Ease of Leak-Down Test During Change of Valve Seals

I recently described a problem with a used engine (not remanufactured) that was installed in my 97 tercel. Some fumes were entering the car when driving, even with the fan on recirculate (but more noticable when set to ventilate). Sometimes smelling like deisle fumes (burnt oil), somtimes like burnt rubber or burnt sugar, sometimes chemical-like, sometimes like dusty air, Most of the time, it is caustic enough to aggravate the eyes and lungs/throat.

My mechanic will change the valve seals and do a pressure test of the air heating system. Considering what he is doing, would it be simple to do a leak-down test? I read about the concept after a friend pointed it out, but I'm not sure if it would be easy to do in practice if one is going change the valve seals and pressure test the cooling system. It /seems/ straightforward, since the shop air is fed through the spark-plug port. I guess the engine doesn't need to be taken apart too much to do this?

Tercel Owner

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Tercel Owner
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it seems you need to be looking for something on the outside of the engine, possibly leaking onto the exhaust manifold or something like crankcase vent dumping into the engine comparment. I don't know why the mechanic is changing the valve seals, does the engine burn a lot of oil?

Reply to
JeB

When you say "pressure test of the air heating system" I assume that you mean pressure test the cooling system.

Pressure testing the cooling system is easy to do if you have the proper kit and adapters. Basically, you attach a pump and gauge to the radiator neck in place of the regular radiator cap. There is also a tool to check the integrity of the radiator cap itself.

A cylinder leak-down test is slightly more involved but not that difficult either if you have the proper tools. Basically, you remove a spark plug and install a pressure gauge in the spark plug port and crank the engine over. Then you remove the gauge, squirt some oil in, and repeat to see if the readings change drastically. A change might indicate a piston ring problem. If the readings are equally low wet or dry, then a valve not seating properly is probably the culprit. If you're burning oil and the rings are good, then valve stem seals are probably the culprit.

The engine does not need to be removed from the car or taken apart to do a cooling system or cylinder compression test.

Reply to
Ray O

Yes, big time. It is possible that there is a outside leak of oil onto a hot piece of the exhaust systemIt is also possible for that to be unrelated to the burning of oil.

Tercel Owner

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Tercel Owner

Yes, big time. It is possible that there is a outside leak of oil onto a hot piece of the exhaust system. It is also possible for that to be unrelated to the burning of oil.

Tercel Owner

Reply to
Tercel Owner

Yes. It was suggested in this group. I always thought of the cooling system as the pathways running through the engine and the rad, and the air-heating system as the place where air gets heated before it enters the part of the car occupied by people. But it's all connected.

From googling (and from speaking to a friend), a leak-down test differs from a compression test in that shop air is pumped into the combustion chamber through the hole for the spark plug. Pressure is measured via a gauge on the hose that supplies the air. One listens for hissing in the exhaust, and the hole where the driver tops up with oil. One also looks for bubbling in the coolant. From my picking people's brains (and googling), the difference with compression testing is that the latter is less revealing, and the pressure for the latter is from turning the engine.

It turns out that pressure testing the cooling system and the leak-down test is not too involved (for a professional mechanic's shop), and it was done. No problems. The leak-down test gave less than 10% (I'm not sure of what), which is suppose to be good; 20% is considered acceptable. I'll ask about whether he listened for hissing or checked for coolant bubbles when I pick up the car. I hope he isn't too aggravated by my telling him how to do his job. He says that the symptoms don't really indicate the kind of problem that these tests would track down. In fact, this same oddity was expressed by the person who told me about the leak-down tests.

Tercel Owner

Reply to
Tercel Owner

Yes, the heater is basically a mini-radiator.

Looking back, I actually described a compression test, not a leak-down test, as you correctly pointed out.

If the engine is holding air that tightly, it is not very unlikely that there is a head gasket leak, which would cause the bubbling in the coolant.

Another sign of a head gasket leak is oil in the coolant or coolant in the oil. In the case of coolant in the oil, the oil will have a milky appearance.

I hope he isn't too

True, which is why I had recommended that you let your technician diagnose the cause of the odor.

Reply to
Ray O

Bit confused by "not very unlikely". Do you mean "not very likely"?

Yes, and I have checked for this. It doesn't appear to be the case. My mechanic also mentioned this symptom, and said it was absent.

I left a phone message saying that I don't presume to be able to advise him on the best course of action, and that these were just ideas that came up in discussion. I also mentioned that the person that introduced the idea of a leak-down test also was puzzled by the disparity between the actual symptoms and those symptoms which the test was suppose to troubleshoot. Basically, I left it the judgement up to the mechanic. The guy who told me about the leak-down test thinks it is actually oil dripping externally onto a hot part of the exhaust system, and I forwarded this to the mechanic in case he thought I was bent on having him do a leak-down test against his better judgement. Externally dripping oil theory makes perfect sense, since that's the most convincing explanation for how fumes are getting into the people-compartment. Even though it is the best explanation, it still has some difficulties. For example, the gasket around the hood is in place, so it is strange that the fumes can get to the vent intakes below the wipers.

As I said, the mechanic said he did those tests, and no problems came up. I asked if he did it just to appease me, and the answer was yes. I think he went beyond the call of duty to be accommodating. The labour was covered by the engine warranty.

Tercel Owner

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Tercel Owner

Sorry, I mean't to say "not very likely."

You have a great guy working on your car - stick with him!

Reply to
Ray O

Yes, I have, and hope I don't wear out his good nature by pestering him too much. I do, however, have to solve this problem or I will no more lungs left. As I said, there seemed to be traces of the caustic fumes yesterday, but the overwhelming scent of cleaning agents makes it hard to gauge. I was coughing quite bit today, something that normally doesn't happen unless I've been driving (I mean after the car problem manifested itself). As I said, it would be awesome if it was just psychological, or some coincidence, as I don't like messing up a good relationship with a good mechanic. To avoid that, I will try to pursue any outstanding problem with less overbearing manner (ie. throwing lots of ideas at him without a complete understanding -- the latter being kind of hard to get if I'm just learning about things). I was hoping to achieve the same by acknowledging my lack of expertise, and explicitly deferring to his judgement.

Tercel Owner

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Tercel Owner

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