FORD 460 Overheating Mystery

[goprolocal]

1997 Fleetwood Southwind 35P ~Ford 460 engine.

I noticed the rig running a bit warm when we first got it 5 years ago. It had 23K miles on it then. It seemed each trip it would run a little more on the hot side of the dash gauge during long interstate trips. During stop and go around town, everything seems just fine, even when it's 110 outside.

Then we started flat-towing a Jeep Wrangler TJ. I expected the temps to increase but I noticed that on inclines, the dash gauge would nearly peg on hot. I could tell the rig was hot.. This would only happen on highway trips...worse on inclines.

One time after traveling for 2.5 hours at 60-65mph, we got off the highway and when we pulled into the gas station, the engine seemed to be vapor-locking..like it was starving for fuel. After 2 hours of letting it cool off, I was able to feather the throttle enough to keep it running to get it home. It doesn't do this vapor-locking thing unless we run long distances at a time, and not every time. It has only done it once before after a 40 minute incline. I actually unscrewed the gas cap thinking that maybe rapid fuel consumption from the tank cause some vacuum or fuel flow resistance..or ?

I then had the radiator, water pump, and thermostat replaced. No difference. I replace the fuel pump, changed the fuel filter, had the carburetor adjusted..no difference.

Thinking that the dash gauge could be off, I replaced the temperature sending unit and gauge with a number dial. The rig runs down the highway at 245 degrees if I'm not towing. If I'm towing, 245 to 258 degrees uphill.

I can hear the clutch fan kick in at 230 to 240 degrees or so...maybe sooner ..and it does cool it down a few degrees so I know it's working.

Are these temps bad? It seems high to me but maybe this is perfectly normal? I don't think it is. The rig runs perfectly..smooth as can be.

The problem seems like it has gotten progressively worse. Our last trip up to the mountains towing, it got to 258 degrees ...the highest I've seen it yet.

There are only 2 things that I can think of that could cause this.

1. Blown head gasket. This makes sense because the problem seems to happen under load. Perhaps there is a leak that's pushing hot exhaust gasses into the coolant? When things are under load, they heat up, causing expansion, and making the leak worse?

If this were true, I would expect to see some foam in the engine oil...but I don't.

2. Transmission issue. I believe the tranny is cooled by the same engine coolant. It shifts perfect, does not slip at all. I have no idea how to test to see if this is the cause of the overheating issue...any suggestions here would be appreciated.

Solutions.
1. Sell it.
2. Take it to a head shop and have the head gaskets replaced.
3. Put STEEL SEAL Head Gasket Sealer in it and cross my fingers. (Has anyone tried this?)
4. Pretend that these temperatures aren't anything to worry about until my rig blows up.
5. ??? Thoughts?

Thanks in advance for any insights.

[garry1p]

goprolocal wrote:
UPDATE:

The shop has had the rig for 6 weeks or so. I've been back 2x to test drive it after they said they had it fixed.

Here's what they did.
Replaced the radiator hoses, replaced the clutch fan, flushed the block and radiator, replaced the thermostat (for the 3rd time in 6 months).

At this point, I drive the rig for 15 minutes down the highway at 65mph. With the overdrive off (to simulate engine rpms while towing) it runs at 220-230 degrees for 12-14 minutes...then in the next 2 minute period, the temp guage clicks ..jumping 10 degrees at a time...in 2 minutes, I'm at 255 degrees. When I turn the overdrive on again, it cools to 245 or so.

Everything I can think of has been checked on the motor...could this be the transmission? The rig sat for a long time before we bought it...in cold temperatures. Could this have something to do with it?

I'm reaching out to a transmission shop next. ugh.

I did not see where the sending unit has been replaced or tested with another gauge and sending unit.

I had a car with temp problems and it was corrosion at the sending unit causing a bad ground and bad reading.

[crawford]

if you have a therm scanner check it cooling in and going out not if radiator restriction in it it may at to slow flow water down. Or prove me wrong get a real book by schools who teach coarse

[time2roll]

crawford wrote:
No thermostat make water flow to quick and no chance to cool down through radiator will make it run even hotter.

Maybe the OP can see for himself. I have done this on several engines. Big blocks, 4 bangers, high performance, stock, all of them always slow to warm up and runs cold.

Not a solution, just for testing.

[crawford]

No thermostat make water flow to quick and no chance to cool down through radiator will make it run even hotter.

[down_home]

No thermostat could actually make it run hotter indicated or not. Coolant has to have time to be saturated with the heat no designed resistance and it can with a high flow high performance water pump overheat. I've sen high performance engines start to run hot as blow by becomes more. Also carbon in the heads increase the need for higher octane. As it is now, getting hot running on down the road and the shroud is in pace and intact a larger radiator might work. Water hoses may be misrouted as I have no idea of what a motor home compartment for a gas engine is configured. Flow though the radiator not around it is essential Perhaps a transmission cooler has been installed in front of the radiator or something is blocking it.
I haven't read all the posts but try higher octane fuel, if you are not already.
Or cheaper add a bottle of octane booster but not the ones not a molded hose but a piece of hose so severly bend it was crimped and no flow.

[time2roll]

I would run no thermostat until you get this sorted out.

Not sure the best way to verify coolant volume and flow. This is the key to expelling heat. Need good engine and radiator flow volume. Possibly a clear tube cut into a radiator hose for observation. Or just fill with plain water and observe how fast the water is expelled as you moderately rev up the engine. (no thermostat)

Was the cooling system ever neglected (prior owner?) where you might suspect there was rust or corrosion issues? This could plug some internal passages such as through the head gasket. Although I doubt this is the issue (long shot and expensive)

[goprolocal]

Does it have normal power? It does. Runs great!
Have you run it with no thermostat? Haven't tried that but we've replaced the thermostat 3 times now in the last year.
Has the water pump ever been replaced? Yep, no change
Has anyone checked the actual coolant flow? I don't believe we have done this but I'll mention it to the shop. The did 'vacuum fill' the block and radiator with coolant in case there was some air bubble or something ...no change.

I'm thinking checking the coolant flow might be the next thing to check. Other than that ??????

[time2roll]

Does it have normal power?
Have you run it with no thermostat?
Has the water pump ever been replaced?
Has anyone checked the actual coolant flow?

[Gjac]

I wouldn't sell it yet before looking at several other things. In my previous post I asked if you can spin the fan clutch when cold by hand, check that. Also check your radiator at temp from inlet to outlet with your IR gun in a 4 in grid pattern and record the readings. Especially check in front of the fan clutch area on the radiator any cold readings will indicate a blockage in the radiator. If your cooling system is operating correctly you should see about a 50 F degree difference from inlet to outlet. Third thing to check is how far does your thermostat open in boiling water. I have seen new ones out of the box only open an 1/8 in, you should see a 1/4 in gap. What temperature thermostat do you have? Does your thermostat have a poppet in the flange? These 3 checks won't cost you anything and will tell you a lot about your issue.

[honda1]

cores inside radiator plugged up , either rot out cores or new radiator, id put new radiator on .

[goprolocal]

Yes, we are grasping at straws now. I spoke to my transmission shop who said that if the tranny was causing this, I'd have other tranny problems. The rig shifts perfectly, no slipping, no noises.

One theory that made sense was that maybe the clutch fan is put on correctly but the BLADES of the fan are put on backwards. This way, the fan would be blowing air AT the back of the radiator instead of sucking air THROUGH the radiator.

We checked, not the case. A piece of tissue paper held in front of the radiator at idle shows suction from the front toward the back.

Ugh, I'm out of ideas on what this could be. I'll ask about the tranny fluid. The fluid that is in there now has only been run about 5K miles since it was replaced.

Starting to think it's time to sell this RV....or drive it until it won't go anymore...or may try installing auxiliary electric fans somehow.

??

[A_Good_Cigar]

Wow, just now saw your update! So when exactly is the clutch fan kicking on as far as temperature? Did the shop wash the outside of the radiator and A/C condenser? What color is the tranny fluid on the dipstick, red or more of a brown, which would indicate a lot of heat dumped into the cooling system? Sorry it looks like you're starting to grasp at straws now:(

[goprolocal]

Hi, Heat works inside and we checked the coolant for exhaust gases...none. 😞
The water pump was replaced early on and didn't change anything. Tranny?

[allbrandauto]

wolfe10 wrote:
Could also be a bad water pump with the impeller loose on the shaft.

if its the water pump impeller you will have no heat inside rv. you have to have a head gasket test with a exhaust analyzer for hydrocarbons in cooling system

[wolfe10]

Could also be a bad water pump with the impeller loose on the shaft.