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DanC
09-06-2005, 06:37 PM
There are some sharp mechanics on this board, maybe someone here can help me.

I have a 1995 Dodge B250, 110k miles, 318, no significant work done it. It overheats when under load. Under 80 degrees outside and the temp gauge only goes up about 1/8 of the gauge. Above 80 degrees and it climbs, above 90 and it will go to 5/6s. While under load (under load here is defined as going up a steep hill, towing on the flats is fine)Turning on the heater will reduce the temp. Speed and rpm are not factors. Turning off the AC will reduce the temp. Towing or not towing is only a factor in that towing up the same hill is more of a load and thus overheats more.

I have replaced the thermostat, water pump, serpentine belt, all hoses, and radiator (transmission cooler is built into this radiator). The new radiator did lower the operating tempurature by about 1/16 to 1/8 of the gauge. Local mechanic tested for hydrocarbons in the coolant, said all was good and thus thinks the head is fine. Oil looks fine. Coolant looks fine. Dealer said the fan clutch needed replacing, local mechanic said the fan clutch was fine. I replaced the spark plugs (all looked the same), wires, dist cap, and rotor. All looked normal. Computer was replaced about 5 years ago. No noticable loss of power under load and no pinging. Catalytic converter was replaced about 4 years ago with a cheapo. Muffler is probably suspect but I have no noticable loss of power under load (second gear holds 55 mph up some really step grades).

My local dealership has gone downhill and one can not even talk directly to the mechanic, just the service associate :huh:
I don't know what to try next.

/And no stupid replies like "get a Ford" :cool:

rodltg2
09-06-2005, 07:02 PM
how about " get a new dodge w/ a hemi"

:D

AirJunky
09-06-2005, 07:04 PM
how about " get a new dodge w/ a hemi"

:D
And don't get too far from a gas station if you do.... :uglyhamme

robisjo
09-06-2005, 07:34 PM
I had a 92 Dodge with the 318 and had some problems with the engine heating up. I replaced the radiator and the fan clutch and did not have any problems after that.

jimmer2880
09-07-2005, 08:23 AM
Fan clutches are usually only good for 80 - 100k miles. Problem is that you don't realise they went out until you hear the new one spin up. Amazing the difference.

Put in the new fan clutch - it'll probably lower your temps.

Something else to thing about is shocks. I know this sounds funny - but a lot of your cooling has to do with air passing through the engine-compartment. If the rear shocks are gone & the springs are sagging - instead of the rear of the truck being higher than the front creating a vaccume, it's lower creating a positive pressure, that will not permit as much air to freely move through the under-hood area.

Thrall
09-07-2005, 01:52 PM
Jimmer, I've never heard that one before, but anything's possible I guess.
Regarding the fan clutch. Seems like the only cooling system part you haven't replaced. They are a temp operated clutch that locks up when the engine gets warm, providing positive pull of air through. To check it, wait until the engine is good and warm, and try to spin the fan. When the motor's cold, the clutch is disengaged and the fan will spin freely w/o moving the pulley. When it's hot, the fan will be "locked" to the pulley and you won't be able to spin it freely. If it spins when the engine is hot, the clutch is bad.
Also, don't try putting a cooler thermostat than wat's reccomended. The engine's ECM keeps the fuel/air ratio enriched until the engine gets over 180 deg, like a choke. Tried a 165 in my Dodge P/U for the hot temps in AZ and it threw a code that the engine wasn't warming up enough.

DanC
09-07-2005, 02:08 PM
Well the fan clutch is the only thing I haven't replaced in the cooling system. I didn't think it could be the fan clutch because if the engine overheats up a hill, pulling over to the side of the road and sitting at idle will allow the engine to cool back down to normal. No problems sitting at idle or in stop and go traffic. Or does the fan do something at high speeds? I haven't tested it myself and the mechanics are a split decision. At this point I might as well replace it.

What about the transmission? Could it be contributing somehow? This is the original transmission and has never been rebuilt. They seem to have a reputation of lasting an average of 40k miles. I have only experienced transmission failures that slip, not bind, and this one is not slipping.

darkbrown
09-07-2005, 10:31 PM
suggestion frum Mountain boy type,.....a 318 in 2 1/2 tons of truck towing a ton and a half of boat on an incline is gunna be working pretty hard. The trans is going to be backshifting a lot. might want to service the trans,(oil/filter) and get the converter checked. The harder the trans works, the warmer the oil, (which transfers/contributes to your engine coolant temp at the rad)...a divorced trans cooler might be worth considering. That little wedge motor is a pretty good one, good luck with it.
newer an' bigger ain't necessarily better..........my $.02

jimmer2880
09-08-2005, 07:11 AM
Jimmer, I've never heard that one before, but anything's possible I guess.
Regarding the fan clutch. Seems like the only cooling system part you haven't replaced. They are a temp operated clutch that locks up when the engine gets warm, providing positive pull of air through. To check it, wait until the engine is good and warm, and try to spin the fan. When the motor's cold, the clutch is disengaged and the fan will spin freely w/o moving the pulley. When it's hot, the fan will be "locked" to the pulley and you won't be able to spin it freely. If it spins when the engine is hot, the clutch is bad.
Also, don't try putting a cooler thermostat than wat's reccomended. The engine's ECM keeps the fuel/air ratio enriched until the engine gets over 180 deg, like a choke. Tried a 165 in my Dodge P/U for the hot temps in AZ and it threw a code that the engine wasn't warming up enough.

Not all fan clutches work off of heat - some work of engine RPM. His though, should be heat activated. However - it's not directly engine heat, rather ambiant heat at the clutch. So - when the engine gets hot, the ambiant heat at the clutch does warm up. The slower you go, the more ambiant heat is available - since the clutch is in front of the motor.

Seriously think about the positive pressure bit though. It did make a difference on my 88 1/2 ton Chevy. It's rear was sagging, so I added "add-a-leaf"s & new heavy-duty shocks which picked her arse up.

It didn't "cure" my problem, but it did make it better.

What also helped was when I replaced my fan clutch. I had similiar problems as you - up-hill overheat. Sit on the side of the road - fine.

DanC
09-08-2005, 12:39 PM
You guys are giving me some good points to ponder, thanks.

Jimmer, it has new shocks and I have air bags so the van rides level when towing, so that shouldn't be a problem.
Mountain Boy, yep it works pretty hard up the hills but used to do a very good job (still does, just runs hot). I never tow with the overdrive on and I always manually shift going up the hills. Otherwise, like you said it, it tries to up and down shift constantly. I'll be taking it in for the tranny service this weekend.
Thinking about the positive pressure thing......There is a grill and the AC condensor in front of the radiator. So maybe the fan is needed at higher speeds to overcome the positive pressure and pull the air through the grill, AC and radiator?
Thrall, I did a quick test. Cold, the fan spins freely by hand. Started up the van and the fan spins. Warmed the engine up to its idle temp which is 1/3 up the temp gauge. This is not very hot but as hot as I could get it sitting in the driveway still hooked up to the boat. Turned off the engine and the fan stills turns easily by hand. How hot should the engine get to lock up the fan clutch?

jimmer2880
09-08-2005, 01:00 PM
If you're riding level - then you may not have a pressure problem.

A new fan clutch will run you about $80.00 & take about an hour to replace. It sounds like yours is toast. Since it's a chemical reaction to the thermo change that engages it - they will spin all the time the car is running - just not as fast (kind of like the prop turning while in neutral).

DanC
09-08-2005, 01:13 PM
Good call, $75 at Pep Boys. In stock. 1 hour? My methods are little more like Brad's "oil change procedure" :uglyhamme

jimmer2880
09-10-2005, 08:12 PM
If your dodge is anything like my Chevy & Jeep - you'll need to un-bolt your fan shroud in order to get the fan out. You shouldn't need to remove it - just be able to move it around. Then - it's just 4 bolts holding the fan & clutch to the motor, then another 4 to remove the fan from the clutch.

Not difficult at all - just a pain. My air ratchet (there wasn't enough room for an impact) paid for itself on that switch.

DanC
09-12-2005, 12:42 PM
Did it last night in 15 minutes. Didn't need to undo the shroud. 4 bolts to the fan blades. One giant nut screws onto the waterpump shaft. It helps that all this hardware had been undone only months previous and all hardware had anti-seize on the threads.

Now I just need to weather to warm up so I can test it. :steering:

Thrall
09-12-2005, 02:38 PM
Dan,
I see you've already replaced it, but to answer the temp question, if you just got up to operating temp from a cold engine, it may not have been warm enough yet. As Jimmer said it is activated off of the ambient temp at the clutch. I don't know what the exact temp is, but it takes the engine to be pretty well heat soaked to lock up.
Another option is can the clutch fan and get a flex fan for it. Downside is it will cool too good in the winter.