Compression Test..

Bluffing024

Active Member

Mar 15, 2006

0

2

48

Somewhere

Apr 11, 2007

#1

• Apr 11, 2007

• #1

Hey everyone.


I am thinking of buying a 99 Cobra and I want to have a compression test done on it to make sure everything is up to par...(link to thread about the cobra http://forums.stangnet.com/showthread.php?p=6824288#post6824288 ) What is a fair price to get one done? I just called Pep Boys and they said anywhere from $99 to $130 (guy sounded like an idiot though). Anything else I could look for? Thanks for any help..:SNSign:

 

Stan Weiss

Member

Dec 8, 2006

347

2

16

Philadelphia, PA

Apr 11, 2007

#2

• Apr 11, 2007

• #2

See if anyone in your area does performance work and get a leak down test done.

 

BennyBlown2v

New Member

Dec 9, 2004

1,233

1

0

Carmel, INdiana

Apr 11, 2007

#3

• Apr 11, 2007

• #3

You don't need a leakdown test unless the compression test is bad (shows one cylinder off). Just check the compression yourself, it's not hard.

 

Bluffing024

Active Member

Mar 15, 2006

0

2

48

Somewhere

Apr 12, 2007

#4

• Apr 12, 2007

• #4

Is there a write up on how to do one and what tools are needed? I am looking at that 99 Cobra and an 98 T/A LS1 (Evil, I know.) So knowing how to do it could help me out so I am not paying to get them both done. The T/A is at a dealership so they may do it for me? Thanks for any further info.

 

CobraRed_96_GT

Active Member

May 20, 2006

1,421

4

39

UCSD/La Jolla

Apr 12, 2007

#5

• Apr 12, 2007

• #5

if you can rent the gauge, it's simple. take out the spark plug, gently thread in the gauge, crank the engine w/ the coils disconected so it doesnt start then go look at where the needle went highest cuz it'll move a limit needle there. If memory serves me right thats how you do it

 

topless98gt

Adhesive Feces

Mar 31, 2005

182

0

17

Arlington, TX

Apr 12, 2007

#6

• Apr 12, 2007

• #6

Sweet. I gotta do this.

 

TC93

Well-Known Member

Sep 11, 2000

2,075

1

57

Ellerslie GA 31807

Apr 13, 2007

#7

• Apr 13, 2007

• #7

Disable igntion, take all plugs out, insert tester and hold throttle wide open and crank motor several(5-7) compression strokes. If you have a helper be sure to look at the 1st reading you get, when you start the test on each cylinder and the highest reading on each cylinder.

If they are all cylinders are with in 10% of each other you should be good. If one or more cylinder are allot lower than the others do a wet test.. Put some(couple squirts) 30wt oil in the cylinder and repeat test. Higher numbers mean, rings or cylinder is bad, no change in number tells you bad valve...