'94 GMC Sierra (OVERHEATING)...

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#1
1994 GMC Sierra 1500
4. 3 (6 cyl. )


Vehicle is overheating after about 10-15 miles of travel. The heater coil has been bypassed for about the last three to four months with no adverse problems. It was bypassed because the coil began to leak. Recently a small amount of radiator fluid began leaking from around or near the harmonic balancer perhaps from behind the front cover. This was "corrected" by using a stop-leak from the auto parts store. The overheating began first from the the loss of water, then from a different undetermined reason. The following is what has been done to fix the problem.

  • The radiator cap was replaced
  • The water pump has been replaced
  • The clutch fan has been replaced
  • The thermostat was first removed then later replaced
  • Water is flowing freely through the radiator
  • Water is flowing freely through the block
  • There is no significant damage to the radiator or its fins.
  • No other leakage has been found

Any ideas that would lead me to figure out this overheating issue would be greatly appreciated. Is it possible that the stop-leak has blocked a port? By the way, this all my brother's doin's'. Not mine. I'm just the computer literate one in the family.
 
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#2
Stop leak is problematic...But unlikely it has caused a complete blockage as they 'usually" foul the T'stat or the heater core...

NOt knowing what order you replaced parts some thoughts...

>water pumps - some are reverse rotation always compare impellars of replacement to origional....
>Serpentine belt- yes you can put it on wrong
>Need to check the radiator for obstruction-old school- turning hot engine off feel around core for different temps, new school use a infared thermometer, a loaner/rental tool or a radiator shop will test

Sorry have GTG quick
any reason to suspect a head gasket or eng crack??
 
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#3
No smoke that would indicate head gasket. Oil is clear, not milky. Will have him check for even heat distribution across the radiator and double check belt routing. Never bothered to check impellers prior to install.
 
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#4
kev2 said:
Stop leak is problematic. . . But unlikely it has caused a complete blockage as they 'usually" foul the T'stat or the heater core. . .

Not knowing what order you replaced parts some thoughts. . .

>water pumps - some are reverse rotation always compare impellars of replacement to origional. . . .
>Serpentine belt- yes you can put it on wrong
>Need to check the radiator for obstruction-old school- turning hot engine off feel around core for different temps, new school use a infared thermometer, a loaner/rental tool or a radiator shop will test

Sorry have GTG quick
any reason to suspect a head gasket or eng crack??
The water pump was replaced twice and given that there was no change in heat distibution before or after each of the installs I'd rule out the impellar being backwards.

The Serpentine belt install has been verified and is installed correctly.

**Aside from the radiator, are there any other components besides what's been mentioned above, that could be the culprit. If not I may advise him to replace the radiator.
 
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#5
observe the lower hose have seen them collapse- suck themselfs closed...


the core is bypasssed not blocked......

then double check  radiator.

PS.....forgot to ask - how much stop leak was used??
a little no harm BUT overdoing it .....??