My aunt has a 4.8 silverado with the 706 heads and its using coolant. She took it to a shop and they did a pressure check on the coolant system for two hours and it didnt show a leak. But it's using coolant and smoking some too. What's the fix on these heads? Is it just head gaskets need to be replaced or the heads them selfs? I've seen issues with these heads but not fix. I have the same heads on the 5.3 I put in my truck with no problems.

 

IIRC. It's the head itself. It gets worn on one of the coolant passages for some reason. The affected heads were castek heads, identified by a battery looking insignia.

The fix is to get a new head

 

I have a set of 862 heads I just took off my 5.3
They have around 10-12k miles on them. Complete with springs that I'll let go for a good price
I put on 243s

 

Thanks for the info. Where is that insignia located at? I have a set of 862 heads off my old engine I could use to fix hers.

 

You have to pull the rockers to see the symbol. Pull the valvecovers and they will have thick snot looking oil buildup underneath , this is a dead giveaway.

 

Am I the only one that is confused why the pressure test held but it is leaking enough to smoke? How does that happen?

 

I thought the same thing. I don't have a lot of info on the truck. She just recently told me about it. The truck is 100% stock 150,000 miles. I was behind her driving it the other day and didnt notice any smoke but she says it does smoke some.

 

There's a thread where someone put that coolant leak fix crap into the coolant and it fixed the head leak. You could try that, replace the heads, or perhaps get them welded around the crack.

 

The leak fix stuff is worth a shot I guess. Do you have to flush the system or just dump it in? What brand of leak fix?

 

If you wanna use stopleak buy some Blue Devil the instructions will be on the bottle. It worked for me. I used it on a service van that had a 4.8 with 706 heads. I had it tested for leaks an they couldn't find anything.. But it would drink coolant everyday. Its been 3 years now since I used the stuff and I haven't had to add anymore coolant.

Buuuttt that's if you don't really care about fixing the leak the correct way lol