What is causing my coolant leak?

Asked by Mar 07, 2016 at 09:14 PM about the 2004 GMC Yukon Denali AWD

Question type: Maintenance & Repair

I was driving and heard a screaming noise. When I got to where I was going
I parked the car, got out, and could hear a leak. I looked under the car and
saw yellow fluid pouring out. When I was done I drove it home and on a 2
mile drive the car overheated. The next day I bought coolant and put a
gallon into the reservoir so I could drive it to the repair shop. It drove fine
and when I got there I looked under the car again. There was still a leak, but
it was only a drip.
The repair shop said I needed a new water pump, new thermostat, and new
upper and lower hoses. I know thermostat and hoses are relatively minor
repairs, so the water pump is what's running the bill up. Would a bad water
pump cause a screaming noise and a pouring out of coolant? Is there any
explanation for why the leak was pouring out the first time and just a slow
drip the next day?
I've gone to this shop before and was very pleased, but this time they
sounded like a really hard sell. They told me I shouldn't drive it even a few
miles home to think about the repair because it could overheat and cause
major damage. They said repairing the hoses and not the water pump
wouldn't do anything and I'd have to come back again later to fix the water
pump and probably the hoses again. Does this repair sound reasonable?
Screaming noise, pouring coolant, overheat, then mostly holding coolant
and maintaining temperature the next day = bad water pump, bad
thermostat, bad hoses?

1 Answer

100,335

You failed to mention engine size so I am going to assume it is a 5.3. The reason my they want to replace the thermostat and hoses is cause they are right there and they have to be removed to gain access to the pump itself, the thermostat should be changed also cause you have to remove the upper Tstat housing and transfer it to the new pump so why not replace the thermostat while the housing is off. I'll send you a pic of the water pump. hope this clears things up. I would recommend the same repairs if it was in my shop, but I would not call them bad unless they actually were. I would just recommend that they be done cause I would be taking them off any way. I am convinced that you major leak is the water pump, and the reason it didn't leak as bad as it did the day before is the pressures could not longer climb to specs because of the leak. Hope this will help you understand the procedure a little better.

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