93 GMC 1500 4.3 running a little hot after it gets off the highway...
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93 GMC 1500 4.3 running a little hot after it gets off the highway...
So i have an old 93 GMC 1500 with 183k on it and the 4.3 v6 in it... the temperature gauge never got above 1/3 ( about 160F?) even on the hottest of days with the AC cranking full blast... Well one day I noticed as i was checking my fluids that my coolant was a little low, maybe a quart or so... a few more weeks go by and it became clear that the water pump bearing was bad, so i changed the water pump...
First thing I noticed while changing the water pump was that the coolant was NASTY... there were copper and aluminum dust in the coolant(maybe some kind of stop leak?) Any way i used my garden hose and blew the radiator out backwards and forwards until it was flowing nice and clear...
Got everything back together (also did a new serpentine belt as well) the truck would run about 1/2 (210F) on the gauge and sky rocket to about 3/4 (235F?) if I would stop... so returned the water pump, and replaced it again... same thing
This time, I replaced the thermostat, and this time I flushed the radiator and the block... and for good measure I got a new radiator cap ...got it all back together and it ran a little cooler
So I figured.... i need to replace the radiator... it must be clogged
I pulled the old radiator, again flushed the block with the garden hose, replaced the radiator with a brand new one and replaced the coolant...
The truck seemed to run cooler, less than 1/2 on the gauge, but then after driving it around town for a few weeks, I hit the highway... temps stayed around 1/3 (160F maybe a tick higher) while running down the highway, all seemed fine... but then i got off the highway and sat at a light... the temps creeped up to about 2/3 (220-225F?) on the gauge, not in danger at all, but still not right... hoped back on the highway and drove it home, within a minute on the highway the truck went back to running around 1/3 (160F maybe a tick higher)
so I get the truck home, no issues... I get my handy dandy block tester and do a block test... no combustion gases in the coolant, I test it again maybe 2 more times, again, no combustion gases in the coolant. (I decided to test the block test fluid by blowing air from my lungs through the fluid and it did change color, so i know the fluid is working)
During all this the truck ran fine, never even acted like it was hot...
I am at a loss here...
First thing I noticed while changing the water pump was that the coolant was NASTY... there were copper and aluminum dust in the coolant(maybe some kind of stop leak?) Any way i used my garden hose and blew the radiator out backwards and forwards until it was flowing nice and clear...
Got everything back together (also did a new serpentine belt as well) the truck would run about 1/2 (210F) on the gauge and sky rocket to about 3/4 (235F?) if I would stop... so returned the water pump, and replaced it again... same thing
This time, I replaced the thermostat, and this time I flushed the radiator and the block... and for good measure I got a new radiator cap ...got it all back together and it ran a little cooler
So I figured.... i need to replace the radiator... it must be clogged
I pulled the old radiator, again flushed the block with the garden hose, replaced the radiator with a brand new one and replaced the coolant...
The truck seemed to run cooler, less than 1/2 on the gauge, but then after driving it around town for a few weeks, I hit the highway... temps stayed around 1/3 (160F maybe a tick higher) while running down the highway, all seemed fine... but then i got off the highway and sat at a light... the temps creeped up to about 2/3 (220-225F?) on the gauge, not in danger at all, but still not right... hoped back on the highway and drove it home, within a minute on the highway the truck went back to running around 1/3 (160F maybe a tick higher)
so I get the truck home, no issues... I get my handy dandy block tester and do a block test... no combustion gases in the coolant, I test it again maybe 2 more times, again, no combustion gases in the coolant. (I decided to test the block test fluid by blowing air from my lungs through the fluid and it did change color, so i know the fluid is working)
During all this the truck ran fine, never even acted like it was hot...
I am at a loss here...
Last edited by ericfx1984; Apr 1, 2020 at 10:12 AM.
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Joined: May 2011
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From: Central Iowa
Sounds like either the fan clutch is shot, there’s still air trapped in the system, or it’s leaking elsewhere.
1) Is the coolant reservoir functional and in use? If so, make sure it’s up to the full cold mark, then check the level with the engine hot - if it’s below the full hot mark, there’s still air working it’s way out. Did you turn the cabin heat on high to bleed the heater core?
2) With the engine up to temp, shut it off and see how difficult it is to spin the fan by hand. It should take moderate effort to spin it, but if it’s freewheeling, replace it. Also check front to back movement - a small amount of play is ok, but if it’s rocking, replace it.
3) Check engine oil and transmission fluid for signs of coolant - either one will appear milky in color if contaminated.
4) What block fluid are you using and how long did you use it for? At work, we use the Lisle tester kit and it’s taken upwards of 10 minutes to get a reaction from the fluid.
1) Is the coolant reservoir functional and in use? If so, make sure it’s up to the full cold mark, then check the level with the engine hot - if it’s below the full hot mark, there’s still air working it’s way out. Did you turn the cabin heat on high to bleed the heater core?
2) With the engine up to temp, shut it off and see how difficult it is to spin the fan by hand. It should take moderate effort to spin it, but if it’s freewheeling, replace it. Also check front to back movement - a small amount of play is ok, but if it’s rocking, replace it.
3) Check engine oil and transmission fluid for signs of coolant - either one will appear milky in color if contaminated.
4) What block fluid are you using and how long did you use it for? At work, we use the Lisle tester kit and it’s taken upwards of 10 minutes to get a reaction from the fluid.
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Joined: Mar 2020
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Sounds like either the fan clutch is shot, there’s still air trapped in the system, or it’s leaking elsewhere.
1) Is the coolant reservoir functional and in use? If so, make sure it’s up to the full cold mark, then check the level with the engine hot - if it’s below the full hot mark, there’s still air working it’s way out. Did you turn the cabin heat on high to bleed the heater core?
2) With the engine up to temp, shut it off and see how difficult it is to spin the fan by hand. It should take moderate effort to spin it, but if it’s freewheeling, replace it. Also check front to back movement - a small amount of play is ok, but if it’s rocking, replace it.
3) Check engine oil and transmission fluid for signs of coolant - either one will appear milky in color if contaminated.
4) What block fluid are you using and how long did you use it for? At work, we use the Lisle tester kit and it’s taken upwards of 10 minutes to get a reaction from the fluid.
1) Is the coolant reservoir functional and in use? If so, make sure it’s up to the full cold mark, then check the level with the engine hot - if it’s below the full hot mark, there’s still air working it’s way out. Did you turn the cabin heat on high to bleed the heater core?
2) With the engine up to temp, shut it off and see how difficult it is to spin the fan by hand. It should take moderate effort to spin it, but if it’s freewheeling, replace it. Also check front to back movement - a small amount of play is ok, but if it’s rocking, replace it.
3) Check engine oil and transmission fluid for signs of coolant - either one will appear milky in color if contaminated.
4) What block fluid are you using and how long did you use it for? At work, we use the Lisle tester kit and it’s taken upwards of 10 minutes to get a reaction from the fluid.
2.) haven't checked like that, but i will tell you that it rips apart a small stick if it's idling and warm
3.) oil and trans fluid are great
4.) Lisle, yes and it works great on other errrr... other projects
Thread Starter
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not original... but not new... the original one was on it(I know the original owner) and was never changed... it had 0 resistance.... my neighbor gave me a use one that seemed to be much better so i never gave it another thought, I mean lets put it this way... I aint sticking my hand in there
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From: kevinkpk
not original... but not new... the original one was on it(I know the original owner) and was never changed... it had 0 resistance.... my neighbor gave me a use one that seemed to be much better so i never gave it another thought, I mean lets put it this way... I aint sticking my hand in there