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Stress cracks


By Steve Schaeber, MACS Manager of Service Training

Some Ford F-Series Super Duty vehicles built with the 6.4-litre turbo diesel engine may show a coolant leak at the front of the vehicle which appears to come from the radiator. These types of leaks can be caused by anything from corrosion to improper coolant mixture, but in certain 2008-2010 models can also come from stress cracks within the radiator tubes themselves. Ford has looked into this issue, and identified it in TSB 11-12-4.

It starts with those slow pesky leaks that can occur at the various hose connections found throughout the system. Sometimes they leak just a tiny amount of coolant which might not puddle up on the ground. Operators don’t always check their fluids, and over time these leaks may result in low coolant levels. Add that to the daily engine warm up and cool down cycles that take place, and this repeated hot and cold can create tiny cracks that appear in the radiator tubes.

This isn’t the first time we’ve heard about situations like this. Other vehicle lines have reported similar issues in the past, and there are a few different TSBs out there for reference, depending on the exact cause. Related bulletins from Ford sometimes require inspecting the thermostat for any possible problems, but it’s not necessary in this case because they’ve released a newer software update that includes a cooling system monitor.

Ford’s solution involves several steps, including a thorough inspection of the degas bottle (which might require upgrading dual port models to the single port design), along with checking the other hoses and connections. Coolant loss on hose exteriors can be identified by a white residue which comes from the dried coolant. But keep in mind that Ford often applies a white colored grease to the inside of many hose ends as an assembly lube. If the technician doesn’t notice the difference between this grease and the dried coolant, it could be mistaken as a leak. However, since it’s not necessary to remove the upper or lower radiator hoses to perform this inspection (as it can be done on the vehicle), unless it’s been disturbed as part of a prior service, finding this grease on the outside of a hose is not likely.

Some early F-Series radiator hoses used a single o-ring seal, which if found to be leaking should be replaced with an updated part. New upper and lower hoses have been made with a dual o-ring design which provides a better seal. Some technicians prefer to replace these hoses in pairs, but it’s not necessary if only one hose is leaking.

Obviously the radiator will need to be replaced, and maybe some of the additional items identified above. But doing a complete job also includes changing the coolant. Plugs can be found on both sides of the engine to drain the block. Be sure to refill the system with a 50/50 mixture of coolant and distilled water. Ford recommends using Motorcraft® Premium Gold Engine Coolant and not reusing what was taken out. An airlift tool is also necessary during refill to remove excessive air from the system.

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