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Thread: water pump replacement + overheat

  1. #1
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    Default water pump replacement + overheat

    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?
    GMC Sierra 2500hd 2004.5 now with ARP studs

  2. #2
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    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.
    "The Constitution is not an instrument for the government to restrain the people, it is an instrument for the people to restrain the government."
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    A5150nut
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    94 6.5 4x4 5spd Sold

  3. #3
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    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
    Kennedy Diesel-owner
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  4. #4
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    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
    GMC Sierra 2500hd 2004.5 now with ARP studs

  5. #5
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    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
    GMC Sierra 2500hd 2004.5 now with ARP studs

  6. #6
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    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.
    1985 Blazer 6.2
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  7. #7
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    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

    Quote Originally Posted by DmaxMaverick View Post
    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.
    GMC Sierra 2500hd 2004.5 now with ARP studs

  8. #8
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    They did a compression check on a diesel for $54???
    How? Does the tech II scanner do it?

  9. #9
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    Yes, loose cap to prevent pressure. If it leaks, it will still leak, just a lot slower. As I said, keep the conditions controlled and the tank full, and it'll be OK.

    Good price for the services. If you get good work from them, they're a keeper.
    1985 Blazer 6.2
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  10. #10
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    Quote Originally Posted by rapidoxidationman View Post
    They did a compression check on a diesel for $54???
    How? Does the tech II scanner do it?
    That's what I thought. The Duramax isn't at all difficult, but it's still 8 cylinders and wrench time.

    The Tech II can't do a compression test, but can do a balance test. Results will usually tell the same story. It isn't the same as "balance rates".
    1985 Blazer 6.2
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  11. #11
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    Maybe what they did was a cooling system pressure check?
    Kennedy Diesel-owner
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  12. #12
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    They stated they put a pressure check on the cooling system and said it was "Leaking pretty good".

    They also explicitly stated that they checked the compression (didn't say how) and that it had no problems in that area... The service manager said: "Your head gaskets are good"

    I'm inclined to head back there, just trying to decide the best way to spend a nite in hope

    G
    GMC Sierra 2500hd 2004.5 now with ARP studs

  13. #13
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    You just may have found yourself a "no bs" dealer. The holy grail. If their service is good, it's worth the trip, and lodging.
    1985 Blazer 6.2
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  14. #14
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    I don't see a compression test as a positive test of a seeping head gasket. The head gaskets tend to "seep" small amounts of combustion gasses at higher cylinder pressures.

    At this point it is probably best to fix the external leak(s) and see what happens.
    Kennedy Diesel-owner
    More than just a salesman-I use and test the products that I sell on a daily basis!
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    2002 Chev K2500HD D/A CC Long LT 11.77@ 124mph at 7700# fuel only-e.t. needs help
    2005 Chev K3500SRW D/A CC Long LT(SOLD)
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    2012 GMC K3500SRW D/A CC Long LTZ Happy Birthday to me! Built 1 working day after my birthday and delivered 7 days later.
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  15. #15
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    Quote Originally Posted by gary_lucas View Post
    They stated they put a pressure check on the cooling system and said it was "Leaking pretty good".

    They also explicitly stated that they checked the compression (didn't say how) and that it had no problems in that area... The service manager said: "Your head gaskets are good"

    I'm inclined to head back there, just trying to decide the best way to spend a nite in hope

    G
    While I hate looking for problems, I'd consider doing a cooling system pressure test on my own. A head gasket or injector cup compression leak can cause excessive pressure in the cooling system, which causes the pressure to ride up against the relief pressure setting of the surge tank cap (theoretically 15-psi). Normal cooling system pressure at operating temperature should be 8-10 psi. Excessive cooling system pressure can produce short water pump seal life.

    Jim

  16. #16
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    Quote Originally Posted by More Power View Post
    While I hate looking for problems, I'd consider doing a cooling system pressure test on my own. A head gasket or injector cup compression leak can cause excessive pressure in the cooling system, which causes the pressure to ride up against the relief pressure setting of the surge tank cap (theoretically 15-psi). Normal cooling system pressure at operating temperature should be 8-10 psi. Excessive cooling system pressure can produce short water pump seal life.

    Jim
    Good idea, well I need the water pump done regardless. And with the leak right now I don't think I'll get much in the way of helpful information... IE if the pressure was super high it would just piss out of the water pump and the PSI would read normal.

    Once I get the leak fixed I'll run a pressure test.

    G
    GMC Sierra 2500hd 2004.5 now with ARP studs

  17. #17
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    Hi all, long time since last update.

    We finally pulled the pump out.

    The water pump housing had substantial wear on it.

    There was a 1-3 mm deep wear in the water pump housing starting about 3cm from the outflow on the housing... All the way up to the outflow.

    Can anyone comment on what kind of impact that would have on pulling under heavy load uphill? I assume it would impact the cooling efficiency substantially but no idea really.

    The water pump was definitely leaking, the seal was cooked.

    Obviously that's been changed, we also did the serpentine belt and the bottom rad hose monstrosity...

    Should be back on the road this week.

    Hopefully that's the last of the overheat problems. I'll get another pressure test done on the cooling system and see if we've got anything showing as abnormal and hope for the best.

    G
    GMC Sierra 2500hd 2004.5 now with ARP studs

  18. #18
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    The water pump housing had substantial wear on it.

    There was a 1-3 mm deep wear in the water pump housing starting about 3cm from the outflow on the housing... All the way up to the outflow.
    What was causing the wear? Was the impeller touching the pump housing (worn seal or bearingcausing the impeller to lean)? Or does it look like something solid was stuck inside the pump and being scrubbed around by the impeller?

    The pump is driven directly off the engine so it isn't going to turn any slower and lose efficiency unless the impeller was actually not bound tightly to the shaft of the pump. Given that it's only a press fit (no key, no D shape to the shaft) then if there's something stuck in the pump that would cause the impeller to bind up then that could be a cause of low/no coolant flow.

    Can you turn the pump impeller by hand and not have the drive gear and shaft turn? Been there, done that...

    http://www.thedieselpageforums.com/t...ad.php?t=40784

  19. #19
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    Quote Originally Posted by rapidoxidationman View Post
    What was causing the wear? Was the impeller touching the pump housing (worn seal or bearingcausing the impeller to lean)? Or does it look like something solid was stuck inside the pump and being scrubbed around by the impeller?

    The pump is driven directly off the engine so it isn't going to turn any slower and lose efficiency unless the impeller was actually not bound tightly to the shaft of the pump. Given that it's only a press fit (no key, no D shape to the shaft) then if there's something stuck in the pump that would cause the impeller to bind up then that could be a cause of low/no coolant flow.

    Can you turn the pump impeller by hand and not have the drive gear and shaft turn? Been there, done that...

    http://www.thedieselpageforums.com/t...ad.php?t=40784
    Interesting read, I'll take a closer look at the old pump. Could be a worn seal / bearing... Given we had a leak too.

    I don't think the shaft is turning without the pump but could be I'll have a closer look.

    We did put a pump in that's had it's shaft welded... So that will never be an issue now.

    G
    GMC Sierra 2500hd 2004.5 now with ARP studs

  20. #20
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    We weld them all now. Thought we could get away with not welding them for street use, but the combination of the heavy cast impeller with a gear drive (no slip) can cause issues with the replacement pumps.
    Kennedy Diesel-owner
    More than just a salesman-I use and test the products that I sell on a daily basis!
    Superflow Lie Detector in house
    2002 Chev K2500HD D/A CC Long LT 11.77@ 124mph at 7700# fuel only-e.t. needs help
    2005 Chev K3500SRW D/A CC Long LT(SOLD)
    2007 Chev K2500 Classic EC Short LT (Sold)
    2012 GMC K3500SRW D/A CC Long LTZ Happy Birthday to me! Built 1 working day after my birthday and delivered 7 days later.
    2016 GMC K3500SRW D/A CC short LTZ

    Custom tuning in house using EFI Live tuning software!

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