Seems that my load-dependent "missing" cylinder misses due to a coolant leak over the passenger's side rear sparkplug.

A while back I re-clamped the heater hoses above the area, and it doesn't seem to have been leaking coolant over the last two, or more, months.

However, all of a suddent I had a 4.6L with a miss. Pullng the plug wires, I found the rear plug wire boot soaked and stained.

My fear is that it's the intake manifold leaking.

Are intake manifold leaks common, to any degree, on the 4.6's, or should I take a better look at my heater hoses again?

1999 F-150, 4.6, m5od

 

I don't think there is any coolant in the intake in the rear. I would inspect the hoses again.

 

I recently had the same trouble. My 97 with a 4.6L was missing. Code came back cyl 4 misfire at Autozone. I purchased plugs and wires, but when I took off the cyl 4 wire it was wet with antifreeze. I also feared intake. I took it to a local shop and he pressure tested it at 17 lbs and determined that is was a clamp on a hose. He tightened it and I returned the plugs and wires to Autozone. That was about a month ago and no more trouble out of that.
However, as soon as he fixed that leak, my heater core started leaking. Not on the floorboard, but it was coming out with a/c condensation. It was fogging my windshield and smelled like antifreeze when I used a/c. Replacing the heater core was no fun at all. Quite a chore.
I think with a pressurized system, when you fix one leak, the next weakest spot is in jeopardy.
I recommend that you have it pressure tested. The shop where I took mine didn't carge me anything at all.

 

Dang,

well, thank you very much, guys, for the help.

Try as I might, the heater hoses did not look like they were leaking. I even ran it around with paper towels between the hoses and the head/plugs, and got no staining. Yet, after putting a new plufg wire in and pulling it out, I found new coolant on it.

I hated to do it, but as of right now it's at the Ford dealership for a diagnosis. Depending on what they report, I may be back at it again, or I may not.

 

Update: typcial large Ford dealership BS - they want to charge me for everything under the sun, but they don't have a clue as to the miss.

I just got back from looking over their "diagnosis" report. They want me to pay 110 for a list of things that -could- be changed out, but have yet to do a definitive test on why it was leaking coolant (pressure test), or why it was missing (for example: the assistant service manager tried to claim the EGR code, which is going to be the EGR ports being blocked up, was part of why it was missing - we all know the trucks run fine with the EGR ports blocked up...)

Plugs, wires - well it has new wires on it - in fact, brand new. In fact, the old wires are sitting on the passenger side floor for the mechanic to see... and I pulled a plug this weekend to check it, so I have a good feeling my 20k mile OEM Motorcraft plugs aren't the issue - yet they want to jsut throw them in there and charge me for 'em?

Crappy service, and I really should have gone elsewhere - I just wasn't bright enough to do it.

The manager of the service department talked with me about it, agreed that 90% of the stuff listed wouldn't lead to a miss like it has, and agreed to finish off at least part of the diagnosis by doing a pressure check to be sure whatever leak they think it might be is actually what it is.

Guess I'm just too used to the garages where, if you ask them a question, they give you an answer - instead of a list of the same guesses I would have.

 

OK, after three days at the FOrd dealership, and a $110 diagnostic charge, they couldn't find the reason for the miss, and they couldn't find the reason I saw brand new coolant in the spark plug hole.

They did want to charge me for a bunch of guesses: new plugs, new plug wires (has new wires on it - brand new right before the dealership got the truck), and they claimed the EGR ports, which are blocked, could be causing the miss, as well as the TPS. What I paid for, in effect, was for some tech monkey to hook up a computer and tell me what he saw, there, instead of what the real problem was from.

I'm mad, but so tired of dealing with Maroone Ford's cheating ways, and lies about when and what they were going to do, that I just gave up.

Avoid the dealership at all costs.

Anyways, I need some help here. If someone could provide a link to the plug wire routings, it would be helpful (just so I have 'em).

THanks!

 

Not that it helps any, I used to have a 98 F-150, with a 4.6 that had the same exact problem that you are describing. After several frustrating trips to several different dealers, one dealer 'rigged' it. Basically all they did was squirt high temp silicone around the plug in the hole. Yup, crappy job I know but it cured the problem immediately. The guy assured me it was coming from the hose direcly over the plug even though, I couldn't find it either. The guy at this dealership (Midway Ford) in Kansas City, said it was a common problem with the 4.6. Good luck!!

 

Thanks so much for trying to help!

Oh man, that makes me sick that I paid the dealership that much, and the reportedly did a pressure check, yet the didn't find the problem.

Are we talking high-temp silicone, like caulk, that would dry up (sort of rubbery) in the hole to protect it?

 

Sorry to hear of the bad dealer experience. I work at a dealer in NC and here is what I have seen: The most common leak point in that area is the heater hose fitting o-rings. The heater core has plastic quick disconnect fittings with 2 o-rings and a plastic spacer between them. On the 4.6s with a plastic intake the heater hose fitting at the back of the intake is prone to leaking. And I have seen one 5.4 with a alu intake get a pinhole in the heater hose fitting at the back. Good luck and don't be scared of the dealer, there are a few good ones left.

 

Yeah, the rubbery stuff. Like what you would make a gasket out of, Permatex etc.

 

I pulled that last plug today to just let whatever water was there drain down in, tried to dry it out as much as possible with paper towels, then replaced it with a new plug.

While I know I saw new green coolant (not much, but more than a drop) on the plug wire boot the last time I pulled it, this time it looked pretty much like a bunch of the old, rusty (and oily) water. I know that antifreeze takes a good while to evaporate off, but I'm surprised that, if I don't now have a leak, the water that was in there did not evaporate off on a 150 mile trip (and 150 miles back). I mean, doesn't that area get hot enough to make antifreeze evaporate faster? do the plug-boots, with their semi-sealing design, trap the water in the plug holes?

I still have this feeling coolant is leaking there, albeit slowly, for some reason.

All plug wires changed, again, a new TPS, and a new coil put on the left side. I think it's running pretty close to regular now (maybe still a slight stumble? It's been so long that I've dealt with the miss that I'm not sure what my Dynomax exhaust felt like before the problem, lol. I need to take it out on the highway tomorrow to test it)