04 LLY Max Water Pump

[Ranger354]

This thing appears to have a leak. Trouble is it does it sporadic at best. Today I started the truck and it seemed to pour out. I shut the truck off for a few min. and started it back up and it didn't leak. I did notice the return hose from the engine back to the top of the radiator was collapsed like it had a vaccum pulling on it.

Could the thermostat be sticking and thus causing a vacuum and that causing the hose to collaps, thus not allowing the water out of the pump, thus preasuring it up and causeing it to leak? That make sense?????

I have had this problem off and on for almost two years. Mechanic had it down to the last bolt two years ago and couldn't get the harmonic balancer off and found an O ring busted. Replaced the O-ring and had no more issues until about two months ago.

I need some good pictures or detail steps on how to replace this thing. May be doing it myself in the next couple of days. I have all the tools including the BIG sockets. And the cheater pipe to get the harmonic balancer bolt off.

The leak appear to coming from the back side of the lower intake hose right at the engine block, but I don't know if that is still the pump or something else. O'Rielly's had a water pump, but it was just the internal pump and NOt the complete pump and houseing.

Thanks for all your help.

[Ranger354]

Thought I would add that my friend with the mechanic shop preasure tested the cooling system today and it held at 15 lbs. I ran the truck for at least an hour on the highway and it didn't leak a drop. I have since noticed a few drops on the highway once I got home. It goes from almost pouring out, to nothing, to a few drops. All my experince with water pumps in the past.......once they leak......they leak from then on out.

[More Power]

I suppose how much it leaks depends somewhat on what the cooling system pressure is at the time.

I took a few photos of a leaking water pump the other day. The engine was out of the truck for a custom build, and I saw the stains and oozings at the water pump weep hole - where you indicated.

I believe these water pumps should last for a long time before the seal begins leaking - at least 200K, up to possibly twice that. If sooner than that, I'd consider a cooling system overpressure problem that results in a water pump seal leak. A cooling system overpressure problem wears out the seal long before its time.

Replace the coolant surge tank cap along with the WP. If you can do it or have it done, monitoring the cooling system pressure will give you a clue as to whether there might be a problem with head gaskets - which leads to cooling system overpressure and a WP leak...

Jim

[Ranger354]

The surge tank cap is an easy try first..... funny how the discharge hose from the engine back to the radiator UN-colapses when I take the tank cap off giving it some breathing room. I plan to replace the top discharge hose tomorrow and see if I can get a cap fast. The discharge hose may be week and adding insult to injury. Being a Holliday week, no one wants to tear into it and do a water pump job on a short week. My buddy with the shop is covered up with work right now too. So I may be breaking bolts on it myself Tuesday morning if I have to replace the pump and gasket.

thanks for the help and input.

[More Power]

The surge tank cap is an easy try first..... funny how the discharge hose from the engine back to the radiator UN-colapses when I take the tank cap off giving it some breathing room. I plan to replace the top discharge hose tomorrow and see if I can get a cap fast. The discharge hose may be week and adding insult to injury. Being a Holliday week, no one wants to tear into it and do a water pump job on a short week. My buddy with the shop is covered up with work right now too. So I may be breaking bolts on it myself Tuesday morning if I have to replace the pump and gasket.

thanks for the help and input.

The collapsing upper radiator hose could be an indication of a pressure/vacuum relief valve problem in the surge tank cap. The cap should prevent a collapsed hose by allowing air back into the cooling system when approximately 1" of cooling system vacuum exists.

Replacing the upper hose every 100K-200K miles might not be a bad idea regardless because the upper hose is usually the first to suffer from the highest engine coolant temps. The lower hose assembly lasts a lot longer because the coolant is much lower in average temp. Incidentally, the lower hose retails for about $130, the last time I checked.

Jim

[Ranger354]

Bought both hoses, but I may have just the top hose replaced. The seal finally let loose in the drive way yesterday. It will be at my buddies shop Monday morning. If I had the tools I would have been into it already, but rather let him do it since he does it for a living. thanks for all the info.

wish I had some pictures to look at so I could get a better idea of this thing. I am not NEW to working on motors and do most of my own stuff, but not this diesel. I have done just about everything to my jeep 304, but it is easy to see everything.

[mastertech]

All Duramax trucks may or may not show the sign of the collpsed radiator hose it is normal. GM calles it a air tight system. the only time it should have air enter is if you have a bad cap or you take off the cap and air is entered that way. if you loose all the coolant out of the system be carful when you refill it make sure you remove the bleeder from the top of the thermastat housing 12mm bolt and fill tell colant comes out and them test drive it tell it reaches operating temp 210 or tell teh light comes on low coolant them recheck caution may have a little pressure form the air that is inside will get hot and expan and can blow coolant out when cap is removed. when the truck is cold the upper hose may be collapised that is normal if you are driving and you notice that the upper hose is hard as a rock then you have a problem head gaskets or injectors sleave the sleave you will only see on a lb7 any ? please let me know

[More Power]

mastertech,

Thank you for helping out here in the forum. Assistance from GM techs is always appreciated. :)

Jim

[D-max Man]

I have seen water pump seals do exactly what you are describing. Some times they leak and other times they don't. Eventually get bad enough to leak all the time.

[mastertech]

I am here to help I know how hard it is now a days to pay any one to do repairs on there cars or trucks. i am here to help.