.

Yes, check the belt tension for the V belt that drives only the water pump and has a manually adjusted idler pulley. Check it from underneath on the driver's side very front of the engine/back of the coach.

And, access the front of the CAC (inside fan shroud/between fan blades). Shine a strong flashlight at the CAC (much easier to see at night). Make sure the perimeter, particularly lower perimeter is as clean as the center (the fan blades sling the dirt to the perimeter.

If both those are OK, next thing I would do is replace the thermostat(s). Caterpillar calls them regulators and recommends replacement every three years.

[Ianinnapa]

I'm a new owner and overheated on the Thursday before the July 4th weekend heading up 50 from Sacramento. Really freaked me out and had to baby it in.

I own a 2005 Bounder Diesel pusher. It has the Cat engine and Alison tranny.

I am taking it out this weekend however will check the rad and clean it as described MULTIPLE times. Seems like the golden ticket.

Thanks everyone.

Oh yea, new FMCA member as well.

Ian

[wildebill308]

Ian, welcome to the forum and FMCA. Are you having this problem when climbing or on the flat. If you have a problem with it overheating climbing try dropping down a gear or two as needed to increase fan speed. this will help bring your temperature down. Bill

[Ianinnapa]

Thanks WILDBILL. I will do that next time. To me, higher revs or RPM equals hotter running so it freaked me out.

Also, cleaned outside rad last night and it was a bit dirty. Also noticed my slober tube is uphill so I need to fix that (read somewhere that a gator aid bottle cut and zip tied also can fix blowback into rad ??). How do I get into the engine compartment from the coach to clean the inside rad?

[wayne77590]

A few weeks ago I came from Texas on I-40 to Calif. I used a trick I learned somewhere along the line. When you see the grade approaching, depress the accelerator pedal to the point of cruise, or just keep it at the speed you are going, say 60 mph. When you start to climb the grad do not give it any more throttle just keep the foot still on the accilerator. The coach will do the rest. It will slow down and automatically down shift keepint the RPM's between 2000 and 2500. This should keep your temps between 195 and 205, back and forth as the fan cools he radiator. If it is bogging down to much use the shifter and down shift to the next lower gear by pressing the down arrow. On every grad but one my lowest speed was 40-45 mph and on one it was 35 but I dropped it down to that to raise the RPM's when the temp got to 210. In just a few seconds it dropped to 207, then 205 and stayed there for the rest of the climb.

Happy trails.

[obedb]

As Bill pointed out, keeping your rpm up on a pull usually helps to keep coolant temp down. It does it in two ways. Fan speed is increased if you have a rear facing radiator and the speed of the water pump increases therefore moving more coolant through the radiator. Find a tranny gear that allows you to climb while easing back on the accelerator as Wayne pointed out. Knowledgeable truckers have used this method for years. Take care of the cleaning issues mentioned on this forum by Brett Wolfe and hopefully you will be good to go. Or running in the dead of winter might help. (Tongue in cheek)

[wildebill308]

Punch a few holes in your catch bottle so it can vent. Look for a panel between the bead and the closet. You will probably have to raise the bed and take part of the base out over the cover. There are two parts the top part with the rug on it slides out and the bottom panel has a couple of screws in it.

Bill

[wolfe10]

Couple of points:

Access to the fan shroud/fan area to clean the front of the CAC varies by coach. Some access is under the bed, some in closet-- really depends on floorplan. You will find 90% of the dirt to be on the FRONT of the CAC. It acts as the "filter" for air going through the CAC and radiator.

To climb a grade at XX speed requires YY HP. If you generate that HP in a lower gear/higher RPM, the fan is turning faster and the water pump is turning faster, so better engine cooling.

[Ianinnapa]

Thanks to everyone for the replies. I naturally assumed that by buying a diesel pusher, the 'hills' would be a piece of cake. I didn't realize that there was an art to it.

We are taking a very small trip this weekend that has no hills. I will pull apart the floor after I return.

Footnote to what I pretty much going to find.

I pulled off the brake light cover to change a burnt bulb yesterday. There was a beach behind. An inch of sand and general crud there. Can't wait to see the inside 'rad'.

Again guys, thanks for the assist.

Ian

[obedb]

In spite of my many years of experience guiding big diesel rigs down the highway I was also taken in by the beauty and diesel power of the higher end Motorhomes that passed me frequently. I was caught up in the ability to finally own one. Did not do my home work. Just assumed that diesel power solved everything. Boy was I wrong. Kinda like a owning an expensive boat. Big hole in the water to dump money in. Sure is nice inside though. Maybe I will finally get things up to snuff and travel with fewer worries. They are in no way as durable as a big rig, but as Brett has pointed out, the bed is nicer.

[wildebill308]

In spite of my many years of experience guiding big diesel rigs down the highway I was also taken in by the beauty and diesel power of the higher end Motorhomes that passed me frequently. I was caught up in the ability to finally own one. Did not do my home work. Just assumed that diesel power solved everything. Boy was I wrong. Kinda like a owning an expensive boat. Big hole in the water to dump money in. Sure is nice inside though. Maybe I will finally get things up to snuff and travel with fewer worries. They are in no way as durable as a big rig, but as Brett has pointed out, the bed is nicer.

If you have experience driving truck you shouldn't have any problems with a motorhome. Just keep up your maintenance items and go have fun.

Bill

[jleamont]

Update; we just returned from a trip upstate PA through the mountains. Ambient temperature was 92 degrees ,100% humidity and the sun was just starting drop off, I pulled an 9% grade (4 miles of this and 3 miles at 7%) in third gear at 35mph fully loaded towing our jeep.

I started the hill at 45mph and 180 degrees on the gauge at the top of the hill I was at 205 degrees and the fan sounded like it was on high, as I started to descend the mountain it immediately dropped back to the 190 degree mark never went that high again through the remaining rolling hills all the way to our destination.

Is this normal?

I am planning on cleaning the radiator and CAC one more time just to be sure I have a good baseline since it was so easy to do.

[wolfe10]

Likely normal.

At what RPM were you during the climb/205 degrees F?

[jleamont]

Brett, I was around 1700-1900ish, I manually brought the transmision into 3rd to raise the RPMs to keep the pump and fan spinning faster.

Just curious, can I change the shift pad to the newer design that shows you what gear the coach is actually in?