https://stream.echo6.co/videos/watch/25c8562a-3284-4624-be51-8f2463e3d79f In this video I show an example of cylinder head on a 5.3 GM leaking coolant. This is a relatively common problem you may discover on GM V8's. TSB: #06-06-01-019B: Information on Gradual Coolant Loss Over Time with No Evidence of Leak Found - (Jun 12, 2007) Subject: Information on Gradual Coolant Loss Over Time With No Evidence of Leak Found Models: 2004-2006 Buick Rainier 2001-2006 Cadillac Escalade Models 2001-2006 Chevrolet Avalanche, Blazer, Silverado, Suburban, Tahoe, TrailBlazer Models 2001-2006 GMC Envoy, Jimmy, Sierra, Yukon Models 2001-2004 Oldsmobile Bravada 2005-2006 Saab 9-7X with 4.8L or 5.3L VORTEC® GEN III, GEN IV V8 Engine (VINs V, T, M, B, Z -- RPOs LR4, LM7, LH6, L33, L59)This bulletin is being revised to include engine RPO L59. Please discard Corporate Bulletin Number 06-06-01-019A (Section 06 - Engine/Propulsion System).Some vehicles may experience a gradual coolant loss over time. A very low percentage of cylinder head(s) manufactured with an embossed Castech logo may develop a porosity crack in a very specific area. Inspect the cylinder head assembly to determine if the casting was manufactured by Castech. This can be accomplished by inspecting for their casting logo located on top of the intake port, under the rocker arm support rail and in the spring deck cavity portion of the cylinder head. Important: If the cylinder head(s) are Not a Castech casting, follow normal diagnostic procedures in SI to determine the cause of the coolant loss. Refer to the following illustrations on how to identify Castech casting and/or the very specific areas of the cylinder head(s) for a coolant leak from porosity.If an SMA Video has helped you out please consider giving using "Patreon" to help support us. The videos take real time to create and pull us away from real work that pays our bills. CLICK HERE: https://www.patreon.com/southmainauto CHECK OUT OUR "SMA SWAG" STORE! Go on Teespring and get your very own SMA merch! https://teespring.com/stores/the-sma-store If you don't like Patreon feel free to use the "PayPal Me" link: https://www.paypal.me/SouthMainAuto The South Main Auto Amazon Store: https://www.amazon.com/shop/southmainautorepairavoca AES Wave Automotive Diagnostic Tools: https://www.aeswave.com/cart.php?m=affiliate_go&affiliateID=2525b91fc8e906e8215984074c9d9e8f&go=https://www.aeswave.com/Miscellaneous-p9347.html Thank you for all the continuing support! --Eric & Vanessa O. Feel like sending some swag to SMA because you love the videos but don't know where to send it? Just ship it here: South Main Auto Repair 47 S. Main St PO Box 471 Avoca, NY 14809 Disclaimer: Due to factors beyond the control of South Main Auto Repair, it cannot guarantee against unauthorized modifications of this information, or improper use of this information. South Main Auto Repair assumes no liability for property damage or injury incurred as a result of any of the information contained in this video. South Main Auto Repair recommends safe practices when working with power tools, automotive lifts, lifting tools, jack stands, electrical equipment, blunt instruments, chemicals, lubricants, or any other tools or equipment seen or implied in this video. Due to factors beyond the control of South Main Auto Repair, no information contained in this video shall create any express or implied warranty or guarantee of any particular result. Any injury, damage or loss that may result from improper use of these tools, equipment, or the information contained. Tue, 12 May 2026 13:32:36 GMT https://validator.w3.org/feed/docs/rss2.html PeerTube - https://stream.echo6.co https://stream.echo6.co/client/assets/images/icons/icon-512x512.png https://stream.echo6.co/videos/watch/25c8562a-3284-4624-be51-8f2463e3d79f All rights reserved, unless otherwise specified in the terms specified at https://stream.echo6.co/about and potential licenses granted by each content's rightholder.