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GMC Yukon 2000–2006

GMC YukonModel years 2000–2006

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Common on this vehicle:Leak

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Possible causes

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.

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

  1. Inspect the cylinder head to determine whether the casting was made by Castech.
  2. On a Castech casting, inspect around the five oil drain holes for witness marks of coolant seepage.
  3. 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.
  4. Pressurizing the cooling system may reveal coolant, air, or both weeping in that area.
  5. 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.
  6. 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

  • Oil Pump: replaced 1(says it came back: 1)
  • Slug: cleaned 1(says it came back: 1)

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)

Forums and Q&A

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

Read every statement and its source →

A cause or a result a complaint states is the owner’s view or what a dealer told them, not an established fact.