Discovered a problem I had never heard of before. My 5.8 started leaking all it's coolant out. Took me a full day to find the leak and it was completely by accident. It was coming from somewhere behind the intake and between the heads. I could never find a way to see back there even with three different sizes of mirrors and two lights. I finally removed the upper intake and while reaching for the valve cover to steady myself my hand slipped and I broke a bolt in half with my thumb. Impressive at first, but quickly found the bolt to be completely rusted out from the inside. Taking the lower intake off revealed two more of the bolts rusted through. All three broke off in the heads. My coolant had somehow been flowing out around the backside intake bolt.
My truck only has 94K miles on it. I explained to my wife that since the heads had to come off and go to the machine shop anyway that the motor was getting rebuilt. I actually didnt' get any argument from her.
I had never heard of this happening before but a couple local mechanics (ford and gm) and my machine shop guy told it was quite common. Has something to do with dissimilar metals? I'm told the bolts go through the aluminum intake into the steel block and somehow that accelerates the corrosive action of the coolant. If I had heard of this a couple of years ago I could have just pulled the bolts and replaced them. A little late now. Just wanted to share this.
Mike

 

True, steel against aluminum will corrode BOTH metals at a higher rate than if they are separated by some insulating material. Its odd to have happen the bolts unless the bolts have been removed before. Typically, the coating on the intake and on the bolts is enough to prevent this from happening. However, if either or both pieces have their coatings scraped off the problem can occur.

The electrolysis of the coolant also contributes to the acceleration of the corrosive properties of the cooling system. Since the engine is constantly carrying a negative electrical charge, the coolant actually accelerates the corrosive effect it has on the internal components. And the coolant travels through both the steel engine block and the aluminum lower intake plenum.

 

I am the second owner, but I've had it since 96 and it only had 18K on it then. I don't think the bolts had ever been removed before. I just hadn't heard of it happening before yet the guys I know at service departments weren't surpised at all.
Oh well, gave me a chance to throw a bunch of toys on it. My new Bassani y-pipe is huge. the headers are nice too. Went with a flowkooler water pump, put the taurus dual-fan in it finally, roller rocker arms, and my distributor housing actually had a small crack in it so my new billet distributor is here also. It's almost too pretty to put in the truck.

 

Nice work... I've had the Bassani complete "Street Thunder" (the original name they gave to the complete stainless system) package under mine since 2002 and I still love it.

 

to keep this from happening again some companies sell a small zinc anode. it is a sacrificial metal that the electrolosis will eat first. you will have to search the web for one. they are cheap.

 

You can also switch to waterless coolant as well.

 

it's got arp stainless bolts in it now. So does the water pump.
Mike