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hoffy30's avatar
hoffy30
Explorer
Aug 24, 2013

Diesel pusher overheating

New owner of 1993 Cobra Riviera 35' diesel pusher with the 230hp Cummins . Only 37,000 miles on coach with a good maintenance history. Driving home from Las Vegas to Moab had temps rise as high as 230 with the heat warning light coming on once. Slowed down and geared down each time as well as ran the heater which got me back to around 210. These all happened while climbing with ambient temps at 100 plus. Got home and read all of the info re pushers and overheating. Cleaned the outside of the radiator with Dawn and a hose but did not seem to be to dirty. Also cleaned radiator with commercial Permatex cleaner and flushed well. Again radiator interior seemed pretty clean. New coolant after done. Waiting for the temps to rise again before trying to duplicate problem. My question is has anyone added an auxiliary puller electric fan to help with pusher heating issues ? Haven't seen any mention of it anywhere but seems like it should work if run in conjunction with a thermostat and only cycles on when climbing/ heating. One question I have is would this fan restrict the engine fan from pulling air through the radiator ? Hopefully new coolant and a clean radiator will solve my problem but if not want some alternatives. Thanks for any help.
Class A
  • hoffy30's avatar
    hoffy30
    Explorer
    Aug 25, 2013
    Thanks for all of the advice. Waiting for a good warm day to take the MH out on some hills and see what it does. Will post results when I get done. Thanks again.
  • gswcgi's avatar
    gswcgi
    Explorer
    Aug 24, 2013
    I have a 2003 Safari 36' rear radiator with a CAT 330 HP engine. I am the original owner and the coach now has 42,000 miles on it. We live in No. Nevada where everything is either up or down long grades from 4,400' to 8,200'. I tow a 4,500 vehicle 100% of the time and my engine has never exceeded 190 degrees, never. Whenever I stop I get my infra-red thermo out and check the radiator, CAC and tranny cooler, they are absolutely consistent! I never downshift on grades as CAT factory techs have told me to lay into the pedal and let the engine and tranny talk to each other. They know what is needed. I travel north from Bishop, CA to Conway Pass (5,000' to 8,200')frequently and do the speed limit all the way (55MPH)& have never had to downshift nor has the engine heated up. In my experience I just don't buy the rear radiator nonsense not being able to handle the heat. Just did this same run 2 weeks ago at 2:00PM and the outside temp was 101. On the last run up to Conway Pass my rig was just about maxed out GVCW.
  • Roman_Duck's avatar
    Roman_Duck
    Explorer
    Aug 24, 2013
    Newer diesels are low rpm high torque engines, in order to keep your temp down it is best to drop to a lower gear when climbing grades, but will not help on level ground/ grades. Check your thermostat it could be a lazy one, I've run into this problem and by changing the coolant performing a raidator flush and installing a tested thermostat I've eliminated the over heating issues.
    Oh by the way you don't buy a tested thermostat, you need to do it yourself. Quite simple; fill a pot with water, put a therometer in the water, throw the thermstat in, put it on the stove, boil the water and watch the theromstat open, record the temp. that it opened and make sure it's within manufactures specs. I've gone thru a few new ones that were either defective, or lazy// slow opening
    good luck
  • Stealth1's avatar
    Stealth1
    Explorer
    Aug 24, 2013
    Had similar issues with a 1999 Safari Serengeti with a CAT 300 engine and rear radiator (which I hate - really bad design). First, check where your engine "blow-by" hose is located. Very often they are routed where the oil blow-by will be directed on to the radiator from the front side. If the hose is not WELL below and aft of the radiator, extend it! Secondly, you MUST drive these units (rear radiators) differently... and it's a pain! When it's hot and you see hills on the horizon you MUST DOWN SHIFT MANUALLY to keep the RPM up BEFORE starting the climb! You want to keep the RPM near peak torque (typically 2,100 RPM)while climbing. To do this you must down shift before the engine starts to lug (where a normal down shift would occur). By keeping the RPM up, you will maximize the air flow across the radiator achieving maximum delta "T" on your cooling system. Remember, it's not the speed your concerned with but the RPMs to achieve maximum cooling. Hope this helps...
  • hoffy30's avatar
    hoffy30
    Explorer
    Aug 24, 2013
    Yes on the rear radiator. Did clean the rad and CAC from the front to the back but water looked pretty clean. Spoke with the previous owner who bought the coach new and he had intermittent heating issues even when new. He tried rigging up some dryer duct with a wall mount dryer vent to bring air in to the engine compartment. I removed this setup as it seemed to me pulling hot air from the roadway was counter productive to cooling. I am hoping to open a dialogue on the positive vs negative effects of a good high flow electric fan mounted on the rear/away from the engine side of the radiator. Would this increase the available air flow available to the radiator and engine mounted fan ? Or would the electric fan impede available flow by blocking part of the radiator. Any thoughts are appreciated.
  • wolfe10's avatar
    wolfe10
    Explorer
    Aug 24, 2013
    Yup, you need to clean the front of the CAC (Charge Air Cooler) from the FRONT. That is where the dirt and debris will be, not on the radiator itself which is behind (called sandwiched)the CAC.

    Access from the bedroom/closet. Look inside the fan shroud/between fan blades. Make sure the perimeter, particularly lower perimeter is as clean as the center-- the fan blades sling the dirt to the perimeter.
  • hershey's avatar
    hershey
    Explorer
    Aug 24, 2013
    Something to think about: As I understand it, there are two air bleeder valves on the top of the engine that you have to bleed the air out of the system when you replace the coolant. If there is any air in the water system, it will/can cause overheating.
    I clean my rear radiator much the same as you but I pressure wash from the very rear of the radiator, blowing the oil and gunk back out the radiator in the reverse direction it entered.
  • wilpower's avatar
    wilpower
    Explorer
    Aug 24, 2013
    I presume rear radiator? Did you clean from the engine side? Oil blow by gums up the works on rear radiators sometimes.

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