I need some help with an overheating issue on my 2000 Fleetwood Bounder Class A Motorhome (Ford F53 Chassis with a Triton 6.8L V10).

Engine overheats (250 degrees on ScanGauge) when pulling a grade, and ambient is above 90, even when RV is empty. My Bounder only has 25k miles and has been serviced regularly, everything else runs like a top.

I've tried the following:

1 - Verified that Cylinder Head Temperature is registering a few degrees above the water temperature (on my ScanGauge), so I don't think it is a temperature sending unit issue.

2- Replaced radiator cap with Motorcraft part

3- Drained and replaced fluid with a 50/50 mix, brought to operating temperature (with heater core open), let it cool, and filled to cold fill line (multiple times).

4- Replaced thermostat (Stant 180degree) and gasket

5- Replaced Fan Clutch (Napa Part)

Those were the easy things to do for a few hundred bucks. Before I swap out the water pump and radiator, does anyone have any other suggestions? Is there something else I should do for a more thorough diagnostic? All I have left is to keep swapping parts and hoping it works.

Appreciate any help!

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2000 Bounder 31w (25k miles)
F53 Chassis / 6.8L Triton V10

 

Vacuum leak?

 

Help me out. I'm not sure how the vacuum system interacts with the cooling system?

 

Could be plugged up cats

 

Not sure what you mean by cats?

 

He means catalytic converters on the exhaust, if it where that I think you would feel a major power lose on the hill climb. Could be another bad thermostat but unlikely.

 

egr valve and sensor will do that. it will give a hot under load, pulling hills type symptom........if you slow down does the temp come back into normal range?? I went thru that recently with mine. so far so good but I also added a high cfm aux. fan too.

 

It will start going down once I crest the hill and am coasting. If I'm on level terrain, it might climb to 225.

 

A collapsing radiator hose would do what you are experiencing. Also, it is not unheard of to get several bad new thermostats in a row.

 

back (reverse) flush the radiator...

kit from Walmart.... and a garden hose.

sounds like a partial blockage of the radiator.

also check between the radiator and the air conditioning condenser.... for grass/dirt/bugs/etc.

 

<p>Good suggestions above, but I really think this has to do with the cooling system itself. &nbsp;How has it been maintained? &nbsp;It's 15 years old without many miles, but the coolant should have been changed at least once or twice. &nbsp;What condition was it when you drained it? &nbsp;Rust and corrosion could have formed and blocked the radiator. &nbsp;</p><p>I'd pull the water pump and inspect the vanes, those could have eroded away as well. &nbsp;</p>

 

Well, if you are going to pull the water pump, may as well flush, then replace hoses, and test the thermostat at the same time.

 

All good suggestions here. Over heating can be many issues singularly or in combination.
Check for inlet (usually the lower hose) collapsing. Is it soft? If so replace all the hoses. The vacuum leak you asked about is one or many of the vacuum lines on the engine are cracked and sucking in air. Or a rat chewed them up...common with an RV. If leaking it will cause the engine to run lean. Lean = hot. If its computer controlled the lean condition could be telling the computer to increase fuel delivery. This will cause(over time) clogging of the catalytic converters(cats). Restriction in the exhaust will cause over heating under load. Have you noticed a degradation in your fuel mileage?
Your radiator may have sediment collecting in the lower portion of the cooling tubes. When a system sits all the scale and contaminants fall to the bottom and plug up the lower cooling tubes. Thus the radiator has a reduced cooling capacity. It will rear its ugly head when full system efficiency is called for e.g. pulling up grades. Feel the radiator tanks and tubes when at idle for 20-30 mins. The tanks n tubes should feel uniform. If the lower portion of the tanks n tubes feel luke warm and the top of the tanks n tubes are at op temp there's your problem, plugged radiator. You can have it "rodded" out or recored by a competent radiator shop. If you decide its a bad rad be sure to NOT install a cheap chineasium POS. Step-up for a good OEM unit. Then from hear on perform regular cooling system maintenance. This consists of flushing at a 5 year interval. And I mean a good back flush to dislodge the contaminate(mud) from all the low spots. Buy some of the PH strips and dip the antifreeze annually to check for proper PH levels. Use the best coolant you can find and don't be afraid to use the additives for the pump and PH level control.
A slipping transmission can cause this as well. A trans should have its fluid and filter serviced at 25-35K or if it sits like an RV at min every 5 years.
Report back with the fix.

 

When you did work to the coolant system, replaced coolant, thermostat, ect., how did you get all the air out of the cooling system? You may have fixed the original problem by replacing the thermostat, but an air pocket in the cooling system could cause overheating when under heavy loads, including water pump cavitation.

 

OK,

First off, thanks to everyone for taking the time to help me out. It was a very frustrating issue, that didn't make sense. Your advice here led me to the problem.

I'm posting back in case someone else has a similar issue. My solution ended up being the radiator itself. I bought a Ford OEM radiator ($286) and installed it this weekend. Before installing, I did a chemical flush (Gunk C2124 Super Heavy Duty Radiator Flush), back-flushed, and drained everything well. I figured since everything was clean and drained, it was a good time to give the radiator a shot. The flush didn't produce any discolored fluid or particles, so I assumed either there wasn't much to flush out, or the Gunk product is a wimpy EPA approved version. In any case, I resisted replacing the radiator since my inspection camera didn't show any corrosion in the top or bottom, but based on the suggestions here, and trying just about everything else, I figured it was worth a shot.

Fortunately, it's not terribly difficult to replace the radiator on the F53 chassis. Disconnect four hoses, four bolts, two nuts, two screws, and it drops out easily. I made sure I had the motorhome jacked up high enough to give room to slip it out the bottom. Probably only 30 minutes to remove and another 20 to install. Since I had done the flush, it was empty and went smoothly.

I put in new 50/50 coolant and then drove back to the 8% grade I had been testing on. Where I used to pull the grade at 4000 RPM for an extended time, I previously would get the temp to 235 - 245 degrees. After the new radiator, I didn't break 195. Ambient was a little cooler, 85 degrees, but it still was at full throttle for five minutes going up the grade at 45 MPH in second gear.

I assume the fan clutch and thermostat were probably ok, so I have a few spares. Not a terrible thing to have replaced them anyway, but it did cost me an extra $200 and some time. Thanks again to everyone for your counsel and advice. It got me where I needed to and the issue is resolved.

Thanks again!