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Big Thompson Diesel and Automotive

Loveland and Northern Colorado's Diesel and Automotive Repair Specialists

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This is an article we wrote back in 2011. It was an attempt to educate our customers. Over the years many repair shops have called in asking if we can help them fix a 6.0 based on just this article. While we are flattered it is kind of funny that many years later not a lot has changed in the 6.0 world. Lots of shops shot gunning parts at them with no real understanding on what causes the failures. So please enjoy this old article. 

     Repeatedly we get a customer into the shop and the complaints are usually the same.

     “I am tired of this truck! I just left another shop, had $3500 worth of repairs done, and the truck still is not fixed! I have had injector after injector installed and they just keep failing! I have replaced the EGR cooler 3 times in the last year, and nobody can tell me why!!! It is blowing white smoke and misfiring! It is hard to start cold, misfires until it is up to temperature and then runs fine all day!”

     The point is we get a lot of questions about 6.0L Ford Powerstroke engines. We have heard many horror stories of trucks being in and out of shop after shop and never really feeling like it is fixed. Here at Big Thompson Diesel and Automotive, we have been diagnosing, fixing and correctly repairing what is broken. We have had great success keeping the engines on the road. I’m going to share knowledge with you to help you feel confident that the repairs you have done to your 6.0L here at BTDAA are actually going to fix your problem and prevent any issues in the near future. This is not a poke at your current repair shop; this is just the cold hard facts about how this engine fails. A lot of times the symptoms are fixed without diagnosing the real cause of the failures. This leads to the same failures time and time again costing significant amounts of money. Here we share the root cause and what can be done to prevent future failures and greatly reduce the repair cost over the life of your truck.

     The 6.0L is a good engine when it is running properly. It has one main failure that is commonly overlooked and is the cause of most of the big issues this engine has. The oil is the life blood of the 6.0L diesel as the injectors are hydraulically actuated using engine oil to drive them. The oil is run through a low pressure oil pump which pushes oil to the oil filter at about 50-80 psi. Once the oil is filtered it is split. Some of the oil is sent to the rod and main bearings, cam, lifters, rocker arms and other moving parts for lubrication purposes. However, the majority of the oil is used to drive the injectors. It is sent into an oil cooler where the oil is cooled with engine coolant in a liquid to liquid heat exchanger. Then it goes into an oil reservoir that directly feeds the high pressure oil pump. The high pressure oil pump ramps the oil pressure up drastically. It will reach 550 psi on startup and varies according to load and rpm up to 3000 psi under wide open throttle full load.

Heat is created any time liquids or gases are pressurized. This is how air conditioners work. Heat is created by pressurizing a gas. It turns into a liquid where it is cooled and then evaporated back into a gas. Diesel engines also work this way. The engine takes in cold air and compresses it. As it is compressed it is heated to a point that the injected fuel ignites. Air is hot enough to ignite the atomized fuel. These are just a few examples of how pressurizing creates heat.

So as far as the 6.0L and oil goes, it has 16 quarts of oil in the sump. Oil is pressurized to 80 psi creating heat than it is supposed to be cooled by engine coolant which is typically 180 degrees or more. After that, the oil that is at about 80 psi and 180 degrees, is squeezed to over 500 psi minimum for idle and upwards of 3000 psi under severe loads. From there, the oil is fed to the back side of the injectors where it serves several purposes. It is the hydraulic force that forces fuel out of the tip of the injector, it lubricates the injector’s spool valve, and it helps cool the injector which is going to divert more heat into the oil. From there it is returned to the oil pan and starts the process all over again. The amount of oil that flows through the engine is the equivalent of 18 gallons per minute. So if you were paying attention before the system only holds 16 quarts of oil. It is flowing at a rate of 18 gal per minute and is under tremendous pressure and heat.

So you ask, what fails? First of all the oil filter tends to only last 3-5k miles, then it can go into bypass mode. This means it is not filtering the oil. That is instantly a recipe for disaster but that is just the start. The main issue becomes the oil cooler. It is a very small cooler that is trying to flow 18 gal per minute of oil and on the other side of it, it has to flow enough antifreeze to keep the EGR cooler cool. The problem just became 2 problems even though it is one component failing. The big failure is caused from the coolant side of the oil cooler plugging. Typically this happens from dirty coolant, improper cooling system maintenance, and some sand left in the block from the factory that washes out of the block into the oil cooler. When the coolant side of the oil cooler plugs, it quits cooling the oil and it flows little or no coolant into the EGR cooler. The EGR cooler will quickly fail because now there is 500-1400 degree exhaust flowing through a cooler that is not being cooled. The cooler bakes from the inside out and eventually ruptures causing hot exhaust gasses to enter the cooling system and coolant to enter the exhaust stream. If caught early enough, it will not cause much damage but if it is run too long the coolant level can drop and start to overheat the engine which puts a hurting on an already weak head gasket design. On the other side now, the oil is not getting cooled so it is becoming excessively hot if the oil filter has too many miles it can stop filtering. Now there is over heated, unfiltered oil being compressed to thousands of psi and shoved through the delicate injectors. This can cause rubber seals in the system to bake and come apart, oil pump seals to bake and leak, scoring of injector pintles, scoring and damage to the oil pressure regulator and baking of the oil pressure sensor. As you can see this one component just caused thousands of dollars in damage and you had no indication that it was failing. In severe cases it can turn a check engine light on for oil to coolant temperature excessive variation but usually there is a lot of damage done before the engine light comes on.

Can you test the oil cooler?

Yes. There is a simple test for the oil cooler. It usually takes about an hour to test the oil cooler.

If I replace the oil cooler will it save my injectors?

It will keep new injectors from having issues but if you have injectors in the truck that have been running with a bad oil cooler, there may already be damage done to the injectors. So no, it will not necessarily save an injector that is already damaged but it can prolong the failure of a damaged injector as there will be no new damage occurring to it. How long the old injectors will last is dependent on how bad the cooler was and how much damage there is to the injectors.

Should I just delete the EGR cooler?

No!!! First of all, the emissions laws will cause an immediate visual emissions failure. Secondly the EGR valve is basically acting as the wastegate for the turbo. So you can cause over pressurization in the cylinders causing head gasket failures. It is best to put a good quality aftermarket EGR cooler in as they are built a lot more durable.

How can I cure the problem?

We offer 2 solutions for the oil cooler problem.

The first option is a factory replacement oil cooler. This works well for the customer who does not pull big trailers and who does not work the truck really hard. It is more cost effective but is not for everyone. If you are frequently towing heavy loads, mountain driving on hot summer days, or in general working the truck hard, our second option might be a better choice for you.
The second option is an aftermarket oil cooler which eliminates the factory oil cooler and relocates an oil to air cooler in front of the radiator. This allows the oil to be cooled by cold air instead of 180 degree+ coolant, thus keeping the oil temperatures a lot cooler and safer for the delicate injectors. There is also no possibility of the oil cooler causing EGR cooler failures since now the EGR cooler gets direct coolant flow. The aftermarket EGR cooler is a stronger than stock design and it gives proper coolant flow.
Regardless of which option you choose, we strongly suggest running a high quality synthetic oil. We use Amsoil 5w40 oil. The oil flows better but still offers all the protection for all of the bearings. This has proven time and time again to help keep the injectors alive a lot longer than conventional oils.

Can I just replace 1 injector?

If we find the oil cooler is the cause of the injector failure it is obviously your choice. We will replace one injector at a time but knowing the injector has been damaged from overheating there is a possibility the rest of the injectors are not far from failing either. Our suggestion at that time would be to replace all 8 to save you labor money in the long run and keep your wheels spinning instead of having the truck back in the shop.

About me

Erik Rud has been prominent in the Diesel and Auto repair industry for over 30 years. He graduated from American Diesel and Automotive College with the highest distinctions and honors available. He is an ASE certified master mechanic in both diesel and automotive. He is current on all technologies in the industry and frequently takes available advance level diagnostic classes whenever available. In 2011, Erik opened Big Thompson Diesel and Automotive in Loveland, Colorado.


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