On Stuck Valves

How I recognize an engine problem — and resolve it — on top of a mesa.

I’d flown Three-Niner-Lima up to Howard Mesa on my birthday, June 30. I was due to work at the Grand Canyon the next day and was looking forward to commuting to and from work daily in my helicopter.

The next day, I climbed aboard, all dressed for work. I started the engine and immediately noticed that it sounded louder and vibrated more than usual. At first, I convinced myself that the louder sound was my imagination, due to spending the night in the absolute silence of Howard Mesa. (It’s amazing how your hearing gets more sensitive when there’s nothing for it to listen to.) The vibration was due to me parking on level but uneven ground.

The blades, however, took longer than usual to start turning. There was no logical explanation to that.

And when I got it up to warm-up RPM (75%), I realize that the manifold pressure gauge read 18 inches. 18 inches is what I need to hover when I fly solo. I didn’t know what it was at warm-up RPM, but I was pretty sure it wasn’t 18 inches.

I applied carb heat, thinking that perhaps there was some icing (not likely but possible). I immediately lost about 10% of my RPM. I normally lose about 2-4%.

The lightbulb over my head came on. I had an engine problem.

I disengaged the clutch and pulled the mixture. The engine cut out gratefully. I checked my watch. It was 6:15 AM. If I didn’t hop in the Jeep soon, I’d be late for work.

I stopped the blades, tied them down, and climbed into the Jeep. It started right up and I started on my way. Of course, I did get a flat tire about 1 mile from pavement that made me late for work anyway, but that’s another story, covered in another blog entry.

I called my R22 mechanic in Prescott, Cody, and talked to him about what I’d experienced. He suggested a few things: sticky valve, fouled plugs, bad magneto (I hadn’t even gotten to the mag check). We came up with a plan of action that included checking the plugs and possibly doing a mag check.

Mike joined me at Howard Mesa a few days later. He pulled the plugs and cleaned one of them. I assumed that was the problem and didn’t bother starting up again. Until it was time to go home. And guess what? The problem was still there, if not worse. I was now pulling 18 inches of manifold pressure at 55% RPM.

We tied down the blades, covered the cockpit, and went home.

I called Paul, my old mechanic in Chandler. Although I’m not allowed to bring my helicopter to him for repairs, he’s told me time and time again that I can call him any time I have a problem. He had the same opinion as Cody about the problem, but added that if it were a stuck valve, we could easily check for bent push rods by pulling off the valve covers. Easy for him.

Cody was leaving town for Montana and would be gone for a while. And I had a feeling his boss, John, wouldn’t be too receptive to a field trip. John had a trailer that we could use to bring the helicopter to Prescott. But I could only imagine what he’d charge for its use. I was pretty financially tapped out (heck, I just put a $25,000 deposit down on a new helicopter I wouldn’t see until January 2005) and didn’t want to spend $1,000 moving my helicopter off a mountain top, just so a mechanic could spend 10 hours repairing it (at $100 per hour).

But Ed, our local mechanic, knew all about Lycoming engines, even though he wasn’t a helicopter guy. I called him and told him my problem. He agreed to make a field trip with us. We drove up yesterday with a bunch of Ed’s tools and lots of water and Gatorade.

Repairs at Howard MesaWe spread out some cardboard and throw rugs and Ed got right to work. He and Mike found another fouled plug. Then they did a compression check, with me cranking the engine. The results were pretty conclusive: Cylinder #4 was not producing any power. Zero.

The reason became apparent when Ed pulled off the valve cover. The exhaust valve was stuck. Really stuck.

He and Mike worked on it for 30 minutes and couldn’t get it to budge. It looked like they’d have to pull the cylinder and drop it off at a repair place in Prescott. Ed looked at the engine cover and all the other things attached to the engine. It looked like a lot of work. I called Paul again and told him the problem. I asked him if there were any shortcuts to getting the cylinder out. Then I turned the phone over to Ed. From Ed’s side of the conversation, I could tell it would not be a fun job.

Stuck ValveEd hung up and told us that it would be best to continue trying to free up the valve. So he and Mike went back to work. With a hammer. A big hammer.

I left to get us lunch. I was gone about 90 minutes. (It’s a half hour drive to Williams and the woman at Safeway was the slowest sandwich maker I’ve ever seen.) When I got back, they were putting things back together. They’d freed the value and had reamed it. It was now smoother than ever. I’d be able to fly.

We had lunch then cleaned up. I climbed on board while Mike and Ed stood outside, looking for leaks. When I started up, my idle manifold pressure was 8 inches. No leaks so Ed climbed on board. (It’s always reassuring to have your mechanic fly with you right after a repair he’s done.) Warm-up manifold pressure was only 12 inches. That’s more like it! Everything sounded good, the unusual vibrations were gone. (The usual vibrations, alas, were still there.) I pulled power and got into a hover at 21 inches of manifold pressure. Great. I pointed it toward the road and we took off.

I took Ed home a scenic route: over Prescott and down the Hassayampa River. He’d never been over the river in that area before and I think he really enjoyed it.

When we got back, he presented the bill. $312. And that included my oil change the previous month. I paid it with pleasure.

Oh, one more thing. Consultation of the engine log books revealed that this was the FIFTH time we’d had to ream the #4 exhaust valve. Hmmm….let’s hope it holds out until January.

What do you think?