Hello All,

revised (04/21/14 10:21 pm) got a new test guage

2003 Cooper (non-S)

Engine Cold

Here are my readings:

Cyl # / Dry Reading / Wet Reading
# 1 / 160 / 210
# 2 / 190 / 240
# 3 / 180 / 230
# 4 / 205 / 255

Can anyone tell me what they might think is going on?

With exception to #1, the numbers look good to me?

Blown head gasket, bad valve, busted piston rings?

I have not done a leak down test at this point.

Comment:

When doing a compression test, crank the engine the same number of times on each test. The Bently books says 4 to 6 TDC strokes. I choose 6 strokes per cylinder. ( I did not do that on my initial test and the readings were all over the range.

Just for kicks, I decided to get the max psi / number of strokes.

Here is the date

#1) 205 psi in 15 strokes
#2) 225 psi in 15 strokes
#3) 210 psi in 15 strokes
#4) 235 psi in 15 strokes

At least is was consistant in the number of strokes to max psi.

Tell me what you think.

 

What is the car doing that lead you to do a compression test?
What are the numbers? Not psi....knda helps to know to make it easier to compare vs other known cars with numbers....

 

I think you better recheck your readings..

 

2003 Cooper (non-S)

Here are my readings:
Engine Cold
Cyl # / Dry Reading / Wet Reading
# 1 / 210 / 290
# 2 / 235 / 275
# 3 / 206 / 265
# 4 / 256 / 300

These numbers are all over the board.

Can anyone tell me what they might think is going on?

Blown head gasket, bad valve, busted piston rings?
I have not done a leak down test at this point.

Here are the Bently Service Manual technician readings :
Compression Specifications
Compression range
Cooper (non-S) : 167 to 247 psi
Cooper S : 131 to 196 psi Max difference between cylinders : 7 psi

 

From all my knowledge to get accurate readings you need to do the compression test with a HOT engine. with a cold engine you will get blow by.... try that first, get the engine up to operating temp. turn it off get the plugs out, disconnect coil pack, pull the fuse for the injectors and crank away.

 

Also, consider getting a second gauge, cheepo, loaner, anything, just to get another reading for comparison and gauge checking purposes.

 

What performance issue are you having....
Numbers seem to be pretty typical of a "runner".... Sure nothing perfect...but wear happens....
Manual numbers fora car/motor are not EXACT.....simple fact is...if it runs well...drive. It is not like a computer with precise readings.... Guages are imprecise....valve seating and even rings tighten and loosen with temp and postion....
So again...what performance issue lead you to do a compression check other than you just want to know....