Wierd compression

[Josh913]

My car has been having an overheating problem..I lose coolant and my temperature gauge will rise and usually falls..so I suspect a BHG. Today I decided to do a compression test and the last three cylinders have oil that pretty much cover the spark plugs which I believe to be the valve cover gaskets. the compression #'s are

1-140
2-150
3-165
4-170
5-280
6-180

I don't understand why the 5th cylinder is so high I checked it a few times and everytime it was right in that area..

Do these compression #'s sound like a BHG...and also what would cause the compression to be so high on the #5.

Any info is appreciated it

Josh

 

[Idealsupra]

did you check to see if all the cylinders were DRY...namely number 5...it is possible that there is a pool of oil or coolant in the cylinders which would raise compression significantly...

also with that much variance im thinking its time to rip it down...

you were doing the test right correct? WOT, EFI fuse pulled, warm engine, crank for about 8 seconds....

 

[Josh913]

No I didnt warm the engine first..and I believe a good bit of oil did drain into the #5cylinder. so when you say it's time to rip it down, do you mean like for HG or the whole engine?

Thanks,

Josh

 

[PynkEye]

no he means, rip it down, take the engine out and put it back in, dont touch anything tho, it does it good sometimes lol jk
Ya, a rebuild

 

[Squid699]

if there was oil in the cylinder, that will definitely effect the reading.....run the car and try it again

 

[Josh913]

alright i'll try that...about how long should I run the car, and are you supposed to have all the spark plugs out, or one at a time? because I have heard both and was wondering which way is more accurate..

Thanks

Josh

 

[Allan_MA70]

i wanna see you run the car with all the plugs out!

 

[Squid699]

run the car long enough to make sure theres no oil or water in there......up to operating temp.

then pull the plugs one by one and do the compression test......thats how i did mine.

 

[Bishop92t]

If you pull the plugs one by one and your HG is blown between cylinders you'll get weird readings. If you pull them all then the two cylinders that are blown will both be low. Either way will work, but will show you different results if you do indeed have BHG.

 

[Josh913]

Ok thanks for all the replies...I'll try it today or tomorrow and post results.

Josh