Expansion Tank over flowing
 

Sorry if this topic had been beatin to death.... So my wife’s new to us D2 is overheating. I just put in a new radiator, t stat, and fixed a bunch of leaking hoses. With the truck cold and the radiator cap off, I start it up and everything is good. Five min later coolant bubbles/flows out of the expansion tank.

I know a lot about the HG problems of these motors but I'm wondering how one tells if the block is bad? If I pull the HG and everything looks good is that a sign the block may be bad? What else should I check or test?

Thanks,
Ryan

My 2001 did the same thing.
Spewed after about 5 minutes with the cap off.

Replaced the head gaskets.
Bleed the system.
Problems all gone.

Before you assume the worst :

1) The cooling system is not designed to be run without the system pressurized. You might have localized boiling at hot spots in the heads. Water boils at 260F at 18 psi, at 212F at atmospheric pressure.

2) There are cheap testers for combustion gases in the coolant, worth getting one.

A few observations.
Following the cooling system "overhaul" did you fit the top hose to the correct port on the thermostat? i.e centre port to top hose.

Remember the thermostat is in the lower hose so auto filling & purge filling is NOT possible without an air purge assist ( burb) as large pockets or air become trapped in the block/head and cause very rapid overheating and engine distress. This is a common problem with many modern vehicles.

You should see a bleed screw in the top hose tee'd fitting this will allow some gas purge but it many cases its not enough when large air pockets are trapped in the block as steam pocketing can occur causing surge.

In a professional repair environment a tool such as an Air Lift is used to create a vacuum on the whole cooling system and coolant is injected to force fill the entire cooling system.

You can do the same as a DIY'r by removing the top hose from the outlet at the engine manifold assy and pour in coolant by using an old hose section into the block/head. Eventually coolant will flow by gravity down the the back side of the thermostat via the cooling jacket. Then you can fill the radiator side in the same manner; then connect the hose. Top off the expansion tank and fire up the engine with the cap off. Run for a few seconds watching the remaining gases purge back into the expansion tank. There may be a drop in level in the tank quickly top it off the the seam and fit the cap before the heat causes overflow.
Test the vehicle for coolant loss & overheating.
T/V

But in the end.
It will be the head gasket.

This photo set shows a head gasket with a breach from the crown to the water jacket area on Cylinder #2.

Flickr: Landroverdude2's Photostream

I bought one of the block test kits to sample for emissions in the coolant. Slick little setup but hard to use with the vent line dumping coolant back in right at the top of the expansion tank. Coolant mixed in will give it a false reading. Tried a bunch of times and think it failed. Ended up pulling both heads last night.

Both HG look good with no sign of failure. The top of the block looks like someone attacked it with an abrasive disk on about 50% of the surface. Not too deep but I'm wondering if that could be the cause.

Finished making the blank off plates to do a block pressure test. Thinking of how I can heat the block to help make it more of a real life test. Also starting to look for a used engine...

Those kits are useless.
Just a way to "wish" the problem will go away.

The problem will not go away.

I wished it was not so for a few weeks.
Then I tore into the engine.
Be decisive.

You can sample all you want.

If the thermostat is jammed shut yes, it will spew from the coolant tank.

Most likely exhaust gasses from a breached head gasket on cylinder #1 or #2.

You may or may not get misfires in the morning when you first start it up.

Not trying to wish anything away with this one, although I wish I could.... Trying to be as realistic as possible and that’s why, as I stated before, I pulled the heads and will be doing a block pressure test.

Thanks for all the responses, they have been helpful and I know I will need more help as I go. Lots of knowledge here!

Make sure you get those heads machined before putting back on. Otherwise this will all be for nothing.

MEH, prolly just a fuse;)