Compression test results.

[mitsuclipsegsx]

Did a comp test on my 97 GSX, not to good. from left to right... 168,170,148,170. i do have 60k on the clock and the HG hasn't been changed yet, will that help bring up compression or is it a valve or something. BTW it does blow lots of black smoke. and one more thing, the cly that was 168 had oil in it, enough to cover the bottom of the plug. maybe rings.

 

[xorti7]

It looks like its just that one cylinder. I understand that they're not supposed to be more than 15 away from each other. If it's the head gasket you would be mixing coolant and oil. Check your oil for frothy white stuff; that would be coolant. You might not have that much since that one cylinder isn't horrendously far off. I would suspect something other than head gasket if it were me.

 

[mitsuclipsegsx]

Yea, the oil is fine and the coolant bottle is all green ,no oil in it so thats good. When you say that one cylinder is bad, what usually has to be fixed. And i did a comp test when i bought it in Feb the cyl that is 148 now was like 160. so it has been going lower.

 

[xorti7]

The next suspects are piston rings or a valve component. If you're blowing black smoke I would lean towards rings; hopefully someone else here can tell you more about it though.

 

[dsm_racing]

Was the test done with the engine warmed up? You can try squirting some oil in the low cylinder and checking it again. Also, a leak down test would help to eliminate some variables. You could have a bent rod.

 

[mitsuclipsegsx]

Yes engine was warm, so just put some oil in the low clyinder, how much?

 

[daren_p]

Yes engine was warm, so just put some oil in the low clyinder, how much?

First I would redo the test, to make sure you get the same results, then redo the test but this time do a wet test (other test you did was a dry test). Same thing, make sure the car is up to operating temps, crank it over at WOT (make sure engine fuse pulled) but this time in the cylinder that has low pressure pour in a capful or two of oil & let it sit about 5 min. If you pressure jumps up alot on the wet test, then the piston rings are bad. If it stays about the same, you have to look at other areas for the cause. At that point you would want to do a leak down test to find what is causing your issue.

 

[mitsuclipsegsx]

Does the gas pedal have to be floored when performing the test? I didnt do that.

 

[Splitpi]

Does the gas pedal have to be floored when performing the test? I didnt do that.

Yes it does.

 

[mitsuclipsegsx]

Your right, just redid it and it was 175,all of them, sweet,thanks guys

 

[95 tsi awd]

Yes it does.

why does it have to be floored? because when i bought my car it was tested and it was a constant 130 across all 4 and i dont think the gas was floored when it was tested

 

[silverbullett]

I've been thinking of doing a compression test on my car. Quick question....Are we looking for consistency across all four cylinders or is there a certain number I'm looking for? Thanks for the help.

 

[pwayzjellyroll]

I've been thinking of doing a compression test on my car. Quick question....Are we looking for consistency across all four cylinders or is there a certain number I'm looking for? Thanks for the help.

http://www.geocities.com/dsmgrrrl/FAQs/compression.htm

Numbers are towards the bottom, good FAQ to I was clueless when I first heard about it. Went out and did it, with zero problems. There are certain ranges for different cars and factory service limits listed. Just check your corresponding Year/model/motor and you'll be all set.

 

[red_devil]

Thought I would just post here hope its ok, didnt want to start a new thread

Did a compression test today, 97 GST with 180k miles, unknown milage on head

engine warm, engine fuse removed, brand new craftsmen comp tester.

dry test was: 150 160 170 180
wet test: 160 175 180 185

From this I would say the bottem end is not original? Is the difference from cyl 1 and 2 ok?

 

[DJYoshaBYD]

I would say the seal between the head and the black... maybe not the head gasket itself though.. it looks like the head was maybe warped a bit, and not decked before putting it on the block.. that is, if the head was even changed...

is it smoking blue/white or black? that does make a difference...

 

[red_devil]

I would say the seal between the head and the black... maybe not the head gasket itself though.. it looks like the head was maybe warped a bit, and not decked before putting it on the block.. that is, if the head was even changed...

is it smoking blue/white or black? that does make a difference...

It does smoke a little blue-oil at full boost but not much. not sure if the head was replaced or rebuilt but it looked really new when I bought the car and the timing belt was new. The car has over heated twice beofre one time really hot so maybe the head was warped.

 

[Inprogress]

Your block can also warp. If it was over heated badly. Also what the dose the throttle have to due with the compression????????