Request: Compression Test Procedure

[south59]

Looking for a writeup or link for the procedure of performing a compression test...the search function didnt turn much up for me.

 

[dogfriend]

see post #12 in this link:

http://www.explorerforum.com/forums/showthread.php?t=73060&highlight=compression+test

 

[south59]

It's one month later and I'm finally ready to do this!

This is how I plan on doing the compression test tomorrow, let me know if im missing anything.

-drive the truck to operating temp for about 5 mins
-remove spark plugs
-tie the throttle plate open
-remove connection to coil pack to disable ignition
-install gauge on #1 cylinder and repeat for each cylinder
-have someone crank the engine for about 8 seconds and record highest reading

thanks

 

[dogfriend]

Sounds correct. You will see that the reading will rise as you crank the first few revs and will then level off at the max reading - Ford says a minimum of five revolutions - it will take less than 8 sec to get the max reading

 

[ExplorerDMB]

I do it a different way, but you'll get the same readings. Good luck getting all 8 spark plugs out before the engine cools down. Get some kevlar gloves so you won't burn yourself

-Drew

EDIT: you normally don't want to see anything with a difference of 30 pounds (in general). If you get 180 on one piston and your lowest was 160 - you're fine

 

[south59]

Thanks for the help guys, i went to harbor freight this morning and bought some welding gloves and a compression tester. wish me luck

 

[south59]

Well, No noticable loss of compression between cylinders! The readings are as follows

#1 165 psi
#2 170 psi
#3 170 psi
#4 168 psi
#5 170 psi
#6 170 psi
#7 165 psi
#8 170 psi

While i was under the hood, i noticed that the thermostat housing had some wet coolant residue which was dropping down onto the engine block...Hopefully that is where my coolant has been going.

Still trying to figure out where the loss of power on the freeway is comin from along with the 20-30 miles per tank that i have been losing lately