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Matt
Matt, Engineer
Category: Ford
Satisfied Customers: 20591
Experience:  BEng hons Mech engineering, in auto industry 22 years
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My RV Cummings Diesel BT6 is running hot on hills, Coolant

Customer Question

My RV Cummings Diesel BT6 is running hot on hills
JA: Have you checked the coolant? Have you noticed any leaking?
Customer: Coolant level is OK , I had a RV repair shop look to see if it had a lot on dirt on the radiator & they said it was OK
JA: What is the model/year of your rv?
Customer: 2008 Fleetwood Expedition
JA: Are you fixing your Expedition yourself? What have you tried so far?
Customer: Just looking into all aspects to see what I can do , Just as adding a switch to keep the fan on , redo the whole system & what is involved with that.I am machinist / maintenance person , do most of my own maintenance on boats , cars & truck but basic things
JA: Anything else you want the mechanic to know before I connect you?
Customer: Just drove the RV to Sturges S Datoka from LA area , had problem with the overheating light coming on on gradual hills like coming out of Vegas , had to go down to 34 / 40 MPH to keep from overheating
Submitted: 1 month ago.
Category: Ford
Expert:  Matt replied 1 month ago.

As a very first check make sure the coolant level is correct / up to the mark on the tank, then I'd first check that the radiator cooling fan is coming on as it should and if thats OK then replace the thermostat in the engine.

Whilst the thermostat is being replaced you might as well also reverse flush the cooling circuit (remove top hose to rad and use a hosepipe to push water into the engine until you get clear water out of the radiator hose) and top up with 30-50% fresh antifreeze. Also check that the small diameter bleed hoses that run from the top of the radiator and the top of the engine aren't blocked as this allow the air to vent back to the header tank automatically.

If you still have a problem then check that the water pump impeller / turbine isn't spinning on its shaft. You should be able to achieve this by removing the bottom hose from the engine and use a screwdriver or similar to feel for the water pump impeller blades, whilst your assistant turns the engine over by hand.

If you can stop the impeller with slight pressure from the screwdriver the pump needs replacing.

Also its possible the belt is slipping so its worth replacing its especially if the rubber ribs are cracked or it looks shiny on flat side of the belt - while its off check that the tensioner and other pulleys all spin freely the exception to this is the AC pump ( if fitted)

I'd also suggest ensuring that you've got all the air out of the system as this sort of episode can leave pockets of air trapped and prevent the coolant from circulating properly.

So check that the small hoses that run from the top of the engine and radiator that run back to the header / expansion tank are free flowing and not blocked

If these are OK then remove the tank pressure cap and run the engine from cold with the heater set to full hot

As the engine starts to warm, squeeze the large hoses running to the radiator to help displace any air - all the time keeping an eye on the level in the header tank, making sure it doesn't drop below the minimum and open any bleed screws built into the top cooling hoses - closing them off as soon as they start to gush water

Once the engine is up to temperature the tank should be quite full. Switch the engine off and leave it to cool

Then top up to the mark once its all cold and replace the cap

Expert:  Matt replied 1 month ago.

Hi

do you still need help?

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