 Leak down results, two (or three) out of four done |
|
|
|
Porsche, and the Porsche crest are registered trademarks of Dr. Ing. h.c. F. Porsche AG.
This site is not affiliated with Porsche in any way. Its only purpose is to provide an online forum for car enthusiasts. All other trademarks are property of their respective owners. |
|
|
  |
| SGB |
  Nov 18 2006, 02:14 PM
Post
#1
|
|
just visiting  Group: Members Posts: 4,086 Joined: 8-March 03 From: Huntsville, AL Member No.: 404 Region Association: South East States  |
Doing my first leak-down test and I'm now seeing some results that seem more beleivable.
On cylinder #1, I appeared to have 100% sealing. Is that actually possible, or did I just not wait long enough? On cylinder #2, I get about 92 or 93% sealing. I don't hear anything at the intake or exhaust, but there is a hiss at the oil filler, so I guess this means rings... On cylinder #3, Also close to 95%, and all escapes appears to be through the rings again. Are these reasonable results? What is acceptable? Then engine has not run for several weeks now, so the cylinders may be "de-filmed" Who has experience in this test that can enlighten me? Thanks y'all. Oh, BTW, Roll Tide. |
   |
 
|
| Mid_Engine_914 |
Nov 18 2006, 02:51 PM
Post
#2
|
|
Member Group: Members Posts: 195 Joined: 22-September 06 From: Left Coast Member No.: 6,888 |
I'm not sure what the specific numbers are for an aircooled motor but leakage should generally not exceed 20%. Did you do a compression test too? |
|
|
|
| Jake Raby |
Nov 18 2006, 03:36 PM
Post
#3
|
|
Engine Surgeon Group: Members Posts: 9,394 Joined: 31-August 03 From: Lost Member No.: 1,095 Region Association: South East States |
Good engines will hold 95% leak or less... I look for a 2-3% variance and no more than that.
Its important to test with the engine at near operating temp with the piston @ TDC and held there.. Compression tests are nominal at their efectiveness, leakdown tells thewhole story if done correctly. I threw the compression tester in the bottom drawer of the tool box 10 years ago... The most important aspect of leakdown tests are WHERE the leakage is coming from. As you test note whats hissing air, if you hear it in the exhaust thats an exhaust valve, if you hear it in the intake, well thats an intake valve.. If you remove the oil cap and hear it hissing thats rings/piston/cylinder... warm and TDC are the two constants that you must maintain |
|
|
|
| SGB |
Nov 18 2006, 06:03 PM
Post
#4
|
|
just visiting Group: Members Posts: 4,086 Joined: 8-March 03 From: Huntsville, AL Member No.: 404 Region Association: South East States |
Thanks Jake-
I think for me with a cold engine these seem like good numbers. Hot Dawg! For my education, I'm thinking the order of concern would usually be exhaust valve leakage (your head will fry or already has- not good), then intake ( your engine could catch fire?- not good again), and lastly, rings (how much smokin' can you tolerate) Thanks fer the info! |
|
|
|
| Jake Raby |
Nov 18 2006, 06:47 PM
Post
#5
|
|
Engine Surgeon Group: Members Posts: 9,394 Joined: 31-August 03 From: Lost Member No.: 1,095 Region Association: South East States |
You may have MORE leakdown when hot...
I have seen engines pass when cold with flying colors and then fail when retested hot. |
|
|
|
| SGB |
Nov 18 2006, 09:06 PM
Post
#6
|
|
just visiting Group: Members Posts: 4,086 Joined: 8-March 03 From: Huntsville, AL Member No.: 404 Region Association: South East States |
Well....
I guess thats semi-bad news. It's not gonna be hot again for another week. I've gotta finish my por-15 gas tank liner and carb rebuilds before I'll be firing up. Thanks, though because I'll be checking it later. My rule is "no shortcuts", so if I'm gonna do a leak-down, I'm gonna do it right. |
|
|
|
|
1 User(s) are reading this topic (1 Guests and 0 Anonymous Users)
0 Members:
|
Lo-Fi Version | Time is now: 29th May 2024 - 03:04 AM |
Invision Power Board
v9.1.4 © 2024 IPS, Inc.