coolant consumption/intake manifild? 2000 4.0L

[waynetn]

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

[btison]

Wayne,

Did you find your leak? Fix it?

My '93 4.0 is leaking out the exhaust. I really want a quick fix but will settle for the truth in how to fix this. All my research point to much later models so I'm a little surprised that it showed up for this '93.

Thanks!

Bill

[rwenzing]

Originally Posted by waynetn

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.

It is quite common for the intake gaskets on the 4.0 OHV to leak coolant into an intake runner or two. Number 4 (LF) is the most common offender but it can occur on other corner cylinders as well. As long as you don't have larger problems like a cracked casting, new gaskets should fix it.

[slsnut]

Think I have this issue, I get a severe miss under load. Plulled the plugs and found #4 wet and badly fouled. I also have lost coolant in the reservoir when I know I topped it off. Intake seals do this? I only have 75K on my 97 Ranger. No Codes picked up on scanner.

[waynetn]

I ended up replacing the cracked heads- fast forward- problem is back, no overheat, no overpressure, now contaminates oil. I replaced heads with the updated ones. I hope it's just the intake this time- but tests are so far inconclusive.