Leakdown test questions

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Leakdown test questions

February 23, 2010, 09:34:59 PM

For those of you that have done this before please lend me your advice.

Background: 1987 Ford Thunderbird Base Model
Mileage: 120,000
Engine: 3.8 liter

I have white smoke emitting from the exhaust with a smell of coolant to it. It does it even after it is warmed up. I am trying to determine where this leak is coming from (HG or intake manifold gasket).

So, I conducted a leak down test (never done it before). I put each cylinder at TDC before conducting test. I also made sure the air pressure on the gauge was the same for each cylinder prior to testing.

The results below are what I tallied:
Cylinder 1: 48% of leak down - I heard air coming through the PCV, it actually pushed it up a little through the valve cover.

Cylinder 4: 44% of leak down
Could not tell where air was escaping

Cylinder 2: The gauge maxed out at 100% loss but after 20 seconds it leveled off to 43%. Could not tell where air was escaping

Cylinder 5: The gauge maxed out at 100% loss, but after 20 seconds it leveled off to 20% leak down. I tested the cylinder again and it went to 20% leak down right off the bat. Could not tell where air was escaping.

Cylinder 3: 38% of leak down

Cylinder 6: 34% of leak down

In all cases I heard air but could not determine where it was going or coming from. It resonated under the carburetor (intake manifold) but I could not ascertain any leakage around the gasket area. I had no air bubbles in the radiator and I had no air coming out of the carburetor.

So, I am not really sure what to make of the results.

I do have a fluid leak coming from the rear of the motor, it drips into a 3-4 inch puddle on the garage floor after running. There is residual oil around the back of the intake manifold. The car does not overheat, but after driving it for a while it has the burnt oil smell/coolant smell coming from the exhaust with the white smoke.

If anyone can shed some light on the subject I would appreciate it.

Shaun

Leakdown test questions

Reply #1 – February 23, 2010, 11:01:09 PM

99% probability that its the HG. Especially if Its burning it. I've never had good luck with leak down tests, but maybe its me. If you pull the plugs, one should be scrubbed clean. Thats probably your leaky cylinder (and I'm willing to bet its the last one on the passenger side).

Pulling the upper intake isn't all that hard. If you find a ruptured gasket, sweet, slap it back together. Otherwise, your halfway to a HG replacement. A HG job is pretty easy.

Leakdown test questions

Reply #2 – February 23, 2010, 11:18:49 PM

Quote from: 88CougarGT;311303

99% probability that its the HG. Especially if Its burning it. I've never had good luck with leak down tests, but maybe its me. If you pull the plugs, one should be scrubbed clean. Thats probably your leaky cylinder (and I'm willing to bet its the last one on the passenger side).

Pulling the upper intake isn't all that hard. If you find a ruptured gasket, sweet, slap it back together. Otherwise, your halfway to a HG replacement. A HG job is pretty easy.

Yeah, I think that is what it will come down to. I have no history on the motor, so I might as well replace gaskets and have the heads resurfaced while I am at it.

Thanks for the reply.

Leakdown test questions

Reply #3 – February 24, 2010, 10:26:06 AM

you may wat to look into a used engine, or going thu yours, with the leeakdown numbers that high, and some of your comments, sounds like the rings are on the way out.

read this.....
http://www.foxtbirdcougarforums.com/showthread.php?t=27017
you may be lucky and the test is faulty and just need HG