5.3 coolant leaker

[GaryLazerEye]

Hello y'all. Got me a 2001 Tahoe 5.3l. 299,900 miles. Runs great, but losing coolant. At 299,600 we changed head gaskets due to yogurt in the pan. Found a breach in the driver's side gasket, so checked, cleaned and reassembled. Ran for 2 days then shit the water pump. Changed that, all sealed up coolant wise. Now losing coolant into the oil once again. Keep seeing posts on the cylinder heads cracking around the bolt area on the vertical surface. I am aware of this issue. Next step is to remove valve covers and pressure test engine to see if we missed those cracks if they are indeed there. THAT BEING SAID....does anyone know of any other things I may have missed or could check I'd appreciate it. I cleaned valve covers, cross tubes, pcv tube, heads and intake. Changed the knock sensors, oil pressure switch as well. Have a spare set of the wonderful castech heads that are already cracked. The heads on the Tahoe now are stamped with a 862 on the rear next to the cover, but I haven't got numbers off the head itself until I pull the covers. Thoughts, questions, hecklers, are all welcome. Thanks y'all

 

[iamdub]

Hello y'all. Got me a 2001 Tahoe 5.3l. 299,900 miles. Runs great, but losing coolant. At 299,600 we changed head gaskets due to yogurt in the pan. Found a breach in the driver's side gasket, so checked, cleaned and reassembled. Ran for 2 days then shit the water pump. Changed that, all sealed up coolant wise. Now losing coolant into the oil once again. Keep seeing posts on the cylinder heads cracking around the bolt area on the vertical surface. I am aware of this issue. Next step is to remove valve covers and pressure test engine to see if we missed those cracks if they are indeed there. THAT BEING SAID....does anyone know of any other things I may have missed or could check I'd appreciate it. I cleaned valve covers, cross tubes, pcv tube, heads and intake. Changed the knock sensors, oil pressure switch as well. Have a spare set of the wonderful castech heads that are already cracked. The heads on the Tahoe now are stamped with a 862 on the rear next to the cover, but I haven't got numbers off the head itself until I pull the covers. Thoughts, questions, hecklers, are all welcome. Thanks y'all

The LS, having a dry manifold, doesn't have many areas for coolant to mix with oil. It's either head(s), in the block or, if so equipped, the engine oil cooler in the radiator. Everything else would be external leaks and not mix it with oil.

As you already know, the best you can do is pop the covers off and take a peek. Also, it's not uncommon for them to not leak (even when pressurized) until it's at operating temp. I don't think pressurizing would be necessary as it's usually pretty obvious where the coolant is washing away the oil if there is a crack in the head(s).

 

[JamesLond]

I'm curious, are your O2 sensors still working?

 

[GaryLazerEye]

Never had a light come on or issue to believe they are bad. I've owned this since 40,000 miles. It has never been opened up, the knock sensors, oil pressure switch, head gaskets valve cover gaskets and even the water pump were all OEM. None of it had been replaced. I know the cats are operating correctly, but I did have an 02 light come on, I cleared it, and it never came back. That's the only time in 259,000 it's come on regarding oxygen sensors, that was about 6 months back, maybe a few thousand miles. I've been losing coolant for at least a year now, but this all began about 6 weeks ago.

 

[rockola1971]

Didnt have that head machined smooth before you put it back on did you?