How do you do a leakdown test?

[A1337STI]

So the motor in my rally car is running like crap. gas milage is WAAY down. (22 ish, i used to get 32)
compression test yeilded 140,90,130,135. it hesitates at times.

I have Kevin's old 1.8L motor from his red car. I also have access to a cheap leak down tester.

when i tried testing it . i adjusted the air flow so the leak down said 0%, turned the motor over until all the valves were closed and hooked it up. it said 7%.

i went to move on to the next cylinder. the guage had 'crept' by then and the needle was burried (like -20% leak down) so i adjust it , and let air out and got the guage to stay at 0%. i get like 10% . i decide to retest the first one since i've had to make an ajustment to the air flow. and now i get a different reading 20% leak. take the gauge off and it won't rest @ zero.

Am i using the gauge wrong or is it junk?

Is there any way to compression test a motor that's out of the car with no tranny atatched ?

[Dean]

Originally Posted by A1337STI

Is there any way to compression test a motor that's out of the car with no tranny atatched ?

Yes, but it won't be perfect since it won't be warm. Bolt the starter on and crank it with a battery.

IheartSTI might have broken bell housing bits to make it easy to bolt one up, but you should be able to Jury rig something otherwise!

Or turn it with the crankshaft bolt.

With and/or without preoiling the cylinders. It will at least give you relative numbers if you go around a couple times.

[A1337STI]

would a 350 ft pound rattle gun (or a 600 ft/pound for that matter) be able to turn the motor over for a compression test?

i like the idea of bolting a broken bell housing up ... BRILLIANT! i have an extra fly wheel ( if i didn't toss it) its got a darn torque converted bolted to it right now...

[Dean]

Originally Posted by A1337STI

would a 350 ft pound rattle gun (or a 600 ft/pound for that matter) be able to turn the motor over for a compression test?

i like the idea of bolting a broken bell housing up ... BRILLIANT! i have an extra fly wheel ( if i didn't toss it) its got a darn torque converted bolted to it right now...

I have spare STI flywheels as well.

I think any gun might work as long as you have a huge amount of air volume. Plugs are out, so it should turn easily. Less impact might be better, so try a cheap gun first. Make sure the accessory pulley or washers are on so you don't bottom out the bolt.

[A1337STI]

1 last Q
if the compression test says 140 (@ 6200 feet) would it read the same at 4500 and at 0 ft altitude?

I'm guessing so , as the D&D dismantlers has a 1.8L that they said tested at 150 comp on all 4. (my subaru service manual says a comp test should read between 140-160) and i can't imagine you'de hit 150 with 80% of the atmospheric pressure if the gauage was absolute ?