Overheats but only when idling

TomP · Post by **TomP** » Tue Jul 17, 2012 7:44 am

Not sure what it could be.

I replaced the belts and the belt tensioner; flushed the radiator; replaced the hoses.

I'm about to take it in the the shop. Any ideas?

1995 24RB

Thanks

TomP

ewagman · Post by **ewagman** » Tue Jul 17, 2012 10:17 am

When my previous MH was nearing 20 years old, it overheated climbing hills. A new radiator completely solved the issue. Flushing an old radiator probably isn't effective enough. The deposits get a tight grip in the radiator tubes. A worn water pump is also a possibility.

Until you get it fixed, you might rev the engine up in neutral when stopped to increase the coolant flow through the radiator. Or turn up the heater temp and fan, not a pleasant thing to do in the heat of summer.

mockturtle · Post by **mockturtle** » Tue Jul 17, 2012 11:11 am

Or turn up the heater temp and fan, not a pleasant thing to do in the heat of summer.

We did this a couple of times when towing a trailer with an SUV in the desert in summer. Yes, it's painful but it works!

whemme · Post by **whemme** » Tue Jul 17, 2012 12:17 pm

TomP,

Since it overheats only while idling, I would check your cooling fan clutch. That clutch unit senses the temperature of the air being drawn thru the radiator past the cooling fan blades and causes the fan to be direct coupled to the fan pulley with no slippage when the air temperature raises to a certain high temperature.

If the fan remains uncoupled while sitting still idling, the engine will overheat.

A small photo of the E450 fan clutch is show below.

karls · Post by **karls** » Wed Jul 25, 2012 9:52 pm

I agree that the first thing to check is the fan clutch, although I'm not sure how you can tell by looking at it. It will turn some even when engine is cool.

The best way is to rev up the engine and listen for a loud howl such as comes from big trucks when they are accelerating.

The fan clutch on my 94RB failed on a recent trip west that took us over the continental divide. It was necessary to turn off the A/C and turn the heater on full hot to keep the temperature reasonable. I had NAPA install a new one, but no change.

Checking with the local radiator shop the guy said after market clutches are unreliable and to get one from a Ford parts department.

An interesting aspect of this over heating business is the information that I got from the scan guage. It gives a numerical readout of the water temperature, and can be compared to the Ford temperature guage in the dashboard. It turns out that the Ford readout is considerably damped from reality, that is it doesn't show an increase until the water temperature is considerably elevated above the highest thermostat limit. Example, my 196 degree thermostat was fully open at 206 degrees, but due to conditions (load, hill, wind) the temperature would keep rising with the Ford guage only beginning to climb at 225 degrees.

One one occasion I took a chance and let the temperature go way up to see if the fan would kick in, but no luck. The temperature got to 248 degrees, the Ford guage went into the red and the check engine light came on. At that point I pulled over and threw water on the radiator, and turned the heater on.

Letting it go that far was taking a chance with a blown head gasket, but I got away with it.

Another avenue to check is clogged radiator fins. If the radiators (actually three of them - A/C, tranmission, engine) are jammed full of bugs it will keep the hot air from getting to the clutch and heating it up enough to cause the viscous clutch to engage.

whemme · Post by **whemme** » Wed Jul 25, 2012 10:53 pm

karls,

We are all wondering. Did a Ford OEM replacement fan clutch fix your over heating problem???

hrgermany · Post by **hrgermany** » Wed Jul 25, 2012 11:05 pm

If the fan clutch is not the problem, flushing the radiator does not do any good. The radiator has to come out, the top has to be removed and the radiator has to be roded out.

Hans Rueckert
1995 BF 26FT RSB

whemme · Post by **whemme** » Thu Jul 26, 2012 11:20 am

Hans,

Not sure what 'roded out' means?

ewagman · Post by **ewagman** » Thu Jul 26, 2012 11:43 am

whemme wrote:Hans,

Not sure what 'roded out' means?

Bill,

In the old days, when things were repaired, not thrown out, a radiator guy would take small long rods and push them through the radiator tubes to remove blockages and scale, flush the debris away, solder any holes, and reassemble the radiator. In a couple a years, he would do it again. Much lower cost than a new radiator. One of my junker cars I had in high school had it done at least twice. Now they just install a new third world built radiator. More cost effective with the current economic conditions. The radiator rods are likely stored alongside the vacuum tube tester. My parents (RIP), who struggled through the depression era, would be appalled.

karls · Post by **karls** » Thu Jul 26, 2012 7:15 pm

Bill,

I haven't gotten around to installing the OEM (Ford) fan clutch yet. I'm going to check for clogged radiator fins first. I'll try to get it done soon while there is some hot weather to test it.

NAPA said they would honor the warranty, but that would be another after-market clutch.

I'll post the results.

hrgermany · Post by **hrgermany** » Thu Jul 26, 2012 7:54 pm

In the old days radiators were made out of brass and could be cleaned.
Now a days they are made out of aluminum and should be replaced.
I have a 1995 E350 that has a brass radiator.

Hans Rueckert

TomP · Post by **TomP** » Fri Jan 04, 2013 6:39 pm

It was the fan clutch. Thank for the info. Sorry for the absurdly long response time from me.