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Why Is My Motorhome Overheating?

by Frustrated RVer
(Chula Vista, CA)

I have a 1983 Fleetwood Southwind 32'. I have a Chevy 454 7.4L engine. I have recently been having trouble with it overheating. I have had the radiator, fan, fan clutch, water pump and thermostat all replaced within the last 6 months. I have no white smoke and am not losing water. I have also removed the entire AC unit including radiator to allow for more air flow. I have also removed all extra weight from inside and outside the Motorhome. I do tow a 1997 Nissan Sentra on a tow dolly.

On straight-aways she does well but on the grades the needle moves fast to the hot mark and nothing slows it down. Any help will be greatly appreciated.

Thank You,

Frustrated RVer

ANSWER: Greetings Frustrated RVer thanks for submitting your question on our Ask An RV Question Page.

I am sorry to hear that you are going through this and I am afraid that I may not be the bearer of any good news for you either. I am assuming that prior to this you did not have an overheating problem. First I also need to assume that you have had the engine cooling system pressure tested using a Cooling System Pressure Tester and you have also replaced the old radiator cap (I know this sounds stupid but a bad radiator cap that is not holding the proper pressure can cause the symptoms you are having and you would not notice a loss of coolant because it would go into the coolant recovery tank and get recycled back into the engine cooling system).

If all of the above has been done then the only thing I can assume is that you have an internal problem in the engine allowing the cooling system to lose pressure. This could be anything from a bad head gasket, a small crack in the head or even a small crack in the engine itself. Just because you are not seeing signs of white smoke or steam coming out of the tail pipe of your Motorhome does not mean that there is not a problem.

For a quick check you should remove the oil filler cap on the engine of the Motorhome and look at the cap itself to see if there is any creamy colored residue in the cap itself. That is a pretty good sign that you have engine coolant mixing into your engine oil.

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The best way of diagnosing the problem is by checking for exhaust gasses that have leaked into your engines cooling system by using a Combustion Leak Tester that uses a chemical reaction to let you know if exhaust gasses are present. If you are not comfortable in conducting this test yourself then you should take your RV into a service center and have them do the test for you.

As I told at the start of my answer I may not be the bearer of good news and based on everything you have done to the cooling system of your Motorhome’s engine there is good chance that the problem may be in one of the engine components I mentioned above.

I hope this helped.

Do you have any suggestions or comments on this topic? You can add them to this page by clicking on the "Click Here To Post Comments" link located near the bottom of this page.

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Comments for Why Is My Motorhome Overheating?

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Good advise
by: Anonymous

Thanks for all the comments. I am on my second motorhome with heating problems. I have been given quite a few good suggestions here. As long as I don't use my air or go over 62mph. I am fine.

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overheating p chassis
by: mike

when it overheats on hills do you hear the fan clutch engage. most p chassis have a 7 blade 19" fan thats very loud when the thermal fan clutch locks up unless it slips. its a special hd gm fan clutch, but i have used the hd hayden clutchs to. no jet engine sound-no good. also on big hills downshift to second and get the engine revs up which also equal high waterpump and fan speeds

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Dirty Radiator?
by: Tom

Under mild pressure (not with real hard pressure) spray the radiator fins to clean them out. Sometimes it's the simple stuff that causes the problem.

If you go to a self serve car wash stand back 2-4' with the nozzle to ensure the soft fins of the radiator aren't mashed under pressure.

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Engine overheating problem
by: luvtheus

Check the lower radiator hose to see if there is a spring on the inside of it that runs the entire length of hose. The reason for this spring is to prevent the hose from collapsing from suction created by the water pump as it draws water from the radiator.This will normally occur at higher rpm's by the engine as it works harder climbing up steeper hills.

I have seen this problem happen numerous times before as the spring will become rusted after a few years and deteriorate thus becoming useless. I dont know why many hose manufacturers quit installing springs in new hoses over the last decade or so but the last hose I bought for my motorhome did not have one but I was lucky enough to have a spring in my shop left over from an older hose that I installed in the replacement hose. Check it out, that may be your problem. John.....

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Check your transmission
by: Anonymous

You might want to check your automatic transmission, specifically the torque converter. Since the transmission uses the engine cooling system to cool the transmission, any excessive heat buildup in the transmission will be reflected in the engine cooling system. This would be most noticable when the unit is under the load, such as climbig hills, and or towing.

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overheating
by: Anonymous

i have a 1985 allegro with 454. it would act like
it wasn,t getting enough fuel and start running
hot, on your thermostat housing there,s a unit
that screws into it with 4 vacume hoses going
to the carburator, check it out, probaly your
problem.

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hose collapse
by: Anonymous

Hose collapse is another problem that might fit this. As flow increases pressure drops in lower hose to radiator, if it's spring shape keeper is dead than it will collapse limiting thru put. I have had this happen on a boat engine with a circulating pump, I see little reason why it couldn't happen on a m/h engine.

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overheating
by: Anonymous

also check for coolant in the motor oil

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