PDA

View Full Version : diagnosing a bad water pump


88Nightmare
10-20-2009, 04:55 PM
Having overheating issues with my 1991 S10 Blazer with the 4.3L TBI motor. I got a new thermostat for it. I ensured I installed it properly (spring side down into the intake manifold). Coolant is topped off. After driving it for just a few miles, the temperature gauge pins. I know its possible that I got a faulty thermostat, these things do happen... but it was doing the exact same thing before swapping them. So what should I do? Take the thermostat back out, and try to exchange it for another one and then see what happens? Is there a way to diagnose if the water pump is bad? It doesn't make any noise (i.e. a bad bearing)
awsomeears
10-20-2009, 05:09 PM
Take the T-stat completely out, and if you still have issues then well its something to do with your water pump or cooling capability's aka radiator ....

All I can think of :-0
88Nightmare
10-20-2009, 05:11 PM
I always thought you can't run without a thermostat...... It has to be in there to provide some sort of restriction in the coolant system, otherwise the water pump will spin too freely or something like that...... Thats just what I've been told in the past, not too sure how reliable that info is
whistlin six
10-20-2009, 05:15 PM
Pegging the temp guage that quick makes me think bad head gasket.

Was the coolant level down before you put a new t-stat?
Do you have a cooling system pressure tester?
86GUTLASS
10-20-2009, 05:26 PM
Sounds like a Head gasket
lordairgtar
10-20-2009, 05:32 PM
Sometimes, the impeller blades in the water pump corrode away and cannot pump the water through, but that's rare. If the impeller is bad, the water won't flow past. You can see this occur if you peer into the radiator. You can test the T-stat by suspending it in a pot of boiling water by a string. A sauce thermometer will tell you what the temp is when the poppet valve opens and the T-stat drops off the string.
rally_scort
10-20-2009, 05:35 PM
check the underside of the hood.If the pump is leaking, there should be a noticable "water pump stripe" across the hood from the fan flinging the coolant.
88Nightmare
10-20-2009, 05:44 PM
Pegging the temp guage that quick makes me think bad head gasket.

Was the coolant level down before you put a new t-stat?
Do you have a cooling system pressure tester?

I shouldn't say it was THAT quick. Basically, I started it in my driveway, idled for about 30 seconds. I then drove it approximately 2 miles down the road to speedway. I idled there for about 3-4min. I pulled out of the lot and waited to turn left at a traffic light. At the light, I noticed the temperature gauge reading two notches above 200º (its a digital dash). By the time I got halfway home, it was maxed. The truck was NOT low on coolant before doing the thermostat. Radiator was filled to the top.

No I do not have a pressure tester. Do you have one I can borrow, Pat? Perhaps you can swing on down here in Oak Creek sometime when you aren't busy.


Sounds like a Head gasket
The truck always ran a little on the warm side (one or two lines above 200º on the temp gauge). A few days ago is when it maxed out the temp gauge for the first time that I've owned it. The truck could sit for only 5 minutes, and in those 5 minutes, the truck has cooled off to a safe temperature for driving... This is what led me to believe the thermostat was failing. The truck runs ok, slightly sluggish, but I think its an old/clogged fuel filter causing that. I don't see it blowing out any smoke indicating a head gasket, and the coolant is never low :confused
PB86MCSS
10-20-2009, 05:56 PM
Your water pump should have a weephole on the top, as rally_scort said, there would be some visible leakage from it...one sure sign its gone bad.
88Nightmare
10-20-2009, 05:59 PM
not seeing any leakage
lilws6
10-20-2009, 06:03 PM
easiest way to see if the system is flowing is pop the cap off and run it to operating temp then twist the throttle by hand and see if the coolant level changes in the radiator. if not then you have a flow problem. if it drops when you throttle it up you don't have a flow issue.
88Nightmare
10-20-2009, 06:05 PM
a flow issue could be a bad t-stat or water pump? I will have to give that a shot.
RanJer
10-20-2009, 06:08 PM
a flow issue could be a bad t-stat or water pump? I will have to give that a shot.

Or a blockage somewhere else...
awsomeears
10-20-2009, 06:10 PM
a flow issue could be a bad t-stat or water pump? I will have to give that a shot.

Water pump blades are shot
88Nightmare
10-20-2009, 06:14 PM
It has 140k miles. I figured a water pump would last longer then that. Unless thats just wishful thinking :D
0TransAm0
10-20-2009, 06:57 PM
is this the same truck i sold ya? digi dash eh? post pics of the build dude.
theavenger333
10-20-2009, 07:02 PM
is the truck actually overheating? especially with the digital dashes, if the coolant temp sensor goes bad, the gauge goes wild. mine did the same thing a few years ago, made the truck run wierd, but it wasn't ever overheating. could just be the sensor.
88Nightmare
10-20-2009, 07:06 PM
is this the same truck i sold ya? digi dash eh? post pics of the build dude. negative. You sold me a 1987. The truck in question is a 1991 :thumbsup


is the truck actually overheating? especially with the digital dashes, if the coolant temp sensor goes bad, the gauge goes wild. mine did the same thing a few years ago, made the truck run wierd, but it wasn't ever overheating. could just be the sensor.

thats what I was wondering too. If the sensor is cheap enough, I may just toss one in there just to see what happens, along with doing everything else suggested in here
0TransAm0
10-20-2009, 07:48 PM
[QUOTE=88Nightmare;588286]negative. You sold me a 1987. The truck in question is a 1991 :thumbsup


ah...i can't remember what i did last week let alone something 8 months ago...:alcoholic:alcoholic lol carry on. :)
88Nightmare
10-20-2009, 08:06 PM
[QUOTE=88Nightmare;588286]negative. You sold me a 1987. The truck in question is a 1991 :thumbsup


ah...i can't remember what i did last week let alone something 8 months ago...:alcoholic:alcoholic lol carry on. :)

its all good. The 87 is coming along nicely. I'm pretty much down to bodywork, and then the interior... if I decide to do something with it. And wheels and tires. You should stop by and check it out sometime. You won't recognize it :thumbsup
Coops Brother
10-20-2009, 08:32 PM
Plugged radiator internally?? or the fins plugged up with leaves or other crud, a/c condenser fins could be plugged up too, it is in front of the radiator.
DirtyMax
10-20-2009, 08:47 PM
Did you burp it once you got done and filled it back up with coolant? Maybe there's air in there jagging stuff up.
juicedimpss
10-20-2009, 09:24 PM
is the truck actually overheating? especially with the digital dashes, if the coolant temp sensor goes bad, the gauge goes wild. mine did the same thing a few years ago, made the truck run wierd, but it wasn't ever overheating. could just be the sensor.

my thoughts as well.
hit the truck with an infared temp gun and make sure its reading correctly
88Nightmare
10-21-2009, 12:01 AM
Plugged radiator internally?? or the fins plugged up with leaves or other crud, a/c condenser fins could be plugged up too, it is in front of the radiator.
didn't look to be. The condenser is in fact in front of the radiator


Did you burp it once you got done and filled it back up with coolant? Maybe there's air in there jagging stuff up.

I thought about that as well, but did not notice a bleeder :confused

my thoughts as well.
hit the truck with an infared temp gun and make sure its reading correctly

ron, if you had one I could borrow for an hour, that would be great.



After making this post, I went out, popped the upper radiator hose off from the radiator end and started the truck. I idled it and varied throttle to 2,000rpms to get it to reach operating temp. The temp gauge was reading two bars above 200º. No coolant ever came out of the upper hose. Either A. Thermostat wouldn't open... B. Thermostat did open and the water pump just wasnt pushing water out, or C. Temp gauge is fucked and it wasn't actually AT operating temperature. If the sensor is cheap enough, I may just start with that first.
indyzmike
10-21-2009, 04:31 AM
I vote for a bad sensor or bad electrical connection. It should not cool down that fast after being so hot.
theavenger333
10-21-2009, 09:08 AM
from what i remember it's less then 20 bucks
-stew-
10-21-2009, 10:02 AM
is the truck actually overheating? especially with the digital dashes, if the coolant temp sensor goes bad, the gauge goes wild. mine did the same thing a few years ago, made the truck run wierd, but it wasn't ever overheating. could just be the sensor.


Also could be the dash. Those digital dashes are prone to failure. As was stated, confirm it is over heating by a means other than the gauge in the dash.
DirtyMax
10-21-2009, 10:17 AM
You don't need a bleeder. Just fill it up cold, leave cap off and let it idle. Once the temp gets up and the tstat opens up, it will sick coolant in and start moving it around. Keep adding til its fill, cap the radiator, and you're done. Could be something that simple. If you didnt do it when you did the tsat, you're going to want to do it anyways.
88Nightmare
10-21-2009, 11:59 AM
sounds good... I will try all that out. Thanks for the help