Mysterious antifreeze leak?

[dailydragger03]

I am losing coolant somewhere! All my hoses are fine,no coolant in the oil, truck runs at normal temperature. The truck is a 5.3. Anybody else had this problem or have any advice.

[Crummy]

Heater core?

[dailydragger03]

I don't think it is a heater core. The experience I have had with a leaky heater core is that the smell will pretty much run you out of the cab. I am almost convinced it is an expansion plug. I'm gonna try some radiator dye this weekend and see what I get. I spoke to a couple mechanics who both said the 5.3 has had some expansion plug issues on the front of the block.

[turbochevy]

these trucks have a problem with water pump gaskets, more than likely that is your source of coolant loss.

[bcj67chevy]

Also could be intake manifold gasket.

[dailydragger03]

Thanks for the advice everybody. I plan to take some time this weekend and figure it out for sure. I'll post when I figure it out.

[turbochevy]

Originally Posted by bcj67chevy

Also could be intake manifold gasket.

The intakes on the GENIII truck is dry, no coolant passages at all.

[dailydragger03]

That's what I was thinking. I work at a NAPA store and I pulled out a gasket set and looked at it, it didn't look like it touched any coolant passages.

[turbochevy]

There is also a coolant crossover pipe in the front of the motor. It is under the manifold in the front of the motor, on the later year NBS trucks they had a problem with those leaking as well.

I am willing to bet that your water pump gaskets are shot, we do one or two of those each month at the shop.

[dailydragger03]

Hey turbochevy are you talking about the gaskets pump to block or the backing plate gasket?

[turbochevy]

Originally Posted by dailydragger03

Hey turbochevy are you talking about the gaskets pump to block or the backing plate gasket?

Pump to block.

[turbochevy]

The have changed the material the o-ring is made of, new GM part # 12588372

[Huck]

Had a leak on my 5.3 somewhere in the back. Never did find it. Poured in some of that powered coolent sealer last year--been good for the past 8 months. PITA to get it into the block via the overflow container but managed --and it worked great.

[dailydragger03]

turbochevy you were right, I replaced the water pump gaskets and flushed the cooling system. NO MORE DEX COOL!

[turbochevy]

Originally Posted by dailydragger03

turbochevy you were right, I replaced the water pump gaskets and flushed the cooling system. NO MORE DEX COOL!

Glad it worked out!

[Black 95 TSI]

Replace the rad cap, i see alot of GMs with this problem, I had the same problem on my truck. new cap fixed me right up

[Huck]

These 99 and up trucks don't have a rad cap!!! You add fluid thru the overfloor tank cap. That tank should always be half full--half empty so no fluid ever gets up to the cap.

[dailydragger03]

The water pump gaskets were my problem. Pretty sure I got it fixed, been keepin an eye on it. Now I got a power steering leak. Think its a shaft seal it about $6. It'll have to wait til I get some time. 18 hours of electrical engineering classes + 30 hours of NAPA = no truck time

[Black 95 TSI]

OK sorry its the surge tank cap, but Stant still calls it a rad cap, but anyways they still work the same way a regluar rad cap works, and when they go bad the coolet will escape past them in the form of steam and you will get the light to come on