Thread: How do I know if my water pump is bad?

2005 pontiac grand prix gp. For a few weeks I noticed that my car gets unusually hot when I am on the freeway. When I am in town It doesn't seem to get as hot as when I cruise at 65-75 mph for 30 min or more. I changed the t-stat, have pretty new coolant, the fans are working, and the cooling system isn't giving me any air bubbles when I open the bleeder valve. The car runs fine, but when I start climbing a mild incline at around 70mph (even if the car doesn't down shift) the temp gauge starts to rise to a few bars before red and takes a while to come back down.

I don't have any leaks or noises. How can I know if my water pump is working properly? Any other ideas on what to check?

Check to make sure your radiator doesn't have a bunch of gunk in it through the fill cap. Other than that when the car is running check to make sure no coolant is coming from the bleeder hole. A pressure test is the best way to find a leak, you can rent one from an auto parts store.

How many miles? Coolant level is fine? A headgasket leak or intake usually results in low coolant levels which
lead to overheating. Your car does not overheatTo the point of blowing coolant. Yes it's warmer but. Never has any coolant spewing issues so that is some info.

Update:
I looked inside the radiator and everything looks clean. I rinsed/cleaned of the radiator and can see daylight through the slats. I just went ahead and pulled the water pump off to look at it and it's perfectly fine. Solid bearing, fins, everything looked fine.

@Cavell: The car has approx 150,000 miles on it. Coolant level is fine. I don't have any leaks. I changed those to plastic elbows that are notorious for breaking near the alternator last year after they failed catastrophically so those should be fine. It hasn't overheated to the point of spewing coolant yet and it hasn't actually gone in the red, but it's come close. Both my fans come on and work like they are supposed to. I looked in the oil filler to see if it was getting foamy from a blown head gasket and it was clean.

The only thing I haven't done is official do a pressure check (do I need to if I'm not leaking?). I'm going to try doing what Scottydogg recommended with the radiator and see if fluid is flowing freely.

Any other ideas?

Drained the radiator and ran water through it. Flows out quick. I went ahead and tried the same thing through the port that the thermostat sits in and I get water out the other end of the block pretty quick too. More ideas?

Check and make sure your lower radiator hose is not collapsing at highway speeds, as this will cause restriction in the cooling system.

QUICKSILVER462: I got the car heated up and had my wife rev up the engine and hold it at about 3000 for a little bit and it couldn't visibly see the lower radiator hose collapse. I looked at as many of the other hoses as I could find and they were fine too Nothing seemed to be collapsing. Should it be pretty obvious when it collapses? I put my hand around it and tried to squeeze it while the engine was revving and it felt solid (although I couldn't squeeze it for long...it was hot obviously!)

Scottydoggs :I cleared out all the gunk from the radiator fins also. There wasn't much, but I cleaned it out.

Here is what I did this week: I bought a radiator flush kit and flushed the system. I then removed the new t-stat that I just put in for the duration of the cleaning, filled with water and added that prestone cleaner. I'll come back to the removed t-stat in a moment.

I noticed something interesting while driving it this last week, however. I was stuck in traffic for about 35 minutes and it was 95 outside. Never exceeded 45 mph and the car never even heated up enough to kick the fans on even though I had the A/C full blast. The second traffic started moving and I got up above 60, the cars temp started climbing I got a few bars before the red. What the crap?!!! But then the other odd thing was that when I turned the temp control knob for the HVAC in the car to hot, the temp dropped fast. I know turning on the heater when a car gets hot can help cool it down, but this seemed like it made it drop unusually fast. The other thing that I noticed is that once the outside temp was around 80, the car temp dropped to just below normal operating temperature (remember...no t-stat at the moment) and held there while I was cruising at 75 mph. It seems like a collapsing hose would explain some of this, but I couldn't get the lower hose (or any others that I looked at) to do it. Could there be something going on when the fluid decides whether it's going to route through the heater core? Is it my hoses and I just don't know it? AHHH!!!!

I had a very similar issue with my 07 gp n/a.. I just did a pretty decent coolant flush... flushed outthe heater core as well... you need about 2-3 gallons of dexcool 50/50 extended life... and roughly 3-5 gallons of distilled water for flushing... drain the coolant ... andthrow the distilled water I there and run the vehicle for 20 minutes on full heat.. and drain the water.. and repeat until all the crap is out... then put the new coolant in and keep adding more as the vehicle runs... squeeze the radiator hoses to get the air out.. and once the radiator is full and stops bubbling... bleed the bleeder while rocking the car a little bit and squeezing the radiator hoses again.. if you dont see bubbles.. thats fine.. you should at least see coolant.. replace the oem thermostat to a Napa Premium 180 degree ... theyre made by Stant which is a top of the line thermostat manufacturer. ... after I did all this.. my car never goes a hair above the half way point.. even after going at high way speeds.. im also noticed better acceleration because my car is finally cooler... you wouldnt believe all the gunk and chunks that comes out of these radiators and coolant hoses.. worth every penny flushing it out and starting fresh.

For posterity, I thought I'd better come back and post what I found.
What I think was going on was I was checking my lower radiator hose for collapsing only when the car was really hot. Because of the amount of pressure built up (it being really hot water and all), the hose wouldn't collapse when revving. However, I checked it when it was cool and it would collapse a little when revving the engine. Not a ton, but some. So, I replaced it and it seemed to fix the problem

At idle, your fans blow, while driving it's the water pump, right? Or did I get that backwards?

If not... Your water pump may be bad after all.

Anything from the weep holes? Are you losing coolant?

A water pump is a cheap replacement anyways, I would have just replaced it when it was off.

And 95*?!? Wtf... Its 42* here today...

the gauge might be bad or have a bad connection. May have a loose connection at the ECT or a failing ECT.