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Had a customer bring in his 2008 F350 that started loosing coolant.

Now when I say it started loosing coolant, I mean the coolant level goes down over time and it can't be found. It's not boiling out, it's not burning out of the exhaust and it's not falling out on the ground. In 200 miles, the truck ate 3 gallons of coolant.

I pulled the truck in to look it over. It started perfectly, ran nice and smooth, so I put it up on the rack to verify there weren't any leaks. Sure enough, everything was dry. But when I pulled the dip stick, I noticed something very interesting. The oil level was WAY high. Back under the truck to pull the drain plug and guess what I found....Yup, you guessed it, his missing 3 gallons of coolant.

There are only a few places where oil and coolant come in close proximity to one another. The oil cooler is an obvious place, but it would not fail in this way. Oil in the oil cooler is under pressure. Engine oil pressure is 60-100psi+. Coolant in the cooling system is only 16psi max. If a breech occors in the oil cooler, oil is pumped into the cooling system and ends up in the bottle (what a nasty mess). The engine ran smooth and started very easilly with no other drivability issues, so that pretty much rules out a head gasket. The only place were water can enter the oil pan is from the back of the water pump housing.

I decided to pull the cab for better access. It can be done with the cab on, but EVERY cooler on the front of the truck has to be removed and you still don't get all the room as you do when the cab is 8' in the air. So with the cab off I could peel all the belts and front accessories off and get to the water pump. Here is what I found behind the water pump...



I pulled the front cover off and got it cleaned up. In one place, I found a pinhole. this let coolant pass thru the cover and drain right into the oil pan.



This is an up close shop of the pinhole with a bright backlight...



The new cover comes with a new oil pump, that's why the damn thing costs so much. The gaskets and seals come in a kit and the new front seal has a new style of wear sleeve.

Once all the accessories and belts are back on, the cab comes back down and the fluids are refilled. Everything worked properly and the job went well.

So the moral of the story is to keep the coolant changed and make sure you use the right stuff.
 

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Wow! Thanks for sharing. How many miles on the truck? Had the coolent system been serviced at all?
 

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118,000 miles and it had green coolant in it. The rest of the system didn't look too bad. I reused the water pump. It was in great shape. Dunno what that tells you, but it's a really good reson to put the right coolant in it.
 

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I'm only asking this because I really don't know... What is the difference between the Ford Coolant and the universal Green coolant? I always run the Ford coolant but never really understood why.
 

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There are some universal or Chameleon coolants out there that do a good job. But for these trucks and all diesels, you should only use the Heavy Duty coolants recommended for diesel engines. They have more additives that fight cavitation erosion. Older diesels would have this happen to the cylinder liners from the shock wave of the cylinders firing. This truck showed cavitation erosion on the front cover.
 

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When I took the time to flush the cooling system and clean it out, I had 8 jugs of CAT ELC to refill it. Totally agree on using diesel coolant and not some one size fits all coolant.

Thanks for the writeup!!
 
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