I've read the new member tag about this issue, but mine is overheating when I shut it off. Runs fine and stays at normal operating temp. Until I shut it off. Just wanted to make sure that the clogged radiator was probably the same issue.

 

All vehicles get hotter after they're shut off since there is no cooling. A clogged radiator won't figure in at that point. How hot does it get?

 

My wife has had it get up to three quarters but I've never had it get but maybe a hair over half (she drives it alot harder than I do). I have replaced the rad cap, but as soon as you shut it off it starts puking out of the resevoir hose end and the heater hose line with the factory junction. I am going to put the stock rad cap back on so at least it will go out the overflow tube. The new cap seems to be a bit strong. It seems like it's building alot of pressure after shut off. Which tells me it's boiling (212) without moving. Never gets over half way on temp gauge while running, so pump must be ok?? If the thermostat is bad, would it survive and stay cool, cooling through it's tiny burp hole? I am baffled. I know on our old suburban with dual air I had a valve in the coolant go out that opened and closed the rear air heater lines. I know my ram doesn't have rear air, but I have heard that they were all equipped for dual climate control but only given the DCC switches on select models? Don't know this to be true, but if it is then a similar switch could be in there and malfunctioning? I grasping at straws now. I'll back flush system tomorrow, and see if that helps.....

 

If it's puking from the reservoir, it's way over 212. Assuming the coolant is mixed properly, it's more like 240 or more. The cap should be a 16#, I think. 3/4 while driving? That's too much, even in traffic. Your fan clutch may be going away. At eight years old, it would certainly be time. That could make it run hot in traffic. When it's hot, can you spin the fan by hand? If so, the clutch is probably gone.

Your 'stat may be sticking - mine was which is why I changed it. That sign would be running hot on the highway.

The 4.7s do tend to run hot for various reasons and they don't like it. Good luck with the flush.

 

Thanks mike, will apply your tests and get back

 

If the clutch fan is shot, you may want to replace it with an e-fan, you can either do the cheap "pick 'n pull" Taurus fans or spend about $250 or so on a fan kit. You'll pick up a couple more HP deleting the parasitic clutch fan and an additional MPG (especially in-town driving) to boot.

The advantage here is that if wired to do so, the controller for the fan will keep the fan spinning after you shut the engine off until the engine reaches a pre-set temperature, so over-heating at shut-off is not a problem.

Some of the better fans on the market, like the Flex-a-Lite kits only draw about 18 amps, so battery drain, even after the engine is shut off would never be an issue unless your battery was shot.

I've been running a Flex-a-Lite 180 Extreme (payed $260 shipped for the full kit from Moe's) since mid-summer '05 and it's worked great. In conjunction with my 180* thermostat, my temp needle has never even come close to the half way line (12 o'clock) even when towing in the deep south in mid-summer...

 

Hammer, thanks for the info I was wanting to do that anyway, but I would like to resolve the issue before I make the swap just for piece of mind knowing that it was fixed before I make the e-fan
swap. I have in the garage a merc mystique fan which I think is the same as a Taurus. I bought it years ago when I was playing with muscle cars. What I don't have is the sensor that zip ties to the rad hose. Or at least thats the way we did it 15 years ago. I'll have to check and see if jegs still carries one or makes an updated version. Eventually I would like to check into putting a dummy 02 sensor on and gutting the cats. I had a friend tell me the 4.7 needed that added back pressure. I don't believe that, if an engine can breathe better it must perform better, but I am always willing to listen to someone whose been there done that.
I drove the truck today wanting to check the clutch fan out but, wouldn't ya know it, today Sookie wouldn't get hot for me. I'll check I tonight when I drive home. If the fan clutch does reveal itself to be a definate problem, then I'll probably go ahead with the e-fan swap. Would love to get back some of the MPG I lost when I switched from the 17" wheels to the factory 20". I lost a full mpg.

 

You can pick up a fan controller at AutoZone for about $35 which is made by the same company as the one Flex-a-Lite supplies with their fan. It uses a probe you insert into the radiator fins.

As far as gutting the cats go, I find it's not necessary. These cats used in the 3rd Gens are NOT your father's 1970's/1980's era cats and are pretty free flowing, at least while in good working condition. I went long tube headers and chose to keep my stock cats, just moved them back about 14" to accommodate the length of the headers.
Sims (fake sensors) are getting hard to come by and ain't cheap. If you just have to omit the cats, use non-foulers (I have a DIY in the FAQ section).

It's a very false conception that you NEED backpressure. It's pure inefficiency - PERIOD. Makes an engine work harder to expel gases, doesn't allow for as much fuel/air mix to enter the cylinders and will, over time, shorten engine life. Free flowing intake/exhaust ALWAYS yields better performance and fuel economy. The down side is that even though over-all HP and Torque are increased, the torque curve moves up in the powerband, so you have the feel of less power down very low in the rpm band. The engine is not working as hard because it does not have to push against the exhaust gases being pushed back into the cylinders.

You can fix this by doing a cam that yields more low end torque or simply by re-gearing to 4.10 or 4.56 gears which will get you up into that powerband sooner...

 

Drove home tonight and was finally able to catch it at a spot where it was where either hammer or mike said was a normal towing temp. (about a 16th past straight up). I am pretty positive that with the coolant blowing out of the overflow the fan clutch SHOULD have been locked up. But it spun like a top. So I will grab that spare e-fan and make sure it works. I will let you guys know if that fixes the over heat at shut off problem so that we can all have a definitive "place to look" for the next guys question. As for now I'm going to jump over to the super chips section and see what I can learn about increasing mpgs without losing performance. Until tomorrow guys!!