AirSpeed VW Community Forums

Technical => Engine Tech Forum => Topic started by: Thomas on July 16, 2011, 06:38:15 PM

Title: Compression Test
Post by: Thomas on July 16, 2011, 06:38:15 PM

I did a compression test on my 1641 tonight.
1-135
2-132
3-130
4-145
Not sure if these number are good or bad. I know that over 120 is usually good but not sure how much of a spread is OK 130-145?

Thanks Tom

Title: Re: Compression Test
Post by: Billyisgr8 on July 16, 2011, 07:04:23 PM

If it was me I would be happy with that.  I have a T4 here with 90 - 95 psi on it, and it still runs, and starts fairly well too.

Title: Re: Compression Test
Post by: josh on July 19, 2011, 11:47:51 AM

yup those are some solid #'s but you may want to do a "leak-down test" as well. this is a better way to check the condition of your rings

Title: Re: Compression Test
Post by: Thomas on July 19, 2011, 09:34:11 PM

What is a leak down test? Can I assume that it how long the cylinder will hold the pressure?

Title: Re: Compression Test
Post by: BUSDADDY on July 19, 2011, 09:54:19 PM

A leak down test uses a tool with a fixed orfice, compressed air is blown into the cylinder at a known rate and pressure loss past the rings or valves is measured. sometimes called a bleed down or differential pressure test.

Title: Re: Compression Test
Post by: buggal on July 28, 2011, 10:55:28 AM

Or there's a simpler less informative test to determine whether it's rings or valves.
Do dry compression test, then one cylinder at a time, squirt a little oil in the cylinder and repeat the test. If the compression comes up it's rings, if not it's valves.
Don't use too much oil or the test is useless, just use a squirt or two, enough to help seal around the rings. It can give you a place to start.

Title: Re: Compression Test
Post by: buggal on July 28, 2011, 10:57:12 AM

Oh yeah, I am a licensed mechanic. Most guys don't take advice or suggestions from a woman, but I got my license in 1985 so I do have some experience.

Good luck.

Title: Re: Compression Test
Post by: Chris on July 28, 2011, 05:19:20 PM

Its a good thing your not a woman then.....

Title: Re: Compression Test
Post by: buggal on July 28, 2011, 05:55:59 PM

I'm not the one who said orifice.... wee_hee