Help please! I have a 03 1500 4.7L. I went through 3 radiators in less then a year due to them busting at the plastic seams. I bought an all aluminum radiator and had to change my resi setup. Now the issue is that the radiator is backflowing into the resi and coming out the overflow tube. Anyone know how to fix this? Please see attached pic of my setup!

This was how I was told to reroute due to radiator being a different setup then factory radiators.

 

Perhaps address the issue of blowing three radiators and why that may be.

Is the truck consuming coolant? Is the upper radiator hose stiff as a rock? Does your exhaust smell sweet? Is there any white smoke coming from the exhaust?

On a cold start, with the reservoir cap off, do you see bubbles being pushed into the container? Is the coolant frothy? Is there any milky residue under the oil cap?

 

I blew 3 radiators due to cheap plastic sides breaking and pouring antifreeze out. Every time the radiators busted my truck was parked and came out to puddles or waterfalls of antifreeze. There's no bubbles, no smell of antifreeze. Ik it's not a bad water pump, thermostat, or bad gaskets. I've never had backflow issues until I had to modify the resi due to the different radiator.

 

One problem could be that your radiator cap is rated below cooling system pressure. Be sure your cap is 16 lbs.
Prismatic's point is right on; figuring out why you busted 3 radiators may tell you why you have current problem. Ok, the plastic failed, but most radiators have plastic components now. Blowing 3 radiators indicates problem may be more than cheap plastic. Now your high-end radiator has flow problems.
How many miles do you have on the truck, and what maintenance have you done on the cooling system? Are you noticing anything else unusual that is cooling system related, like coolant puddles or erratic cab heating?
I recommend that you check your plugs for coolant. Not easy to detect on plugs, but if you have been having this problem a while you may see white chalk on some plugs. I'd also suggest using a coolant flush product, then replace the upper and lower hoses and thermostat.
Inspect your radiator for bulging passages.
I'd confirm if there are combustion gasses in the coolant or not. One way is the bubbling radiator test that Prismatic recommends, and there is also a dye available that will work.

 

When the engine is up to temp, and you park it, the engine is still hot, thus, the coolant gets hotter, as it is no longer flowing. That can raise cooling system pressure a fair bit, and if it exceeds the mechanical limits of the seams on the radiator...... you get the puddle on the ground. Checking what your radiator cap pressure rating is a great place to start..... I might be tempted to put a pressure tester on the system, and just let the engine idle, and see what pressure does.

 

The caps are the correct PSI. Brand new hoses all the way around, new water pump, thermostat. My truck I proudly say has 310,000 miles. No coolant on the plugs, no burnt plugs, has been flushed. Clearly no one is understanding the fact that it's BACKFLOWING into the resi! The puddles weren't from the resi...its was from the busted radiators. Also it's pretty bad when the 3 different parts store say that it's been happening with the radiators.

 

The extra tank on the top of the radiator there, connected by the hose, also has a pressure cap on it. That would imply that part of the system is ALSO under pressure. Coolant flowing into it as the engine warms is normal operation. When the coolant gets hot, it expands, and it's gotta go somewhere. As it cools, it contracts, and the level in the upper tank should go down. Is that not what its doing?

 

A radiator pressure tester should not be used while the engine is running. The cap of the pressure tester is basically a solid plug and will not allow coolant to have a path to the overflow, so the system will bust for sure if you do this.... like a sealed pressure cooker.
I'm having trouble understanding "back flowing in the resi"....

If the radiator is full while cold and you run the engine, the coolant heats up, expands and overflows into the tank. Now as it cools, it the coolant contracts and should back flow back into the radiator due to the system falling below atmospheric pressure. If it doesn't flow back into the radiator for whatever reason, then the overflow stays full. If the overflow stays full, the level in your rad should drop when cold.

Now why it's busting radiators, well I wouldn't blame three busted radiators on them being cheap. Obviously there is an issue. With system cold, take off the rad cap and start the vehicle. Does the coolant move? It wouldn't hurt to pressure test the system. Also you can use a block tester to test the HG. Both these items can be rented for free from the auto parts stores (once you return them), so you've got nothing to lose in trying them.

I got you beat on mileage

 

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That's the problem it's not going back into the radiator until I release the pressure from both caps

 

You have a 2003. The puke tanks that year are designed to have the pressure cap and not the radiator (even the 03 hemi is like this):



You changed that and now have two caps. In 2004 they redesigned the system and put the cap on the rad. Your system is fighting itself. Either put the correct style rad back in or change the puke tank to something like the later style (looks like this):