leak down test results - Page 2 - PeachParts Mercedes-Benz Forum

kerry · #16 04-01-2011, 10:02 AM

Did you replace the valve springs? Could be a bad spring on that valve??

leathermang · #17 04-01-2011, 10:08 AM

Quote:

Originally Posted by kerry

Did you replace the valve springs? Could be a bad spring on that valve??

That is a good potential cause...especially at higher rpm's...

but I can not imagine a shop doing a valve job without either checking ( pressing at certain lb and measuring the distance compressed ) or ( my favorite since they are cheap ) replacing the springs while everything is taken apart.

Chas H · #18 04-01-2011, 10:31 AM

Instead of all this speculation, why not pull off the intake manifold, reconnect your leakdown tool and observe the source of the leak?

leathermang · #19 04-01-2011, 11:58 AM

I am still trying to determine how he came to those percentages he reported...

Chas H · #20 04-01-2011, 12:22 PM

Quote:

Originally Posted by leathermang

I am still trying to determine how he came to those percentages he reported...

I believe the problem is compression leaking into the intake tract, not numbers.

llm4 · #21 04-01-2011, 12:28 PM

Percentage answers-
Total leakage percentage= was determined by subtracting one guage reading from the other (tester instructions).

On-line manual say max leakage for valves is 10%, rings 20%, and total is 25%. All cylinders have similar amount of noise passing rings (assume 10%, each cylinder based on good cylinders).

Valve cover vs turbo leakage= I taped a blue rubber glove to the turbo inlet and taped another to the pipe going to the air filter housing. Applied pressure and watched them swell up. The valve cover glove was very slow but the turbo glove almost busted

Hope this helps, thanks again!

kerry · #22 04-01-2011, 12:48 PM

What was the time period for the leakdown test?

leathermang · #23 04-01-2011, 01:08 PM

Quote:

Originally Posted by Chas H

I believe the problem is compression leaking into the intake tract, not numbers.

We have had long discussions on trying to set up and do leak down tests on these engines to give helpful results...

Do you mind if I try to determine how he got such specific numbers and if the system seems reasonable ?

leathermang · #24 04-01-2011, 01:09 PM

Quote:

Originally Posted by kerry

What was the time period for the leakdown test?

Yes, I asked that back in post #14 ....

Chas H · #25 04-01-2011, 01:57 PM

Quote:

Originally Posted by leathermang

We have had long discussions on trying to set up and do leak down tests on these engines to give helpful results...

Do you mind if I try to determine how he got such specific numbers and if the system seems reasonable ?

Go ahead. But the inflating glove over turbo intake tells us much more than any numbers can. I'm just offring suggestions, same as you.

llm4 · #26 04-01-2011, 02:05 PM

For the time period, not real sure what you are asking, but i left the pressure on each cylinder for about 2-3 minutes. It took me approximately 45 minutes to test all five cylinders.

I have done the proceedure above twice, before and after valve job. This past weekend I just did #1 and #4 cylinders and the readings have been very consistant each time.

The valve springs were not replaced but were okay. I believe the valve/intake port build-up is a result of the leakage (my opinion). I don't mind pulling it back apart but, I hate to do it and find it was something simple.

Thanks again for your help with this!

leathermang · #27 04-01-2011, 02:09 PM

Quote:

Originally Posted by Chas H

Go ahead. But the inflating glove over turbo intake tells us much more than any numbers can. I'm just offring suggestions, same as you.

Thank You, You have not been here as long as I have... so you probably missed the posts about attaching garbage bags to that spot and trying to get some kind of baseline blowby figures with which to compare each other's cars and known good engines to unknown condition engines...
It was a funny discussion and visual ....

leathermang · #28 04-01-2011, 02:11 PM

Quote:

Originally Posted by llm4

For the time period, not real sure what you are asking, but i left the pressure on each cylinder for about 2-3 minutes. It took me approximately 45 minutes to test all five cylinders.

I have done the proceedure above twice, before and after valve job. This past weekend I just did #1 and #4 cylinders and the readings have been very consistant each time.

The valve springs were not replaced but were okay. I believe the valve/intake port build-up is a result of the leakage (my opinion). I don't mind pulling it back apart but, I hate to do it and find it was something simple.

Thanks again for your help with this!

Where were the gauges attached..
Did you use the glowplug holes ?
The injector holes ?
How did you determine the springs were OK ?
If the build up was a result of leakage.. why was it the same after the head job ?
Was the test done with the piston at TDC or BDC ?
If not at BDC did you lock the crank?
If you locked it did you do that at the ring gear or at the front pulley ?

Chas H · #29 04-01-2011, 02:34 PM

Quote:

Originally Posted by leathermang

Thank You, You have not been here as long as I have... so you probably missed the posts about attaching garbage bags to that spot and trying to get some kind of baseline blowby figures with which to compare each other's cars and known good engines to unknown condition engines...
It was a funny discussion and visual ....

Sounds comical, too bad I missed it.
I never tried to quantify engine leakage or blowby, other than a compression test, because it was never neccessary to do so.

leathermang · #30 04-01-2011, 02:38 PM

Quote:

Originally Posted by Chas H

Sounds comical, too bad I missed it.
I never tried to quantify engine leakage or blowby, other than a compression test, because it was never neccessary to do so.

Having read the FSM... I knew that MB has an actual tool/gauge for reading this... but everyone was gung ho on the garbage bags... so we had a lot or little fun depending on whether one was serious about using it or making fun of those trying to engineer/standardize that 'method'....