Hey guys,

My Silverado is at 190K, and its's a 4.8 2001.

So I replaced my coolant about 8 or so months ago and it was a bit low. I figured no big deal. Then about two months ago, my "low coolant" indicator came on, so I filled the overflow with distilled, but I was and am too busy to look into it. Yesterday I was travelling South and hour and the light came on again, so I topped it off. The truc.kh hasn't run hot at all. While running, I don't notice anything dripping. I changed the oil today and it was clean of any coolant milkiness. I know that back in the day V8 water pumps would weep when the bearing was going, so I'll check that. Heater hoses and their connections, I'll check that. I read that there is a coolant line running under the intake manifold?

Anyway, do you have any "first place to look" kind of list? I know there are some real experts out there who have "been there" and "done that."

Thanks in advance!

PROBLEM SOLVED - SOLUTION MADE (See last post) THANKS!!

 

you re on the right track....water pump, remove the belt to check for play in the pulley....spin all pulley while the belt is off...replace any that have play and are noisey. Water pump gaskets, rad tank...look for dried red goo where the tank meets the core. If you smell anything sweet in the cab, wet passenger floor or have fog forming on the glass its the heater core.

if you have a coolant pressure tester...pressurize the system to the psi on the rad cap.....leaks will be easier to f ind under pressure

 

Cool, I'll do that today. Thanks so much!
One fact I will add, I did notice when I changed the oil (it looked really good, not to dark and no milkiness or bubbles at all), the little bit, last tiny, thin stream of oil (I ran the engine 15 mins prior, so it was very warm) had some sludge deposits, about a tablespoon or so that was pushed out in small amounts by the stream of oil. I don't recall this prior, but I never waited for it all to drain under the truck typically either. That something like a tell or not related?

 

water is a byproduct of combustion so it can dilute the oil. if you do lots of short trips in town it can build up and not burn off as the system doesn't get hot enough long enough.

1 tbsp isn't indicative of a larger problem without other symptoms. imo.
most coolant leaks are external so start there.

if you find nothing external...inspect the spark plugs...if they seem really clean...coolant going into the engine will wash the plug, cylinder and valve face. if you see that...we use a combustion gas leak detect solution...it changes colour if it detect comb gas in the coolant.

 

There’re plastic connectors between the heater core coolant lines and the heater core that’ll rot and weep, eventually breaking. Check those first as it doesn’t require disassembling anything. My 05 did the same thing before eventually dumping most of its coolant all over the backside of the motor while driving, sending me into a panic over a possible intake manifold gasket.

Whether they’re good or bad, plan on deleting them. They serve no purpose beyond easier installation at the factory.

 

Hey all, I finally located the leaks, and I appreciate all of the assistance and ideas!
Water Pump was fine, tight and not leaking.
Heater hoses, heater core, attachments and plastic connections were fine, tight and not leaking.
Coolant hoses and radiator were fine, tight and not leaking.

Here's what I found when looking at the Coolant Crossover pipe that runs between the heads in the front of the engine, just behind and under where the intake vent pipe (plastic) meets the aluminum intake input connector. There was no leak on ether side. However, I learned through diagrams that the 4.8 heads are universal, and therefore they have coolant crossover connection ports on both ends of the heads. When I looked at the rear ports (with bolted down blocks on them), I found staining where leaks obviously occurred, but quickly evaporated due to their location. I replaced all 4 of the o-ring infused metal pieces, even the front ones that didn't leak, as the Fel-Pro set was a pack of 4, which costs about $19. Just as a note, the dealership wants oner $12 each for these tiny parts, so get the Fel-Pro set to be sure.

Thanks again everyone!