Dakota overheats at highway...

[AltaSkier]

I'm running a 2000 Dakota Club Cab 4X4 with the 4.7L V8. Last summer it started to overheat 230-240 when towing and in the city (no towing -but outside temp 95). During the winter I had the cooling system power flushed (BG Products) and the thermostat changed. No problems.

On a recent trip in mild temps (60s) - no load or towing - the engine was running at 200/210, then ran up to 230 at 70 mph. As I slowed down to 55 or so the temp fell back to 210.

The fools in the shop are trying to tell me it's the fan clutch. Yes, the fan clutch might be weak but they can't get it through their heads that the fan clutch is not an issue at 70mph.

I'm guessing it's a radiator blockage to some degree and thinking of running a course of Zerex Super Cleaner through the system.

I hate putting that stuff into my system but I don't know what else to try. It's obviously not the fan clutch. If anyone has any comments or suggestions I'm all ears. Thanks!

[AwPhuch]

Do you have a 2nd transmission cooler block? It could be the transmission cooler block in the radiator is dumping all that heat in the radiator at tow

What kind of load, plus on hot days the radiator is less efficient, 230 isnt all that extremely hot under a heavy load...It would appear high, but would still be in the normal operating temperature

Just make sure you have a good 50/50 or even a 60/40 mix of antifreeze and you should be good to go..if you do much towing though I would STONGLY recommend a 2nd bolt-on tranny cooler (plus it helps in that 95 degree temp during stop/go driving)

Brian
AwPhuch

[AltaSkier]

With outside temps in the 60s, one passenger, no load and no trailer, the temp ran to 230 at 70 mph - and fell to 210 or so when I reduced speed - but never to the normal 195 area.

[AwPhuch]

Then you might need to replace with a cooler thermostat...

Going slower wouldnt help it run cooler, it should have been the other way around..faster = cooler temps because more air is being pushed thru radiator...were you running your A/C?

Go ahead and run the radiator flush thru it, just wash it out and see if it gets a ton of funk out of it

Brian
AwPhuch

[riverat440]

I have a 94 with the 318 and was going through an on going battle for the last 6 months. I bought this truck without a radiator shroud and the A/C wasn't working. When I put the new evaporator in and charged the A/C I thought life was good. First time in traffic it overheated bad. I got a new shroud and still no luck. Then I changed over to electric fans. When I cut into the top radiator hose to install my temp sensor for the fans I noticed that the top hose was empty but yet the radiator was full. Well I ended up changing back to the clutch fan with a severe duty clutch(about $50 at the local wanna be auto supply) and used the new sensor port to fill the top rad hose. Now everything is good again as my temp never goes above half way even in traffic with the a/C on. Don't know for sure if your hose is above your rad fill but it sure did make a difference in mine. If you even take the hose off at the radiator you should be able to see if it is full of coolant or not. It has got to be the cheapest thing to try. Good luck

[AwPhuch]

Isnt the top radiator hose the outlet from engine to radiator..filling that wouldnt matter, unless your waterpump or whatnot was going bad..
Mine the heater stops heating in winder at idle, but once I get the rpms up it works just fine

P.S. I dont have a shrowd either, and mine gets hot at idle in traffic...does the fan clutch also turn the waterpump?

Brian
AwPhuch

[riverat440]

Allowing air in a sealed system will cause coolant to boil at a lower temperature. The purpose of a sealed system is to allow pressure to build and thus raise the boiling point of the coolant. If your heater doesn't heat at an idle it may be clogged and in need of a flush. The water pump isn't a positive displacement pump so at a lower RPM it may not overcome a partial clog. The shroud is supposed to help direct the air flow, if it isn't there the fan will pull air from the place of less resistance-on the engine side. With the shroud in place it helps the fan pull air through the radiator. The purpose of the fan clutch is to engage the fan when the coolant-radiator starts reaching a moderatly warm temperature and disengage when it is not needed. If the clutch is bad the fan will not engage when it is needed and cause higher engine temperature.

[WarHawk1974]

Originally Posted by riverat440

Allowing air in a sealed system will cause coolant to boil at a lower temperature. The purpose of a sealed system is to allow pressure to build and thus raise the boiling point of the coolant. If your heater doesn't heat at an idle it may be clogged and in need of a flush. The water pump isn't a positive displacement pump so at a lower RPM it may not overcome a partial clog. The shroud is supposed to help direct the air flow, if it isn't there the fan will pull air from the place of less resistance-on the engine side. With the shroud in place it helps the fan pull air through the radiator. The purpose of the fan clutch is to engage the fan when the coolant-radiator starts reaching a moderatly warm temperature and disengage when it is not needed. If the clutch is bad the fan will not engage when it is needed and cause higher engine temperature.

This is AwPhuch..I figured out what the problem was that the truck had sat for over a year in a parkinglot without being run

The fuel pump had pitted and the tolerance of the pump frame to the splines had gotten so bad that if the engine wasnt running at higher than idle rpm it wasnt pushing water, and the thermostat was spit in two (the guts were sitting on the inside of the intake manifold)

Once I replaced the water pump, and the thermostat, and the fan clutch not overheat problems whatsoever...I also recommend pulling the powersteering pump housing and replacing the small hose from the intake manifold to the water pump, mine was all stretched and was about to blow anytime!