Blown head gasket?

294,000 MILES • 6.8L • V10 • 4WD • AUTOMATIC
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SAM422026
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I recently had a lot of engine overheating due to a failing water pump, a dirty radiator and a sticking thermostat. I had a mechanic flush out the radiator then replace the water pump and the thermostat. They only added about 3 1/2 gallons of antifreeze it’s I’m assuming the other 3 1/2 gallons, my truck holds about 7 gallons, was left in the engine block. They also added a new overflow bottle and then fill up the vehicle with new coolant, 3 1/2 gallons. My vehicle was overheating a little bit after that because the thermostat was sticking but now it has been running fine and I have drove it about 1000 miles since then and I’ve only had the thermostat stick just a few few times but it seems to be working normally if you let idle at a cold start up to operating temperature then the thermostat works like it should. My problem is, there is still garbage in the overflow and wondering if it was that old dirty antifreeze that was left in the block that’s mixed with the new. I did have gone under my overflow cap, but it wasn’t like a milkshake. It was a little wet but mostly dry. There is nothing in the oil as the oil is clean and underneath the oil cap there is no gunk either. Do you think I have a blown head gasket or do you think oil is mixing in somehow causing the coolant to be dirty even though there is no coolant in the oil, possibly a bad oil cooler, or do you think that the garbage that was left in the engine block mixed with the new coolant and that is why the overflow has gunk in it? do you think it’s a blown head gasket even though the bucket truck is driving fine?
Mar 25, 2026 at 9:42 AM

What to check next

Diagnostic guidance. Suggested checks and possible repairs are separate from the owner's reported results.

Have the recurring temperature rise investigated before relying on the planned parts replacements. The assessment should document coolant condition and level, leaks, circulation and thermostat operation using the correct filling and test procedures. If overheating occurs, stop safely and arrange assistance; do not open a hot pressurized cooling system. Ask the shop to determine whether additional engine-sealing tests are warranted. This discussion does not contain test evidence establishing or excluding a head-gasket fault.

Guidance references and applicability

2CarPros: Original discussion 1712432 https://2carpros.com/questions/blown-head-gasket-32149204 Source for the owner's reported history and outcome. Contributor suggestions are not independently confirmed diagnoses. No attachment content was verified. HELLA: Cooling-system checks https://www.hella.com/techworld/en/technical/car-cooling-system/cooling-system-check/ General support for checking coolant condition, leaks, circulation and thermostat operation. Vehicle-specific filling procedures and limits require matching service information.

Read the replies · Discussion summary and reported outcome

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CANNON1349
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Hello, if you take the cap off the radiator/reservoir, whichever is pressurized, and then start the truck, you can watch for bubbles in the coolant. If you immediately get bubbles it can be a bad head gasket. If not, you should be fine. It sounds like you have corrosion in the block/head passages and I would recommend an appropriate cooling system flush with a machine under pressure. The new thermostat should not stick, however the corrosion will cause problems that act like a bad thermostat.

William
Mar 25, 2026 at 12:22 PM
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SAM422026
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Thanks for the information
Mar 25, 2026 at 12:32 PM
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CANNON1349
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No problem, please let us know how it turns out. If we can help any further just reply here.

William
Mar 25, 2026 at 12:33 PM
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SAM422026
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I do have one more question, regarding engine temperature and the thermostat. It seems for some reason that the engine temperature will climb, Whether it is at idle or I’m driving, It will climb till about 3/4 Of the entire gauge, Between normal and hot, And then it seems the thermostat will open and then the temperature goes back to normal. The thermostat was replaced by a mobile mechanic a few weeks ago And the thermostat was from Napa and I think it was a cheap thermostat. Once I get driving though after its at normal operating temperature , I have no more issues, it’s only on a cold startup when this happens. Should I go ahead and replace the thermostat for a gates brand or Motorcraft? Do you guys have one brand in particular that has a high temperature rating since I’m driving a bucket truck?
Mar 31, 2026 at 7:06 AM
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CANNON1349
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Gates is good and of course OEM is better. However I am still thinking corrosion is still an issue or some kind of flow issue.

William
Mar 31, 2026 at 7:27 AM
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SAM422026
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I’m going to take the truck to my main mechanic in about three or four weeks as I am out of town at the moment. I’m going to get him to do a complete flush and a new radiator install. Hopefully with a new thermostat change and a clean engine that should correct the issue
Mar 31, 2026 at 8:11 AM
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CANNON1349
  • ✓Experienced Mechanic
  • 861 POSTS
Sounds like a good plan. Please let us know how it turns out.

William
Mar 31, 2026 at 12:48 PM

Discussion summary

Blown head gasket?

The owner of a high-mileage 2004 Ford 6.8-liter bucket truck reported previous overheating, cooling-system repairs and continued debris in the reservoir. The owner later described the gauge rising above normal during warm-up before returning to normal. A further flush, radiator replacement and thermostat change were planned.

Reported outcome: The owner planned further work, but no completed repair or follow-up result was reported.

The claimed coolant capacity and amount remaining in the block were not verified. Dirty coolant, clean engine oil and the contributor's proposed bubble observation do not provide a confirmed diagnosis in this record. A sticking thermostat was the owner's interpretation of the temperature behavior.

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