Leakdown Test

[thomas91169]

Any pointers? Tips and tricks?

drivers bank is 135-155-165-175 from front to rear, passenger bank is sitting pretty at perfect 180 across. 70k on the motor. possible head gasket failure due to a few overheat occurances from lack of proper filling technique.

 

[Silverboost]

that looks like a compression test not a leak down test. Looks like it is time to tear the engine apart to see what is going on.

 

[T-Pain808]

Looks bad, how does the car run?

 

[Silverboost]

the low compression probably explains your low torque numbers.

 

[Steve2050]

Leakdown should give a loss in percentage.

 

[thomas91169]

that looks like a compression test not a leak down test. Looks like it is time to tear the engine apart to see what is going on.

yeah lol kinda why im now going to do a leakdown, to pinpoint the issue.

the low compression probably explains your low torque numbers.

i was told its due to having a 2.93" and rather rich afr's.

its not too totally bad, ive seen people far worse compression here pushing their cars still. its just low on that bank and i have a week off coming up and might use it to pull motor and rebuild, hoping its just a new head gasket.

 

[T-Pain808]

Thats why I asked, how does it run. You mine as well start saving up for now, but run it till she's done.

 

[rotor_powerd]

Even if it runs fine, and you've seen lower numbers, the difference between 180 and 135, or even 155, is way too much. You are causing some serious stress onto your rotating assembly with those kind of differences. I would stop running it if possible, to save from further damage - spun bearings, etc. - until you pinpoint the problem and fix it.

If not - run it 'till she burns up!!

 

[04gtstang]

For comparison

176 175
162 158
156 159
170 167

Cold engine, all plugs out, with TB blade closed. 4-5 cranks.

How were your tests run?

 

[thomas91169]

http://www.svtperformance.com/forums/engine-tuning-214/514412-compression-test-results.html

^^^for the compression test thread.

last test was done with a very warm motor.

i cant for the life of me find TDC. im using the "stick a long thing int he plug hole and wait till it reaches the top" method. each time the piston is at top i still cant get the cylinder to pressurize. However i can hear a slight hiss when i stick my ear to the tailpipe. maybe i am at TDC and i have a dead exhaust valve? It also seems like the tester isnt sealing the plug hole properly, thought maybe i have fubar'd threads but it holds a plug fine and no signs of gases escaping into the plug valley.

 

[Silverboost]

if you hear a "hiss" out the tailpipe you have a burnt exhaust valve. Sounds like to me it is time for a head job.

 

[thomas91169]

if you hear a "hiss" out the tailpipe you have a burnt exhaust valve. Sounds like to me it is time for a head job.

:banana: head job.....its always time for one of those.

 

[03cobra#694]

:banana: head job.....its always time for one of those.

:lol::lol::lol:
I`ve been reading your posts on your problems for a few days,hope everything works out for ya:beer:

 

[thomas91169]

i just hope its not the bottom end/blowby. top end is rather cheap.

 

[Fred Brown]

just because your lining up your marks, doesnt mean you have a burned exhaust valve. your timing marks will line up twice on every power cycle. Hence tdc, could be on intake, compression. or tdc on exhaust stroke. if you are hearing a hiss at the tail pipe ,you may be on tdc exhust FRED

 

[Fred Brown]

interesting, ive been a member here since early 2002, and im still a rookie poster. fred

 

[thomas91169]

you have 31 posts in forums that count, thusly still a rook.

i dunno how i became a SVT God nor do i remember posting 3k times in anything but Smackdown/Roadside.

 

[thomas91169]

OK dunno if i am doing this right.

i have the motor at TDC, im pretty sure cause ive tried it a 4 different TDC events and the same results on every one.

Im using a Harbor Freight tester.

Screw it into the sparkplug hole (i hear thats important), and hook up the tool. My compressor is regulating at 100psi. Now the directions say to use the regulator knob and add or take away pressure till you reach 0 on the percentage drop gauge. It only takes me till around 15-20psi on the tool's regulator gauge to hit 0% pressure loss. and then what?

i can still hear a hiss from the exhaust, even at 15-20psi of air going into the cylinder.

I am a leakdown n00b. Any other car i would have just pulled the motor (dsm so easy, low compression and oh well, pull the head in an hour or so), but i want to diagnose the issue before proceeding, instead of proceeding then diagnosing, this motor looks like such a pita to remove just for shits and giggles, and it is my DD so i want it down for as short as possible, so id like to get necessary parts in and then pull motor or whatnot, instead of pulling motor then waiting for parts.

 

[Silverboost]

pulling the head on one of our cars is a big undertaking. I have pulled the heads on a 2 valve in the engine bay and it was a lot of work. The 4 valve has got to be a lot worse.

 

[thomas91169]

cant be much more difficult than the 4g63's im used to, as they are dohc as well, so it should be pretty much the same concept (aside from being chain drive instead of belt) but just twice the work (two banks instead of one).

Shitty part is pulling the motor.