Truck Blows Coolant Out Bypass What's Wrong?

I'd say it's a head gasket. I drove a company truck, a Freightliner Century, with a Detroit 60 series, around for over a year like that, my company didn't think it was worth fixing. Finally one summer day I was climbing that hill on I77 coming out of NC into VA and it just let loose, and wouldn't hold water at all after that.

 

Sounds like a head gasket. What does your oil look like? It should look like chocolate milk if it's getting in the pan.

 

Before you panic check the pressure on the rad cap and the rad itself. How's your coolant flow? Is your clutch fan operating properly? Rad hoses? What's your temp guage showing? Lots of less expensive things to look at before you go tearing the engine down.

 

I agree with Mr. Kittyfoot. However, when you test your rad pressure, pump it up to 14 psi and do a leakdown test, but also, if that shows nothing, leave the pressure tester on the radiator and idle the truck with it on there. When the thermostat opens, watch what your pressure goes to. It should go to about 14 psi and no higher. If it does go much higher than that, I would say head gasket or cracked head. Since the truck is running well, I would lean toward head gasket...if the coolant system is over pressurizing.

I have a 60 Series that ran like crap for the longest time and kept losing water...the way it was figured out was with the running pressure test. I had a cracked head...but, again, mine was running like crap. There was no water in my oil and no oil in my water. The water was going out my exhaust pipe.

 

Is it coolant, or just blow by? Detroits smoke and drip quite a bit out the blow by hose.

 

Blow by,

he stated Behind the oil pan !!!!!!!!!!!

 

An oil sample analysis would eliminate some of the guess work.

 

Could be a head gasket, but it might be the head gasket on the air compressor. Try shutting the engine off and letting it cool down and see if there your radiator has a lot of pressure in it by removing the cap. If it does put the cap back on and after 10 minutes without starting the engine, see if the pressure has returned. If it has, get every ounce of air out of every air tank on the truck, put the cap back on and if it doesn't do it again, you have compressed air going though the gasket on the compressor into the water jacket in the compressor into the water jacket in the engine and on into the radiator.

The pressure has to go somewhere. If it is not the head gasket on the engine, I would check the compressor.

We are having the same problem with one of our companies truck and I cannot for the life for me convince the shop that the compressor could be pressurizing the radiator enough to blow coolant out the overflow.

 

I agree with checking it out throughly before tear down. Cracked block would be of suspect since you state that she run's good, Normally a Cracked head will exhibit a drop in performance as would a head gasket. I hope for your sake it turns out to be a gasket or less. And of course theres always Bar's leak and trade it back to the dealer that sold it to you.