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bkahler 02-27-2007 09:45 PM

Cooling at idle
Just wondering how many of you can have your MH sitting at idle for long periods of time without any significant temperature rise or over heating issues. Our previous SOB MH built on the P30 chassis would start getting excessive temperatures if sitting and idling for a period of time, even with a new replacement radiator. I've noticed (while idling) that our 84 310 temperature can rise to as high as 220 or so (before I finally shut it down) and that was with an ambient temperature of around 65 degrees. This particular engine has about 17,000 miles on it and was a factory Gen 5 crate engine. From Savannah GA to Arkansas it ran pretty much right at 200 degrees. Of course we were traveling with ambient temperatures only in the upper 50s max, however we were towing our Honda behind it so that did add some overall weight.

It does have a new fan clutch, water pump and radiator all within the last 5 years. The PO did comment that when going up grades in the mountains towing his Jeep he had to keep his eye on the temp gauge. That just doesn't seem right to me. I would think a properly designed (and maintained) cooling system should be able to deal with these conditions. Am I missing something?

Anyway, any input would be greatly appreciated :)


overlander63 02-28-2007 06:41 AM

It's an ongoing issue, since there really isn't a lot of area to cool with. Also, the radiator sits way far back into the body getting air to it is a challenge. Does your moho have an auxillary cooling fan on the radiator? If not, this is one method of helping with the issue.

Druupy 02-28-2007 08:12 AM

You probably have a 195 degree thermostat in the motor.
That gives the best fuel mileage as long as it ses only light duty.
What you have is at least medium duty 180 degree,
or heavy demand 165 degree.
Get a cooler thermostat and see what happens.

guy99 02-28-2007 09:51 AM

My 1984 310 Limited ran 200-210 no matter what I did to the cooling system until I replaced the temp gauge and sender. Now runs 180-190 unless under heavy load with high ambient temps.

I suggest you validate the reading you are getting.

Silvertwinkie 02-28-2007 10:26 AM

There are several things that can be done in cars that I would assume can be done to mohos and the P30 in particular.

One is do a good flush of the system. Clean the radiator from the inside out by pushing water from a hose from the engine side to dislodge any bugs, dirt, etc the came in from the other way. These two alone lowered my coolant temps by 3-4 degrees.

I added water wetter and frankly found no benefit, though some swear by it.

Some folks have place an all alum radiator in place of the current designed units. These puppies will drop temps like a rock, but be prepared to shell out some war bucks for them!

Of course as has been suggested, a thermostat replacement can do. I have a 160 stat in my SS, but it has reverse cooling, where the heads get cooled first as part of the LT1 design, which I doubt the 454 has. Going too cool on a non reverse cooled engine can be problematic, particularly for engines that have temperature controlled functions, not computer controlled. Going from 195 to 180 might not be too bad, but going from 195 to say 160 on that engine might not be such a hot idea (literally). :D

Poprivet 02-28-2007 11:36 AM

I like two of the suggestions provided - Do a verification of the actual temp and if it turns out high, look into auxiliary electric fans to increase the airflow though the radiator when the moho is not moving. It sounds like you cooling system is working ok, just can't get enough air to provide a suitable heat sink when the moho is at idle.

GlenCoombe 02-28-2007 01:25 PM

I changed my thermostat out last summer for a 160 and saw a great drop of course. Didn't put the 195 back in til the cold snap last month. Now with the temps returning to normal I'll be looking for an opportunity to change back to the summer stat.
I also have a fast idle setup from the old engine driven bus type a/c. If things get too hot I can always wind it up some.
The big block at idle is just kind of loping along so consider shutting down if you're idle time and temp is of concern.
But the bottom line is to change that thermostat for the summer.
Heat is the enemy.

bkahler 03-01-2007 05:41 PM

Wow :D Thanks for all the replies. As yet I don't know what range thermostat is in the engine and I really like the idea of verifying what the real temperature is. Any suggestions on how to best determine what the real temperature is? I've been thinking of using something like a laser temperature probe, would that work?

I'm still hoping someone will post pictures of their electric cooling fan installations so I can see what that looks like.



guy99 03-01-2007 05:55 PM

When I had my radiator replaced the shop used a laser temp gauge on the thermostat housing and got a much lower reading than my gauges. Also the engine did not seem hot, it didn't smell like a hot engine, didn't ping, and cooled down very quickly when I parked.

lewster 03-01-2007 07:36 PM

Along with the great suggestions above, you might also consider an oil cooler as a desired engine mod. It will do a lot to keep your engine at lower temps, along with a functional cooling system.:D

str8strm 03-01-2007 08:00 PM

We're going try to get over to where our 345 is stored this weekend and do some tinkering. I'll take some pix of the fans and post them. Ron

bkahler 03-01-2007 08:32 PM


Originally Posted by str8strm
We're going try to get over to where our 345 is stored this weekend and do some tinkering. I'll take some pix of the fans and post them. Ron


Photos would be great! Like my wife says, men are visual oriented and women are intellectually oriented :D


I had been thinking about an oil cooler and will have to include that to the list of upgrades to be done. In our last MH I really hated sitting in traffic having to turn the a/c off just to try and keep the temp from climbing through the roof.


Sounds like the laser probe might just do the trick.

Thanks for all the feedback!


Poprivet 03-01-2007 09:15 PM

Heres a test you can do -
With your motor home near an A/C electrical supply, hook up an ordinary household box fan against the grill, on fast, and blowing streight into the radiator. See if the idle temp goes down any.

bkahler 03-02-2007 05:34 AM


Originally Posted by David Alan
Heres a test you can do -
With your motor home near an A/C electrical supply, hook up an ordinary household box fan against the grill, on fast, and blowing streight into the radiator. See if the idle temp goes down any.

David, I should have thought of that myself. Thats exactly what I used to do with my wifes race car before we installed the electric fan in front of the radiator. She used to run with no fan at all so we had to use one of those square box fans while doing tune up work on it at idle.

Thanks for the reminder :D


IPM 04-08-2007 11:48 AM

I moved the aux trans cooler and engine oil cooler to right of radiator, put an electric suck thru fan on stacked engine oil cooler/aux trans cooler, installed exhaust headers which moved heat under chasis, removed radiator and had cleaned out, installed 180 thermostat, new water pump, hoses, belts and it runs very cool at all times. Before it got hot like yours.

bobchevy89 04-08-2007 01:52 PM

try flushing the fins of the radiator out with a hose .do you have a trans cooler and a oil cooler in front of the radiator? the help trap dirt in the fins .causing poor air flow.

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