sr1032 Posted November 16, 2015 Report Share Posted November 16, 2015 Hoping to sanity check my thought processes here. 03 Silverado SS, around 124k miles. No engine MODS at all. Replaced the coolant twice since I've owned the vehicle, only owner. The last change was about a year and a half ago and the truck never misses a beat. Took it out today, it's about 57 out so not hot or too cold. About 20 minutes into my drive I hear the ding ding ding that my coolant is hot, shortly after is the awesome reduced engine power and engine overheating, i dropped it to neutral and coasted to a good safe place, by the time I got there it already had dropped back down to about 240ish. I checked the engine bay and everything seemed normal and there were no major leaks so I nursed her home. She would get up to about 250 and never much higher and only have me the engine overheat once, there seemed to be heat coming out at the time but by the time I got home there was zero heat coming out. Here's where I'm at. I let her cool down completely. The belt spins fine, I don't see any water leaks but I haven't checked the weep hole just yet. I topped off the overflow tank and started it up with the cap off, let it run until it hit about 210 and still no heat, no gurgling noise at the time. Replaced the cap and let it go longer, still wouldn't climb higher than around 210ish which is still warmer than normal and there is still zero heat, in fact the hoses to and from the heater don't seem hot. It did take quite a while before I could notice and coolant running through either the upper or the lower lines but I'm not sure how firm they should get and they weren't terribly hot. I'm an old car guy so I'm used to the hoses firming up quite a bit. The water pump seems to be a bit different than what I'm used to so it looks like the thermostat is right there on the front with a couple small bolts and the heater lines both go to the pump as well. So my logic seems to think something is wrong with either the thermostat or the pump but it seems that I have flow on the upper and lower hoses so a thermostat seems a little unlikely to me but I've only ever seen water pumps seize and no other failures. The only other thing to note was that when I pulled the radiator cap after I shut down the coolant dropped back down into the water pump quite a bit, I'm assuming that is normal for the most part and there is still some in the tank so it's obviously not running super low on fluid. Any help or ideas would be greatly appreciated, thanks! Quote Link to comment Share on other sites More sharing options...
lucky03 Posted November 16, 2015 Report Share Posted November 16, 2015 I would check the bottom radiator hose and see if its getting hot. Could be that the thermostat is not opening or the radiator could be plugged. If you have no heat no coolant is going through the heater core. Quote Link to comment Share on other sites More sharing options...
03SSBoy Posted November 16, 2015 Report Share Posted November 16, 2015 Replace the thermostat. if its not that then your heater core is plugged Quote Link to comment Share on other sites More sharing options...
SS-GTP Posted November 16, 2015 Report Share Posted November 16, 2015 To me your symptoms suggest you have very little flow possibly due to a water pump impeller coming loose, not sure that's been much of an issue on this design though. If you have a bad thermostat you should still have cab heat. 2nd if you have a plugged heater core cutting off cab heat, the engine itself would still be able to control its temperature and not overheat. The other thing I thought about is a restriction in the main cooling circuit such as a blocked radiator or collapsing lower radiator hose should still allow you to have cab heat. Quote Link to comment Share on other sites More sharing options...
sr1032 Posted November 17, 2015 Author Report Share Posted November 17, 2015 (edited) All signs lead to a jacked water pump. I've never seen anything like it, the bottom hose doesn't ever get warm and I can now hear a weird whirring noise from that area. I tried a thermostat tonight and no workie so I'll swap out the pump tomorrow and hope for the best, hoses are good to go and the radiator would have to be royally screwed up to cause this but when I burp the tank there is coolant in the top hose which suggests the radiator is somewhat fine. When I get the pump out I'll fill the radiator and check to make sure it's flowing fine from top to bottom. I don't see how a heater core could cause this at all since the truck overheats and you are correct, it should be able to manage engine heat regardless of heater core flow. I was going to do it tonight but it's dark so I'll wait until tomorrow so I can hook a hose up to the drain barb on the radiator and re-use the brand new coolant I dumped in rather than fork over more money To me your symptoms suggest you have very little flow possibly due to a water pump impeller coming loose, not sure that's been much of an issue on this design though. If you have a bad thermostat you should still have cab heat. 2nd if you have a plugged heater core cutting off cab heat, the engine itself would still be able to control its temperature and not overheat. The other thing I thought about is a restriction in the main cooling circuit such as a blocked radiator or collapsing lower radiator hose should still allow you to have cab heat. Edited November 17, 2015 by sr1032 (see edit history) Quote Link to comment Share on other sites More sharing options...
sr1032 Posted November 18, 2015 Author Report Share Posted November 18, 2015 Took the water pump off and pulled the cover for the impeller off. Smoking gun there, the impeller is pressed onto the shaft (not the best design) and it wasn't even on there anymore, so it would seem it was making contact occasionally allowing coolant to somewhat flow and not ruin my motor but finally busted loose. Swapped it out and she's back to normal. Quote Link to comment Share on other sites More sharing options...
Downeast Johnny Posted November 18, 2015 Report Share Posted November 18, 2015 Took the water pump off and pulled the cover for the impeller off. Smoking gun there, the impeller is pressed onto the shaft (not the best design) and it wasn't even on there anymore, so it would seem it was making contact occasionally allowing coolant to somewhat flow and not ruin my motor but finally busted loose. Swapped it out and she's back to normal. That's great brother. Glad to hear that you got it figured out. Quote Link to comment Share on other sites More sharing options...
EXGM Posted November 30, 2015 Report Share Posted November 30, 2015 Took the water pump off and pulled the cover for the impeller off. Smoking gun there, the impeller is pressed onto the shaft (not the best design) and it wasn't even on there anymore, so it would seem it was making contact occasionally allowing coolant to somewhat flow and not ruin my motor but finally busted loose. Swapped it out and she's back to normal. Well it did last 12 years and 124K what do you expect? Quote Link to comment Share on other sites More sharing options...
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