Compression numbers are in- what is going on with 5 cylinder?

[clydesdale]

For a history please look at one of my recent threads.
But here are the numbers:
I am labeling the cylinder 1-6 starting with the front of the motor, radiator end.
1 170
2 170
3 170
4 170
5 100-150- This cylinder varied and did not have consistent hits on the guage
6 180

Sooooo, what is possibly a happening on the 5 cylinder? The inconsisent hits on the gauge with the compression test on this cylinder are interesting. What could the problem be?

[KenC]

Bad rings or a bad valve seat. Add a little oil to it and test again.

[phreshkid]

What he said^

[clydesdale]

Ok I added oil and got 210 on the previous 170 cylinders and about 220 or so on the 180. The cylinder in question only bumped up to 170. But, here is the real question:
Why are the hits inconsistent on cylinder 5. The motor will turn 2-3 times and not get any reaction on the compression guage. Then it will bump up and couple of times and then may go a cycle or two with no reaction.
I was cycling the motor for 5-6 pulses on the guage. The other cylinders all hit the gauge consistently, #5 would sit out a couple of cranks with no reaction, even with the oil.

[AndrewBird]

Seems like a bent valve that is sticking open only some of the time.

[clydesdale]

Does this at all explain why I have some oil in my coolant or is this a separate problem?

[billybobjoseph]

Headgasket failure could explain both the compression problem and the coolant in the oil problem

[blacksport325]

Does this at all explain why I have some oil in my coolant or is this a separate problem?

Just change the HG, and do a write up while your at it;)