Leak Down Test OM617.952 Which tester to use? - PeachParts Mercedes-Benz Forum

hobberslobbers · #1 07-04-2011, 05:51 PM

Which leak down tester is everyone using for a 617? Also, is it best to go through the injector hole or glow plug hole? I have a cheapo leak down tester (US General) and the adapter for the glow plug hole hits the side of the injection pump, so I can't even get it in there. And, I do not have an adapter big enough for the injector hole.

whunter · #2 07-04-2011, 06:11 PM

Leak-down Tester and ?'s
http://www.peachparts.com/shopforum/diesel-discussion/57178-leakdown-tester-s.html#post999381

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hobberslobbers · #3 07-05-2011, 03:28 PM

thanks for the info. i was able to get my leakdown tester adapter jerry-rigged to work.

ok, so here are the results of the leakdown. i did not see or hear anything from dipstick, radiator, or tailpipe when performing the test on any of the cylinders. i performed the test on a cold engine with the intake valve pointed straight up where both valves were closed (confirmed with feeler gauge at .004" / .012" intake and exhaust).

LEAKDOWN RESULTS
Cyl 1 - 15%

Cyl 2 - 8%

Cyl 3 - 17%

Cyl 4 - 11%

Cyl 5 - 22%

COMPRESSION RESULTS
Cyl 1 - 400
Cyl 2 - 405
Cyl 3 - 390
Cyl 4 - 390
Cyl 5 - 340

so, what can be told from cyl's 1,3,5 leakdown numbers? they still showed in the middle to high green area on my cheapo leakdown tester. compression numbers seemed alright to me. i have lots of blow-by under the valve cover. i replaced the valve seals last summer and rebuilt the turbo last week, but am still getting oil at the actuator on the turbo. about 3 drips per day.

if the above looks good to all, where should i check next? vacuum pump? could it still be loose valve guides causing the blow-by? again, i could not hear any air anywhere on the leakdown and there were no bubbles in the radiator.

leathermang · #4 07-05-2011, 04:38 PM

Could you give us an overview of how you are conducting this ' leak down ' test ?
A detailed description of the theory and how you are implementing it ?
and/or can you post the instructions from your meter ?

Diesel911 · #5 07-05-2011, 08:41 PM

Harbor Freight has a PDF on instructions that you can Down Load.
Of course the Instructions are for their setup but I think the procedure and percentages would be the same.

Also the Harbor Freight Instructions seemed the same as the other internet DIY instructions I looked at on the internet.

You need an Air compressor that you can adjust the output pressure on.

hobberslobbers · #6 07-05-2011, 09:05 PM

Using information gathered from this forum and others to determine the source of what I believe to be a high level of blow-by observed at the oil filler cap. I did the compression test and posted the numbers above. I performed the leakdown test to try to determine the source of the source of the blow-by, namely rings, head gasket, and/or valves. I probably should be posting the above and this information as a new topic as the title of the original question no longer applies at this point. Methodology on the leakdown test:

1. Cold engine
2. Removed valve cover
3. Adjusted valves. These were actually in good shape and I only had to touch up the exhaust valve on #1 cyl approx. .002" to get it in good at .012". The intake valve on #3 also needed opened up to get a .004". The other 8 valves checked good, as in dead on. Reasoning behind adjusting the valves before doing either the compression or leakdown tests was to confirm that both the intake and exhaust valves were opening/closing all the way in order to get accurate results.
4. Performed compression test. The numbers above (previous post) were on the #10 turnover. I was satisfied with the numbers given the fact this engine has 106k miles. I would have liked a better compression on #5, but I am not too concerned about it at this point.

COMPRESSION RESULTS
Cyl 1 - 400
Cyl 2 - 405
Cyl 3 - 390
Cyl 4 - 390
Cyl 5 - 340
5. Performed leakdown test on cold engine. Rotated engine to TDC on the intake valve of each cylinder. I confirmed both valves closed by checking .004" gap on intake and .012" on exhaust. I was very careful in this regard b/c I wanted to get accurate values. The instrux that came with the cheapo US General leakdown tester were geared more toward gas engines and I found them generally unhelpful (pun intended~!~). So, I used cam position to confirm location of TDC. (I used the same method when I changed the valve stem seals a little over a year ago, so I am quite sure I was at TDC on all cylinders when I performed the leakdown test, evidenced by the fact that I didn't lose any valves down in the cylinders.)

So, are my results valid and based upon what I am seeing in the pictures above, should I have any concern for cylinders 1,3,5 on the leakdown or do these values look good to go. As an afterthought when reassembling everything, I took a look at the L/S fender well and there is some oil spray adjacent to the vacuum pump. Should I be looking at this (possible vac pump failure) as a possible root cause for the excessive blow-by in the valve cover?

leathermang · #7 07-05-2011, 09:14 PM

Since yall don't want to share what the overall theory is..

Why is it called a ' leak down test ' if you are inputting a constant psi of air ?

The leak down tests I have read about involve putting a certain psi into the engine and comparing cylinders for how fast the leak down relative to each other.... and listening for relative escape routes in the process... thus it was called a ' leak down test '....not a constant input test...

kerry · #8 07-05-2011, 09:31 PM

What do you consider excessive blowby? Do you have a video of it? Have you measured it using the MB blowby tester or this forum's comparative garbage bag test?

hobberslobbers · #9 07-05-2011, 09:37 PM

leather, i suppose it is because "leakdown" is the common term everyone is using these days. yes, it is a constant 20psi that the manifold supplies to the gauge on the right, which simply shows a loss of psi back from the 5:00 position. this allows you to see the percentage drop, or so the theory goes. some leak is fine because only new engines theoretically have 0% leak. i'm still in the green part of the tester, so i'm hoping that is still acceptable.

kerry, yes i will post a video of the tea kettle'ing at the oil fill lid and then with the cap off. gimmee a few mins to get this up.

hobberslobbers · #10 07-05-2011, 09:59 PM

QuickTime vid of the blow-by (may take some time to load):

http://discounterz.com/300d/blow-by.mov

kerry · #11 07-05-2011, 10:06 PM

Couldn't play the video. Something about the way it was compressed.

hobberslobbers · #12 07-05-2011, 10:59 PM

pop-up blocker settings maybe? plays fine here but i had to disable my pop-up blocker. anyone else able to view?

kerry · #13 07-05-2011, 11:02 PM

It downloaded but wouldn't play on Windows Media Player.

Diesel911 · #14 07-05-2011, 11:04 PM

Quote:

Originally Posted by leathermang

Since yall don't want to share what the overall theory is..

Why is it called a ' leak down test ' if you are inputting a constant psi of air ?

The leak down tests I have read about involve putting a certain psi into the engine and comparing cylinders for how fast the leak down relative to each other.... and listening for relative escape routes in the process... thus it was called a ' leak down test '....not a constant input test...

He did not invent the Leak Down Test so he might not be aware of the theory behind it.
This site might better explain:
http://en.wikipedia.org/wiki/Leak-down_tester

leathermang · #15 07-05-2011, 11:06 PM

I assumed he had a theory for the actions He was taking... in order to know how to read the results....