Questions and Answers

Ford F-250 Intake & Head Gasket Tabs Q. Hi Vince, I had new heads installed in my truck about 3,000 miles ago due to a broken spark plug in the right head. When the head was removed to remove the seized plug I realized it needed to be replaced, or I would just be having it done again in a short while. Then I said, while we're here I might as well have them both done.

Anyway, I just noticed that at the right (passenger) side of the intake manifold, almost over to the head there is a piece of thin metal sticking out from under the manifold end/ridge seal. There was a small amount of oil collected under the piece of metal and you can see that some oil has run down along the head. I know that the small piece of thin metal has to be the interlocking alignment tabs from the intake manifold gasket.

It appears that either they were not properly engaged into the manifold end seals, or somehow it poked through. Although it looks like it comes from under the end seal rather than through it, you can see the end seal ride slightly over the metal. The leak is new, so the end seal either held on like that for some time or the metal just poked through.

Question, #1: How embedded is that interlocking alignment tab? Can it be carefully extracted and hope that the end seal closes down behind it? Or, do I have to re-remove the intake manifold and replace the gasket and end seal?

Question #2: Would something like this cause a slightly erratic idle, or any type of engine noise?

The reason I ask is, I had tuned the truck up right after the heads were replaced with new spark plugs, wires, cap, rotor, and readjusted the timing with a timing light. I also replaced the Idle Air bypass valve, Throttle Position Sensor, Tested the Manifold Absolute Pressure Sensor (checked out okay), and tested and replaced the ignition coil (tested weak). Recently, my idle has become rough and low. It idles between 650 to 700 rpm, steady but with a slight shake.

I also get an inconsistent light tapping that seems to be coming from the rear end of the engine between the oil pan and flywheel cover. It's more of a tick than a knock, but not constant. I replaced the flywheel recently because I noticed broken teeth when I was replacing the starter.

I'm not the original owner of the truck so I don't know why the teeth were chipped, but the ticking is still there, I had hoped the ticking was due to the flywheel maybe being out of balance as well as chipped, guess not.

Unfortunately the truck has a two piece bearing and seal rather than a one piece so I couldn't replace the bearing and seal with the flywheel without lifting the engine and removing the oil pan. Although, the seal looked good and everything else seemed to check out okay, including the front transmission seal.

I'm wondering if the leak in the intake manifold and the low rough Idle are related. I don't think I want to hear what you have to say about the rear end engine tick, but I was hoping at an off chance that the tapping could also be related.

I was questioning the exhaust as the ticking culprit but I'm leaning away from that now, because before the heads were done, I replaced the exhaust from the manifolds back, including the catalytic converter. When the heads were done I completed the job by also replacing the exhaust manifolds. One was cracked and the other didn't look too good. Again, since I was already there and I got a great price on the new manifolds online.

Sorry for running on, but as you can see I have put a lot of TLC into this truck, plus the frame and body are in great shape, and I want to get to the root cause of these problems in case it's something that can cause serious damage if not taken care of.

Just to complete the picture, since I have gotten the truck I have also replaced the shocks on all four corners, all four tires, the alternator, steering gear box, power steering pump and pulley, belts, rear stabilizer, tie rod ends (inner and outer), drag link, adjusting sleeves, pitman arm, rear brakes, front brakes (rotors, calipers, pads), fuel injectors, fuel regulator, fuel rails, tail house seal and bushing, rear drive shaft U-joints, front wheel bearings, removed and cleaned the locking hubs, and replaced the rear axle oil seals.

I've done about 90% of the work myself (pretty much everything except the heads and manifolds) and for this truck to die now would be such a let down, especially seeing I had never tried my hand at auto mechanics that much before the truck other than general maintenance, and it has been a great feeling of accomplishment each time I complete a job.

Not to mention the amount of money I have saved by buying a Haynes manual and rolling up my sleeves, and getting a bit of advice here and there, a lot from you, by the way, thank you. So, needless to say I have become very attached to the truck now, my 5 year old son thinks it's "so cool", and a point in any direction from you would be greatly appreciated.

• 1990 Ford F-250 XLT Lariat 4X4
• 7.5 liter 460 Fuel injected
• C-6 Automatic Transmission
• 97,000 miles
• Rear Drum ABS brakes
• P/S, A/C, Cruise control

Thanks,
Ed

A. The joint between the intake manifold gasket and head gasket is a tough one to seal. You need to take extra special care to seal it properly before assembly to insure that it doesn't leak. If it does leak, it will cause a vacuum leak that will make the idle slightly rough, as you describe. It will also leak oil. If it does make any noise, it will be a slight hiss of a vacuum leak.

The joints are designed so the intake manifold gasket can be replaced without having to replace the head gaskets. So, at the very worst you would need to remove the intake manifold to fix it.

I don't know if you replaced the lifters or not, from the list of parts I would have to guess no. It is possible one of the lifters are air bound and will need some time to properly bleed out. Or there may be a lifter(s) going bad. If that is the case, you would need to remove the intake manifold to replace them.

Oh, by the way, nice looking truck. You can be proud of it.