Low Compression on #2

[vault415]

Basically my car has been running ok, other than running hot (you can see my other posts about that issue). Today I did a compression test and came up with these results:

Cylinder #1 - 180
Cylinder #2 - 120 ***
Cylinder #3 - 195
Cylinder #4 - 195

This was the first time I've ever done a compression test but I followed the directions from vfaq as closely as possible. I used an Advance Auto $25 gauge.

After I added a cap full of oil to cylinder #2, I got 195 on that cylinder, so from what I've read that indicates a worn or damaged ring. Is there anything else that it could be? Like I've said, I'm having some over heating issues, so could that side of the block just be warped (resulting in a BHG) because #1 is also slightly lower than #3 and #4?

If it's a bad ring, can I replace it without tearing the head off? I thought I read that pistons can be dropped out the bottom of the engine...

What's the cost involved when I do this myself? Do I need a new piston to go along with the rings? Should I just bite the bullet and take the head off and do ARP's and a new head gasket?

Basically is it time to do a thorough rebuild rather than just replacing the rings or piston in #2? The car just turned 100,000 miles. Thanks!

 

[Hitchhikkr]

More than likely your block isnt warped, but a BHG is possible. Its hard to diagnose a car without actually looking at it, but if you have that much difference in pressure between cylinders you can pretty much bet on a BHG. How hot is the car running idling? Cruising? How often do you add coolant? What does the coolant look like? What does the oil look like?
More than likely you are going to have to pull the head off the car. If it is ring problems, you can pull the piston/rod assembly out thru the bottom, but its a pain in the A** to put it back. Keep in mind, if it does turn out to be just a worn ring, then there is a reason for it. Either oil or fuel control issues on that cyl.

 

[vault415]

Duh, I meant I wondered if my HEAD was warped.

My oil has been jet black every time I've changed it since I got the car at 60kmi, and since I've been checking the water so often lately, I've noticed that it sometimes has some little flecks of rust and gunk in it, but it's not blatantly obvious that there is any oil in the water or water in the oil. I haven't been adding more than 8 ounces of coolant to it a month, and there's no white smoke coming out the tail pipe, but I DO add a quart of oil every 1500 miles or so (2 quarts per oil change).

Idle temps go up to 210 then the passenger side fan turns on.
Cruise temps are anywhere from 200-225 depending on the temp outside. Now that it's only in the 70's-low 80's they've stayed around 200-210, but when it gets hot and muggy they go up to 220-223 (All of this logged via DSMLink).

Plugs are the normal white color they've always been.

I tried answering your questions, so maybe there will be a clue in there somewhere. Thanks!

 

[Bostedquest]

About in the same boat as me.
The overheating could have caused a warp in the head creating a bad seal.

When I first put my engine back togeather I had 190 all 4. Checked before doing anything else and with added fluids. Ran like a raped ape first day. Yesterday was the first day since I have gotten it to run on its own in 2-3 weeks.
Now I just redid it today and had very dire numbers indeed. 90/120/120/110. I even checked the Trq on the head bolts, still at 70, which is what I set them at when I first installed the head. Well 1 was at 68... but still...
I am not worried about the HG because it is a cometic MLS, and those fail... like never.
And the oil/coolant is fine.
When I was doing the initial start up break in/warm up, I was a little slow in putting some coolant in and it was steaming like no tommorrow. So, I now get to pull the head and have it checked. I am almost certain that is what the issue is now.
As I have done boost leak test (no leaks)
And got it to run, some-what decently by holding the throttle full open.

So that is what I get to do 4th of July weekend.. fun huh?

 

[vault415]

Ok, so then I guess after I perform a leak down test I will pull the head, get it checked and do the head gasket...does that sound like a good plan?

 

[Bostedquest]

Ok, so then I guess after I perform a leak down test I will pull the head, get it checked and do the head gasket...does that sound like a good plan?

pretty much...

 

[half-cocked]

Basically my car has been running ok, other than running hot (you can see my other posts about that issue). Today I did a compression test and came up with these results:

Cylinder #1 - 180
Cylinder #2 - 120 ***
Cylinder #3 - 195
Cylinder #4 - 195

This was the first time I've ever done a compression test but I followed the directions from vfaq as closely as possible. I used an Advance Auto $25 gauge.

After I added a cap full of oil to cylinder #2, I got 195 on that cylinder, so from what I've read that indicates a worn or damaged ring. Is there anything else that it could be? Like I've said, I'm having some over heating issues, so could that side of the block just be warped (resulting in a BHG) because #1 is also slightly lower than #3 and #4?

If it's a bad ring, can I replace it without tearing the head off? I thought I read that pistons can be dropped out the bottom of the engine...

What's the cost involved when I do this myself? Do I need a new piston to go along with the rings? Should I just bite the bullet and take the head off and do ARP's and a new head gasket?

Basically is it time to do a thorough rebuild rather than just replacing the rings or piston in #2? The car just turned 100,000 miles. Thanks!

First off trying to re-ring a motor properly cannot be done with the head on because you should hone the cylinder out. I'm also an advocate for, if its running fast/good, dont #### with it. You can get a 280 grit cylinder hone for about the same price you got that compression tester for. Now we can go on all day about plateau honing, which I have never tried but if someone has I would like them to chime in because I would like to learn more about it, but break the glaze on the cylinder and put some decent cross hatches on it and it should be good. The basic weekend-warrior-parts-changer re-ring should include 4 new rod bearings ($7.99 each @ autozone), 4 new ring sets (around $20 a piece @ autozone), head gasket of your choice, ARP studs and associated tools. Its more time consuming that it is hard. I would clear a whole weekend if its the first time you have done it.

 

[vault415]

Thanks a lot. I'm going to take her off the road and start tearing her apart in a month or so.

After I take the head off I know I should take it to a machine shop to get it checked out. After I get the results from them, then should I know if I need a thicker head gasket and larger rings? If I put something like .01 or .02 over rings on then do I have to have the block matched also? (Obviously I know very little about this part)

 

[92awddsm]

Thanks a lot. I'm going to take her off the road and start tearing her apart in a month or so.

After I take the head off I know I should take it to a machine shop to get it checked out. After I get the results from them, then should I know if I need a thicker head gasket and larger rings? If I put something like .01 or .02 over rings on then do I have to have the block matched also? (Obviously I know very little about this part)

Before you start tearing it apart, I would run some seafoam or mccc through it and see if it helps compression. Since it has overheated, its a good chance that there could be carbon built up around the rings and basically cusing them to stick in the pistons. This could also cause your oil consumption problem and make the oil black like you speak of due to exhaust blowing by the rings. Ive seen this before and also seen people do costly rebuilds when seafoam could have cured their problems. Just give it a try, recheck compression and let us know the outcome.

 

[vault415]

Ok, I'm all for taking an easier route Thanks!