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1987 Ford 460 Overheating - Please Help!

My very small RV (20ft) is a converted Ford Econoline with the carburated 460 engine.



It is overheating under fairly low load running on the freeway.



This happens when outside temps are 70 degrees or more. At low outside temps I have no problem.



The temp gauge will peg and I have checked coolant temp with heat gun to be up to 238 degrees.



I have tried the usual: New 180 degree thermostat, new radiator, new water pump, new clutch fan.



I have tried 4 different shops, and currently waiting to get a Ford original fan clutch installed (previous shop used an aftermarket one).



The shop working on it now says they think I have a coolant flow problem, that the engine heats up un-usually fast, that there is a fairly large temp differential between the banks of 20 degrees.



Can’t somebody do a test where the coolant flow through the radiator is checked while the engine is running? This would check radiator, waterpump, restrictions etc. The coolant and the engine oil looks perfect (no contaminations etc.).



Any other ideas? I have told all shops to do whatever it takes to fix this but so far no fix.



I am hoping the fan-cluth will help, but does it make sense that the fan is needed at easy, flat highway driving?



I am looking at the AC condenser right in front of the radiator, and the condenser looks clean but very, very restrictive in terms of airflow over the radiator. I could remove the AC system, but I am worried that I am not fixing the real problem.



Any help appreciated!

Hans

The AC system is not the problem. Has anyone looked at the head gaskets? With a new radiator and water pump, flow shouldn’t be your problem. Was the coolant ever allowed to get old and gunky? I’d stop throwing parts at the problem until you can figure out the cause.

If this vehicle has the original radiator, the problem could be a restriction of coolant flow thru the radiator.

You can also use the heat gun to check for restricted cores in the radiator. While the engine is hot and running, point the gun at the radiator cores. Those that show a lower temp than the rest are the restricted ones.

Tester

Thanks for replying!

No, the coolant system was well maintained. I have about 85,000 miles on the RV.

This issue came about in a weird way:

For 10 years coolant gauge worked fine as far as I know. It showed no overheating, running slightly below “vertical” in general, and hitting 3/4 when climbing mountain passes - never into hot.

Last June the gauge went dead. The shop replaced the thermostate (I do not know why), and then replaced the temp sending unit. Now gauge worked again, but would run close to “hot” going down the freeway.

I had Ford dealer look at it. They replaced the thermostate and sending unit again - no change.

Ford recommended that I have the radiator flow tested. I took the RV to a recommended truck repair shop. They said the radiator could not be cored and they replaced it with a new high end 4-core radiator and per their advise replaced the fan-clutch and the water pump at the same time. After this it seemed to run even hotter, go figure!

Ford says that 238 degrees climbing a local mountain pass is way too hot. I can climb easier, but I have also measured 230 degrees going down the freeway. The truck repair shop did not seem interested in fixing this, so I moved on to a small local shop with good recommendations from the local Ford dealer (local Ford does not take RVs).

An RV repair expert (not local) said that aftermarket fan-clutches are often a problem, so that is why I am getting a Ford clutch put in next Monday.

I did mention head gasket etc. to the shop, but they did not seem to think this is the issue. I paid them 2 hours to debug, but I am pretty sure they did not pull anything off the top of the engine. They did adjust the timing by quite a bit. RV seems to run a little less powerful after that and I got 9mpg on the freeway versus 10mpg a couple of weeks ago - not sure if that is significant. I think 9-10mpg is decent for an RV. I used to get 11-12mpg 10 years ago on this same RV.

The RV is old and I could just move on, but I have heard that the 460’s are great engines and that it should last much longer than 85,000 miles.

I would not mind doing an “engine overhaul” to get it all up to snuff - surely it must be fixable :o)

What should I ask the shop to do next?

You’ve changed all the obvious components, the radiator, T-stat, pump, and fan clutch, but not yet the less obvious ones…the hoses. Hoses are constructed in plys, and on old hoses the inner liner can become detached and collapse, restricting flow. It’s not common, but it does happen.

Hopefully it’s only this and not a headgasket.

Oh, by the way, did you change the radiator cap when you changed the radiator?

Hoses are almost new and look great. I have read that lower hose can collapse. It looks good, but does not feel like it has steel reinforced wall to ensure no collaps. Shop replacing radiator said hoses were in great shape.

Radiator cap was replaced with radiator. To clarify, it has never boiled on me, just gets very hot (238 degrees).

Thanks for the help, keep the ideas coming and I will definately share with you all what is was if it ever gets fixed ;o)

I would next check to make sure the EGR circuit is working properly.

The purpose of the EGR circuit is to reduce combustion temperatures to reduce NOx emissions. And if the combustion temperatures get out of hand the engine can overheat. Especially on extended trips.

Tester

Interesting, this was also mentioned by the RV expert and I did in turn mentioned it to the shop.

The temperature is actually perfect starting out on the freeway, and it then slowly creeps up from “vertical”. It typically takes about 15 miles for it to get into the hot zone. Does this mean anything in particular?

Thanks again for helping out!!!

Longshot: did this vehicle ever have an air deflector under the front valance panel that’s no longer there?

Does it have an automatic transmission? A transmission that’s running hot can also cause the engine to overheat. Because the transmission cooler is inside the radiator.

You have to look down all avenues.

Tester

Thanks for mentioning this. Yes, it is an automatic and first when it was overheating climbing we thought this could be it, but I would imagine transmission would not slip on freeway under almost no load. But I am not an expert at all. I will mention it to the shop again - can they easily test if tranny is OK?

What about the temperature differential between banks and engine heating up to working temperature too fast, does that sound like a big deal? Seems to me like coolant flow rate could expain this, as could a head gasket :o(

Thanks, I do not think so, I will ask shop. Thanks!

Shop did mention that aftermarket fan-clutch is not far enough inside the shroud. It looks about 1/2 way inside the shroud, is that not about right?

The clue is in where the fan blade is. The fan clutch moves no air, only the blades do

Check for worn front suspension parts and alignment, dragging brakes and slipped timing chain.