I’m pretty sure the water pump on my 77 Chevy LUV is dead but, I was hoping the teeming millions could help me verify this.
Basically the truck runs HOT when I’m driving around the city, but once I’m on the freeway it cools down. Although even on the freeway if I have to work the engine i.e. a long uphill stretch, it gets a little warmer.
Any advice? Anyone know a simple troubleshooting tip to verify the water pump?
Probably not the water pump. They generally leak, or make an awful noise when they go. I’d first look for loose belts, at slower speeds your fan is necessary to suck air through your radiator to cool the engine. Above about 25 MPH, the air rushing through due to your movement does the trick. So first I’d suspect that your fan is not operating correctly. (Belts, or fan clutch) Second, more likely that your radiator is clogged. When was the last time your radiator was flushed?
It’s normal on the highway to have your tempature go up a bit during a long hual. In city driving, if you turn on your heater to full heat, full fan, you might be able to get around without overheating. (The car at least)
Dan
Unless you see coolant leaking from the weep hole or the pump
sounds like BBs in a coffee can, the pump should be just fine.
Maybe its your thermostat? If you haven’t changed it in the past
10-15-20 years, go do that. Its only about 7 bucks at the auto
supply store. While you’re at it, might as well flush and change
your cooling system.
Maybe simply turning on your heater will dissipate some of the
heat when you enter a high load situation.
If ALL that dosen’t work, maybe you need to have a Chevy or
Isuzu dealership look it over (The Chevy LUV is a rebadged Isuzu
P’UP).
Your pump sounds fine. Get your coolant system flushed out (if it hasn’t been for more that 4 years) and through a new thermostat in. It is also possible your rad is getting clogged with crap, so the flush should help that. You should be fine.
Hinted above, but not said outright…
You should also check your thermo switch, especially if there’s an aux. fan for the radiator. Again, cheap.
The symptoms are not typical of a water pump problem. It’s rare for water pumps to directly cause overheating. The impeller blade inside would have to be badly worn or slipping on its shaft. If it had this type of problem, I’d expect it to run hot under all conditions.
Water pumps can cause overheating indirectly if they leak. Running low on engine coolant will cause overheating, often with loss of heat from the heater. You can easily check the coolant level (check with a cold engine so you don’t get scalded). If it were significantly low, I’d again expect it to run hot under all conditions.
Your symptoms are typical of an airflow problem. If it has a belt driven fan, check the belt, the fan clutch (if it uses one), and the condition of the fan blades. It it has an electric fan, that circuit needs to be tested. It could be a fuse, fan thermal switch, relay, or fan motor (or a wiring problem).
As danvanf mentioned, on the highway there is plenty of airflow across the radiator and a fan isn’t necessary. At town speeds, especially stop and go driving, there is little or no airflow and the fan must be working to get the heat out of the radiator.
Coolant flow problems–clogged radiator, stuck thermostat, water pump not pumping–are typically worse at highway speed than at low speed. While there may be something to be gained by replacing the thermostat, flushing the system, and/or having the radiator cleaned out or replaced, I would not expect any of these to address the symptom you described. If you had a significant restriction of the coolant flow, it would overheat on the highway.
If it were the water pump, the gauge needle would keep going to hot. Look at the radiator, does it have holes in it?
Well, I found the problem.
The shaft bearing on the water pump is completely shot! You can actually turn the fan side to side about 25 degrees in each direction. With that bearing as bad as it is, the water pump is getting insanely hot! So when the cooled water comes in from the radiator its getting heated back up before it goes into the engine. Thus the reason it cooled back down on the freeway, the pump was getting cooled by all the air passing across it.
Thanks to all that posted. I had already picked up a new thermostat and will probably change it just because I know the one in there is the original.
Pretty soon the LUVmoblile will be back on the road!!!
Handy, that is a classic.
Glad you found something, counsel…
cornflakes, this situation happened once (Temperature guage), & thats what the mechanic said.& it turned out to be right.
Cars, like computers, can have more than one answer.