I bought the truck new, 02 1500 4.7
3 years ago I replaced the complete timing set and water pump. It’s had 3 radiators over the years, because of cracks.
problem . Temp stays normal until you floor it, then the temperature drops to cold in the winter. Replaced the thermostat 3 times. This last time I replaced it and over filled the radiator. It’s seems better, but now when I shut it off , like getting gas. Up on restart the temp goes up 3/4 😱 it will eventually come down. It’s never done this before.
no it doesn’t have any leaks or engine problems. Why ?

 

Does the thermostat have a jiggle valve on it? A little loose stud looking thing that is in the flat round disc. That jiggle valve goes to the top and it allows air to be burped to the radiator where the air will then get burped to the expansion tank and overboard... Not sure if we have this or if it is even a thing with the 4.7L installation.

So, in the 18 years prior to the timing set and water pump, had the cooling system been previously serviced, flushed, coolant exchange.... things like that?
Do you know about how there are various formula engine coolant and that color doesn't (surprisingly) mean anything as far as formulation?
Do you know that mixing some of the formulations of coolant can supposedly create a gelling situation?

I am certainly not trying t point fingers or shame anyone for forgetting to service the coolant, I have a 2010 that I bought new and only has 58k... a year ago I remembered that coolant is time based and not mileage and although I am in the tropics (no freeze) that it is the anti corrosion properties that need to be refreshed regardless...

I hope this helps you.

Please return and tell how this information worked for you, what you find, and how you eventually fix your vehicle (even if it is that you brought it to a mechanic / dealership for repair)
It is your feedback and final repair report that will make these forums useful to others in the future.
Many times I search and find the same exact fault that I am having, someone suggests how to fix it, the patron follows the suggestion and then never returns to say YEA! or NAY...


The forum thread just goes dead because the person fixed their fault and has not a care to offer the answer anymore. Please don't be that guy.

Cheers!

 

First, I do all my repairs. I’m a Journeyman machine repairman by trade and I built street rods for a hobby. With that said. Yes I change the coolant every 3 years or less. Depending on when or if the top radiator hoses breaks. It’s done that since new. Just like a 68 Road Runner I bought new. It would push out the freeze plugs of over rived . Learned to live with it. Anyhow, everything is by the book 👍

 

Just thinking out loud brother. No offence intended.

I was trying to help determine if maybe the system is slugged up with something. I had a work truck at my job overheating as a kid and I remember while we could see strong circulation through the radiator cap when the thermostat opened it took an old timer mechanic to point out that the bottom of the radiator was all fouled up and we only were getting 25% cooling capacity.

I will be curious to hear what you eventually find
Cheers!

 

Thanks, I’ve taken it to several shops and they are baffled too. They say nothing is wrong when they drive it, but they don’t floor it and hold it WOT for 10-20 seconds. That’s when it happens. Like passing a truck going uphill, pulling a trailer. Over heating I can understand, but this, Never in my lifetime.
I’ll definitely post something if and when I find something 👍

 

For higher temp at restart, that may be normal. The engine is still rather hot, and the coolant isn't flowing..... Maybe the current temp sensor is more sensitive than the previous one?

As for why it drops off at WOT.... that one is a mystery to me. About the only thing I can think of, is the engine torques itself over a bit, and maybe shorts the harness, or pulls it enough that it loses connection? (depends on if resistance goes up with temp, or down....) Could try letting it idle up to temp, and the tug/pull/twist/bend/spindle/mutiliate the harness, and see if anything interesting happens.

 

I believe that in the 3.8L Mopar minivan engine circa 2002, that sometimes the temp sensor is in a bubble of air and it doesn't read the heat... what they were thinking?
And that is why I asked about the jiggle as it needs to be installed orientated up at the top.

If only there were a way to get a secondary temp sensor somewhere else on the circuit to verify the indicated conditions you are noting...

 

Isn't the stat down on the bottom on the 4.7 though??

 

yeah, I don't know the 4.7 block. , I am greener than grass
I have only been a RAM enthusiast for 39 hours. I am here trying to find answers to repair my HVAC and try to help where I can...
Perhaps I should keep to myself. the last thing I want to do is confuse the issues.

 

But what fun would that be?

Sometimes, it's the 'throw it against the wall, and see what sticks' suggestions that get a member going in the right direction.