Don Terrill’s Speed-Talk

This topic is about stock GM LS heads. Is anyone having problems with water leaking into the oil with these heads? There's been stories going around that some of the GM LS castings have porosity problems and leak water in the oil around the top of the heads (head bolt area). See the link if you want to read about it:

http://www.gm-trucks.com/forums/index.p ... opic=57746

I noticed my 2001 Silverado with a 5.3L motor is starting to use water with not much showing up below, and the oil pressure is starting to do strange things. I just changed the oil and it seems to be running better now. I also put some stop leak in it and figure I'll just change the oil every 3 months. Sounds cheaper then redoing the heads if my heads have cracks in it and it's slowly leaking in the oil. Just wondering if anyone else is having the same problem. I haven't heard of anyone talking about it on this site and just somewhat recently ran into some stories on other sites. If it gets worse, I guess I'll have to replace the heads, or get a new truck. Replacing the heads sounds cheaper.

yes JOE your right, I dont know what years are affected ,but they leak where you describe. If you pressure test them you may need to torque them on a block or a plate, the leaks dont always show up on machine alone.

Yes, have seen at least 10 sets do that. Farely common issue.

Joe,
This is a common issue on the castech cast heads. Easy enough to zip the VC off to verify. Replacement cores are as cheap as can be. If you find that they are c-tech cast I would replace both heads.

airflowdevelop wrote:Joe,
This is a common issue on the castech cast heads. Easy enough to zip the VC off to verify. Replacement cores are as cheap as can be. If you find that they are c-tech cast I would replace both heads.

How do you determine who cast the heads?

castech logo (looks like a AA battery) will be on top of the end intake runner.

Like this Dennis? So this is the core with issues? Was this with all GM LS cores??

That is the logo. Looks like an L92 head which is unaffected.

Its only the castech 706 5.3/4.8 head that has issues that I know of. Not all 706's are made by castech though so you have to pull the valve covers and check.

Here is a copy of the Technical Service Bulleton (TSB) that GM put out:

http://ww2.justanswer.com/uploads/Blueg ... ss_5.3.pdf

It covers alot of vehicles from around 2001 to 2006. Must affect millions of GM cars, trucks, and suv's. So I wouldn't recommend using these "Castech" heads for any performance use. The problem is suppose to get worse in time, so I suspect this will be a bigger problem years from now.

airflowdevelop wrote:castech logo (looks like a AA battery) will be on top of the end intake runner.

Thanks, I'll be checking my 2003 Yukon and LS2 crate motor(just in case) tonight.

Cole

colebalster wrote:

airflowdevelop wrote:castech logo (looks like a AA battery) will be on top of the end intake runner.

Thanks, I'll be checking my 2003 Yukon and LS2 crate motor(just in case) tonight.

Cole

An LS2 would not have 706 casting heads.

if your heads are cracked and leaking replace them rather than just changing the oil, your bearings will thank you!

could this apply to any 243 castings? I have a set but dont know what motor they came off of. Not an LS6 car tho since the valves arent sodium filled. It has a Castech logo and I know some of the 4.8-5.3 motors came with 243's

If your 243's have yellow springs but not the lightweight valves, they are probably ls2, Blue spings early ls6, and steel colored then gen 4 4.8/5.3. This all from memory so theres a chance some of it could be wrong.

I'm under the assumption the ls4 would be yellow springs. No 243s or 799 have the casting defect that I've heard, it was pretty isolated to the castech only 706's on gen III 4.8/5.3's. There are 2 other sets of 706's that are not affected. The early sand cast heads come as 862s and 706's, and a die cast 706 that isn't made by castech.