still getting hot

[rapidoxidationman]

Need help.

I just finished up replacing the passenger side head gasket (found a cracked gasket and scratched/cracked head, both over the #7 cylinder). The head was cleaned, flattened, and pressure tested at the machinist and went back together flawlessly.

The temperature guage still spikes.
Thermostats are both new GM parts, last week.
The heater still doesn't blow hot air.
The lower radiator hose stays at rroom temperature.
The water pump is 6 months old.

Is the water pump bad?

I'm in the shop now banging my head against the firewall...
Help.

[DmaxMaverick]

Remove the heater core inlet hose and give it a spin (route the hose to a container).

If no flow, well, it's pump time. The only other possibility I can think of is perhaps a blockage, possibly at/near the lower hose. Still, doesn't explain the cold heater. If the heater is hot/cold, it points back to a lot of air in the system. I can't imagine an intermittent water pump.

[DmaxMaverick]

Thinking back, there was some discussion in regards to water pump designs, different designs with the same part number. The wrong pump fit, but was noisy, perhaps do to improper gear alignment. It's worth checking into.

Other than that, it has to be something so simple, we'll all be banging our heads.

[rapidoxidationman]

The water pump is not turning. I pulled the lower radiator hose off and can see the impeller. Had someone turn the key and the engine turns but the impeller doesn't. Next step: Pull the water pump..:mad:

[DmaxMaverick]

Found the thread regarding the different pumps: http://www.thedieselpageforums.com/tdpforum/showthread.php?t=35311

If the pump isn't turning, for whatever reason, it sure explains a lot. Possibly the head gasket failure, as well.

[rapidoxidationman]

The gear drive spun loose from the pump shaft hence no turning impeller hence no moving water.

Let the reassembly begin!!!

Thanks for the advice John Kennedy. Sounds like the local GM dealer will be willing to at least swap out the AC Delco pump for another, then I'll have a new one on hand if this happens again. They offer a 12 month, 12,000 mile warranty.
I replaced it with one from NAPA - $150 and a lifetime warranty against defects...

Fingers crossed for a good outcome.

[rapidoxidationman]

Let others learn from my previous lack of knowledge:

If the heater blows cold, especially when the temperature guage says it should be blowing hot, there's probably not any coolant flowing.

A water pump CAN intermittently be bad, as evidenced by my last week's adventures (cold air from the heater, temp spike, then a rapid temp decrease and LOADS of hot air from the heater). My theory is that the pump drive gear was sometimes able to grab the shaft and spin the pump impeller until the shaft simply got too worn out by only a thousandth of an inch or so.

WHY does GM/ACDelco/Napa not put a shaft on these pumps that is either not round or simply employs a woodruff key to stop this ridiculous failure from happening on a $150-$350 pump (the $150 NAPA pump with a lifetime warranty looks pretty much the same as GM's $300 pump)?:mad:

A water pump is sooo much easier to change out than a head gasket. Had I listened to myself and followed through on it I might've discovered the bad pump and saved the $400 I spent on replacing the right bank head gasket (though I did find some justification on the head - scratches and a crack in the gasket).

The geyser I experienced last week was caused not by pressurization by exhaust gases but by overheating and a steam explosion when I released the pressure.

Live and learn. :cool:

Cheers!

[rapidoxidationman]

The only thing I find trouble with now is the odd whine I'm hearing in time with the turbocharger:eek:

Given the fact that it was not getting coolant (although oil flow should not have been an issue and I was certainly babying the engine during the times of trouble), I wonder if some coke didn't build up on the bearing surfaces... That or I just have an air leak in a charged air line.

All because a water pump is cheaper to make with a pressed on gear and impeller without a woodruff key...:mad::mad::mad:

[Kennedy]

For the high perf guys we've been tig welding the shaft to the gear and impeller with some success. I spun the impeller on my 2002, but this is usually only when runing high RPM. What we ened up running to keep it together is a hybrid LBZ pump as the LBZ has a lighter composite/plastic impeller. We still welded the shaft to the gear to be safe.

[Kennedy]

The gear drive spun loose from the pump shaft hence no turning impeller hence no moving water.

Let the reassembly begin!!!

Thanks for the advice John Kennedy. Sounds like the local GM dealer will be willing to at least swap out the AC Delco pump for another, then I'll have a new one on hand if this happens again. They offer a 12 month, 12,000 mile warranty.
I replaced it with one from NAPA - $150 and a lifetime warranty against defects...

Fingers crossed for a good outcome.

My advice was genuine GM and only genuine GM or at the very least weld the gear to the shaft. It's rare to see this type of failure in a street application, but...

[More Power]

The only thing I find trouble with now is the odd whine I'm hearing in time with the turbocharger:eek:

Given the fact that it was not getting coolant (although oil flow should not have been an issue and I was certainly babying the engine during the times of trouble), I wonder if some coke didn't build up on the bearing surfaces... That or I just have an air leak in a charged air line.

All because a water pump is cheaper to make with a pressed on gear and impeller without a woodruff key...:mad::mad::mad:

Glad you found the cause of the problem... Water-cooled turbochargers are a somewhat recent application for diesel pickups. The turbo used in the GM 6.5L diesel, for example, is not water cooled. Neither is the Holset used in the <2003 Dodge. I suspect a Duramax with an inop water pump would exhibit a few other trip canceling symptoms well before a lack of coolant damaged a turbocharger.

Let us know what you discover.

Jim

[More Power]

My advice was genuine GM and only genuine GM or at the very least weld the gear to the shaft. It's rare to see this type of failure in a street application, but...

As power is increased so are the harmonic spikes in the crankshaft. In talking to the folks at Fluidampr, they report that extensively modified Ford/Dodge/Duramax all see higher instances of OEM harmonic damper failures. During a SEMA show a few years ago, they had a display of failed dampers from these engines. Cam key failures in modified engines have also been reported, likely due to the same reasons. It's unfortunate to hear about a "press-fit" water pump gear without a key. My guess is that harmonic spikes in the crank could be a contributor.

[rapidoxidationman]

I do believe the turbo is OK. The EGR cooler has a gasket between the cooler can and the exhaust pipe that doesn't seem to be sealing properly, even though the bolts are tight. There's evidence (soot) of an exhaust leak at the flange, and it was making a whistling sound in coordination with the exhaust pressure. No performance loss, and in fact the sound is gone now (sealed with soot?).

All is right with the world under my hood.:cool:

[Kennedy]

As power is increased so are the harmonic spikes in the crankshaft. In talking to the folks at Fluidampr, they report that extensively modified Ford/Dodge/Duramax all see higher instances of OEM harmonic damper failures. During a SEMA show a few years ago, they had a display of failed dampers from these engines. Cam key failures in modified engines have also been reported, likely due to the same reasons. It's unfortunate to hear about a "press-fit" water pump gear without a key. My guess is that harmonic spikes in the crank could be a contributor.

Mine's a 7.1 billet fully counterweighted crank internally balanced with a press fit ATI Super Damper on it. It doesn't get much better than this.

[More Power]

Mine's a 7.1 billet fully counterweighted crank internally balanced with a press fit ATI Super Damper on it. It doesn't get much better than this.

Both items help deal with the huge momentary torque spikes felt by the crankshaft in a big power engine. I'd guess you also pinned the cam gear to the cam. Billet flexplate?

Has anyone had problems with the gear-driven Bosch high-pressure fuel linjection pump losing a key?

Jim

[Kennedy]

Everything gets a real key rather than the OE style pin and yes billet flywheel. I hesitate to call it a flexplate as there is no flex to speak of.