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jintx 07-07-2011 12:56 PM

Broken water pump impeller
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Just recently had the water pump go out. No weep hole leakage, just instant failure. As a result of the failure, the middle was broken out of the plastic impeller. There are pieces unaccounted for. I've already disconnected the lower radiator hose and removed the thermostat, no pieces in there.

I'm looking for advice on how to proceed. This is my first time working on this truck and am completely new to this 4.7, though I've logged plenty of hours on the old 318. Should I be worried about the missing pieces?

None of the pieces missing from the impeller pictured below have been recovered.

Update: I just flushed the radiator with both the top hose disconnected from the radiator and the lower hose disconnected at the thermostat housing. I also flushed into the upper radiator hose (where it connects to the radiator) into the engine, water came out of the thermostat housing. I did this with the old water pump on and off. Still no plastic pieces.

Another Update: After numerous flushings I found that the pieces had become lodged in the passage way between the water pump and thermostat housing. I got them out by keeping a flow of water from the top while jabbing a stiff 1/4 rubber hose into where they were blocked from the bottom. It was just Murphy's law that these 3 pieces had become locked into place where the flow of water (from a garden hose) wasn't enough to dislodge them.

I'll leave this post up, maybe it'll help somebody else. Now I'm just wondering why Dodge used a plastic impeller. Less rotating mass? Who knows...

RedRam10 07-07-2011 05:10 PM

Glad you were able to get this cleaned out and thanks for the post. Others will appreciate the help. :rep: (I'm out but will get you some points when I'm able).

aviatorcoastie 07-07-2011 11:10 PM

Just a quick note on this. I recently went through 3 water pumps in about a month and a half. The bearings went out on all of them which left me perplexed. Come to find out that the belt tensioner was bad causing them to fail. Anyway, the water pump that is installed right now is a BRAND NEW unit from O'Reilly Auto Parts and it has a cast steel impeller. The first 3 were plastic and I asked the sales person if they had a brand new unit with a steel impeller. Low and behold they did!! If you need to replace your water pump, I recommend finding one with a steel impeller to avoid having to find the pieces of the plastic one.

jintx 07-08-2011 09:03 PM

RedRam10, Thanks!

Aviatorcoastie, that's good to know. The water pump I bought was a new (not refurb) from NAPA, P/N TFW 43263. It's standard thread. I hope the bearing don't go out anytime soon, but if they do I'll be sure to update this thread.

I've been thinking about the plastic impeller...I wonder if plastic is used in order to limit the damage to the surrounding parts, which I think are aluminum....but I've done no research on this. Maybe the steel ones act as a sort of harmonic balancer which extends the bearings life. Either way, it's a somewhat simple part that should not go out very frequently IMHO.

440Magnum 07-11-2011 12:07 PM

I think its mostly about cost (plastic is cheaper) but also about flow. Plastic is generally very smooth and so the impeller doesn't have roughness that can trip the flow turbulent and create cavitation.

Also, the impeller really shouldn't break (yes, I know you have direct evidence to the contrary). Its never subjected to any forces that should break plastic- my wife put >250,000 miles on her old 1993 3.5L v6 with a plastic water pump impeller and we never had that failure mode. That engine has a timing belt driven water pump, so the water pump got replaced every 90,000 miles along with the timing belt just as a precaution, though. In fact the one waterpump "failure" we had was the first aftermarket pump with a steel impeller- the drive pulley sheared off the shaft. After that I went back to plastic impeller pumps and had no worries. I'm wondering if some piece of casting debris went through yours and caused the plastic to break that way.

RamTech 07-11-2011 12:19 PM

Plastic impeller failure isn't uncommon with the 3.7/4.7 pumps although the most common failure is with the bearings. As for why they chose plastic, only the engineers can answer that question.

jintx 07-12-2011 12:46 AM

So yet another update.

When putting everything back together I saw that the indicator on the belt tensioner was at about 80%. I didn't worry too much about it, the belt looked fine. I assumed just a little stretched. I went and bought a replacement today, installed it, and the indicator was still at 80%. Turns out whoever had the truck before me was a bit creative in their routing. Nothing was running backwards or anything, but instead of going from the compressor->water pump->alternator, it went compressor->alternator->water pump->power steering. I guess it's possible that having tension on the shaft of the water pump at about the 1:30 position rather than the 12:00 *maybe* had something to do with the failure. But it's a shaft, and I don't really think so.

There was no belt routing sticker under the hood, else maybe I would have caught this sooner.

aviatorcoastie 07-13-2011 09:27 PM

The same thing happened to me. I wound up replacing the belt tensioner and have not had any problems since. The replacement does not have the indicator on it, so I will have to keep an eye on it. I'll just check it at every oil change.

bigdogfire 07-15-2011 06:57 PM

The water pump went in my 07 at 30k miles, in my 02 it didn't go until 70k. was not happy when it went at 30k!

Maccanuck 07-08-2013 10:11 AM

Hi Folks I am stuck here in Springfield, MA with a 2001 4.7 L quad cab SLT 125,000mi, on route to Canada from Houston. My truck was overheating first discovered after crossing the George Washington Bridge in NYC and getting stuck (1st time in Bronx). Some great guys came over and had extra antifreeze . . . filled it up again and replaced the fan clutch and ended up in Springfield with another plastic bottle of antifreeze fill up. The Dodge tech here checked for leaks none found and thinks it is the impeller. The heater blows extra hot. Any ideas in what could be causing empty radiator with overfilling and overheating. Thx. Maccanuck

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