LOW LOW #s on compresion test!! HELP!!

funkytrunk92

New Member

Aug 28, 2003

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Indianapolis, IN

Jul 7, 2006

#1

• Jul 7, 2006

• #1

1993 Cobra (had a week) leaks ALOT of oil...replaced pcv valve and screen and just did compression test. OK, I have done everything instructed in my manual as to how to perform a compression test. I have the car up to operating temperature. All cylinders are EXTREMELY LOW and two are dead...Here are the results:

(1) 40
(2) 40
(3) 40
(4) 42
(5) 40
(6) 43
(7) 0 completely dead
(8) 0 completely dead

first, why are the number SOO low....i was told the numbers would be in the mid 100s (which the guage does go up to)

second, do the back two both dead mean blown head gasket or could it still be blown piston rings?


thanks in advance guys!

Scott

 

fidstang

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Jul 19, 2005

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South Lansing

Jul 7, 2006

#2

• Jul 7, 2006

• #2

Where's the oil leaking from? Does the exhaust have smoke coming out. If so is it all the time? Is it blue or white with a sweet smell? How about the heads, are they stock iron or aluminum?

 

funkytrunk92

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Aug 28, 2003

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Indianapolis, IN

Jul 7, 2006

#3

• Jul 7, 2006

• #3

Leaking from everywhere! just kidding...rear main seal (most likely), oil pan (unsure)...when i removed the cap on the oil filler you can feel blow by coming out (ALOT more than normal)...also, discovered valve covers loose (i've only owned it a week) which has been source of much oil

Exhaust has light smoke which appears to be white but is really faint and mostly when you get on it. I know that indicates coolant, I guess what I'm primarily trying to fix is the blow-by causing my many leaks.

Heads are stock iron with work done to them but unsure EXACTLY what...again, only owned the car a week...

it's supposedly now a 306...it's covered in oil...everywhere...found oil on top of bolt on lower intake...in throttle body...the list goes on...

thanks!

 

fidstang

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Jul 19, 2005

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South Lansing

Jul 7, 2006

#4

• Jul 7, 2006

• #4

Wow! I would suggest pulling that sucker apart. Oil in the throttle body maybe a sign that the previous owner had a blower/turbo on it that was damaged. Just a thought. I would tear it down to the block and check everything out. Valve seals, gaskets, cylinder bores and deck flatness. Plus, you can put new gaskets and bolts back on if no problem is found and have peice of mind! new gasket= $80.00 bolts= $70.00 knowing your motor= priceless.

White smoke+sweet smell= head gasket.

 

funkytrunk92

New Member

Aug 28, 2003

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Indianapolis, IN

Jul 7, 2006

#5

• Jul 7, 2006

• #5

beginning to pull motor as we speak...

(1) i know u can have water in your oil, but can u get oil in your coolant in the radiator??????

(2) why are numbers so low (the 40s)????

 

Skoobie

Damn...Tyler65's hot!

May 25, 2003

655

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17

Vancouver, WA

Jul 7, 2006

#6

• Jul 7, 2006

• #6

Wow...those are low. Last time I ran compression (188k on the short block) I got 160 across the board with one 155 on #7. You really need to do a leak down to see how bad the rings are getting. Start pulling your intake and heads to check for damaged gaskets after youve done the leak-down. As for the valve covers get a good set of reusable metal gaskets, they seal like no other. Does the car even run? Feel low on power? More details. Yes you can get oil in your coolant. If one (or more) cyls are low, try squirting in a bit of engine oil from a squirt can and retry the compression test. If pressure increases this means time for piston rings. If no increase, likely a bad valve (most likely exhaust)- which means a cyl head rebuild job.

If you have low compression on two adjacent cyls, it could indicate a head gasket problem - in which case you'd have to pull the cyl head and replace the gasket. This type of head gasket failure might not mix your coolant and oil and might not show up that way

 

funkytrunk92

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Aug 28, 2003

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Indianapolis, IN

Jul 7, 2006

#7

• Jul 7, 2006

• #7

I'm pulling it...I agree with fidstang that knowing your motor is priceless. So, out she comes. The car ran great, I even drove it 130 miles home when I bought it...it has 163,000 miles on it, it is probably time. It just leaks oil and blows smoke when you get on it. thanks for your help guys, you've confirmed what I got to do. My burning question is why the numbers are so extremely low...I know I have issues and will take care of each as I tear it apart, but WHY SO LOW? Does anybody have a reason for the really low #s??

This isn't a daily driver...i just didn't get to enjoy it yet

 

fidstang

New Member

Jul 19, 2005

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South Lansing

Jul 7, 2006

#8

• Jul 7, 2006

• #8

funkytrunk92 said:

beginning to pull motor as we speak...

(1) i know u can have water in your oil, but can u get oil in your coolant in the radiator??????

(2) why are numbers so low (the 40s)????

Click to expand...

oil in the colant/radiatior is a sure sign of blown head gasket!
Have Fun! remember, if things go wrong and seem to get wrose. Take a break for the day, drink some beer and you'll be refresh for the next headache.

 

FastDriver

I was uncomfortably high & wearing a helmet

SN Certified Technician

Sep 5, 2001

6,068

2,671

224

Vass, NC

Jul 8, 2006

#9

• Jul 8, 2006

• #9

If your numbers were that low, your car wouldn't run. You're either messing up the compression test, or your gauge is broken. Did you leave the TB open? Did you turn the engine over several times to get the cylinder pressure up? is the gauge getting a good seal? Have you tried another gauge?

Oil in the intake doesn't necessarily have anything to do with whether or not the previous owner had a blower/turbo. Could be that the oil baffle in the passenger valve cover has been removed and the pickup tube to the intake is collecting a lot of oil as a result, which is sucked into the intake. Could be that the filter on your PCV valve needs to be replaced. I personally don't believe in breathers instead of caps on valve covers if there is a functional PCV valve. Even with boost, it can be routed in front of the compressor (whatever type of compressor it is).

Chris

 

M

mercurycapri

Member

May 30, 2006

211

2

18

washington

Jul 8, 2006

#10

• Jul 8, 2006

• #10

sounds like you need a new engine. Have you checked your timing. Is the timing chain bad? Hook up the timing light and see if the timing is bouncing around. Or you can check your vacuum too.

 

funkytrunk92

New Member

Aug 28, 2003

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Indianapolis, IN

Jul 8, 2006

#11

• Jul 8, 2006

• #11

That's the crazy part, FastDriver, I went through 2 different guages, left throttle body open and turned the engine over MANY times just to make sure. All cylinders would never go over 40ish. The first thing I did was replace PCV valve and screen to no avail. Thanks fidstang for the encouragement! I'm evicting my wife's car from the garage today

 

D

Daggar

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Jul 19, 2004

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Jul 8, 2006

#12

• Jul 8, 2006

• #12

Regardless of what the numbers are whether the car runs or what problems you find and fix... that motor is El-Crappo. I wouldn't trust it to run down the corner store and back.

Time to pull and rebuild it. It's the only way to ensure that you get a first hand look at all that ails it.

 

5ive.oh

Founding Member

Feb 23, 2001

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Rocky Mountain House, AB

Jul 8, 2006

#13

• Jul 8, 2006

• #13

I would guess that you do a wet compression test, same as a normal test but squirt a small amount of oil into the cylinder first then crank it over. If you see an increase of compression in the 5% area the rings are shot. If it doesn't improve then I would think the valves in the heads are the culprit. Also if it has an agressive cam that will lower the compression numbers as well, not that low of course.