Details: 2006 Ford 4.6 E250 on it's second motor. Consumes a little oil and about 1/2 gallon of coolant per 1k miles. Runs pretty well, with an occasional misfire type of feeling on low load and high load situations. Mechanic #1 diagnosed it as HG failure. Here's a past thread I made: LINK.
Since then, Mechanic #2 pressurized the coolant system, and found no leaks. Did a test of the coolant and the fluid in the brake test or whatever its called changed color, indicating exhaust gasses in the coolant.
My question, is there any chance this blown head gasket is actually the common 4.6 intake gasket issue? It's likely just wishful thinking... but then again, it would explain the coolant loss and the occasional misfire. Would that somehow explain the coolant-exhaust test results? Or the strange compression test numbers and leak down test?
Just wanted to check before I go further. It's funny, this van still runs pretty well, so I hate to punt or replace the engine.
Have you tested the coolant overflow pressure cap? If it is popping open too easily, it lets water evaporate rather quickly from the tank giving you the appearance that it's consuming or leaking coolant when it actually is just evaporating faster.
If you have no leaks under a pressure test, but you do have exhaust in the coolant, I'm not sure what to make of that. I suppose it could mean a HG failure. After all, a pressure test is 25 psi and compression and combustion is eleventy quillion, so I guess it's possible to push combustion into the coolant without coolant pushing the other way.
I didn't think the trucks had the intake problem. I thought that was Crown Vics with the plastic intake. Did they switch the trucks to plastic? My last one was an 02, so I'm out of the loop. Either way, it wouldn't explain the exhaust in the coolant. There isn't exhaust in the intake other than EGR, and it's a ways away from the coolant crossover.
I would do the following (if you haven't already)
- Go around the intake gasket joints with a can of starting fluid and listen for any idle changes. You can't get to all of it, but that might reveal a vaccum leak which would explain the misfire.
- Do a compression test. If you have the tools, do a leakdown test. Compression test will reveal if a cylinder is low, which doesn't prove a HG problem, but it would also explain the misfire.
- Does it give you a misfire code? If so, move the coil of the offending cylinder to a different one and see if the code changes.
Thanks Curtis. I've tested the cap, seems fine. I'll double check though. I will try your idea of spraying the intake in the first bullet point.
My understanding is that its not just the cars that had the IG issue.
To answer your other questions: A compression test was done by Mechanic 1. I just reviewed the notes again--
"Cylinder 1: 113 Cylinder 2: 178 Cylinder 3: 127." (They didn't give me numbers for any other cylinders, so maybe they stopped there.)
"Leak down: "Leaked down instantly. Exhaust gas leak test, within 2 pumps leaking."
No misfire codes. Codes were PO133 (02 sensor) It's had P0420 in the past). P0297 - vehicle overspeed condition
Thing is, Mechanic 2 put as much pressure on the coolant system as possible, and no leaks were shown. I am not sure I trust Mechanic 1. Mechanic 2 thought there might be oil in cyl 2 causing the high compression.
I'm probably just in a state of denial that this motor is toast, but I wanted to get thoughts from GRM.
If you think you have a head gasket issue, you pressurize the cylinders, not the cooling system.
If a block test (the blue fluid that turns yellow in the presence of, I think, CO) failed, then it's probably indeed a head gasket or cracked head. I have had leaky head gaskets pass a block test but fail a cylinder pressurization, so that method is an even better indicator than the block test method.
Ok thanks Pete. Very helpful information. Yeah, it definitely failed the block test, fluid changed color, at the second shop. First shop did the leak down, which failed, so seems consistent with what you are saying. Just wanted to make sure it wasn't somehow the infamous intake gasket issue. Esp given that the oil looks so good, and no bubbles in the coolant.
Dang. It drives so well now, I'm considering just driving it until it no longer runs. I have a trip from NC to MO coming up, and I may roll the dice.... tho I may regret it.
What will happen, will it start to overheat when it's on its last legs?
The most common failure is that it will start to overheat and boil over. In rare cases where the cooling system is able to keep up for a bit longer, you sometimes get enough coolant in the oil to wipe bearings, but nearly always, overheating is first.
This thing has tons of miles on it, right? I'd be real tempted to throw some headgasket in a bottle in it, drive it for a few more years, then sell it or change the engine when something else fails (or when the headgasket finishes failing).
If you lose coolant, the system is designed to run without it for a little while- called fail safe cooling. One of the small things I worked on in my career- it was developed because of the aluminum head- which would warp if run without coolant, unlike cast iron heads. Old trucks could limp their way someplace, so that capability was developed for the modular engine. The system would swap running cylinders, so it would essentially be an air cooled 4 cyl engine.
One of the tests to prove it works was a drive from Dearborn to Toledo and back without coolant.
K seal, regular inspection of oil and coolant levels and prayer is your short term answer.
Thanks all. Really appreciate it. I think I'm just going to keep driving it and keep an eye on coolant level. Maybe try K seal or the like. Then replace the engine or sell it.
@Alfadriver, that's fascinating. Good to know that this motor has that capability. Thank you.
In reply to alfadriver :
That's amazing.
I mean, yeah, it's a pretty flat drive, but still!
In reply to alfadriver :
Wow, that's a cool bit of trivia!
Seriously. I'm considering driving this thing across the country just to see what happens! Ha.
Pete. (l33t FS) said:
In reply to alfadriver :
That's amazing.
I mean, yeah, it's a pretty flat drive, but still!
It's kind of interesting that you've not encountered this before- back when the modular engines were put into trucks, everyone predicted massive problems. Which is why it was developed. Instead we have blown out spark plug threads.....
It's pretty old code- when I worked on it, it was 1993, and I'm sure it went into the first F150 with a 4.6l. So this is pushing 30 years in service.
Ironically, it was needed on smaller, more recent engines, where it somehow was ignored. Could have saved a bunch of money on the 1.6l GTDI motors, but enough were grenaded and just enough caught on fire that it turned into a crisis. Thank Europe, for not filling all of the development requirements.
CyberEric said:
Seriously. I'm considering driving this thing across the country just to see what happens! Ha.
HG in a bottle, regular fills, and tow insurance- you should be good to go!
alfadriver said: HG in a bottle, regular fills, and tow insurance- you should be good to go!
That seems like its the commandments of grm!
alfadriver said:
Pete. (l33t FS) said:
In reply to alfadriver :
That's amazing.
I mean, yeah, it's a pretty flat drive, but still!
It's kind of interesting that you've not encountered this before- back when the modular engines were put into trucks, everyone predicted massive problems. Which is why it was developed. Instead we have blown out spark plug threads.....
It's pretty old code- when I worked on it, it was 1993, and I'm sure it went into the first F150 with a 4.6l. So this is pushing 30 years in service.
Ironically, it was needed on smaller, more recent engines, where it somehow was ignored. Could have saved a bunch of money on the 1.6l GTDI motors, but enough were grenaded and just enough caught on fire that it turned into a crisis. Thank Europe, for not filling all of the development requirements.
Oh, I've encountered the technology, not in person but second hand. I've also used it to limp my aging Quantum along after a loss of coolant event by coasting down hill with the ignition off and throttle wide open, then starting it and babying it up the next hill.
But the LENGTH of the drive is what amazes me. It was my impression that engines that do bank switching for emegency cooling will still have to shut down after five minutes or so, and the bank switching was just an emergency measure to give you time to pull the vehicle to a place safe to park. Not drive a couple hours.
