L33 Casting #'s, help!

kennjame62 · May 23, 2015

Hey All,

I'm hoping you all can help me here. I know this topic has been beat half to death, but I still can't seem to find this answer!

I have an 06 Sierra SLT Z71 Extended Cab, 122k. 5.3, L33, Aluminum HO Engine. Bought it about two months ago. 4:10 gears, but still averages 15 mpg surprisingly...

About a month ago, I suddenly noticed the coolant reservoir was completely empty. That took a whole gallon of coolant to fill to full. The truck has had a slight "knocking" noise that I assumed to just be piston slap. Then I read all about those Castech heads last night, and that's where I'll get into detail.

The dealer I bought the truck from was very shady. I have several issues I have to fix. Luckily the extended powertrain warranty will cover any heads/cylinder/valves, etc.

When I got the truck the oil was changed. The oil still looks like new, but I can see what looks like an outline of "brown" on the underneath of the oil cap where somebody wiped it off? After filling the coolant, it is now (after a month), down gradually, maybe 1/4 of a gallon. So I just got around to pulling off the valve covers, and what I found is interesting...

The driver side I pulled completely off. It looked very clean. Underneath of valve cover was very clean, EXCEPT for the front corner, which looked like sludge. The bolt (a common entry point) in the valve looked like it may be leaking behind this corner of the valve, but that was all I could see. And I couldn't find any Castech identification symbols! I didn't even see a 799 or 243. I saw what looked like "A1" and 308. I also noticed a symbol, which looks like there is a ring around it. No battery symbol. The BOLT, however, did have a symbol that looked like a castech symbol. Is it possible they used a different cover with Castech parts (mixed and matched)? Is 308 a Casting number and is it known for this issue? By the way, the oil was a quart low (it's been three months since a change, though).

Now, I haven't gotten the passenger off, but I did get the oil fill tube off. The same bolt on this side has the same logo and also looks to be leaking (looks to be a slight ring below it). Then I also noticed a battery symbol on the side new to one of the valves. This was NOT on the driver side valve. I am certain that the passenger side is Castech. So,

Is it possible to have one Castech and one non-Castech head? Is it possible for the parts to be interchanged? Is it possible to have a 308 Casting?

Is "A1" another symbol for another Casting Company? What would the driver side be?

Do you think, with the light knock, gradual loss of coolant, and brown residue (on the ring of the oil cap) could be a good indicator? I don't know where else the coolant would be going? Maybe this was already fixed before?

It only has 122k, I am bringing it to my mechanic to see what he thinks in a few days. I'm not so sure though. It is an L33. Does piston slap occur all the time? at least I have an extended powertrain warranty!

Thanks for all the help everyone.

James

Chris · May 23, 2015

L33 had either 243 or 799 head castings. Those are not the bad Castech heads, they are the LS2 heads

06pirate · May 24, 2015

So.....does the "L33" on my RPO code sticker mean I have the L33 engine, no worry about the bad Castech heads? Truck is 2006 Sierra SLT X-cab short box. 5.3 aluminum, 4x4.

Sticker pic below:

Chris · May 24, 2015

If an 06 and the 5.3 is aluminum, then it is an L33. That was the only aluminum 5.3 in that generation. Also those never got the Castech heads

06pirate · May 24, 2015

If an 06 and the 5.3 is aluminum, then it is an L33. That was the only aluminum 5.3 in that generation. Also those never got the Castech heads

Excellent. Thanks for the info.

kennjame62 · January 16, 2016

So.....does the "L33" on my RPO code sticker mean I have the L33 engine, no worry about the bad Castech heads? Truck is 2006 Sierra SLT X-cab short box. 5.3 aluminum, 4x4.

Sticker pic below:

Sorry it took so long to get back to you. Yes- atleast from what I've read. Is it a Z71 extended cab?

kennjame62 · January 16, 2016

If an 06 and the 5.3 is aluminum, then it is an L33. That was the only aluminum 5.3 in that generation. Also those never got the Castech heads

Hmmmm.... I read that they did have Castech heads, but the batch they came from did not have the problem. I took apart on of the valve covers the other day- and I do have a Castech stamping.

Chris · January 16, 2016

Hmmmm.... I read that they did have Castech heads, but the batch they came from did not have the problem. I took apart on of the valve covers the other day- and I do have a Castech stamping.

In here when it is refered as a Castech head it is used as a problematic one. The bad batch. Castech made a lot of heads for GM but only a few castings had issues

kennjame62 · January 16, 2016

So.....does the "L33" on my RPO code sticker mean I have the L33 engine, no worry about the bad Castech heads? Truck is 2006 Sierra SLT X-cab short box. 5.3 aluminum, 4x4.

Sticker pic below:

BTW the GT4 means you have a 3.73 rear axle if you were wondering.

Buddy67Lincoln · January 18, 2016

Dual electric fans are a giveaway of the L33. But looks like you have it. I also have the 3.73

Gears with my 06 Sierra 4x4 extended cab.

Badass69 · January 18, 2016

Dual electric fans are a giveaway of the L33. But looks like you have it. I also have the 3.73

Gears with my 06 Sierra 4x4 extended cab.

A 4.3 V6 from 2005 and up will have dual electric fans... so will a 4.8... and any variation of 5.3 or 6 liter in a regular half ton truck. The e fans mean absolutely nothing other than the truck is 2005 or newer. ... or has been swapped lol. Vin code "B" and the L33 rpo code in the glove box give it away... other than looking and seeing if the block is cast iron or aluminum.

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Buddy67Lincoln · January 18, 2016

i stand corrected! Thought my buddies steel 5.3 had a fan off the block.

A 4.3 V6 from 2005 and up will have dual electric fans... so will a 4.8... and any variation of 5.3 or 6 liter in a regular half ton truck. The e fans mean absolutely nothing other than the truck is 2005 or newer. ... or has been swapped lol. Vin code "B" and the L33 rpo code in the glove box give it away... other than looking and seeing if the block is cast iron or aluminum.

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