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'04 Avalanche Radiator and leak

BAS-Sr

Full Member
Joined
Sep 11, 2015
Messages
66
Location
Millstone Township, New Jersey
My wife's '04 Avalanche has a slight drip from about the center of the engine. Not much, drips a spot on the driveway when she backs it out of the garage, leaks all the way down the driveway, each drip is about 6' to 7' apart. Tried looking underneath to see if I could see anything such as drips or indication of a drip spot so I could trace to the problem, but nothing obvious.

Was going to check the cooling system (heater hoses, radiator, water pump from what I could see of it), but nothing obvious there either. I have an older style pressure tester (one that you attach to the radiator fill where the cap is) but there is no radiator cap?

I also thought about flushing the cooling system, but hesitant to just plunge in! Guess it is like the classic style, put a T in the heater hose?

What am I missing about the radiator cap?
 
Radiator caps are long gone, a guess would be the water pump.

Try some white aerosol powder like foot powder to find the trail.
 
Sure it is not AC drip line?
 
AC runs when the defroster is on as well.

Have you checked your coolant level to see if it is going down?
Chances are likely it is a water pump if it is leaking that small amount but you need to verify where it is coming from before you start just part changing.

Rodney
 
redheadedrod said:
AC runs when the defroster is on as well.

Have you checked your coolant level to see if it is going down?
Chances are likely it is a water pump if it is leaking that small amount but you need to verify where it is coming from before you start just part changing.

Rodney

The coolant level is going down very little in the overflow. The defroster really would not create enough water to drip in just a few seconds of running, but I think you guys are probably right, it is probably the water pump, but I just don't see any indications from under it? In the older SBC you could see the leak at the bottom of the water pump weep hole.

It is an '04, motor has ~120k on it.....
 
Coolant leaking from the weep hole on the water pump is usually gradual enough that it does not cause a large enough puddle under the truck until the water pump seal is pretty shot.

A slow loss of coolant from the seal on the water pump, without any noticeable coolant on the ground, is usually because that coolant gets dispersed while the engine is running and the truck is in motion.

You may smell it long before you see it.

When the seal is almost shot, you begin to see coolant under the engine and on the ground, as you first describe.

If it were me, I would be planning on installing a new water pump pretty soon.

This would be a good time to replace the thermostat, belts and hoses.

If the belt pulley and tensioner haven't been replaced in recent memory, those items would be a good idea to replace, as well.
 
EXT4ME said:
Coolant leaking from the weep hole on the water pump is usually gradual enough that it does not cause a large enough puddle under the truck until the water pump seal is pretty shot.

A slow loss of coolant from the seal on the water pump, without any noticeable coolant on the ground, is usually because that coolant gets dispersed while the engine is running and the truck is in motion.

You may smell it long before you see it.

When the seal is almost shot, you begin to see coolant under the engine and on the ground, as you first describe.

If it were me, I would be planning on installing a new water pump pretty soon.

This would be a good time to replace the thermostat, belts and hoses.

If the belt pulley and tensioner haven't been replaced in recent memory, those items would be a good idea to replace, as well.

Exactly some of my thoughts! I am not new to repairs, do frame off restorations on older ('68 el Camino.....etc...) and built over 15 BBC and can't count how many SBC, but these newer LS motors have changes not that familiar with!

So, yes, looks like the water pump is the culprit, have to plan this and get the parts!

That said, just how do you fill the radiator?
 
You fill the radiator through the overflow tank.

(The overflow tank is pressurized during normal operation and that is where you attach a pressure testing device.)

The procedure I read, the last time I changed out my radiator, said to fill the tank close to the top with coolant first.

Then, once filled, start the engine with the coolant tank cap off.

Adjust your truck's heater to full on hot.

Run the engine and vary the RPM's between idle and 3000 RPM, alternating every 30 seconds or so and running up to 3000 RPM's slowly until the engine has warmed up.

Do not race the engine quickly or you will cause coolant to burst out of the open coolant tank.

Slowly change your RPM's both up and down.

Check the coolant tank and refill to the halfway mark on the side of the tank.

Secure the coolant tank cap and drive the truck around varying the RPMs for half an hour or better.

After the engine has cooled, check the coolant level and add as needed to the halfway point.

DO NOT remove the coolant tank cap if the engine is warm as it is under pressure.

I check mine a few times over the next couple of days worth of driving.

Done.
 
EXT4ME said:
You fill the radiator through the overflow tank.

(The overflow tank is pressurized during normal operation and that is where you attach a pressure testing device.)

The procedure I read, the last time I changed out my radiator, said to fill the tank close to the top with coolant first.

Then, once filled, start the engine with the coolant tank cap off.

Adjust your truck's heater to full on hot.

Run the engine and vary the RPM's between idle and 3000 RPM, alternating every 30 seconds or so and running up to 3000 RPM's slowly until the engine has warmed up.

Do not race the engine quickly or you will cause coolant to burst out of the open coolant tank.

Slowly change your RPM's both up and down.

Check the coolant tank and refill to the halfway mark on the side of the tank.

Secure the coolant tank cap and drive the truck around varying the RPMs for half an hour or better.

After the engine has cooled, check the coolant level and add as needed to the halfway point.

DO NOT remove the coolant tank cap if the engine is warm as it is under pressure.

I check mine a few times over the next couple of days worth of driving.

Done.

Thanks! Only modern technology could make this process this much of a PITA!
 
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