Internal coolant leak confirmed by Blackstone UOA - repair decisions

[350Rocket]

I've topped up coolant more than usual lately. The most likely culprit on these ls engines is either a head gasket or cracked head. I had the drivers valve cover off for a PCV issue a couple years back and the head was not the "Castech" one that is known to crack. But the passenger side could be.

It's the original 4.8 with 11,400 hours and I have a couple 5.3 engines as spares. If I just have the engine swapped I would probably prep one of the 5.3s with all new gaskets since it's sitting on a stand.

 

[Donald]

With that many hours on the engine it would seem to me you might want to pull both heads and have a valve job done after checking for cracks.

How does the compression read across the cylinders.

And what about the condition of the rest of the truck? Body, frame, interior, transmission?

 

[350Rocket]

With that many hours on the engine it would seem to me you might want to pull both heads and have a valve job done after checking for cracks.

How does the compression read across the cylinders.

And what about the condition of the rest of the truck? Body, frame, interior, transmission?

It had a leakdown test done just before the valve cover job so almost 3 years ago. It passed with flying colors and I did a compression test sometime around then also was good. It runs like new other than a bit of lifter noise on cold start. Oil pressure is down to 30psi at hot idle, maxes out at 70 at high RPM.

The frame is really good other than a bit of rust on a couple of the cross tubes that I noticed when it got new rocker panels and cab corners about 4 years ago. One new fender installed a couple years ago. The other one I plan to do next year. New bumper is getting installed next week when I'm going north on a 4k mile surveying job in a much newer truck. It's in pretty good shape for the mileage and usage but there is a lot of wear and tear on the drivers door panel and it needs a driver's seat soon.

 

[350Rocket]

I've just bought a few gallons of demineralized water do when I get back from up north in 10 days I can drain the coolant and replace with mostly water for now ...and I think I'll add those old gm coolant crush tabs from back in the day when I worked at a gm dealer.

Then I can spend my time preparing my 2000 5.3 LM7 engine with all new gaskets, etc before swapping it.

 

[Gladtojoin88]

If it has a vin t 5.3 it is a cracked head. Pull off a valve cover to confirm which head. You should see sludge. They had an issue with pourous heads! I'd likely just replace both since you caught it early

 

[cptbarkey]

Its worth fixing for the long term, these trucks are priceless.

 

[Gladtojoin88]

I see now it says 4.8! I would still pull valve covers to see if you can find the sludgy side

 

[350Rocket]

If it has a vin t 5.3 it is a cracked head. Pull off a valve cover to confirm which head. You should see sludge. They had an issue with pourous heads! I'd likely just replace both since you caught it early

It's not a 5.3 but the 4.8 falls under that tsb also....the issue is apparently only if it has Castech heads which I thought it didn't on the drivers side I had the valve cover off, but I now realize I would have had to pull the rocker bridge off to see the logo.

It could be a head gasket but the cracked head is probably the more likely scenario. There was sludge which had plugged up the PCV, causing it to suck oil into the throttle body until I added a catch can which would fill in a day or use. The replacement valve cover cured that problem but I'm going to find out how much sludge is in there now 3 years later.

 

[350Rocket]

I see now it says 4.8! I would still pull valve covers to see if you can find the sludgy side

They are the same 706 heads on either 4.8/5.3. I do have to confirm the issue. The tsb shows exactly where to look.

 

[Gladtojoin88]

They are the same 706 heads on either 4.8/5.3. I do have to confirm the issue. The tsb shows exactly where to look.

Keep us updated ! Didn't have many at my GMC days but had enough to remember! That being said my 2003 5.3 vin t truck is driven daily by me because they truly are great trucks !

 

[350Rocket]

Keep us updated ! Didn't have many at my GMC days but had enough to remember! That being said my 2003 5.3 vin t truck is driven daily by me because they truly are great trucks !

Will do. It's been a great truck. The most dependable vehicle I've experienced. So I'm going to fix it anyway. I also can't afford a newer truck and I'd be buying another one of these if I had to replace it.

 

[350Rocket]

I got around to pulling both valve covers tonight and think I have confirmed a cracked head on the passenger side. It has worse sludge than the PCV side (drivers side) which was sludgy previously due to a sludged up PCV. The drivers side appears to have cleaned up some since a year and a half ago when I replaced the valve cover so I'm not sure if there is any coolant leaking on that side or just the passenger side.

Anyway my solution is to drain all the antifreeze and refill with demineralized water and gm cooling system sealant tabs and start preparing my spare 130k mile 5.3 with new oil pump pickup tube p ring, all new gaskets etc knock sensors. Every known failure point while the engine is out so I can just swap out the 4.8 for the 5.3 sometime next year. Short oil changes for now until I can do that.

 

[350Rocket]

Got the rocker arms off and confirmed they are the problematic castech heads.

 

[350Rocket]

New video by Mike Kennedy

photos.app.goo.gl

I almost had a heart attack because after I got it all back together and very carefully torquing each rocker at the base circle. I thought I messed something up because it ticked like crazy for at least 5 minutes before a lifter that must have lost its prime finally pumped up.

 

[Chris142]

With that many hours on the engine it would seem to me you might want to pull both heads and have a valve job done after checking for cracks.

How does the compression read across the cylinders.

And what about the condition of the rest of the truck? Body, frame, interior, transmission?

Those heads crack around the valvespring area.

 

[350Rocket]

Those heads crack around the valvespring area.

Well I found evidence in the drainback hole area exactly as the tsb said. Perfectly cleaned areas where it's getting steam cleaned. Hadn't heard of the valve spring area cracking.

 

[Gladtojoin88]

Where did you get heads from ? Great work by the way !

 

[350Rocket]

Where did you get heads from ? Great work by the way !

The current heads are the factory ones from 2005 with 260k miles and 11,600 hours on them.
The engine hasn't had any work except a valve cover replaced, so it has some other potential failure points as the miles and hours add up, like the pick up tube O ring for the oil pump, rear main seal, intake gaskets and knock sensors, and every other gasket. Considering this and that the engine has a lot of sludge inside, potentially more down in the pan...I'm prepping a 130k mile 5.3 by replacing all those potential failure points (and making sure it doesn't have Castech heads on it) on the engine stand and get ready to replace it in a couple of years. At that point it will be over 300k miles and 14,000 hours.

 

[350Rocket]

Anyone have any thoughts on using the gm cooling system seal tabs in deionized water with nothing else added but some Rislone hyper cool super coolant (basically like Redline water wetter) because I wanted some kind of lubricant for the water pump.

The gm crush tabs have a pretty high success rate but I haven't been able to find anything on using them without antifreeze.

I will do another uoa before winter to see how much improvement occurred before I have to put antifreeze back in for the cold weather.

 

[Gladtojoin88]

The tabs I think are overkill on the 4.8 , 5.3 , 6.0 ! They were definitely needed on all the lower intake failure engines ! 3800 , 4.3 3.1 3.4!