So as part of my "how are my head gaskets" project, I did a compression test tonight. The coolant pressure test to be done tomorrow.

Anyway, here are the numbers. It seemed to take a little longer for the compression to build that I would have liked, but I have never tested one of these trucks before. What do you think of these numbers?

By the way, the truck has 116k on it.

Thanks!

~Max

#1
Stroke 1: 75
Stroke 2: 100
Stroke 3: 120
Stroke 4: 135
Stroke 5: 145
Stroke 6: 155
Stroke 7: 165
Stroke 8: 170
Stroke 9: 180
Stroke 10: 190
Stroke 11: 190
Stroke 12: 190


#2
Stroke 1: 55
Stroke 2: 80
Stroke 3: 100
Stroke 4: 120
Stroke 5: 130
Stroke 6: 140
Stroke 7: 150
Stroke 8: 160
Stroke 9: 170
Stroke 10: 175
Stroke 11: 175
Stroke 12: 175


#3
Stroke 1: 60
Stroke 2: 85
Stroke 3: 105
Stroke 4: 130
Stroke 5: 135
Stroke 6: 145
Stroke 7: 150
Stroke 8: 160
Stroke 9: 165
Stroke 10: 175
Stroke 11: 180
Stroke 12: 180

#4
Stroke 1: 60
Stroke 2: 80
Stroke 3: 100
Stroke 4: 110
Stroke 5: 130
Stroke 6: 145
Stroke 7: 150
Stroke 8: 155
Stroke 9: 160
Stroke 10: 165
Stroke 11: 165
Stroke 12: 165

#5
Stroke 1: 65
Stroke 2: 90
Stroke 3: 110
Stroke 4: 125
Stroke 5: 135
Stroke 6: 150
Stroke 7: 150
Stroke 8: 150
Stroke 9: 150
Stroke 10: 150
Stroke 11: 150
Stroke 12: 150
Note: A second test topped out at 160, a third at 165.

#6
Stroke 1: 50
Stroke 2: 70
Stroke 3: 90
Stroke 4: 100
Stroke 5: 110
Stroke 6: 120
Stroke 7: 130
Stroke 8: 135
Stroke 9: 140
Stroke 10: 140
Stroke 11: 140
Stroke 12: 140


#7
Stroke 1: 75
Stroke 2: 95
Stroke 3: 115
Stroke 4: 135
Stroke 5: 145
Stroke 6: 155
Stroke 7: 165
Stroke 8: 175
Stroke 9: 180
Stroke 10: 180
Stroke 11: 185
Stroke 12: 190

#8
Stroke 1: 70
Stroke 2: 90
Stroke 3: 110
Stroke 4: 120
Stroke 5: 130
Stroke 6: 140
Stroke 7: 150
Stroke 8: 155
Stroke 9: 160
Stroke 10: ? (Stopped at 9 strokes)
Stroke 11: ?
Stroke 12: ?

 

Your gauge is not calibrated/accurate. An engine with your mileage won't have 190 numbers.
The main thing to look for is there should not be more then a 10% difference between cylinders.
Why are you testing/looking for?

 

For OP/Maxman:

Did you do this yourself or did you take it to a mechanic shop?

If you did it yourself, I'm interested to know what you used to do your compression testing?

I'm too much of a novice/amateur mechanic to know which tool or system is capable of giving you per stroke compression readings.

If a shop did it, I'm assuming they did the compression test electronically etc.

For DiscoMike:

In general, wouldn't a 190 PSI be a really high compression even if the engine had low miles or was new?

Is there a benefit for knowing the PSI compression for each stroke?

Thanks and cheers to both of you,

Thomas

 

The test is done with a thread in compression tester. Normal compression is measured by the highest reading not from each stroke.

 

Thomas,

I did the compression test myself using what I refer to as "the worst compression test ever" that I borrowed from the local parts store. The thing that I really hate about it is that there is a rotating joint were the hose meets the threaded insert, meaning you can't use the hose to gently snug it into the hole. Furthermore, the finger grip that you are supposed to use to tighten it down, sits about an 1/8" above the threads, which is well within the spark plug clevis on the rover. Anyway, I'm venting.

I initially planned to just record the highest compression obtained per cylinder. I expected the pressure to max out after 3 or 4 strokes. When I saw that it took 8 or 9 or 10 to get all the way to the top, I thought it would be worth recording the progression. So, I used the video camera on my cell phone to record video of the gauge while the truck was being cranked. I then stepped/scrubbed though the videos on my computer and noted the progression of the compression with each stroke.

I agree with Mike, I think this tester might suck in more ways than one. I'm going to see if I can test it against another one.

 

Just a question, did you disable the fuel? I was thinking that may be why more pressure built up in subsequent tests... I don't know, just wondering ???

 

All other particulars aside, I'll call those good numbers. I'm not worried about the down in the weeds accuracy of a gauge or fuel lines disconnected. These are ditch mechanic rules.
Look at them in banks, odd and even.

Odd had 190-180-165-190
Even had 175-165-140-160

Your third cylinder on each side had lower numbers. I don't recall your mileage, but might we worn/dirty valve seats.
I would not say your block is cracked.

I'd look elsewhere

 

Good point, both of those numbers are more then 10% off from the high cylinders and should bee rechecked, first by a wet test, then, if need be by pulling down the heads.