water pump replacement + overheat

[gary_lucas]

So, my water pump is probably going. It seems to be bleeding out of the weep hole. About 1-2 tablespoons everytime it warms up and cools down. Nothing substantial. I always keep the overflow tank pretty full.

Wondering if it's worth getting the 'welded impeller' water pumps that seem to be all over the place. Has anyone had a quick failure? I guess for $100 it's a deal.

Also, truck overheated pretty badly on the highway with the trailer... Twice...

I'm not sure if that's related to the water pump or not, could well be.

I saw 250f on the edge insight once, after the DIC chimed I pulled over immediately and let it idle for about 15 minutes and it dropped back down to 210. That was on what was mostly a flat highway with a few dips, rises and curves.

I figured I'd be ok if I drove slowly and carefully... However, the next chunk of highway was longer and steeper (still not more then 3 or 4 degrees, but fairly long) and that killed it, 260 before I could pull over... Ended up calling BCAA to tow me out as I didn't want to risk trashing the engine.

Truck does seem to run hot, I hit 230 today going up a 4 block, but steep hill... No load...

I'm doing the thermostats in a few days, I know I need to get the water pump done but I'm wondering if I should be replacing the rad as well. May as well while everything is exposed and then I hopefully wouldn't have to worry about overheating any more.

Thoughts?

[a5150nut]

Gary,

I have been towing heavy with my 2006 (21500 lbs) and I have seen the engine temps start to spike, But most of the time if I keep pyro temps in check there is no problem. You can't rely on the speedometer but must watch the pyro. It is surprising how little you can back off the throttle or as Robyn refers to it as the loud peddle, and the temps will drop. Dropping down a gear doesn't always help but got to love the Allison.

I know my radiator stack is clean but have you checked yours? Remove radiator and clean ac condenser and oil cooler from the back side and clean out the radiator while out. Might want to check your air filter too.

On the highway if you can tuck in behind a semi it helps too. At least with my fifth wheel I have a very large sail that catches a lot of wind.

The main thing is to learn what your truck is capable of and work within those limits. You can work it hard, just don't over work it.

[gary_lucas]

That all makes sense, it never occurred to me that you could / should hose out the cooling stack.

My AC also goes warm when I'm idling so that's probably in need of a cleaning.

I'm going to do the fan clutch and thermostat and get the water cooler done by someone who is more competent (and do the fan clutch at hte same time).

I ordered a welded waterpump.

Hopefully between all this the overheating will be done with.

G

[gary_lucas]

Thermostats done.

I brought the trailer to my camping spot again this long weekend, truck started heating up again on pretty moderate hills.

The dealer near my spot (gardner GM in hope, BC) is known for having a good service department. I asked them to take a peak.

They confirmed the leak is in the water pump, refused to say if it was ok to drive back to Vancouver, however I made it and it's more down than up on the way back.

They could not find a definite cause for the overheating so they suspect air in the coolant and stated that I needed to get the water pump resolved before spending time on doing anything else.

They also checked the compression and said there's nothing wrong with the head gaskets so I'm good there.

Now I just need to either get back up there so they do the water pump or find somewhere nearer to home to get it done. I'm in Port Moody BC if anyone has a recommendation that's more local than hope (150km)

Also, with the weeping water pump (and they said it was leaking a reasonable amount, which sounds like it's worse than when we first found the problem)... Is there any point in trying to bleed the system until it's resolved?

Thanks much

Gary

[DmaxMaverick]

I agree with the dealer. It should replaced at your soonest convenience. I can't help with a local shop. Good hunting. If it's leaking a "reasonable amount", it may be significant, but not much volume. You made a loaded trip and didn't dry it up, and that speaks volumes, so to speak.

If you must drive it, avoid loading it or driving hard or far enough to get the temp up. Fill the reservoir, leave the cap loose about 1/2 turn, and place a container below the water pump overnight. This will show if it has a static leak, and how much. If it doesn't leak, or much at all, then keep it full with the cap loose. Don't overload/heat it, during short-ish, local trips only. Keep it topped off and it should be OK for a short period until you get it fixed. Keep in mind, it will "push" coolant out at a much lower temp with the cap loose, so it's important to keep it as cool as possible, and keep the reservoir full to prevent air in the system.

[gary_lucas]

Thanks, I don't understand why I would want to keep the cap loose. Is that to prevent pressure build up?

I'm kind of torn, that dealer is an hour or so drive, and it's an 8 hour job. However, I've heard good things about them and I've brought my truck there a couple of times. They charge $54 for diagnosis (that included a compression check) and the last time I brought it in for work they estimated $700 and billed me $430.

Generally around here it's a minimum $100 to put a vehicle on the scan tool and I've never in my life heard of a mechanic's shop bill coming in at below the estimate. Their quoting me about $800 to do the water pump. I've already bought a kennedy pump...

It's basically that or a specialty / duramax shop as my local mechanic doesn't feel comfortable charging 8 hours for something he knows is going to take at least twice as long (don't blame him, he's not a diesel mechanic).

I did top up the coolant before I got on the road this morning, I was seeing flat ground temps @ 200-212 and on very moderate, short hills it would spike to 230... so definitly not normal.

I'm probably going to drive up there in the next 2 weeks.

Gary

I agree with the dealer. It should replaced at your soonest convenience. I can't help with a local shop. Good hunting. If it's leaking a "reasonable amount", it may be significant, but not much volume. You made a loaded trip and didn't dry it up, and that speaks volumes, so to speak.

If you must drive it, avoid loading it or driving hard or far enough to get the temp up. Fill the reservoir, leave the cap loose about 1/2 turn, and place a container below the water pump overnight. This will show if it has a static leak, and how much. If it doesn't leak, or much at all, then keep it full with the cap loose. Don't overload/heat it, during short-ish, local trips only. Keep it topped off and it should be OK for a short period until you get it fixed. Keep in mind, it will "push" coolant out at a much lower temp with the cap loose, so it's important to keep it as cool as possible, and keep the reservoir full to prevent air in the system.

[Kennedy]

Thermostats-OE only

Water pump-welded to prevent spin

Fan clutch-if you don't hear yours roar

Radiator-clean the air side thoroughly including the rest of the coolers. The coolant side will be like new as the Dex Cool keeps it that way.

Coolant-Dex cool 50/50

[gary_lucas]

Hrm, I'm restricted to whatever they have in stock at this point need to head back on Friday or Monday. Will give them a call today and see where there at.

WHat a massive pain in the ass, the crazy part is I did pull all those hills before the water pump started to fail. So something has gone south since then or the t-stats / fan clutch that got replaced we're defective.

I don't think it's possible to screw up a water pump install in a way that's not obvious.

[Kennedy]

Refresh my memory has the cooling stack been removed and cleaned?

Thermostats replaced? and if so GM or aftermarket?

[gary_lucas]

I blew it out with a light pressure washing and visual inspection.

Thermostats are definitely OEM / GM.

G

[Kennedy]

I blew it out with a light pressure washing and visual inspection.

Was it in vehicle or removed? In order to get all the chaff and junk out you really need to remove the rad and IC and clean independently.

The fan clutch only knows what it sees for coil temp and if the air in that area does not get it to that temp it will not engage.

[gary_lucas]

Was it in vehicle or removed? In order to get all the chaff and junk out you really need to remove the rad and IC and clean independently.

The fan clutch only knows what it sees for coil temp and if the air in that area does not get it to that temp it will not engage.

In vehicle, I'll get it out and cleaned. Didn't look gunked up, but worth the check.

G

[DmaxMaverick]

....Or, perhaps, the condition that (may have) caused the initial WP failure is still at work.

[rapidoxidationman]

pretty easy to tell if the fan clutch is engaged just by trying to spin the fan. Like already stated, when it is cold or when it is HOT the fan should be bound to the serpentine belt and spinning in time with the engine. When the clutch is not engaged, the fan will spin more easily. Not freewheel easy, but easier than when it is engaged.

So... What does YOUR fan feel like when it's hot/lukewarm/cold?

[gary_lucas]

For the fan clutch, can't tell right now, but I'll be checking when I get the truck back. Didn't know that was how you tested it.

For DMaxMaverick: Yah, that's my real fear.

I don't think I've got a gasket issue, none of the the signs I've seen so far point in that direction. But who knows.

Oil looks good, coolant looks good. No abnormal smoke, compression tested properly coolant system pressure tested properly.

truck worked until the water pump cacked out. Confounding variables are:
* New thermostats - Are they bunk?
* New fan clutch - is it bunk?
* Hard to isolate issue, only appears pulling 9500+lbs on 6% grades 2+ miles long.
** One thing to note, the initial overheat issue from before the WP fix took much, much less time to materialize. I essentially overheated on a gentle incline. Whatever's going on now is at least 2 orders of magnitude less severe.
* I did put a couple water wetters in near the beginning of this trip when I saw some warmer temperatures on more gentle climbs.

Things that may be causing problems, but have been on the truck since it last pulled the trailer up a severe grade:
* Air box is not stock and it's garbage.
* Tuned ECM

Things that are potential unknowns:
* Non stock exhaust.

Additional info:
* Not empirical data but the truck does seem to run alternately hot and cold... Sometimes when i"m on a long gentle slope it runs 190ish... Sometimes on what feels like the same slope or just slightly steeper it seems to hit 225 - 230 pretty quickly. Take this with a grain of salt, there's no data to back this up.