One of the handiest engine analyzing tools you can have around is the leakdown tester. It provides more info than a compression tester and is just about as easy to use.

To build a low dollar leak-down tester, get 2 air line gauges, an air regulator, a couple of pipes to connect the gauges to the regulator and a couple of air line fittings to connect air in and out. I wish i could insert a pic so those who aren't familiar can understand how it all goes together. Oh well, just use your imagination and ingenuity.


Like a compression test, a leak down is performed cylinder by cylinder, but in this case, the piston stays at TDC on the compression stroke (both valves closed) and air is fed into the cylinder and the amount of air that escapes is measured.

Not a complicated device, a leak down tester consists of two gauges and a regulator. One gauge indicates the the pressure in the supply line, the regulator is used to set the pressure supplied to the cylinder being tested, and the second gauge indicates the air pressure the cylinder will hold.

The procedure for a leak down test is just about as uncomplicated as the equipment itself. First, the tester is connected to an air supply, the line pressure gauge will indicate available pressure ( as an example, our shops compressor supplies 150psi, so thats what the gauge reads). Next the regulator is set so the leak-down gauge shows 100psi ( I use that figure to simplify the math later). Finally a hose with a threaded end ( i use the one out of my compression tester kit) is screwed into the sparkplug hole of the cylinder to be tested and then connected to the tester. Fill the cylinder with air until the leakdown gauge reaches 100psi then close off the air. If there is a problem, you'll know right away; the amount the leak-down gauge drops is the amount of leakage in that cylinder. As an example, if it now shows 80psi, theres a 20psi or 20% leak.(thats where the math is simplified)

The advantage to a leakdown test is that not only does it indicate an engines integrity, but makes pinpointing the problem quite simple. The leak will be audible. So if air can be heard coming out the tail pipe ( or exhaust port if engine is out of car) it's obvious that its a bad exhaust valve. Whistling through the throttle body or intake means its a bad intake valve. Air escaping into an adjacent cylinder or the rad(not normally audible but you'll see a stream of bubbles with the rad cap off) indicates a blown head gasket or a cracked head or block. And if air can be heard blowing around in the oil pan or crankcase area, the rings are tired or a piston is damaged. Simple enough!!!

Mine cost me like 12 bucks to make cuz i had some parts but it still beats like $100 for a cheap one, all to do the same job. If you send me an extra 50 bucks ill give you a lil Snap-on sticker to put on it if it makes you feel better. LOL




Modified by JustG at 9:29 PM 1/18/2006

 

WE WANT PICS! .

I like your explanation with what a leakdown is, this will help out plenty of people.

 

Sorry i dont know how to put the pic in here, i only have it on paper, hence the typing!!

But hey i shoulda known, some else got it. they posted this link in another thread as i was typing mine. Sheesh!!!

http://www.xs11.com/tips/misc/misc3.shtml

This link courtesy of Snail. Thanks buddy


Modified by JustG at 9:36 PM 1/18/2006

 

Very nicely done. That link did a good job on the picture.

 

Thanks justg

 

with 17 posts good stuff add it to the faq!!

 

good info

 

Now I have to just figure out how to use it

Great info

 

haha same here ^^^

Good stuff though.

 

quote-with 17 posts good stuff add it to the faq!!

Ya i know i only have 17 posts but that doesnt mean i havent been here long. I usually just read and research, i will only put in my 2 cents if im sure. none of this "well it might be this or it might be that..." Thats what everyone should do on their own, thats trouble shooting .then ask if your stumped. But hey we're all here to help each other one way or another right!

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by SkoundrelUSA &raquo;</TD></TR><TR><TD CLASS="quote">Now I have to just figure out how to use it

Great info </TD></TR></TABLE>

If the write up is'nt clear then i dont know wat to tell ya!

Basically, you measuer the amount of air you put in the cylinder, from your air compressor, like 100 psi. Since the cylinder is at tdc on compression stroke, it should be sealed tight. so now, when you put 100psi in and wait for 5secs, any air that escapes is the percent of leakdown you have. 100psi in---wait 5 secs---80psi left=20% leak down

if you leave it long enough, every cylinder will leak to an extent. hence 5SECS if you realize you have high leakdown you can apply the air again and listen to where it is escaping to determine the repair you have to do.

Hope that sums it up a lil better and quicker!

 

Very nice. Much props for the info!

 

Great Info! this will help me out sometime

 

bump!

 

http://www.c-speedracing.com/h...n.php

This is a good link for a leak down test.

 

Where can you buy the fitting that goes into the spark plug hole? You said you had one from a previous leak down tester.

edit: read the other thread. The author used a drilled out spark plug.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by JustG &raquo;</TD></TR><TR><TD CLASS="quote">quote-with 17 posts good stuff add it to the faq!!

Ya i know i only have 17 posts but that doesnt mean i havent been here long. I usually just read and research, i will only put in my 2 cents if im sure. none of this "well it might be this or it might be that..." Thats what everyone should do on their own, thats trouble shooting .then ask if your stumped. But hey we're all here to help each other one way or another right! </TD></TR></TABLE> very admirable. somebody give this guy +10% and a some

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Everyones Hero &raquo;</TD></TR><TR><TD CLASS="quote">Where can you buy the fitting that goes into the spark plug hole? You said you had one from a previous leak down tester.

edit: read the other thread. The author used a drilled out spark plug.</TD></TR></TABLE>

Actuall mine is from a compression tester set but a drilled out plug might work as long as its sealed and can hold back 100+ psi.

BTW thanks for the props thisisntjared!

 

double post ownz me.........

 

Bringing this back. Very cool post. I just made my own tester tonight in my shop at work using this tutorial and thought I would post some picts so that we could have a description and pictures in the same thread.

Pictures of separate pieces.....


The pieces are (from right to left, which is also the direction of flow) listed below...
1) 1/4npt male to mail quick disc
2) 1/4npt female to female ball valve (Decided to use this instead of damper valve, also more correctly called an orifice. . I will just ease the pressure in by opening this valve slowly)
3) 1/4npt male to male check valve (Not really needed but I liked it. It would be needed if the reg valve did not have an internal check)
4) generic regulator (250psi max inlet, 100psi max outlet) w/internal check valve and 0-100psi gauge. The gauge measures regulated pressure.
5) 1/4npt male to female quick disc

The pieces will differ from tester to tester and I gave reasons why I used what I did. Also, the flow on the regulator I had went the opposite way of the one shown in the previous diagram that is why mine looks as if it were backwards.

All put together.....


And tested for leaks....


Hope this helps someone else, cause it helped me out.

I will just use the hose from the compression tester that I have.

 

yay, for piece list + pics
this will help me lots

 

Wow.

Looks like it's just a gauge with a spark plug threaded end and a valve to keep back-feeding or added air from the compressor. Is there anything else I'm missing?

Very cool, btw. I feel like I have to leakdown test my car now .

 

Now this is what Honda-tech is all about. Good stuff here guys

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Syndacate &raquo;</TD></TR><TR><TD CLASS="quote">Wow.

Looks like it's just a gauge with a spark plug threaded end and a valve to keep back-feeding or added air from the compressor. Is there anything else I'm missing?

Very cool, btw. I feel like I have to leakdown test my car now .</TD></TR></TABLE>

The comp tester and the leakdown tester are different units.

-The comp tester is just a gauge that you hook up to where the spark plug was.

-The leakdown tester is a regulator so that you can determine how much air pressure you have put into the cylinder and after a set amount of time you can calculate how much air you have lost. You need a check valve somewhere in the system to accomplish this. Otherwise, the air would just be pushed back out of where it was put in at instead of where the potential problem might be. I.E. the hg, valveseals or piston rings.

 

This is great info. In fact, compression testers are not that great of a tool for really finding how good your engine is sealed up. Leakdown tests on the otehr hand are GREAT and tell you a LOT more about the condition of your engine.

Everyone one needs to know how to do this test.

Also, I didn't see it mentioned; When you do the test make sure your car is warm. If its cold the metal may have not expanded and you may get a higher leakdown that what you actually have... So this test doesn't really work on engines that have been out of cars for awhile. (I tested my b18 before I bought it and it was at 60%. I bought it anyways and when I put it in my car and drove it for about about a week and tested it again and it tested at 5%! pretty damn good.)

 

Whats this? Something actually useful on HT?