coolant loss/ intake

I have a 2002 silverado with the 5.3.

I had been losing coolant for about 6 months, 12oz week. I saw small amount of staining at water pump, figuired the rest just evaporated away on the block. So I replaced the water pump.

Still losing coolant and it was getting worse. But I could find no leaks and I have no coolant in my oil.

Pressure test showed,small pressure loss but no leaks on outside of engine. Than we noticed steam coming from tail pipe. Was told it was a leak in intake manifold. I removed the intake ( which has no coolant running through it!) BUT the intake was wet. A mechanic told me I must have a small leak in the throttle body. So I bypassed the hoses at the throttle body.

I thought it was fixed. I didn't have to add water for a week. Than it started again!!

How can you get water into your intake, but not in your oil?

Thanks

1. you can have internal leak into combustion chambers/cylinders. head gasket. you need to watch for grey smoke coming out of tailpipe. som of those show themselves only on cold, as mini cracks in the gasket sealing rings close as metal expends
2. i am not sure it's possible, but you have studs holding intake in place, right? might be a crack in the engine head where the stud is seated.
3. does exhaust smell of coolant? right after the start up, stick sheet of paper towel next to tailpipe and let it "breath in" some of exhaust. ask someone to revv it for a second or 2. take a good look at what you see - and smell - on the paper towel.

these vehicles require dexcool of the proper 50% ratio...if not used this engine will corrode...

when you replaced the water pump how did the gasket area look ?
was the metal black, and pitted ?

the intake may also be cracked as well as a leak into the intake manifold from a corroded gasket...

the other problem your gonna get is the cat is damaged from long term coolant exposure..

j cAt- The water pump mating surface was silver and flat.

HOW could a cracked intake or bad gasket let coolant into the intake??

j cAt- The water pump mating surface was silver and flat.

HOW could a cracked intake or bad gasket let coolant into the intake??

coolant flows thru the throttle body....

I would remove all plugs line them up side by side and mark what cylinder they came out from...do they look exactly the same ? if so its the intake some where....

There is a very good possiblity that the water pump to block gskts are leaking...it occurs mostly when the engine is cold and at first start up. These engines are notorious for this condition. To confirm it to be the cause...add some dye and run it for a few days. Then get a black light and scan directly under both sides of the water pump to block surfaces...you'll most likely find traces of dye.

Another thing to consider. I have a 2004 Ext cab Z71 5.3. Although there was never a recall, there is a bulletin for possible head cracks on "Cast-tek" heads. I am not sure what all years this apply's to. You will have to go to a dealer or get the numbers off your heads and give them to a service person to check and see if these are used on your truck. They will replace the heads if they are found to be these. You must check for lifter damage from water. My truck had around 50,000 miles when I noticed the water disapearing. It was no longer under warr. They still did it at their cost. Hope this helps.