Leak Test Results - What Now?

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Sjschmidtky
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Leak Test Results - What Now?

Post by Sjschmidtky » Tue Jun 09, 2020 1:54 pm

Hi!

Through a series of other posts, I'm progressing through diagnosing and fixing the loud puffing sound from my muffler and diagnosing one of my coils was not working. From the first piece of advice, I had the coils rebuilt recently (one had been found to be faulty, but I had them all rebuilt to avoid future issues). I have found the car starts faster with all the cylinders - dah! Although, it is still struggling to start and seems I have to idle too fast for the car to not stall.

With that I've moved back to the loud puffing noise from the muffler. As suggested in a previous post, I took all of the spark plugs out and looked for stuck valves. I did find one, sprayed some WD-40 best I could, and it snapped back down with a small snap after I pushed on it with a wooden dowel.

Next up, I purchased a leak tester (as also suggested in a previous post). I didn't purchase a compression tester (maybe I should?). I tried to find TDC for each cylinder and did the test per the instructions that came with it. But, I also found that if I cranked the engine by hand with the tester connected to each cylinder, I would find the least leak, presumably when TDC was reached. Is this an acceptable test method?

Here's the leak test findings:
#1: 60%
#2: 70% (this is where the stuck valve was found, did not recheck to see it it's still sticking after running for awhile - I'll do that when the engine cools).
#3: 50%
#4: 70%

So,
a. Did I do the test correctly?
b. Do the numbers indicate a value job is needed or something else?
c. Are there other suggestions before I progress further?
d. Are there good instructions somewhere for me to the valve job myself? (e.g., blue book , videos, etc.)

I'm been relying on the forum for get help since my experience is still limited. Thanks in advance for any further suggestions and help.

Steve
Last edited by Sjschmidtky on Tue Jun 09, 2020 4:47 pm, edited 1 time in total.

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Mark Gregush
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Re: Lead Test Results - What Now?

Post by Mark Gregush » Tue Jun 09, 2020 3:05 pm

"is still struggling to start and seems I have to idle too fast for the car to not stall." Try adjusting the spray needle, may be too lean.
You do know that a Model T at idle is going to go putt-putt-putt? ;)
Without knowing what test kit you got? If you are talking about a leak down test, it would only work at TDC for the cylinder being check and is used mostly to find leaky valves, there is no way that the pressure used would not leak past the rings after some point. Your description of how you ran the test, cranking the engine over and without context, the % you posted may not tell us anything.
AS far as valve jobs go, look on You Tube or the "Ford Service" manual.
Trying to diagnose an issue from a distance is not really the way to find out if there is an issue and what it might be. Have you reached out to anyone that might be close by to take a look?

KENTUCKY

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Re: Lead Test Results - What Now?

Post by Wayfarer » Tue Jun 09, 2020 3:58 pm

for leakdown on a model T I would think you'd want close to cranking compression for your pressure - 50 to 60 psi, no more. Then adjust to see what the leakage is. 20% should be the limit.

I've recently become a fan (again after many years of not using one) of vacuum gauge diagnosis. The vaccum gauge will show a leaky or stuck valve, though the leakdown will pinpoint which valve specifically
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Topic author
Sjschmidtky
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Re: Leak Test Results - What Now?

Post by Sjschmidtky » Tue Jun 09, 2020 5:15 pm

Mark,

I cranked until the piston was TDC and saw the valves were closed (all with the aid of a flashlight. Then I used the leak down tester per the instructions. I had to calibrate the tester first with the right amount air pressure (via my separate air compressor) and then attach to the spark plug hole. It also seemed that just attaching everything and slowly cranking, I could tell when the leak down test reached its least % loss that that was the point where the cylinder/valves were at TDC (when valves are closed and piston is at the top).

I'd love to have someone closeby and more knowledgeable than me have a look. I live in Northern Kentucky (by Cincinnati) and there is a club here - need to find someone who is willing to help out. I'll keep trying that route, but appreciate any help via the forum too.

Steve

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Mark Gregush
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Re: Leak Test Results - What Now?

Post by Mark Gregush » Tue Jun 09, 2020 5:42 pm

AT TDC at the end of the compression stroke, both valves would be closed. So if you are getting air leak ether exhaust or intake valve when air is put in the cylinder then you have a non sealing valve or it going past the gaps in the rings or past the rings into the crankcase.
WHAT leak down tester are you using?
The leak down test that I would be doing would be simple; a 1/2" NPT fitting, Tee screwed into that. One branch with a gauge and other with a tire type valve. Screw into cylinder you are testing with engine set at TDC put the parking brake lever forward and chock the wheels. Put in air and check for leaks.
Have you considered just putting the spark plugs back in and taking it for a drive? I don't know how much you have driven a T and hope you are not expecting it to run like a modern car?
You have a rebuilt set of coils, just open the spray needle a little more, pull the spark lever down after it starts till runs Model T smooth and go for it.
I know the voices aren't real but damn they have some good ideas! :shock:

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Re: Leak Test Results - What Now?

Post by Norman Kling » Tue Jun 09, 2020 9:26 pm

the leak down test should be done with the piston at top dead center. You can find it by checking the pin on the crank shaft pulley. When it is straight across you are at top dead center. if both valves are closed, that piston is top dead center. if one or both are open, that cylinder is not top dead center. Once you find top dead center for one cylinder, the can find the top for each by turning the crankshaft one half turn. Firing order 1,2,4,3. So if you find top center for 2 the next haft turn would be 4 etc. When you pump in the air, you can listen for air at the crankcase through the oil filler. for the exhaust by the muffler and for the intake through the carburetor. Note, if you had a stuck valve, it might still be slow in closing and cause some exhaust leak and if it has been sticking for a while, it could even be burnt from hot gasses passing by when it is partly closed.
Norm


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Sjschmidtky
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Re: Leak Test Results - What Now?

Post by Sjschmidtky » Tue Jun 09, 2020 11:35 pm

Would this work to do a leak test vs find TDC? Calibrate the leak gauge with the air compressor attached first. Attach to spark plug hole. Turn the crank until you see least % leak. Would this not be the place when TDC is achieved for each cylinder vs. watching pin? BTW, since I’m a novice, where is the pin on the crank shaft - is it easy to see looking from above while turning the crank?

Thanks, Steve

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Mark Gregush
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Re: Leak Test Results - What Now?

Post by Mark Gregush » Wed Jun 10, 2020 1:31 am

What tester are you talking about? I know I am not the only one that does not used a leak down test that shows %'s.
Between using a vacuum gauge test, doing a compression test and simple leak down would be more then enough to find out how healthy the motor is.
The pin is the one that holds the pulley on the crankshaft.
Do you know any of the history of the motor, has it been rebuilt or is it old and tired?

Going back to your first post back in June of 1919, seems like you were having somewhat the same issues.

That would have been real fast service on the coils as you were only talking about sending them out on June 2ed or did you buy the new ones:
"Post by Sjschmidtky » Tue Jun 02, 2020 1:31 pm
Thanks everyone! I’m getting them rebuilt (and getting an extra too). I’ll likely be back to the forum once I see how things are running (or not) with rebuilt coils. I’m curious to see what changes with suspected open valves with good functioning coils."
and in this posting you talk about having rebuilt ones." I had the coils rebuilt recently (one had been found to be faulty, but I had them all rebuilt to avoid future issues)."

Maybe post a new video (You Tube might be better choice, it will stick around longer) of how it is running now.
I know the voices aren't real but damn they have some good ideas! :shock:

1925 Cut down pickup
1920 Dodge touring
1948 Ford F2 pickup


Topic author
Sjschmidtky
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Re: Leak Test Results - What Now?

Post by Sjschmidtky » Wed Jun 10, 2020 7:50 am

Mark,

I used this leak down tester from Amazon. I just ordered a compression tester too, since they’re pretty cheap.

I don’t know the history of the car or motor, wish I did. I’ll look for the pin and do the leak down tests again. Should I run the engine for very long before doing the test.

On coil turnaround, I took them to Ron Patterson (drove them to him since he’s only 1.5 hours away). I got him at a good time and he had them fixed in a matter of days.

Thanks for your interest and help.

Steve
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Re: Leak Test Results - What Now?

Post by John Illinois » Wed Jun 10, 2020 8:29 am

I was an aircraft mechanic for several years. Diferential compression tests (leakdown) were part of every piston engine inspection. In general you put in 80lbs and 60lbs on second gauge is minimum requirement. I have never seen a second gage that reads percent.
John


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Sjschmidtky
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Re: Leak Test Results - What Now?

Post by Sjschmidtky » Wed Jun 10, 2020 8:54 am

John,

Do you think that using this leak down tester is not a valid test then?

Steve

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Mark Gregush
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Re: Leak Test Results - What Now?

Post by Mark Gregush » Wed Jun 10, 2020 10:00 am

I wondered if Ron had done them. Great!
Ok now we are on the same page re the %, learned something new. I looked up how this tool is used, but don't see anything about cranking the engine over when doing the test, just bringing to TDC, pressurizing the cylinder, checking for air leaks and reading the % gauge after a few minutes.
https://shop.advanceautoparts.com/r/car ... w-to-do-it
Now that some of us that didn't know can see what tool you are using. I would think leaving out the cranking the engine over when doing the test should be fine for the type of test you are doing. Without seeing the instructions that come with the kit may be a different test that may or may not apply here. Did you make your own 1/2NPT to 14MM adapter that I talked about last year?
I know the voices aren't real but damn they have some good ideas! :shock:

1925 Cut down pickup
1920 Dodge touring
1948 Ford F2 pickup


Topic author
Sjschmidtky
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Re: Leak Test Results - What Now?

Post by Sjschmidtky » Wed Jun 10, 2020 12:26 pm

No, I have no equipment or knowledge to make the adapter, bought one from one of the Model T parts suppliers (don’t recall which one).

I’ll test again without cranking engine and see what I get.

More advice is always welcome!

Thanks, Steve

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Re: Leak Test Results - What Now?

Post by Charlie B in N.J. » Wed Jun 10, 2020 12:40 pm

Wet/dry compression test will reveal all. With 0 guessing.
Forget everything you thought you knew.


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Re: Leak Test Results - What Now?

Post by Wayfarer » Wed Jun 10, 2020 1:19 pm

vacuum test while running will indicate specific issues, but not which cylinder
compression test will tell you which cylinder, but not what the specific issue is
leakdown will tell you which cylinder, and what the specific issue is
cylinder balance test can indicate which cylinder, but not what the specific issue is

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Re: Leak Test Results - What Now?

Post by Ruxstel24 » Wed Jun 10, 2020 2:46 pm

Steve...
What Mark is sayin is what you need.
Don’t worry about the gauges on the leak tester.
Just get one cylinder at a time at TDC, valves closed, hold engine from turning, chock wheels and blow air in. Listen for air coming out of either the exhaust or carb. (Open the throttle all the way).
If you hear air from one or both, that’s the culprit. Pretty simple really.
Sounds like the head will be coming off for a valve job anyway, but this will indicate the exact problem beforehand.
You’ll get there !
Dave

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Re: Leak Test Results - What Now?

Post by John.Zibell » Wed Jun 10, 2020 4:08 pm

Part of a leak down test is to listen for where the leak is from. Listen at the crankcase will tell you if it is ring leakage, and listening at the intake and exhaust points will tell you if it is a valve leakage.
1926 Tudor

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