Leakdown test om606 - how to? - PeachParts Mercedes-Benz Forum

jake12tech · #1 12-21-2018, 11:22 PM

On my 606 that has a head issue. How does one perform a leakdown test on a diesel?

Diesel911 · #2 12-21-2018, 11:54 PM

If you go to the Harbor Freight site and look up their leak back tester you will find there is a .pdf of instructions you can view.----------

Instead of removing one of the spark plugs you have to remove the injectors or glow plugs (you are going to need to buy or make a compression tester adapter for one of those areas) and us that to connect the compressed air to the leak back tester.----------

If all you want to do is listen to where possible leak is all you need is the compression tester adapter and a fitting to attach the compressed air. A filter in the airline to keep out any water vapor would be a good idea.----------There also may be youtube videos on doing the leak back test with the leak back tester.For specific values of the test you should consult the actual Mercedes Manual.

jake12tech · #3 12-21-2018, 11:59 PM

Quote:

Originally Posted by Diesel911

If you go to the Harbor Freight site and look up their leak back tester you will find there is a .pdf of instructions you can view.

Instead of removing one of the spark plugs you have to remove the injectors or glow plugs (you are going to need to buy or make a compression tester adapter for one of those areas) and us that to connect the compressed air to the leak back tester.

If all you want to do is listen to where possible leak is all you need is the compression tester adapter and a fitting to attach the compressed air. A filter in the airline to keep out any water vapor would be a good idea.

Thank you. I just need to hear where the leak is from. Not concerned with how much seal I have. I already know I have a compression leak or I wouldn’t have a misfire. So I’m going to try your method you mentioned in the second paragraph.

I am wondering if my harbor freight compression tester injector adapter will work on the 606? It worked on my 603. Not sure if them injectors are the same thread.

Father Of Giants · #4 12-22-2018, 12:19 AM

Long story short, buy the biggest timing wheel you can buy, set the engine to TDC, mark the firing order(what exactly is the firing order?) and go town.

No guesswork.

This guy is helpful.
https://www.youtube.com/watch?v=_3wNGGs5fXM

Stretch · #5 12-22-2018, 07:56 AM

If you know there's a problem with the head why bother with the test?

Diesel911 · #6 12-22-2018, 11:43 AM

Quote:

Originally Posted by jake12tech

Thank you. I just need to hear where the leak is from. Not concerned with how much seal I have. I already know I have a compression leak or I wouldn’t have a misfire. So I’m going to try your method you mentioned in the second paragraph.

----------I am wondering if my harbor freight compression tester injector adapter will work on the 606? It worked on my 603. Not sure if them injectors are the same thread.

<----------Harbor Freight used to sell 2 different diesel compression test kits. Again both kits have instructions and if you click on the individual kit a you will see somewhere where you can access the instruction .pdf. ----------In the Instructions will tell you what each adapter can be used for.----------I am not sure what our sponsor sells but you can get the individual compression test adapters on places like eBay and amazon. However, I have never looked them up for your engine. You will have to weigh the price of one adapter verses buying a Kit that works for multiple applications.

Diesel911 · #7 12-22-2018, 12:05 PM

my own kit is over 10 years old and shows only glow plug adapters for (1988-89) 190E 2.5L, 1991-99) E300, and 2005 E320 CDI. However, since 10 years ago the 2 Harbor Freight kits have been re-configured. Not sure how much room is available to connect a glow plug adapter with an air hose on it.

Perhaps one of our Members has the adapter you need and could rent or loan it to you.

Diesel911 · #8 12-22-2018, 12:10 PM

Note that some of the compression tester adapters have a tire valve stem type Schrader valve that needs to be removed from then before you do a leak back test.

jake12tech · #9 12-22-2018, 12:17 PM

Thanks diesel. I’m kind of curious to test it to see where the leak is from. What if it’s a breach in the head gasket? And I don’t need a head. So why wouldn’t I.

Diesel911 · #10 12-23-2018, 03:02 AM

Quote:

Originally Posted by jake12tech

Thanks diesel. I’m kind of curious to test it to see where the leak is from. What if it’s a breach in the head gasket? And I don’t need a head. So why wouldn’t I.

I like to get a better idea of what is going on also.-----But, a head gasket leak can be caused by a warped or even cracked cylinder head or even the same with the Block (that is rare).----I think more importantly is if it turns out the leak is getting by one of the pistons/cylinders it would be a new ball game.---------------Also look for leaks around the pre-combustion chamber locking nuts.-----On the aluminum heads the sealing area of the Pre-combustion chamber sometimes warps.

jake12tech · #11 12-23-2018, 03:36 AM

Quote:

Originally Posted by Diesel911

I like to get a better idea of what is going on also.-----But, a head gasket leak can be caused by a warped or even cracked cylinder head or even the same with the Block (that is rare).----I think more importantly is if it turns out the leak is getting by one of the pistons/cylinders it would be a new ball game.---------------Also look for leaks around the pre-combustion chamber locking nuts.-----On the aluminum heads the sealing area of the Pre-combustion chamber sometimes warps.

Thank you. I did try to pin point my compression leak with a stethoscope in the areas it sounded like it was coming from. It’s odd, you can only hear it from the valve cover and the exhaust side of the engine. Completely silent on the intake side. I’m confident it is something top end related considering I have minimal blowby (comparable to my E300 in the 200k range). Also, something I learned along the way was if you have a significant compression leak from the bottom end, you can pull the dipstick out about a inch and feel the compression leak or push the dipstick out further if a bad enough seal.

I also do have disappearing coolant, no visible leaks, but I can’t smell it out the exhaust either. Just the odor of I burned diesel. And have a semi dead cylinder in #2. I think it’s going to be real interesting to pin point the problem.

Stretch · #12 12-23-2018, 05:49 AM

I don't think you're gonna be able to pin point problems as precisely as you hope - nice experiment if you can - but with the information you already have it seems to me to be time to pull it to pieces and use the old MK1 eyeballs

For that generation of Mercedes engines I suspect corrosion around the head gasket area to be present