GMC Yukon 2000–2006
Possible causes
Causes with no correction stated (1)
Causes the records name for which no check or repair is stated, in a technical document or in a record. Press one for the records that name it.
- Engine
- Engine: failed (3)
The documents say what to doOnly records name itThe size of a node, the width of a link and the numbers are records matching this search, not likelihoods.
FaultCrate・GMC Yukon 2000–2006・Engine
Candidate cause (the documents say what to do)
Castech cylinder head porosity crack (gradual coolant loss)
Applies to: 4.8L, 5.3L only
Some vehicles may lose coolant gradually over time.
A very low percentage of cylinder heads with an embossed Castech logo may develop a porosity crack in a very specific area.
What to do
- Inspect the cylinder head to determine whether the casting was made by Castech.
- On a Castech casting, inspect around the five oil drain holes for witness marks of coolant seepage.
- The crack can be at any of the five cylinder head oil drains and shows as a clean or shiny area on an otherwise stained surface.
- Pressurizing the cooling system may reveal coolant, air, or both weeping in that area.
- Check whether the head is a Castech casting by looking for the casting logo on top of the intake port, under the rocker arm support rail and in the spring deck cavity portion of the cylinder head.
- If coolant witness marks are found, replace the entire cylinder head assembly.
Caution: If the heads are not Castech castings, follow normal diagnostic procedures to find the cause of the coolant loss.
What is needed
- Parts and materials
- The entire cylinder head assembly (if coolant witness marks are found)
- Labor time
- Not stated
- Special tools
- Not stated
- Scan tool
- Not stated
Only what the technical documents state. "Not stated" does not mean not needed.
In the records
No record states work done for this cause.
Outside the documents and the records
The five pages read are all question-and-advice exchanges on Q&A sites, and none records that the vehicle's heads were confirmed to be Castech castings. A repair outcome is reported in only two places: the head replacement another poster describes on the 2004 Tahoe page, and the water pump replacement on a 2000 Silverado. The one 2003 Yukon page ends with the cause unknown. No Japanese shop record was found.
- A 2008 question on 2CarPros (2004 Tahoe, 103,000 miles (= 165,762 km)) says a mechanic's cooling-system pressure test found no leak. Another poster on the same page writes that the same symptom turned out to be a cracked head, that the coolant loss stopped once the heads were replaced, and that the engine has had a "skip" since. 2CarPros
- A 2016 question on 2CarPros (2003 Yukon, 5.3L, 272,000 miles (= 437,742 km)) says coolant had been going down slowly for months, and that on a cold start water or coolant sprays onto the ground with one puff of white smoke or steam. The radiator, hoses, water pump and thermostat were renewed, the intake manifold gasket was replaced after sludge was seen in the oil pan, a reagent colour-change test at the coolant reservoir was negative and compression was 210 on all eight cylinders, yet the cause was still not found. 2CarPros
- Two 2009 questions on 2CarPros (a 2003 Silverado at 66,000 miles (= 106,217 km) and a 2004 Silverado at 108,000 miles (= 173,809 km)) put the loss at roughly a quart each week and at over a gallon since late November respectively; both say there is no sign of an external leak and no coolant seen in the oil. The answerer on the 2004 page writes that he has replaced many heads for this symptom, that the cracks are hard to see and that a pressure test is the only way to find the leak. Neither page reports what was found on that truck. 2CarPros2CarPros
- A 2018 question on Car Talk Community (2000 Silverado 1500, 5.3L) is a case where the head was not the cause: the owner, who had asked about a coolant leak of unknown origin, later writes that the water pump failed and was replaced, and reports no further trouble after that (there had been no overheating, and no coolant in the oil as far as the dipstick showed). Car Talk Community
The sentences above were written by FaultCrate from what shops' public pages and Q&A sites state as fact (none of the pages' wording is shown; a second reader checked each against its pages). A record of another vehicle says which vehicle. A Q&A thread is a question and advice, and may not say how the repair ended. The links below are places to look; the contents of pages not read were not checked.
The pages read, and other places to look (13)
Repair videos
- 2005 Avalanche Episode 19: Coolant Loss TSB & Cracked Head Case Study - GM LS Castech Cylinder HeadsYouTube, 2005 Avalanche, not read
- 5.3L Vortec Cracked Heads (Castech 706)YouTube, no vehicle stated, not read
- Chevy 5.3L Coolant Loss - Chevy Silverado Avalanche Cracked HeadYouTube, Silverado / Avalanche, not read
- What the inside of a chevy 5.3 with cracked 706 castech heads looks likeYouTube, no vehicle stated, not read
Forums and Q&A
- 2004 Chevy Tahoe Disappearing coolant2CarPros, 2004 Chevrolet Tahoe, 2008
- 2003 Gmc Yukon Slowly Losing Coolant for Months2CarPros, 2003 GMC Yukon, 2016
- 2003 Chevrolet Silverado Coolant Leak2CarPros, 2003 Chevrolet Silverado, 2009
- 2004 Chevrolet Silverado Loosing Coolant Leak2CarPros, 2004 Chevrolet Silverado, 2009
- 5.3 vortec coolant leakCar Talk Community, 2000 Silverado 1500, 2018
- bad heads any advice on the castech head issuetahoeyukonforum.com, no vehicle stated, not read
- Castech heads question/opinions welcometahoeyukonforum.com, no vehicle stated, not read
- 2003 Tahoe coolant system leak or head gasket leak?tahoeyukonforum.com, 2003 Tahoe, not read
- I think I have cracked castec headsgm-trucks.com, no vehicle stated, not read
See the evidence (1 technical documents, 1 records)
Passages of the technical documents
The bulletin covers 2001-2006 GMC Envoy, Jimmy, Sierra and Yukon models.
2001-2006 GMC Envoy, Jimmy, Sierra, Yukon Models
General Motors (published by NHTSA) 2024-03-14
It applies to the 4.8L, 5.3L or 5.7L Vortec Gen III / Gen IV V8.
with 4.8L, 5.3L, or 5.7L VORTEC® GEN III, GEN IV V8 Engine
General Motors (published by NHTSA) 2024-03-14
Some vehicles may lose coolant gradually over time.
Some vehicles may experience a gradual coolant loss over time.
General Motors (published by NHTSA) 2024-03-14
A very low percentage of cylinder heads with an embossed Castech logo may develop a porosity crack in a very specific area.
A very low percentage of cylinder head(s) manufactured with an embossed Castech logo may develop a porosity crack in a very specific area.
General Motors (published by NHTSA) 2024-03-14
Records
- Engine losing coolant with no apparent external leakage Owner complaint 2016-07-18
A cause or a result a complaint states is the owner’s view or what a dealer told them, not an established fact.
Put together by FaultCrate from public records and technical documents. The cause and the repair are for the workshop to decide with the vehicle in front of it. Counts are records, not failure rates.

