Engine Overheat

If you have you have an Engine Overheating condition with a REAR RADIATOR CHASSIS, chances are good that your rear radiator is clogged with oil film and dirt. Until the new 2007 EPA clean air standards for diesels, the engine builders DID NOT have to count their crankcase breather emissions. Consequently the engines still have a CRANKCASE BREATHER TUBE ('Slobber Tube') to vent the crankcase. Since engine builders make engines for different applications, they do not extend this tube beyond the engine...this allows oil fumes and oil droplets (usually called 'oil blow-by') to contaminate the bottom half of your rear radiator. That oil film collects dirt and over time, your radiator loses much of it's cooling capacity, your Charge Air Cooler (a special radiator to cool compressed air from the turbo charger before it enters the air intake to the engine) gets clogged ...and bingo, the engine starts overheating and you lose power due to intake air being too hot.

To avoid this problem and to 'fix' overheating caused by this 'oil blow-by', use a good spray on detergent (Simple Green is a good biodegradable, safe cleaner available at most stores), spray the radiator inside and out...let soak for 10-15 minutes then flush with a garden hose and nozzle. If really dirty, you may have to repeat the process several times. Important, the dirt is on the inside closest to the engine and may be hard to access...you will likely have to crawl under the coach or maybe access it from inside via the engine cover to get the cleaner and water on the inside of the radiator and CAC.

A long term fix has finally been added by FCCC extending the 'slobber tube' back to the rear frame member to keep the oil 'blow by' from getting into the rear radiators. However, this did not start until the end of Feb. 2005.

[NOTE - this whole oil blow-by situation goes away on new coaches with 2007 EPA compliant engines...they all use closed crankcase ventilation systems...remember PCV valves on gas engines? Diesel engines are finally implementing a similar system for EPA reasons.] Also, side radiator chassis do not have this problem. Any blow-by may get on your towed vehicle, but doesn't get sucked into the radiator.

It is my understanding that Cummins started putting their Enviro Guard crankcase ventilation filter system on their ISC and ISL engines sometime in 2003. So, Cummins engines stopped having this problem sometime in 2003. If anyone has exact dates on this, let me know.

CAT engines had a minor problem with this oil blow-by on their older 3126 series engines, but it was not a very big problem. When the new CAT C7 entered the market in July 2003 (model year 2004), it had a new side mounted breather cap which turned out to be much more sensitive to oil levels and had a pronounced 'blow-by' problem with the original 22 Qt. oil level. In March, 2005, CAT changed their C7 oil level from 22qts. to 19qts. which solved most of the blow-by problem. With FCCC extending the 'slobber tube' in Feb. 2005, most of the radiator contamination problems have been eliminated. If your rear radiator engine was built prior to Feb. - Mar. 2005, you may encounter this 'oil blow-by' problem which can cause your radiator and Charge Air Cooler to become clogged.

FCCC considers this problem to be an owner maintenance issue (not a warranty item) and has been explaining to folks that they should clean their radiator and the Charge Air Cooler periodically to prevent this oily, dirt build-up on rear radiators. That was fine if you were a FMCA/FCOC club member, and attended FMCA conventions or FCOC rallies where this information was verbally presented with the 'Knowing Your Chassis' maintenance presentation at least twice per year for several years (note - scant info is in the owner's manual and with no pics or details). However, if you never attended FMCA or FCOC rallies, you might just be learning about this situation. Fortunately, they finally started putting the 'slobber tube' extender hoses on at the factory in Feb. 2005 and have eliminated the problem with new radiators. This doesn't prevent the blow-by from getting on your towed vehicle, but at least it doesn't clog up your radiator and CAC.

There are several economical 'home brew' filter designs where folks have added a small plastic bottle to the end of the 'slobber tube' to catch the oil droplets and solves this problem very well and cheaply.

For further info on this topic, see the CAT RV Club Yahoo discussion group and do a search on 'oil blow by' or 'slobber tube'...there are extensive discussion threads on this topic - See http://autos.groups.yahoo.com/groups/CATRVCLUB/ . Also on the FCOC Yahoo discussion group...http://autos.groups.yahoo.com/groups/FCOC/ similar discussion threads are available.

Overheating - how to clean your CAC & Radiator

Posted by: "Brett Wolfe" wolfe10@earthlink.net wolfe102001

Thu May 22, 2008 2:27 pm (PDT)

On all coaches, but PARTICULARLY REAR RADIATOR coaches, the after-
cooler and radiator need to be cleaned AT LEAST ONCE A YEAR.

You can verify that you actually need to clean them by taking a strong flashlight. Access the engine from the TOP (bedroom). Shine the flashlight inside the fan shroud/between fan blades. The fan blades "sling" the dirt toward the perimeter, so you want to make sure that the perimeter is as clean as the center (You are looking at the front [Front of coach] of the after-cooler. The radiator is behind that the after-cooler(back of coach). Yes, there are a few coaches with stacked radiator/after-cooler and these can be cleaned from the back (back of coach).

If you just have dirt on the after-cooler, a hose with garden nozzle will work fine. If there is oil/greasy deposit, get the engine a little warmed up and turn it off. Wet the after-cooler and spray some Dawn dish washing detergent (Some use Simple Green) along with water on it (AFTER-COOLER) from the FRONT inside the fan shroud. Let sit, but not until it dries out. Hose out.

Repeat.

Pressure washers are dangerous-- it is hard to maneuver them around the fan blades and VERY easy to bend the fins.

You will also want to clean the radiator which is done from the back/outside of the coach. But this is NOT where most of the dirt will be deposited.

And make sure the crankcase breather (1" ID open hose on most Caterpillar engines) is extended to behind the air intake (shroud) for the cooling system. Also verify that the extension ONLY goes downhill from the engine (no dip loop or sag) or you could do serious engine damage in cold weather. One of the byproducts of combustion is water vapor which can freeze if allowed to collect in the extension
and if it blocked the whole tube BAD NEWS.

Now, if you are climbing a hill and experiencing overheating, use the transmission down arrow to select a lower gear. For a given road speed, XX number of HP are required (read that also as heat produced). Producing XX HP (same heat load) but with the water pump turning at say 2,100 RPM instead of 1,600 RPM WILL reduce engine temperatures. But it will also increase fuel consumption. So I view this as a short range fix ONLY. Best answer is to get the cooling system back to 100%.

I have previously posted on changing coolant and thermostat(s) which is also important.

Brett Wolfe