coolant consumption/intake manifold?

Hi,

I have a question for you. A few months ago, my wife's 2000 Ranger 4X4, 4.0 Vin X, began to consume coolant, and miss at startup. The problem was coolant in the LF and RR cylinders. Never overheated, never pressurized the cooling system. I assumed a leak into the intake port. Fast forward, problem is much worse, misses at idle always, runs great above 1000 RPM. Actually fouled ALL the plugs with coolant a few days ago- cool morning, no start. Cleaned them, drove it two days, basically the same. Misses, collant smell from exhaust now quite pronounced. NO oil contamination.

I pulled the lower intake. The coolant ports are SO FAR away from the intake ports that I have trouble believing that it is the source of the coolant, although the intake valves on the two cylinders it misses on are QUITE washed of carbon, and there is a nice clean swath through the carbon in the intake port. The rearmost bolt at the RR was quite loose.

I called my friend who runs a machine shop and he said the 4.0 heads are bad to crack between the valve springs (isn't that pre-1998?), and told me where to look. I see no cracks. I have read of the exact same symptoms on other forums, but no EXACT fix. I am about to seal the coolant ports with small plates, fill the intake ports with soapy water, use my regulated cooling system pressurizer to put 18 PSI or so on the cooling system, and look for bubbles in the intake ports, unless someone in the know about these rats tells me this is a common failure, and here's the fix.

Last thing- are there coolant passages sealed by the gasket between the fuel rail and the lower intake? It's dark out back, so I haven't taken that apart yet. SOMEHOW coolant is getting into the intake side of this engine, but not directly into the combustion chambers. No pressurization. Do the heads crack ABOVE the valve seats into a coolant passage?

Just for reference, I am a 30+ year veteran ASE Master, Chrysler Master, blah, blah, blah. Just never seen this before, and having trouble believing the vacuum from the port pulls the coolant over to the intake port without getting enough in the oil to show up. See what I mean?

Your response GREATLY appreciated,

Wayne Wright

I wish you luck...my 1991 explorer sport was suffering from many hard miles at over 200K+ miles, and I dealt with a mystery leak of antifreeze, until I discover it was the intake manifold seals...I took the easy way out however on mine and sold it as is on ebay to a kid because I didn't want to mess with it.
The heads were a problem child, {those, and the 3.8L the mustangs had in the mid-late 90's}, but not honestly sure on the newer stuff such as yours...I assumed they fixed the issues though.

I imagine there has to be some TSB's out there, but I don't have access to Ford's database, after my buddy quit the dealer he was working at.

I thought the leak on the manifold was typically towards the front of the intake?
{sorry, I am probably not much help here-I fought my problem for two years and gave up}

With that clean swath through the carbon deposits in those cylinders I wouldn't expect a cracked head, but rather an intake fault somewhere prior to the head in the intake it's self. A poorly sealed upper?

I'd proceed with the soapy water test just for peace of mind.


FE