Insane Hydraulics

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Air Bubbles and the Importance of Independent Troubleshooting

I must say I was quite uncertain where to place this article, or better, this sad tale of mine. Finally, I decided to put it in the Battlefield section as it was, indeed, a lost battle of mine...

This story may not be directly related to oil hydraulics, but it is still a perfect example of how it's important to use your own head while troubleshooting a malfunction, instead of blindly following an "expert's" opinion. Don't get me wrong here, I am not against the "expert", I am against the "blindly".

Some years ago (more than I care to admit) I was very happy to present my wife, who had recently (and finally) gotten her driver's license, with a "brand new" 1995 Peugeot-306, powered by a generous 1.8-liter turbocharged and inter-cooled diesel engine with mechanical fuel injection - the feature that alone was more than enough to convince me into buying this particular vehicle, because the presence of a Bosch fuel injecting piston pump was filling me with warm feelings... The hatchback cost me 2000 euro, which seemed quite a bargain at the time as it had air conditioning, power steering, electric windows and mirrors, central lock, FM radio, and even five doors!

For about a week I was delirious with joy at the car. Then the perfectionist inside took over and the nightmare started... Yes, yes - I am one of those unfortunate fellows who seek an explanation to anything around them that is not yet explained, and are compelled to make things work "the way they are supposed to". Like when my brand new Vista computer (few days after the infamous Vista launch and crash) went gu-gu and refused to accept USB drives by freezing whenever a memory pen was inserted, it became impossible for me to work on it even when I was not using any pen at all. The itching feeling of incomplete functionality was there... driving me crazy and demanding an immediate fix!

Anyway, the automobile was running perfectly fine except for the fact that every now and then the engine seemed to loose power. Like, when I would accelerate, the acceleration rate would be kind of jerky - sometimes the car would leap forward like a muscle car, and sometimes it would feel like I wasn't accelerating at all, even though I was pedaling to the floor. Another symptom was the inability to maintain a steady speed while cruising. There were always these small, almost imperceptible jerks present. My foot wouldn't change the position and yet I could feel the car to accelerate and decelerate on its own. My wife didn't see it as a problem, and indeed it was almost imperceptible, especially for a passenger, but the problem was there and it was demanding, no, crying for a solution. All the joy of driving had been sadly gone...

Confident that it was a fuel-related problem I went to my car mechanic to see if he could "take a look". Unfortunately, my good friend had left for Angola and I dealt with an employee of his, who inspired confidence with many years of experience and lots of Grey hair... As soon as I related the problem he said:

"Don't you worry, my good sir, it's the injector pump problem! We will repair it and it's gonna be all right!"

A week later I went to the shop to pick up the car.

"Does it run smooth?" - I asked

"Like a missile!" - said the mechanic.

The bill showed that the car, besides the injection pump repair, also got a new fuel and air filter, which seemed logical, so I went home happy. First few miles, however, showed that "the missile" was missiling in the same jerky manner it had before. Pretty disappointed, I called the shop and arranged for another visit.

"Don't you worry, my good sir, we'll replace the injection pump and it's gonna be all right! The one you have seems to be damaged beyond repair." - said the mechanic.

Although the price of the new injector pump was a little high, it was already a matter of principle, so I gave it a "go". A week later I went to the shop to pick up the car.

"Does it run smooth?" - I asked.

"Like a jet fighter" - said the mechanic.

A quick glance under the hood revealed a "new used" Lucas injector. The bill showed, besides the fuel injection pump, an original inter-cooler air duct.

"Just in case" - explained the "artist".

So, I went home happy. First few miles, however, showed that the "jet fighter" was jetting in the same freakin' jerky way as before! Pretty pissed off, I called the shop and arranged for another visit.

"Looks like we've got ourselves a tuff one here" - said the mechanic - "But don't you worry, we'll replace the turbocharger, and it's gonna be all right!"

When I asked why the turbo, the answer was:

"Well, there's not much left to replace, is there? It's got to be the turbo!"

Then I told him I had actually measured the air pressure inside the intercooler and it was not too different from what was considered normal, in fact, I asked him the correct pressure value, which he didn't know, and I am guessing, considered the question as an offense to his experienced self.

"Anyway"- he said - "It's not a "normal" turbo, but a "volumetric" one, which is far more complicated and prone to malfunction".

My wife, who had been presented with the car and hadn't driven it yet was beginning to worry, so I gave the new turbo a "go". A week later I went to the shop to pick up the car.

"Does it run smooth?" - I asked.

"You will not believe it!" - said the mechanic - "like a rocket it does!!!"

The bill showed the turbocharger and tons of labor, and some other crap I can't remember now. "Well, it's life" - thought I, and went home happy. First miles, however, proved that rocket science had a lot to achieve yet, as the "rocket" was rocketing in the same freaking jerky way as before. I didn't call the shop anymore, I decided to pay a surprise visit one of the next days.

The next time I showed myself in the workshop I heard the sound of a glass breaking and a person running away. I guess my facial expression and clenched hands had given me away... Or maybe it was the blood-filled eyes...

Anyhow, the "artist" wasn't present, but there was an assistant of his, changing oil on some car, and he asked me what the matter was. Frustrated, I shared my story, which surprised him a lot.

"I am no mechanic" - he said - "But I do agree it's fuel related, and the most probable explanation for the non linear fuel delivery would be air bubbles inside the fuel line."

"You see" - he kept on - "in this car, there's no auxiliary pump inside the fuel tank, so the injector pump creates depression inside the suction line and if you have even the smallest opening to the atmosphere along the fuel line, air gets sucked in, air bubbles are formed, and there you go - the jerky engine work, especially on high regimes during acceleration. Besides the most probable cause, it's also the easiest to confirm - all you need to do is install a piece of transparent hose in the admission line of the fuel pump and check it for air bubbles. But since you're here, let's inspect the fuel filter assembly, as it's the part that gets tampered with the most."

Stumbled, I didn't utter a word and watched the man open the filter. It turned out that underneath the filter element, at the bottom of the enclosure, there was a small plug that had a suspiciously dry and dead-stiff O-ring seal. After 2 minutes spent replacing the O-ring and closing the filter the problem was gone... Gone for good!!! For the first time in my life, I felt like kissing another man. (Please don't use this phrase out of the context!)

Then came the feeling of enormous shame.

I, more than anyone, should have thought about air entering the suction line of a pump. I am the one who has used transparent hoses for air detection. I am the one who has always advocated independent troubleshooting. I am tired of finding oil leaks and air entering hydraulic systems through faulty O-ring seals... The list goes on...

My brain got frozen by the fact that I was dealing with an area beyond my expertise, so I completely surrendered myself to an opinion without questioning it. I have absolutely no excuse and the whole expense I suffered (doubling the initial price of the car) served me as a lesson to be never forgotten.

The point here is that even the most experienced experts mistake. Don't be afraid to ask questions when you see something you don't understand, there's no shame in it. Whenever in a troubleshooting situation, look for educating yourself about the subject. Don't surrender yourself to an expert's opinion blindly, seek for a logical explanation, or ask him for one. In my example, my dumbness and mental inertia cost me two times the initial price of a used car. In the case of a hydraulic machine, an incorrect or illogical troubleshooting can easily cost as much as several new cars! Make your own conclusions. As for me, I find my inner peace considering this predicament as a piece of education I paid for.