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funky compression numbers- update with pic

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95talontime

Probationary Member
13
1
Nov 15, 2015
CHALMETTE, Louisiana
So when I checked my compression with the crappy oreilly compression gauge, i got 120,90,60,0. the tester wouldn't hold pressure, but I'm 90% sure its head gasket, but i wanna see if theres any other opinions on it first
 

crash

Proven Member
81
18
Nov 2, 2015
Huntersville, North_Carolina
Is there water in your oil? Hard to tell if the numbers aren't accurate but even a bad tester with a crappy connection should get better numbers than that on an engine with good compression.
 

2gmitsueclipse

DSM Wiseman
2,393
766
Jul 13, 2005
Auburn Hills, Michigan

JacksonAuto

15+ Year Contributor
753
128
Nov 21, 2005
Hanover, Maryland
Next step is to perform a leakdown test. That will tell you where the compression is going. Could be head gasket, piston, cylinder head, bent valve, bad valve seat or a number of other factors.
 

bluegsx1996

Probationary Member
16
0
Feb 12, 2015
Stuart, Florida
So when I checked my compression with the crappy oreilly compression gauge, i got 120,90,60,0. the tester wouldn't hold pressure, but I'm 90% sure its head gasket, but i wanna see if theres any other opinions on it first
If it shows zero you have a bent valve on that cylinder
 

97 eclenger

Proven Member
460
42
Jan 22, 2014
Durham, North_Carolina
leak down test time. cylinder 4 is most likely going to be a bent valve. 2 and 3 could be bad rings or a valve that was tapped but not bent too much. pull the head and check it out after you run another compression test with no spark plugs in and leak down test
 

bluegsx1996

Probationary Member
16
0
Feb 12, 2015
Stuart, Florida
Doesnt even matter.just pull the head it needs rebuilt/replaced .have you checked your timing?looks like a classic case of it jumped timing
 

JacksonAuto

15+ Year Contributor
753
128
Nov 21, 2005
Hanover, Maryland
Doesnt even matter.just pull the head it needs rebuilt/replaced .have you checked your timing?looks like a classic case of it jumped timing
It does matter. What if he removes the head and the problem isn't a bent valve? Then he's got no way to properly diagnose the problem without comitting to a full overhaul. Taking the time to properly diagnose the problem now will save a lot of time in the long run.
 

bluegsx1996

Probationary Member
16
0
Feb 12, 2015
Stuart, Florida
It does matter. What if he removes the head and the problem isn't a bent valve? Then he's got no way to properly diagnose the problem without comitting to a full overhaul. Taking the time to properly diagnose the problem now will save a lot of time in the long run.
If it showed zero its a bent valve.head gasket or bad rings will never show zero or anything below 60.if u think its not the valve dump oil in the cylinder do another compression test and watch the numbers climb.if it does the same thing then valves are the culprit. Seriously check your timing its gotta be off
 

95talontime

Probationary Member
13
1
Nov 15, 2015
CHALMETTE, Louisiana
If it showed zero its a bent valve.head gasket or bad rings will never show zero or anything below 60.if u think its not the valve dump oil in the cylinder do another compression test and watch the numbers climb.if it does the same thing then valves are the culprit. Seriously check your timing its gotta be off

timing is dead on, checked that first and double checked it.

Is there water in your oil? Hard to tell if the numbers aren't accurate but even a bad tester with a crappy connection should get better numbers than that on an engine with good compression.
no water in the oil, but there is a little shimmer on top of the coolant, kinda looked like oil, but it wasn't much so it was hard to tell.

It does matter. What if he removes the head and the problem isn't a bent valve? Then he's got no way to properly diagnose the problem without comitting to a full overhaul. Taking the time to properly diagnose the problem now will save a lot of time in the long run.
my thoughts exactly, i damn sure don't wanna do a head gasket and put it back together to find out its a ring
 

bluegsx1996

Probationary Member
16
0
Feb 12, 2015
Stuart, Florida
timing is dead on, checked that first and double checked it.


no water in the oil, but there is a little shimmer on top of the coolant, kinda looked like oil, but it wasn't much so it was hard to tell.


my thoughts exactly, i damn sure don't wanna do a head gasket and put it back together to find out its a ring
Thats why you out oil in the cylinder and do another compression test.if it comes up its rings.if not then its valve/head related. Take your valve cover off put that cylinder tdc.chances are if its a valve it wont return fully
 

donniekak

DSM Wiseman
5,671
1,035
Mar 23, 2008
Surprise, Arizona
Thats why you out oil in the cylinder and do another compression test.if it comes up its rings.if not then its valve/head related. Take your valve cover off put that cylinder tdc.chances are if its a valve it wont return fully
In an engine with dished Pistons the oil just sits in the piston dish and ups compression numbers by lowering the dish cc of the piston.

A leak down test will tell you what you need to know.
 

bluegsx1996

Probationary Member
16
0
Feb 12, 2015
Stuart, Florida
In an engine with dished Pistons the oil just sits in the piston dish and ups compression numbers by lowering the dish cc of the piston.

A leak down test will tell you what you need to know.
Very true.what do you estimate about a shot glass worth?
 

95talontime

Probationary Member
13
1
Nov 15, 2015
CHALMETTE, Louisiana
Tried to do a leakdown test and couldn't get any pressure in one cylinder and another one was leaking into an adjacent cylinder, took the head off and here's what I found. One toasty exhaust valve. The weirdest part is I drove it home before I got a no start in the morning.
 

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